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COVID-19 research v1.58 ABO Arina Puzriakova reviewed gene: ABO: Rating: GREEN; Mode of pathogenicity: None; Publications: ; Phenotypes: Virus susceptibility; Mode of inheritance: Unknown
COVID-19 research v1.58 ABO Eleanor Williams changed review comment from: Preprint https://doi.org/10.1101/2020.06.07.20124610.t Pourali et al 2020 - meta-analysis of blood group and risk of infect ion and death in COVID-19. Supports the finding that those with blood group A are at higher risk for COVID-19 infection while those with blood group O are at lower risk.; to: Preprint https://doi.org/10.1101/2020.06.07.20124610 Pourali et al 2020 - meta-analysis of blood group and risk of infect ion and death in COVID-19. Supports the finding that those with blood group A are at higher risk for COVID-19 infection while those with blood group O are at lower risk.
COVID-19 research v1.58 ABO Eleanor Williams commented on gene: ABO
COVID-19 research v1.38 TNF Sarah Leigh changed review comment from: TNF was identified through an OMIM search for potential viral susceptibility genes. Initial triage by Illumina (Alison Coffey and team) was given a Tier 3 grouping (experimental evidence and association data consistent with viral susceptibility); to: TNF was identified through an OMIM search for potential viral susceptibility genes. Initial triage by Illumina (Alison Coffey and team) was given a Tier 3 grouping (experimental evidence and association data consistent with viral susceptibility). Illumina review: PMID: 10719836: Herbein et al. (Review) TNF is a proinflammatory cytokine plays a key role in the host response to viral infection. TNF enhances or inhibits viral replication depending on the virus involved and the cell type infected. The binding of TNF to the TNF receptors can activate, differentiate, or kill target cells thereby interfering with the viral life cycle. In contrast, viruses have evolved to appropriate the TNF/TNFR pathway to evade immune responses and favor viral dissemination. From OMIM: PMID: 12915457;Kim et al. (2003) To investigate whether TNF-alpha promoter polymorphisms are associated with clearance of hepatitis B virus (HBV) infection, Kim et al. (2003) genotyped 1,400 Korean subjects, 1,109 of whom were chronic HBV carriers and 291 who spontaneously recovered. The TNF promoter alleles that were previously reported to be associated with higher plasma levels (presence of -308A or the absence of -863A alleles), were strongly associated with the resolution of HBV infection. Haplotype analysis revealed that TNF-alpha haplotype 1 (-1031T; -863C; -857C; -308G; -238G; -163G) and haplotype 2 (-1031C; -863A; -857C; -308G; -238G; -163G) were significantly associated with HBV clearance, showing protective antibody production and persistent HBV infection, respectively (P = 0.003-0.02). From OMIM: PMID: 11506397 Quasney et al. The presence of the A allele at the TNF-alpha-308 site was overrepresented among adults with HIV dementia compared to those without dementia (0.28 vs 0.07; OR 5.5; 95% CI 1.8-17.0) and a healthy control population (0.28 vs 0.11). The increased frequency of the A allele in HlV-infected adults with dementia suggests that this locus may play a role in the pathophysiology of dementia and suggests a genetic predisposition for the development of HIV dementia. PMID: 26657940 García-Ramírez et al. (2015) - 145 patients with influenza A (H1N1) (pA/H1N1), 133 patients with influenza-like illness (ILI), and 360 asymptomatic healthy contacts (AHCs) were included from a Mexican population were studied. The TNF-238 GA genotype was associated with an increased risk of disease severity (OR =16.06, p = 0.007). PMID: 31986264: Huang et al. (2020) Study of 41 patients admitted to hospital with laboratory-confirmed 2019-nCoV. Compared with non-ICU patients, ICU patients had higher plasma levels of proinflammatory cytokines and chemokines including IL2, IL7, IL10, GSCF, IP10, MCP1, MIP1A, and TNFα.
COVID-19 research v1.23 DPP4 Sarah Leigh changed review comment from: DPP4 was identified through an OMIM search for potential viral susceptibility genes. Initial triage by Illumina (Alison Coffey and team) was given a Tier 2 grouping (experimental and/or genetic evidence, suggesting a biological role linking to corona viruses, may not be a GDA); to: DPP4 was identified through an OMIM search for potential viral susceptibility genes. Initial triage by Illumina (Alison Coffey and team) was given a Tier 2 grouping (experimental and/or genetic evidence, suggesting a biological role linking to corona viruses, may not be a GDA). "Illumina review: Cell surface glycoprotein receptor involved in the costimulatory signal essential for T-cell receptor (TCR)-mediated T-cell activation. DPP4 acts as a receptor for MERS-CoV - PMID: 24554656 - Barlan et al. (2014). MERS virus cell entry begins with the receptor-binding domains (RBDs) of the MERS-CoV protein virus spike (S) protein binding to blades 4 and 5 of the 8-blade propeller domain of DPP4. PMID:23486063 - Raj et al. (2013) - identified DPP4 as a functional receptor for hCoV-EMS (MERS CoV). Evidence from mouse models of involvment in susceptibility to MERS-CoV infection. PMID:24599590 - Zhao et al. (2014) - noted that rodents are not susceptible to MERS-CoV. They used an adenovirus vector expressing human DPP4 to generate mice sensitized to infection with MERS-CoV. These mice developed pneumonia characterized by extensive inflammatory cell infiltration with virus clearance after 6 to 8 days in a type I IFN- and T cell-dependent manner. Treatment with poly(I:C) was also efficacious in this model. PMID: 25589660 - Agrawal et al. (2015) developed a transgenic mouse model expressing human DPP4 that was susceptible to MERS-CoV infection, with high titers of virus detectable in brain and lung and later in other organs. PMID: 26124093 - Pascal et al. (2015) - obtained a mouse model susceptible to intranasal infection with MERS-CoV. Human monoclonal antibodies binding to the MERS-CoV S protein neutralized all variants of the virus and prevented entry into target cells. The antibodies could both prevent and treat mice humanized for DPP4. Pascal et al. (2015) concluded that the model will be valuable for assessing treatments for MERS-CoV infection and disease. PMID:31883094 - Leist et al. (2020) - generated a mouse model susceptible to MERS-CoV infection - used C57BL/6J mice and CRISPR/Cas9 to substitute human residues at positions 288 and 330 (A288L and T330R). Strollo et al. (2020) and Bassedine et al. (2020) suggested that DPP4 could affect severity of infection and also be a therapeutic target: PMID:32336077 - Strollo et al. (2020) - propose a role for DDP4 as a functional receptor for SARS-CoV-2 and ask the question if DPP4 is directly involved in SARS-CoV-2 cell adhesion/virulence, and whether DPP4 inhibition might be a therapeutic strategy for preventing infection. PMID:32394639 - Bassedine et al. (2020) - modeling of the structure of SARS-CoV-2 spike glycoprotein predicts that it can interact with human DPP4 in addition to ACE2. Notes that increased DPP4 expression and activity are associated with diabetes, obesity, and metabolic syndrome, all of which have been reported to influence COVID‐19 severity. DPP4 inhibitors (gliptins), which vary in their interactions with the active site of the enzyme, may have immunomodulatory and cardioprotective effects that could be beneficial in COVID‐19 cases. PMID:31964246 - Keline-Weber at al. (2020) - Identified 14 polymorphisms in DPP4 from public databases that alter amino acid residus required for MERS-CoV S binding. Introduction of the respective variants into DPP4 revealed that all except one (Δ346-348) were compatible with robust DPP4 expression. Four polymorphisms (K267E, K267N, A291P and Δ346-348) strongly reduced binding of MERS-CoV S to DPP4 and S protein-driven host cell entry, as determined using soluble S protein and S protein bearing rhabdoviral vectors, respectively. Two polymorphisms (K267E and A291P) were analyzed in the context of authentic MERS-CoV and were found to attenuate viral replication. Collectively, we identified naturally-occurring polymorphisms in DPP4 that negatively impact cellular entry of MERS-CoV and might thus modulate MERS development in infected patients.
COVID-19 research v1.17 CLEC4M Sarah Leigh changed review comment from: CLEC4M was identified through an OMIM search for potential viral susceptibility genes. Initial triage by Illumina (Alison Coffey and team) was given a Tier 2 grouping (experimental and/or genetic evidence, suggesting a biological role linking to corona viruses, may not be a GDA); to: CLEC4M was identified through an OMIM search for potential viral susceptibility genes. Initial triage by Illumina (Alison Coffey and team) was given a Tier 2 grouping (experimental and/or genetic evidence, suggesting a biological role linking to corona viruses, may not be a GDA). Illumina review: CLEC4M is a C-type lectin gene serving as cell adhesion receptor and pathogen recognition receptor. It functions as a cellular receptor for variety of viruses, including HIV-1, hepatitis C, Ebola, and SARS-coronavirus. A highly polymorphic variable number tandem repeat (VNTR) at the neck-region of CLEC4M had been associated with genetic predisposition to some infectious diseases, however, genetic association studies have shown conflicting results about these associations (PMID:16991095;16369534;12738250;16364081;17321900;18697825;17534354;17534355). From OMIM: Associated with protection against SARs infection. PMID: 15496474: Jeffers et al. (2004) identified the cellular gylcoprotein CD209L (CLEC4M) as as an alternative receptor for SARS-CoV. CD209L is expressed in human lung in type II alveolar cells and endothelial cells, both potential targets for SARS-CoV. Several other enveloped viruses, including Ebola and Sindbis, also use CD209L as a portal of entry, and HIV and hepatitis C virus can bind to CD209L on cell membranes but do not use it to mediate virus entry. Jeffers et al. (2004) suggested that the large S glycoprotein of SARS-CoV may use both ACE2 and CD209L in virus infection and pathogenesis. PMID 16369534: Chan et al. (2006) - demonstrated that individuals homozygous for CLEC4M tandem repeats are less susceptible to SARS infection. CLEC4M was expressed in both non-SARS and SARS-CoV-infected lung. Compared with cells heterozygous for CLEC4M, cells homozygous for CLEC4M showed higher binding capacity for SARS-CoV, higher proteasome-dependent viral degradation, and a lower capacity for trans infection. Thus, homozygosity for CLEC4M plays a protective role during SARS infection. PMID: 17534354: Tang et al. (2007) - performed genotyping studies in SARS patients and controls and found no support for an association between homozygosity for CLEC4M and protection against SARS. PMID:17534355: Zhi et al. (2007) also failed to replicate the study by Chan et al. (2006). Chan et al. (2007) disputed the validity of both studies. PMID 18697825:Li et al. (2008) - genotyped SNPs in CLEC4M and other genes in the C-type lectin cluster in 181 Chinese SARS patients and 172 controls from an ethnically matched population and found no significant association with disease predisposition or prognosis. However, they detected a population stratification of the CLEC4M variable number tandem repeat (VNTR) alleles in a sample of 1,145 Han Chinese from different parts of China (northeast, south, and southwest). Analysis extended to 742 individuals from 7 ethnic minorities showed that those located along the Silk Road in northwestern China, where there is significant admixture with the European gene pool, had a low level of homozygosity, similar to European populations. Li et al. (2008) concluded that there is no SARS predisposition allele in the lectin gene cluster at chromosome 19p13.3, and that the previously reported association with polymorphisms in the CLEC4M neck region may be due to population stratification.
COVID-19 research v0.349 CXCL8 Rebecca Foulger commented on gene: CXCL8: Evidence Summary from Illumina curation team (Alison Coffey and Julie Taylor):

• CXCL8 is a proinflammatory chemokine that plays a role in inflammatory response and immune cell trafficking
• Multiple studies show IL-8 levels were shown to be elevated in plasma of patients with COVID-19, SARS-CoV, or MERS-CoV compared to controls. These include a number of recent COVID-19 studies (Coperchini et al. 2020).
• Higher levels were detected in more severe cases (Gong et al. 2020; Qin et al. 2020; Yan et al. 2020), although one study shows the levels are within the normal range (Qin et al. 2020)
• Gong et al. (2020) suggest that IL-8 might be a therapeutic target COVID-19

Literature:
PMID 32446778; Coperchini et al. (2020)
• Review article describing the involvement of chemokine/chemokine-receptor system in COVID-19
• Discusses the concept of cytokine storm where the immune system is ‘attacking’ the body resulting in acute respiratory distress syndrome.
• Multiple studies are mentioned that show high levels of CXCL8 in the plasma and broncho-alveolar fluid in patients with acute respiratory distress syndrome. Reference a paper that notes that pre-treatment with an anti-CXCL8 antibody prevented acute lung injury that generally develops.
• In vivo studies showed elevated CXCL8 in patients with SARS-CoV.
• In vitro studies where peripheral blood mononuclear cells from healthy donor inoculated with SARS-CoV showed enhancement in the expression of CXCL8
• Similarly, CXCL8 was upregulated in cells lysates when with MERS-CoV infection of polarized airway epithelial cells (higher expression than SARS-CoV).
• Higher plasma levels of CXCL8 in patients with COVID-19 compared to healthy controls; however, transcription of CSCL8 was not upregulated

MedRxiv; Gong et al. (2020)
• Evaluated disease severity in a total of 100 patients with COVID-19 pneumonia
• CXCL8 (IL-8 in this paper) was detected in these patients and IL-8 levels were shown to be associated with disease severity (P<0.001); significant differences were noted between critical and severe patients or critical and mild groups (Tables 2 and 3)
• Suggest that IL-8 might be a therapeutic target COVID-19

PMID 32161940; Qin et al. (2020)
• Retrospective study of 452 patients with COVID-19; severity of COVID-19 defined according to the Fifth Revised Trial Version of the Novel Coronavirus Pneumonia Diagnosis and Treatment Guidance
• Clinical and laboratory data were collected
• A majority of the severe cases (n=286) had elevated levels of IL-8 (18.4 pg/mL vs 13.7 pg/mL, respectively; p<0.001) compared to the nonsevere cases (n=166), although they were all in the normal (0-62.0 pg/mL) (Table 2)

MedRxiv; Yan et al. (2020)
• Identified 25 genes that showed highly conserved kinetics in COVID-19 patients
• Figure 3F shows expression of CXCL8 and plasma levels of IL-8 from four individuals with COVID-19 compared to four healthy controls was higher in patients especially in the severe stage (p<0.001)

PMID 15585888; Chang et al. (2004)
• Introduction has a summary of previously published papers and notes that high serum levels of IL-8 were detected during acute phase and associated with lung lesions in patients with SARS in one study. Another study suggests use of corticosteroids in reducing pulmonary inflammation due to IL-8.

• Chang et al. (2004) used transient transfection of the SARS-CoV S protein-encoding plasmid on the IL-8 promoter. Measure of IL-8 release in lung cells showed an upregulation of IL-8 release. In addition, a specific region of the S protein was identified as a potentially important region for inducing IL-8 release.

There are additional case-control studies suggesting possible association of polymorphisms in CXCL8 and acute bronchiolitis susceptibility (Pinto et al. 2017; PMID 27890033), asthma (Charrad et al. 2017; PMID 28993876), or human papillomavirus infection (weaker evidence; Junior et al. 2016; PMID 27783717).
COVID-19 research v0.348 NPC1 Rebecca Foulger commented on gene: NPC1: Evidence Summary from Illumina curation team (Alison Coffey and Julie Taylor): NPC1 encodes a polytopic protein that resides in the limiting membrane of late endosomes and lysosomes (LE/LY) and mediates distribution of lipoprotein-derived cholesterol in cells (Cote et al. (2011). NPC1 expression is critical for filovirus infection (EboV and MarV) and the mechanism of infection is not dependent on NPC1 cholesterol transport activity (Carette et al. 2011). Structural studies demonstrate that the C-domain of NPC1 binds to the primed EBOV glycoprotein (Wang et al. 2016; Gong et al. 2016).

PMID 21866103: Carette et al. (2011)
Genome-wide haploid genetic screen was performed in primary fibroblasts derived from human Niemann-Pick type C1 disease patients to identify host factors required for Filovirus infection. These cells are resistant to infection by EboV and MarV but remain fully susceptible to other unrelated viruses (Figure 2A, B). Resistance of NPC1-deficient cells was not caused by cholesterol transport defects (Fig S8). Infection in these cells was restored by expression of wild type NPC1 (Figure 2C). Similar results were observed in NPC1-null Chinese hamster ovary (CHO) cells, with loss of NPC1 conferring complete resistance to viral infection (Figure S6D) that was reversed by expression of human NPC1 (Figure S6E). Electron micrographs of NPC1 mutant cells infected with rVSV-GP-EboV indicate that NPC1 is required in downstream process in filovirus entry leading to viral membrane fusion and escape from the lysosomal compartment. Knockdown of NPC1 in HUVEC diminished infection by filoviruses (Figure 4D and S18) suggesting that NPC1 is critical for authentic filovirus infection. Furthermore, NPC1+/+ mice rapidly succumb to infection with either filovirus while NPC1−/+ mice were largely protected (Figure 4E).

PMID 2186610: Cote et al. (2011)
HeLa cells treated with benzylpiperazine adamantane diamide-derived compounds (3.0 and 3.47) developed cytoplasmic vacuoles indicating that that they target one or more proteins involved in regulation of cholesterol uptake in cells. CHO cells lacking NPC1 were completely resistant to infection by this virus and infection of these cells was fully restored when NPC1 was expressed. NPC1 expression but not NPC1-dependent cholesterol transport activity is essential for EboV infection (Fig 2c). 3.0-derived compounds inhibit EboV infection by interfering with binding of cleaved glycoprotein to NPC1 (Fig 4).

PMID 26771495: Wang et al. (2016)
The crystal structure of the primed glycoprotein (GPcl) of Ebola virus and domain C of NPC1 (NPC1-C) demonstrates that the NPC1-C binds to the primed EBOV GP (Fig 1, 3). Further, it suggests that a membrane-fusion-priming conformational change occurs in GPcl or the binding of GPcl, and this is a unique feature for all the filoviruses. NPC1-interacting compound 3.47 competitively blocks the primed GP binding to the membrane probably binds to the two protruding loops of NPC1-C. Compound U18666A binds to a different site on NPC1 causing endosomal calcium depletion. Furthermore, peptide inhibitors or small molecules, which can easily penetrate the cell membrane and reach the primed GP in the late endosomes could also act as potential therapeutic agents.

PMID 27238017: Gong et al. (2016)
Full-length human NPC1 and a low-resolution reconstruction of NPC1 in complex with the cleaved glycoprotein (GPcl) of EBOV was determined by single-particle electron cryomicroscopy. NPC1 contains 13 transmembrane segments (TMs) and three lumenal domains, A (NTD), C, and I. TMs 2–13 exhibit a typical resistance-nodulation-cell division fold, among which TMs 3–7 constitute the sterol-sensing domain conserved in several proteins involved in cholesterol metabolism and signaling. EBOV-GPcl binds to NPC1 through the domain C.
COVID-19 research v0.348 DICER1 Rebecca Foulger changed review comment from: Evidence Summary from Illumina curation team: The DICER1 gene, located on chromosome 14, position q32.13, was discovered in 2001 by Bernstein and is a member of the RNase III family, (also known as dicer 1, ribonuclease III; dicer1, Dcr-1 homolog (Drosophila); multinodular goitre 1). DICER1 is involved in the generation of double-stranded microRNAs (miRNAs), short non-coding RNAs, the cleavage of dsRNA into siRNAs, along with the biogenesis of numerous other small RNAs. There is increasing evidence DICER1 is also involved in regulating many other essential cellular processes such as those related to chromatin remodeling, inflammation, apoptosis and cell survival (Kurzynska-Kokorniak et al. 2015; Song and Rossi, 2017). DICER1 encodes a ∼220-KDa protein (RNase III endoribonuclease) which is a crucial component of the RNA Induced Silencing Complex (RISC) loading complex (RLC), comprised of dicer, Argonaute-2 (AGO-2), and trans-activation-responsive RNA binding protein 2 (TARBP2). The encoded protein is required by the RNA interference (RNAi) and small temporal RNA (stRNA) pathways to produce the active small RNA component which has a role in modulating gene expression at the post-transcriptional level. Research has shown that expression levels of cellular transcript and protein dicer are strictly controlled, with aberrant regulation contributing to carcinogenesis, neurodegenerative, rheumatic and immune system disorders. Studies have concluded that the encoded dicer ribonuclease-dependent processing of dsRNA viral replication intermediates into successive siRNAs is a conserved mammalian immune response to infection by positive-strand RNA viruses (Svobodova et al. 2016 summary & fig1; Li et al. 2013; Ding et al. 2018). Moreover, miRNAs play an important role in host-virus interactions in mammals (See Maillard et al. 2019 REVIEW; Foulkes et al. 2014 REVIEW).

IMMUNE SYSTEM
The cre-lox method for dicer1 gene knockout has been employed for studies into the role of dicer1 in immune cell development and function. Studies of dicer1 fl/fl mice have indicated short survival times along with severely impaired GMP differentiation into monocytes, neutrophils, myeloid DCs & mature macrophages. (Devasthanam et al. 2014). Results conclude that dicer1 is important in immune response and also vital for cell survival and apoptosis pathways. Muljo et al. (2005) investigated a conditional allele of dicer-1 (dcr-1) within a mouse model and showed that specific dcr-1 deletion in the T-cell lineage, resulted in impaired development of T-cells & aberrant cell differentiation of T-helper cells & cytokine production. Dcr-1 deletion in the thymus resulted in severe block in development of CD8+ T cells and resulted in defective microRNA processing in CD4+ T-cells. The results demonstrate Dicer regulates diverse aspects of T-cell biology along with cytokine production during T-cell differentiation where dicer-deficient T-cells preferentially express interferon-ƴ.

VIRUSES
Research by Galiana-Arnoux et al. (2006), of DICER in drosophila (drosophila have two dicer genes) have identified that DICER genes (Dcr1, miRNA pathway and Dcr2, RNAi pathway) control production of siRNA and a loss-of-function mutation in Dcr2 resulted in increased susceptibility to three different families of RNA viruses. Qi et al. (2012) research into RNAi gene silencing mechanism show that the B2 protein in Wuhan nodavirus (WhNV) suppresses Dcr2 in drosophila by direct interaction with the PAZ and RNAse III domains therefore blocking processing of dsRNA and siRNA. Evidence of a dicer antiviral system was also reported by Machitani et al. (2016) for mammalian human adenoviruses where DICER1 gene knockdown increased the copy number of adenovirus-encoding small RNAs (VA-RNAs) leading to the promotion of adenovirus replication; conversely, dicer overexpression significantly inhibited viral replication.
Modai et al. (2019) conclude that HIV-1 infection inhibits DICER1 by altering miRNA expression. They conclude that upon HIV-1 infection, human miR-186, 210 and 222 directly regulate DICER1 gene expression causing down-regulation of the gene contributing to impaired cell-mediated immunity (fig6). Other methods of inhibition are from viral proteins, termed viral suppressors of RNA silencing, which interact and inhibit dicer ribonuclease activity in HIV-1 and hepatitis C infections. These viral proteins may mediate proteasomal degradation of endoribonuclease dicer through CRL4DCAF1 ubiquitin ligase complex (Klockow et al. 2013), interact directly via the core protein (Chen et al. 2008) or HIV-1 transactivation of transcription (Bennasser and Jeang, 2006). Through these methods they can block dicer interactions with TRBP2 or ADAR1, boost macrophage infection, and subsequently reduce the function of short hairpin RNAs (shRNAs) which thus inhibit RNA silencing. Ultimately these viruses, though various methods, supress the ability of dicer to process dsRNAs into siRNAs boosting viral infection and pathogenesis.
Downregulation of DICER1 gene expression has additionally been found in cord blood of infants with severe respiratory syncytial virus (RSV), prior to RSV exposure, indicating this reduced expression may predispose newborns to RSV disease. Inchley et al. (2011) theorize that this occurs via disruption of leukocyte gene regulation of miRNA and direct anti-viral RNAi mechanisms. (Inchley et al. 2011 see section on “Dicer Gene Expression”).
Otsuka et al. (2007) have shown using gene-trap methods to obtain viable dicer1 fl/fl mice where dicer1 deficiency caused impairment of miR24 and miR93 production resulting in susceptibility to vesticular stomatitis virus (VSV) and herpes simplex-1 virus, but not other viruses tested.

SARS CoV & SARS CoV-2
Recently, Pasquier and Robichon, 2020 (preprint) have investigated the Dicer host immunity system regarding SARs-CoV-2 within a computational approach, concluding SARS-CoV2 may manipulate this system of immunity against its host, requiring further research. Mu et al., 2020 suggest SARs-CoV2 suppresses RNAi thus preventing recognition by the encoded ribonuclease dicer protein
Viral suppressors of RNA silencing (VSRs) suppress RNAi at pre or post-dicer level to overcome host defense and establish infection. Cui et al. (2015) from Wuhan University laboratory of virology, identified a novel VSR from coronaviruses (CoVs) including Severe acute respiratory syndrome coronavirus (SARS-CoV) and showed that the coronavirus nucelocaspid protein (N-protein), conserved and expressed in all coronaviruses, suppressed RNAi triggered by either short hairpin RNAs or small interfering RNAs in mammalian cells. They went on to show using mouse hepatitis virus A-59 (MHV-A59) which is closely linked to SARS-CoV in the family coronaviridae, that the viral replication was increased when the N proteins (novel VSR) were expressed but that knockdown of DICER1 gene or Ago2 transcripts facilitated the viral replication specifically in mammalian cells. They demonstrate that the N-protein of CoVs could efficiently inhibit dicer-mediated dsRNA cleavage and post-Dicer activities by sequestering dsRNAs and siRNAs. Kannan et al. (2020) performed clustal W analysis of N-Protein for SARS-CoV and COVID-19 demonstrating 90% sequence identity from an NCBI amino acid blast of both nucleocapsid (N) protein sequences (figure2). They suggest that the N-protein of COVID-19 may also function as a VSR for RNAi to overcome host defense. Ding et al. (2017) show that both MHV and SARS-CoV N proteins can also disrupt protein activator of protein kinase R (PACT), a cellular dsRNA-binding protein which binds to RIG-I and MDA5 to activate interferon (IFN) production to prevent antiviral host response.

Literature Review
PMID: 17181864: Bennasser and Jeang, 2006
• HIV-1 Tat Interaction With Dicer: Requirement for RNA
• Tat-Dicer interaction depends on RNA, requires the helicase domain of Dicer, and is independent of Tat's transactivation domain.

PMID: 18325616: Chen et al., 2008
• HCV Core Protein Interacts With Dicer to Antagonize RNA Silencing

PMID: 26085159: Cui et al., 2015
• The Nucleocapsid Protein of Coronaviruses Acts as a Viral Suppressor of RNA Silencing in Mammalian Cells

PMID: 24303839: Devasthanam et al, 2014
• This study investigates the role of the dicer protein in immune cell development and function using dicer1 cre-lox knockout models to conditionally ablate dicer1 in different immune cell subsets.

PMID: 28591694: Ding et al., 2017
• The nucleocapsid proteins of mouse hepatitis virus and severe acute respiratory syndrome coronavirus share the same IFN-β antagonizing mechanism: attenuation of PACT-mediated RIG-I/MDA5 activation

PMID: 30015086: Ding et al., 2018
• Antiviral RNA Interference in Mammals: Indicates infection of plants and insects with RNA and DNA viruses triggers Dicer-dependent production of virus-derived small interfering RNAs (vsiRNAs), which subsequently guide specific virus clearance by RNA interference (RNAi).

PMID: 25176334: Foulkes et al., 2012-REVIEW
• Review of DICER1: DICER1 Mutations, microRNAs and Mechanisms

PMID: 16554838: Galiana-Arnoux et al., 2006
• Essential function in vivo for Dicer-2 in host defense against RNA viruses in drosophila.
• https://pubmed.ncbi.nlm.nih.gov/16554838/ or https://www.nature.com/articles/ni1335

PMID: 21385408: Inchley et al., 2011
• Investigates ribonuclease Dicer and analyzed the gene expression of Dicer in newborns of which 37 infants had sufficient cord blood RNA with confirmed RSV disease <1yr. Demonstrates significant reduced Dicer expression in cord blood prior to severe disease in infants <1yr later. Conclude downregulation may predispose infants to RSV disease.

PMID: 32141569: Kannan et al., 2020
• COVID-19 (Novel Coronavirus 2019) - Recent Trends
• Perform W cluster analysis of COVID-19 and SARS-CoV nucleocapsid (N) protein sequences of the viruses showing 90% amino acid sequence similarity. Suggest the N-protein may be a VSR in RNAi by targeting DICER.

PMID: 23849790: Klockow et al., 2013
• The HIV-1 Protein Vpr Targets the Endoribonuclease Dicer for Proteasomal Degradation to Boost Macrophage Infection

PMID: 25883138: Kurzynska-Kokorniak et al., 2015
• Investigating the complexity of the mechanisms regulating Dicer gene expression and enzyme activities

PMID: 24115437: Li et al, 2013
• Investigates RNA interference pathways in antiviral immunity in mammals overviewing dicer processing of dsRNA viral replication intermediates into siRNAs.

PMID: 27273616: Machitani et al., 2016
• Dicer functions as an antiviral system against human adenoviruses via cleavage of adenovirus-encoded noncoding RNA

PMID: 30872283: Maillard et al., 2019- REVIEW
• Reviewing DICER1 within the anti-viral RNAi pathway in mammals

PMID: 30682089: Modai et al, 2019
• HIV-1 infection increases miRNAs which inhibit Dicer

PMID: 32291557: Mu et al, 2020
• SARS-CoV-2-encoded nucleocapsid protein acts as a viral suppressor of RNA interference in cells

PMID: 16009718: Muljo et al., 2005
• Indicates absence of dicer results in abberant T-cell differentiation.

PMID: 17613256: Otsuka, et al 2007
• Hypersusceptibility to Vesicular Stomatitis Virus Infection in Dicer1-Deficient Mice Is Due to Impaired miR24 and miR93 Expression

No PMID: Preprint : Pasquier and Rubichon, 2020
• SARS-CoV-2 might manipulate against its host the immunity RNAi/Dicer/Ago system

PMID: 22438534: Qi et al., 2012
• Targeting of Dicer-2 and RNA by a Viral RNA Silencing Suppressor in Drosophila Cells

PMID: 28473628: Song and Rossi, 2017
• Molecular Mechanisms of Dicer: Endonuclease and Enzymatic Activity; to: Evidence Summary from Illumina curation team (Alison Coffey and Julie Taylor): The DICER1 gene, located on chromosome 14, position q32.13, was discovered in 2001 by Bernstein and is a member of the RNase III family, (also known as dicer 1, ribonuclease III; dicer1, Dcr-1 homolog (Drosophila); multinodular goitre 1). DICER1 is involved in the generation of double-stranded microRNAs (miRNAs), short non-coding RNAs, the cleavage of dsRNA into siRNAs, along with the biogenesis of numerous other small RNAs. There is increasing evidence DICER1 is also involved in regulating many other essential cellular processes such as those related to chromatin remodeling, inflammation, apoptosis and cell survival (Kurzynska-Kokorniak et al. 2015; Song and Rossi, 2017). DICER1 encodes a ∼220-KDa protein (RNase III endoribonuclease) which is a crucial component of the RNA Induced Silencing Complex (RISC) loading complex (RLC), comprised of dicer, Argonaute-2 (AGO-2), and trans-activation-responsive RNA binding protein 2 (TARBP2). The encoded protein is required by the RNA interference (RNAi) and small temporal RNA (stRNA) pathways to produce the active small RNA component which has a role in modulating gene expression at the post-transcriptional level. Research has shown that expression levels of cellular transcript and protein dicer are strictly controlled, with aberrant regulation contributing to carcinogenesis, neurodegenerative, rheumatic and immune system disorders. Studies have concluded that the encoded dicer ribonuclease-dependent processing of dsRNA viral replication intermediates into successive siRNAs is a conserved mammalian immune response to infection by positive-strand RNA viruses (Svobodova et al. 2016 summary & fig1; Li et al. 2013; Ding et al. 2018). Moreover, miRNAs play an important role in host-virus interactions in mammals (See Maillard et al. 2019 REVIEW; Foulkes et al. 2014 REVIEW).

IMMUNE SYSTEM
The cre-lox method for dicer1 gene knockout has been employed for studies into the role of dicer1 in immune cell development and function. Studies of dicer1 fl/fl mice have indicated short survival times along with severely impaired GMP differentiation into monocytes, neutrophils, myeloid DCs & mature macrophages. (Devasthanam et al. 2014). Results conclude that dicer1 is important in immune response and also vital for cell survival and apoptosis pathways. Muljo et al. (2005) investigated a conditional allele of dicer-1 (dcr-1) within a mouse model and showed that specific dcr-1 deletion in the T-cell lineage, resulted in impaired development of T-cells & aberrant cell differentiation of T-helper cells & cytokine production. Dcr-1 deletion in the thymus resulted in severe block in development of CD8+ T cells and resulted in defective microRNA processing in CD4+ T-cells. The results demonstrate Dicer regulates diverse aspects of T-cell biology along with cytokine production during T-cell differentiation where dicer-deficient T-cells preferentially express interferon-ƴ.

VIRUSES
Research by Galiana-Arnoux et al. (2006), of DICER in drosophila (drosophila have two dicer genes) have identified that DICER genes (Dcr1, miRNA pathway and Dcr2, RNAi pathway) control production of siRNA and a loss-of-function mutation in Dcr2 resulted in increased susceptibility to three different families of RNA viruses. Qi et al. (2012) research into RNAi gene silencing mechanism show that the B2 protein in Wuhan nodavirus (WhNV) suppresses Dcr2 in drosophila by direct interaction with the PAZ and RNAse III domains therefore blocking processing of dsRNA and siRNA. Evidence of a dicer antiviral system was also reported by Machitani et al. (2016) for mammalian human adenoviruses where DICER1 gene knockdown increased the copy number of adenovirus-encoding small RNAs (VA-RNAs) leading to the promotion of adenovirus replication; conversely, dicer overexpression significantly inhibited viral replication.
Modai et al. (2019) conclude that HIV-1 infection inhibits DICER1 by altering miRNA expression. They conclude that upon HIV-1 infection, human miR-186, 210 and 222 directly regulate DICER1 gene expression causing down-regulation of the gene contributing to impaired cell-mediated immunity (fig6). Other methods of inhibition are from viral proteins, termed viral suppressors of RNA silencing, which interact and inhibit dicer ribonuclease activity in HIV-1 and hepatitis C infections. These viral proteins may mediate proteasomal degradation of endoribonuclease dicer through CRL4DCAF1 ubiquitin ligase complex (Klockow et al. 2013), interact directly via the core protein (Chen et al. 2008) or HIV-1 transactivation of transcription (Bennasser and Jeang, 2006). Through these methods they can block dicer interactions with TRBP2 or ADAR1, boost macrophage infection, and subsequently reduce the function of short hairpin RNAs (shRNAs) which thus inhibit RNA silencing. Ultimately these viruses, though various methods, supress the ability of dicer to process dsRNAs into siRNAs boosting viral infection and pathogenesis.
Downregulation of DICER1 gene expression has additionally been found in cord blood of infants with severe respiratory syncytial virus (RSV), prior to RSV exposure, indicating this reduced expression may predispose newborns to RSV disease. Inchley et al. (2011) theorize that this occurs via disruption of leukocyte gene regulation of miRNA and direct anti-viral RNAi mechanisms. (Inchley et al. 2011 see section on “Dicer Gene Expression”).
Otsuka et al. (2007) have shown using gene-trap methods to obtain viable dicer1 fl/fl mice where dicer1 deficiency caused impairment of miR24 and miR93 production resulting in susceptibility to vesticular stomatitis virus (VSV) and herpes simplex-1 virus, but not other viruses tested.

SARS CoV & SARS CoV-2
Recently, Pasquier and Robichon, 2020 (preprint) have investigated the Dicer host immunity system regarding SARs-CoV-2 within a computational approach, concluding SARS-CoV2 may manipulate this system of immunity against its host, requiring further research. Mu et al., 2020 suggest SARs-CoV2 suppresses RNAi thus preventing recognition by the encoded ribonuclease dicer protein
Viral suppressors of RNA silencing (VSRs) suppress RNAi at pre or post-dicer level to overcome host defense and establish infection. Cui et al. (2015) from Wuhan University laboratory of virology, identified a novel VSR from coronaviruses (CoVs) including Severe acute respiratory syndrome coronavirus (SARS-CoV) and showed that the coronavirus nucelocaspid protein (N-protein), conserved and expressed in all coronaviruses, suppressed RNAi triggered by either short hairpin RNAs or small interfering RNAs in mammalian cells. They went on to show using mouse hepatitis virus A-59 (MHV-A59) which is closely linked to SARS-CoV in the family coronaviridae, that the viral replication was increased when the N proteins (novel VSR) were expressed but that knockdown of DICER1 gene or Ago2 transcripts facilitated the viral replication specifically in mammalian cells. They demonstrate that the N-protein of CoVs could efficiently inhibit dicer-mediated dsRNA cleavage and post-Dicer activities by sequestering dsRNAs and siRNAs. Kannan et al. (2020) performed clustal W analysis of N-Protein for SARS-CoV and COVID-19 demonstrating 90% sequence identity from an NCBI amino acid blast of both nucleocapsid (N) protein sequences (figure2). They suggest that the N-protein of COVID-19 may also function as a VSR for RNAi to overcome host defense. Ding et al. (2017) show that both MHV and SARS-CoV N proteins can also disrupt protein activator of protein kinase R (PACT), a cellular dsRNA-binding protein which binds to RIG-I and MDA5 to activate interferon (IFN) production to prevent antiviral host response.

Literature Review
PMID: 17181864: Bennasser and Jeang, 2006
• HIV-1 Tat Interaction With Dicer: Requirement for RNA
• Tat-Dicer interaction depends on RNA, requires the helicase domain of Dicer, and is independent of Tat's transactivation domain.

PMID: 18325616: Chen et al., 2008
• HCV Core Protein Interacts With Dicer to Antagonize RNA Silencing

PMID: 26085159: Cui et al., 2015
• The Nucleocapsid Protein of Coronaviruses Acts as a Viral Suppressor of RNA Silencing in Mammalian Cells

PMID: 24303839: Devasthanam et al, 2014
• This study investigates the role of the dicer protein in immune cell development and function using dicer1 cre-lox knockout models to conditionally ablate dicer1 in different immune cell subsets.

PMID: 28591694: Ding et al., 2017
• The nucleocapsid proteins of mouse hepatitis virus and severe acute respiratory syndrome coronavirus share the same IFN-β antagonizing mechanism: attenuation of PACT-mediated RIG-I/MDA5 activation

PMID: 30015086: Ding et al., 2018
• Antiviral RNA Interference in Mammals: Indicates infection of plants and insects with RNA and DNA viruses triggers Dicer-dependent production of virus-derived small interfering RNAs (vsiRNAs), which subsequently guide specific virus clearance by RNA interference (RNAi).

PMID: 25176334: Foulkes et al., 2012-REVIEW
• Review of DICER1: DICER1 Mutations, microRNAs and Mechanisms

PMID: 16554838: Galiana-Arnoux et al., 2006
• Essential function in vivo for Dicer-2 in host defense against RNA viruses in drosophila.
• https://pubmed.ncbi.nlm.nih.gov/16554838/ or https://www.nature.com/articles/ni1335

PMID: 21385408: Inchley et al., 2011
• Investigates ribonuclease Dicer and analyzed the gene expression of Dicer in newborns of which 37 infants had sufficient cord blood RNA with confirmed RSV disease <1yr. Demonstrates significant reduced Dicer expression in cord blood prior to severe disease in infants <1yr later. Conclude downregulation may predispose infants to RSV disease.

PMID: 32141569: Kannan et al., 2020
• COVID-19 (Novel Coronavirus 2019) - Recent Trends
• Perform W cluster analysis of COVID-19 and SARS-CoV nucleocapsid (N) protein sequences of the viruses showing 90% amino acid sequence similarity. Suggest the N-protein may be a VSR in RNAi by targeting DICER.

PMID: 23849790: Klockow et al., 2013
• The HIV-1 Protein Vpr Targets the Endoribonuclease Dicer for Proteasomal Degradation to Boost Macrophage Infection

PMID: 25883138: Kurzynska-Kokorniak et al., 2015
• Investigating the complexity of the mechanisms regulating Dicer gene expression and enzyme activities

PMID: 24115437: Li et al, 2013
• Investigates RNA interference pathways in antiviral immunity in mammals overviewing dicer processing of dsRNA viral replication intermediates into siRNAs.

PMID: 27273616: Machitani et al., 2016
• Dicer functions as an antiviral system against human adenoviruses via cleavage of adenovirus-encoded noncoding RNA

PMID: 30872283: Maillard et al., 2019- REVIEW
• Reviewing DICER1 within the anti-viral RNAi pathway in mammals

PMID: 30682089: Modai et al, 2019
• HIV-1 infection increases miRNAs which inhibit Dicer

PMID: 32291557: Mu et al, 2020
• SARS-CoV-2-encoded nucleocapsid protein acts as a viral suppressor of RNA interference in cells

PMID: 16009718: Muljo et al., 2005
• Indicates absence of dicer results in abberant T-cell differentiation.

PMID: 17613256: Otsuka, et al 2007
• Hypersusceptibility to Vesicular Stomatitis Virus Infection in Dicer1-Deficient Mice Is Due to Impaired miR24 and miR93 Expression

No PMID: Preprint : Pasquier and Rubichon, 2020
• SARS-CoV-2 might manipulate against its host the immunity RNAi/Dicer/Ago system

PMID: 22438534: Qi et al., 2012
• Targeting of Dicer-2 and RNA by a Viral RNA Silencing Suppressor in Drosophila Cells

PMID: 28473628: Song and Rossi, 2017
• Molecular Mechanisms of Dicer: Endonuclease and Enzymatic Activity
COVID-19 research v0.348 DICER1 Rebecca Foulger commented on gene: DICER1: Evidence Summary from Illumina curation team: The DICER1 gene, located on chromosome 14, position q32.13, was discovered in 2001 by Bernstein and is a member of the RNase III family, (also known as dicer 1, ribonuclease III; dicer1, Dcr-1 homolog (Drosophila); multinodular goitre 1). DICER1 is involved in the generation of double-stranded microRNAs (miRNAs), short non-coding RNAs, the cleavage of dsRNA into siRNAs, along with the biogenesis of numerous other small RNAs. There is increasing evidence DICER1 is also involved in regulating many other essential cellular processes such as those related to chromatin remodeling, inflammation, apoptosis and cell survival (Kurzynska-Kokorniak et al. 2015; Song and Rossi, 2017). DICER1 encodes a ∼220-KDa protein (RNase III endoribonuclease) which is a crucial component of the RNA Induced Silencing Complex (RISC) loading complex (RLC), comprised of dicer, Argonaute-2 (AGO-2), and trans-activation-responsive RNA binding protein 2 (TARBP2). The encoded protein is required by the RNA interference (RNAi) and small temporal RNA (stRNA) pathways to produce the active small RNA component which has a role in modulating gene expression at the post-transcriptional level. Research has shown that expression levels of cellular transcript and protein dicer are strictly controlled, with aberrant regulation contributing to carcinogenesis, neurodegenerative, rheumatic and immune system disorders. Studies have concluded that the encoded dicer ribonuclease-dependent processing of dsRNA viral replication intermediates into successive siRNAs is a conserved mammalian immune response to infection by positive-strand RNA viruses (Svobodova et al. 2016 summary & fig1; Li et al. 2013; Ding et al. 2018). Moreover, miRNAs play an important role in host-virus interactions in mammals (See Maillard et al. 2019 REVIEW; Foulkes et al. 2014 REVIEW).

IMMUNE SYSTEM
The cre-lox method for dicer1 gene knockout has been employed for studies into the role of dicer1 in immune cell development and function. Studies of dicer1 fl/fl mice have indicated short survival times along with severely impaired GMP differentiation into monocytes, neutrophils, myeloid DCs & mature macrophages. (Devasthanam et al. 2014). Results conclude that dicer1 is important in immune response and also vital for cell survival and apoptosis pathways. Muljo et al. (2005) investigated a conditional allele of dicer-1 (dcr-1) within a mouse model and showed that specific dcr-1 deletion in the T-cell lineage, resulted in impaired development of T-cells & aberrant cell differentiation of T-helper cells & cytokine production. Dcr-1 deletion in the thymus resulted in severe block in development of CD8+ T cells and resulted in defective microRNA processing in CD4+ T-cells. The results demonstrate Dicer regulates diverse aspects of T-cell biology along with cytokine production during T-cell differentiation where dicer-deficient T-cells preferentially express interferon-ƴ.

VIRUSES
Research by Galiana-Arnoux et al. (2006), of DICER in drosophila (drosophila have two dicer genes) have identified that DICER genes (Dcr1, miRNA pathway and Dcr2, RNAi pathway) control production of siRNA and a loss-of-function mutation in Dcr2 resulted in increased susceptibility to three different families of RNA viruses. Qi et al. (2012) research into RNAi gene silencing mechanism show that the B2 protein in Wuhan nodavirus (WhNV) suppresses Dcr2 in drosophila by direct interaction with the PAZ and RNAse III domains therefore blocking processing of dsRNA and siRNA. Evidence of a dicer antiviral system was also reported by Machitani et al. (2016) for mammalian human adenoviruses where DICER1 gene knockdown increased the copy number of adenovirus-encoding small RNAs (VA-RNAs) leading to the promotion of adenovirus replication; conversely, dicer overexpression significantly inhibited viral replication.
Modai et al. (2019) conclude that HIV-1 infection inhibits DICER1 by altering miRNA expression. They conclude that upon HIV-1 infection, human miR-186, 210 and 222 directly regulate DICER1 gene expression causing down-regulation of the gene contributing to impaired cell-mediated immunity (fig6). Other methods of inhibition are from viral proteins, termed viral suppressors of RNA silencing, which interact and inhibit dicer ribonuclease activity in HIV-1 and hepatitis C infections. These viral proteins may mediate proteasomal degradation of endoribonuclease dicer through CRL4DCAF1 ubiquitin ligase complex (Klockow et al. 2013), interact directly via the core protein (Chen et al. 2008) or HIV-1 transactivation of transcription (Bennasser and Jeang, 2006). Through these methods they can block dicer interactions with TRBP2 or ADAR1, boost macrophage infection, and subsequently reduce the function of short hairpin RNAs (shRNAs) which thus inhibit RNA silencing. Ultimately these viruses, though various methods, supress the ability of dicer to process dsRNAs into siRNAs boosting viral infection and pathogenesis.
Downregulation of DICER1 gene expression has additionally been found in cord blood of infants with severe respiratory syncytial virus (RSV), prior to RSV exposure, indicating this reduced expression may predispose newborns to RSV disease. Inchley et al. (2011) theorize that this occurs via disruption of leukocyte gene regulation of miRNA and direct anti-viral RNAi mechanisms. (Inchley et al. 2011 see section on “Dicer Gene Expression”).
Otsuka et al. (2007) have shown using gene-trap methods to obtain viable dicer1 fl/fl mice where dicer1 deficiency caused impairment of miR24 and miR93 production resulting in susceptibility to vesticular stomatitis virus (VSV) and herpes simplex-1 virus, but not other viruses tested.

SARS CoV & SARS CoV-2
Recently, Pasquier and Robichon, 2020 (preprint) have investigated the Dicer host immunity system regarding SARs-CoV-2 within a computational approach, concluding SARS-CoV2 may manipulate this system of immunity against its host, requiring further research. Mu et al., 2020 suggest SARs-CoV2 suppresses RNAi thus preventing recognition by the encoded ribonuclease dicer protein
Viral suppressors of RNA silencing (VSRs) suppress RNAi at pre or post-dicer level to overcome host defense and establish infection. Cui et al. (2015) from Wuhan University laboratory of virology, identified a novel VSR from coronaviruses (CoVs) including Severe acute respiratory syndrome coronavirus (SARS-CoV) and showed that the coronavirus nucelocaspid protein (N-protein), conserved and expressed in all coronaviruses, suppressed RNAi triggered by either short hairpin RNAs or small interfering RNAs in mammalian cells. They went on to show using mouse hepatitis virus A-59 (MHV-A59) which is closely linked to SARS-CoV in the family coronaviridae, that the viral replication was increased when the N proteins (novel VSR) were expressed but that knockdown of DICER1 gene or Ago2 transcripts facilitated the viral replication specifically in mammalian cells. They demonstrate that the N-protein of CoVs could efficiently inhibit dicer-mediated dsRNA cleavage and post-Dicer activities by sequestering dsRNAs and siRNAs. Kannan et al. (2020) performed clustal W analysis of N-Protein for SARS-CoV and COVID-19 demonstrating 90% sequence identity from an NCBI amino acid blast of both nucleocapsid (N) protein sequences (figure2). They suggest that the N-protein of COVID-19 may also function as a VSR for RNAi to overcome host defense. Ding et al. (2017) show that both MHV and SARS-CoV N proteins can also disrupt protein activator of protein kinase R (PACT), a cellular dsRNA-binding protein which binds to RIG-I and MDA5 to activate interferon (IFN) production to prevent antiviral host response.

Literature Review
PMID: 17181864: Bennasser and Jeang, 2006
• HIV-1 Tat Interaction With Dicer: Requirement for RNA
• Tat-Dicer interaction depends on RNA, requires the helicase domain of Dicer, and is independent of Tat's transactivation domain.

PMID: 18325616: Chen et al., 2008
• HCV Core Protein Interacts With Dicer to Antagonize RNA Silencing

PMID: 26085159: Cui et al., 2015
• The Nucleocapsid Protein of Coronaviruses Acts as a Viral Suppressor of RNA Silencing in Mammalian Cells

PMID: 24303839: Devasthanam et al, 2014
• This study investigates the role of the dicer protein in immune cell development and function using dicer1 cre-lox knockout models to conditionally ablate dicer1 in different immune cell subsets.

PMID: 28591694: Ding et al., 2017
• The nucleocapsid proteins of mouse hepatitis virus and severe acute respiratory syndrome coronavirus share the same IFN-β antagonizing mechanism: attenuation of PACT-mediated RIG-I/MDA5 activation

PMID: 30015086: Ding et al., 2018
• Antiviral RNA Interference in Mammals: Indicates infection of plants and insects with RNA and DNA viruses triggers Dicer-dependent production of virus-derived small interfering RNAs (vsiRNAs), which subsequently guide specific virus clearance by RNA interference (RNAi).

PMID: 25176334: Foulkes et al., 2012-REVIEW
• Review of DICER1: DICER1 Mutations, microRNAs and Mechanisms

PMID: 16554838: Galiana-Arnoux et al., 2006
• Essential function in vivo for Dicer-2 in host defense against RNA viruses in drosophila.
• https://pubmed.ncbi.nlm.nih.gov/16554838/ or https://www.nature.com/articles/ni1335

PMID: 21385408: Inchley et al., 2011
• Investigates ribonuclease Dicer and analyzed the gene expression of Dicer in newborns of which 37 infants had sufficient cord blood RNA with confirmed RSV disease <1yr. Demonstrates significant reduced Dicer expression in cord blood prior to severe disease in infants <1yr later. Conclude downregulation may predispose infants to RSV disease.

PMID: 32141569: Kannan et al., 2020
• COVID-19 (Novel Coronavirus 2019) - Recent Trends
• Perform W cluster analysis of COVID-19 and SARS-CoV nucleocapsid (N) protein sequences of the viruses showing 90% amino acid sequence similarity. Suggest the N-protein may be a VSR in RNAi by targeting DICER.

PMID: 23849790: Klockow et al., 2013
• The HIV-1 Protein Vpr Targets the Endoribonuclease Dicer for Proteasomal Degradation to Boost Macrophage Infection

PMID: 25883138: Kurzynska-Kokorniak et al., 2015
• Investigating the complexity of the mechanisms regulating Dicer gene expression and enzyme activities

PMID: 24115437: Li et al, 2013
• Investigates RNA interference pathways in antiviral immunity in mammals overviewing dicer processing of dsRNA viral replication intermediates into siRNAs.

PMID: 27273616: Machitani et al., 2016
• Dicer functions as an antiviral system against human adenoviruses via cleavage of adenovirus-encoded noncoding RNA

PMID: 30872283: Maillard et al., 2019- REVIEW
• Reviewing DICER1 within the anti-viral RNAi pathway in mammals

PMID: 30682089: Modai et al, 2019
• HIV-1 infection increases miRNAs which inhibit Dicer

PMID: 32291557: Mu et al, 2020
• SARS-CoV-2-encoded nucleocapsid protein acts as a viral suppressor of RNA interference in cells

PMID: 16009718: Muljo et al., 2005
• Indicates absence of dicer results in abberant T-cell differentiation.

PMID: 17613256: Otsuka, et al 2007
• Hypersusceptibility to Vesicular Stomatitis Virus Infection in Dicer1-Deficient Mice Is Due to Impaired miR24 and miR93 Expression

No PMID: Preprint : Pasquier and Rubichon, 2020
• SARS-CoV-2 might manipulate against its host the immunity RNAi/Dicer/Ago system

PMID: 22438534: Qi et al., 2012
• Targeting of Dicer-2 and RNA by a Viral RNA Silencing Suppressor in Drosophila Cells

PMID: 28473628: Song and Rossi, 2017
• Molecular Mechanisms of Dicer: Endonuclease and Enzymatic Activity
COVID-19 research v0.347 PDGFRA Alison Coffey commented on gene: PDGFRA: Evidence Summary from Illumina curation team: The PDGFRA gene encodes the platelet-derived growth factor receptor alpha protein, a tyrosine-protein kinase that acts as a cell-surface receptor for PDGFA, PDGFB and PDGFC, binding of which leads to the activation of several signaling cascades, and plays an essential role in the regulation of embryonic development, cell proliferation, survival and chemotaxis. PDGFRA has been demonstrated to be a critical receptor for human cytomegalovirus infection (PMID 18701889: Soroceanu et al. 2008). Di Pasquale et al. (2003) (PMID 14502277). also confirmed the role of PDGFRA and PDGFRB as receptors for adeno-associated virus type 5 (AAV-5). PMID 18701889: Soroceanu et al. 2008 - PDGFRA is specifically phosphorylated by both laboratory and clinical isolates of human cytomegalovirus (CMV) in various human cell types, resulting in activation of the phosphoinositide-3-kinase signaling pathway. Cells in which PDGFRA was genetically deleted or functionally blocked were nonpermissive to human CMV entry, viral gene expression, or infectious virus production. Reintroducing the human PDGFRA gene into knockout cells restored susceptibility to viral entry and essential viral gene expression. Blockade of receptor function with a humanized PDGFRA blocking antibody (IMC-3G3) or targeted inhibition of its kinase activity with a small molecule (Gleevec) completely inhibited human CMV viral internalization and gene expression in human epithelial, endothelial, and fibroblast cells. Viral entry in cells harboring endogenous PDGFRA was competitively inhibited by pretreatment with PDGF-AA. It was demonstrated that human CMV glycoprotein B directly interacts with PDGFRA, resulting in receptor tyrosine phosphorylation, and that glycoprotein B neutralizing antibodies inhibit human CMV-induced PDGFRA phosphorylation. The authors concluded that PDGFRA is a critical receptor required for human CMV infection, and thus a target for novel antiviral therapies.
COVID-19 research v0.332 ZFHX3 Sarah Leigh edited their review of gene: ZFHX3: Added comment: Using Collaborative Cross mouse genetic reference population, PMID 32348764 studied the genetic regulation of variation in antibody response to influenza A virus (IAV) infection. This enabled the identification of 23 quantitative trait loci (QTL) associated with variation in specific antibody isotypes across time points; this allowed a subset to be found that broadly affect the antibody response to IAV as well as other viruses. This gene is the equivalent human for the mouse gene that was classified as a candidate from one of the QTLs, based on the predicted variant consequences and haplotype-specific expression patterns (PMID 32348764 table 2).; Changed mode of inheritance: Unknown
COVID-19 research v0.332 WSCD1 Sarah Leigh edited their review of gene: WSCD1: Added comment: Using Collaborative Cross mouse genetic reference population, PMID 32348764 studied the genetic regulation of variation in antibody response to influenza A virus (IAV) infection. This enabled the identification of 23 quantitative trait loci (QTL) associated with variation in specific antibody isotypes across time points; this allowed a subset to be found that broadly affect the antibody response to IAV as well as other viruses. This gene is the equivalent human for the mouse gene that was classified as a candidate from one of the QTLs, based on the predicted variant consequences and haplotype-specific expression patterns (PMID 32348764 table 2).; Changed mode of inheritance: Unknown
COVID-19 research v0.332 UNC5CL Sarah Leigh edited their review of gene: UNC5CL: Added comment: Using Collaborative Cross mouse genetic reference population, PMID 32348764 studied the genetic regulation of variation in antibody response to influenza A virus (IAV) infection. This enabled the identification of 23 quantitative trait loci (QTL) associated with variation in specific antibody isotypes across time points; this allowed a subset to be found that broadly affect the antibody response to IAV as well as other viruses. This gene is the equivalent human for the mouse gene that was classified as a candidate from one of the QTLs, based on the predicted variant consequences and haplotype-specific expression patterns (PMID 32348764 table 2).; Changed mode of inheritance: Unknown
COVID-19 research v0.332 TAPT1 Sarah Leigh edited their review of gene: TAPT1: Added comment: Using Collaborative Cross mouse genetic reference population, PMID 32348764 studied the genetic regulation of variation in antibody response to influenza A virus (IAV) infection. This enabled the identification of 23 quantitative trait loci (QTL) associated with variation in specific antibody isotypes across time points; this allowed a subset to be found that broadly affect the antibody response to IAV as well as other viruses. This gene is the equivalent human for the mouse gene that was classified as a candidate from one of the QTLs, based on the predicted variant consequences and haplotype-specific expression patterns (PMID 32348764 table 2).; Changed mode of inheritance: Unknown
COVID-19 research v0.332 SPNS3 Sarah Leigh edited their review of gene: SPNS3: Added comment: Using Collaborative Cross mouse genetic reference population, PMID 32348764 studied the genetic regulation of variation in antibody response to influenza A virus (IAV) infection. This enabled the identification of 23 quantitative trait loci (QTL) associated with variation in specific antibody isotypes across time points; this allowed a subset to be found that broadly affect the antibody response to IAV as well as other viruses. This gene is the equivalent human for the mouse gene that was classified as a candidate from one of the QTLs, based on the predicted variant consequences and haplotype-specific expression patterns (PMID 32348764 table 2).; Changed mode of inheritance: Unknown
COVID-19 research v0.332 RPAIN Sarah Leigh edited their review of gene: RPAIN: Added comment: Using Collaborative Cross mouse genetic reference population, PMID 32348764 studied the genetic regulation of variation in antibody response to influenza A virus (IAV) infection. This enabled the identification of 23 quantitative trait loci (QTL) associated with variation in specific antibody isotypes across time points; this allowed a subset to be found that broadly affect the antibody response to IAV as well as other viruses. This gene is the equivalent human for the mouse gene that was classified as a candidate from one of the QTLs, based on the predicted variant consequences and haplotype-specific expression patterns (PMID 32348764 table 2).; Changed mode of inheritance: Unknown
COVID-19 research v0.332 PROM1 Sarah Leigh edited their review of gene: PROM1: Added comment: Using Collaborative Cross mouse genetic reference population, PMID 32348764 studied the genetic regulation of variation in antibody response to influenza A virus (IAV) infection. This enabled the identification of 23 quantitative trait loci (QTL) associated with variation in specific antibody isotypes across time points; this allowed a subset to be found that broadly affect the antibody response to IAV as well as other viruses. This gene is the equivalent human for the mouse gene that was classified as a candidate from one of the QTLs, based on the predicted variant consequences and haplotype-specific expression patterns (PMID 32348764 table 2).; Changed mode of inheritance: Unknown
COVID-19 research v0.332 PKD1L3 Sarah Leigh edited their review of gene: PKD1L3: Added comment: Using Collaborative Cross mouse genetic reference population, PMID 32348764 studied the genetic regulation of variation in antibody response to influenza A virus (IAV) infection. This enabled the identification of 23 quantitative trait loci (QTL) associated with variation in specific antibody isotypes across time points; this allowed a subset to be found that broadly affect the antibody response to IAV as well as other viruses. This gene is the equivalent human for the mouse gene that was classified as a candidate from one of the QTLs, based on the predicted variant consequences and haplotype-specific expression patterns (PMID 32348764 table 2).; Changed mode of inheritance: Unknown
COVID-19 research v0.332 NUP88 Sarah Leigh edited their review of gene: NUP88: Added comment: Using Collaborative Cross mouse genetic reference population, PMID 32348764 studied the genetic regulation of variation in antibody response to influenza A virus (IAV) infection. This enabled the identification of 23 quantitative trait loci (QTL) associated with variation in specific antibody isotypes across time points; this allowed a subset to be found that broadly affect the antibody response to IAV as well as other viruses. This gene is the equivalent human for the mouse gene that was classified as a candidate from one of the QTLs, based on the predicted variant consequences and haplotype-specific expression patterns (PMID 32348764 table 2).; Changed mode of inheritance: Unknown
COVID-19 research v0.332 MLKL Sarah Leigh edited their review of gene: MLKL: Added comment: Using Collaborative Cross mouse genetic reference population, PMID 32348764 studied the genetic regulation of variation in antibody response to influenza A virus (IAV) infection. This enabled the identification of 23 quantitative trait loci (QTL) associated with variation in specific antibody isotypes across time points; this allowed a subset to be found that broadly affect the antibody response to IAV as well as other viruses. This gene is the equivalent human for the mouse gene that was classified as a candidate from one of the QTLs, based on the predicted variant consequences and haplotype-specific expression patterns (PMID 32348764 table 2).; Changed mode of inheritance: Unknown
COVID-19 research v0.332 MIS12 Sarah Leigh edited their review of gene: MIS12: Added comment: Using Collaborative Cross mouse genetic reference population, PMID 32348764 studied the genetic regulation of variation in antibody response to influenza A virus (IAV) infection. This enabled the identification of 23 quantitative trait loci (QTL) associated with variation in specific antibody isotypes across time points; this allowed a subset to be found that broadly affect the antibody response to IAV as well as other viruses. This gene is the equivalent human for the mouse gene that was classified as a candidate from one of the QTLs, based on the predicted variant consequences and haplotype-specific expression patterns (PMID 32348764 table 2).; Changed mode of inheritance: Unknown
COVID-19 research v0.332 LDB2 Sarah Leigh edited their review of gene: LDB2: Added comment: Using Collaborative Cross mouse genetic reference population, PMID 32348764 studied the genetic regulation of variation in antibody response to influenza A virus (IAV) infection. This enabled the identification of 23 quantitative trait loci (QTL) associated with variation in specific antibody isotypes across time points; this allowed a subset to be found that broadly affect the antibody response to IAV as well as other viruses. This gene is the equivalent human for the mouse gene that was classified as a candidate from one of the QTLs, based on the predicted variant consequences and haplotype-specific expression patterns (PMID 32348764 table 2).; Changed mode of inheritance: Unknown
COVID-19 research v0.332 KARS Sarah Leigh edited their review of gene: KARS: Added comment: Using Collaborative Cross mouse genetic reference population, PMID 32348764 studied the genetic regulation of variation in antibody response to influenza A virus (IAV) infection. This enabled the identification of 23 quantitative trait loci (QTL) associated with variation in specific antibody isotypes across time points; this allowed a subset to be found that broadly affect the antibody response to IAV as well as other viruses. This gene is the equivalent human for the mouse gene that was classified as a candidate from one of the QTLs, based on the predicted variant consequences and haplotype-specific expression patterns (PMID 32348764 table 2).; Changed mode of inheritance: Unknown
COVID-19 research v0.332 HYDIN Sarah Leigh edited their review of gene: HYDIN: Added comment: Using Collaborative Cross mouse genetic reference population, PMID 32348764 studied the genetic regulation of variation in antibody response to influenza A virus (IAV) infection. This enabled the identification of 23 quantitative trait loci (QTL) associated with variation in specific antibody isotypes across time points; this allowed a subset to be found that broadly affect the antibody response to IAV as well as other viruses. This gene is the equivalent human for the mouse gene that was classified as a candidate from one of the QTLs, based on the predicted variant consequences and haplotype-specific expression patterns (PMID 32348764 table 2).; Changed mode of inheritance: Unknown
COVID-19 research v0.332 CC2D2A Sarah Leigh edited their review of gene: CC2D2A: Added comment: Using Collaborative Cross mouse genetic reference population, PMID 32348764 studied the genetic regulation of variation in antibody response to influenza A virus (IAV) infection. This enabled the identification of 23 quantitative trait loci (QTL) associated with variation in specific antibody isotypes across time points; this allowed a subset to be found that broadly affect the antibody response to IAV as well as other viruses. This gene is the equivalent human for the mouse gene that was classified as a candidate from one of the QTLs, based on the predicted variant consequences and haplotype-specific expression patterns (PMID 32348764 table 2).; Changed mode of inheritance: Unknown
COVID-19 research v0.332 BCAR1 Sarah Leigh edited their review of gene: BCAR1: Added comment: Using Collaborative Cross mouse genetic reference population, PMID 32348764 studied the genetic regulation of variation in antibody response to influenza A virus (IAV) infection. This enabled the identification of 23 quantitative trait loci (QTL) associated with variation in specific antibody isotypes across time points; this allowed a subset to be found that broadly affect the antibody response to IAV as well as other viruses. This gene is the equivalent human for the mouse gene that was classified as a candidate from one of the QTLs, based on the predicted variant consequences and haplotype-specific expression patterns (PMID 32348764 table 2).; Changed mode of inheritance: Unknown
COVID-19 research v0.326 ABO Catherine Snow Mode of inheritance for gene: ABO was changed from Other to Unknown
COVID-19 research v0.320 SLC2A1 Ivone Leong gene: SLC2A1 was added
gene: SLC2A1 was added to COVID-19 research. Sources: Expert list
Mode of inheritance for gene: SLC2A1 was set to Unknown
Publications for gene: SLC2A1 were set to 15767416; 22308487
Review for gene: SLC2A1 was set to AMBER
Added comment: GLUT1 is a receptor for HTLV and suggested that perturbations in glucose metabolism resulting from interactions of HTLV envelope glycoproteins with GLUT1 are likely to contribute to HTLV-associated disorders (PMID: 15767416).

PMID: 22308487 shows that IL-7 induced upregulation of Glut1 changes glucos uptake and causes T lymphocyptes susceptible to HIV-1 infection.
Sources: Expert list
COVID-19 research v0.208 ABO Catherine Snow Classified gene: ABO as Green List (high evidence)
COVID-19 research v0.208 ABO Catherine Snow Added comment: Comment on list classification: Upgrade to Green based on expert review
COVID-19 research v0.208 ABO Catherine Snow Gene: abo has been classified as Green List (High Evidence).
COVID-19 research v0.204 ABO Sophie Hambleton reviewed gene: ABO: Rating: GREEN; Mode of pathogenicity: None; Publications: ; Phenotypes: ; Mode of inheritance: None
COVID-19 research v0.179 ABO Catherine Snow Phenotypes for gene: ABO were changed from to Virus susceptibility
COVID-19 research v0.178 ABO Catherine Snow Classified gene: ABO as Amber List (moderate evidence)
COVID-19 research v0.178 ABO Catherine Snow Added comment: Comment on list classification: Identified by expert review. Two preprints and publication relating to ABO and Sars-COV. https://doi.org/10.1101/2020.04.08.20058073 authors found that COVID-19 positive vs negative test results were increased in blood groups A and decreased in blood groups O, consistent with previous results from Wuhan and Shenzhen (https://doi.org/10.1101/2020.03.11.20031096)
COVID-19 research v0.178 ABO Catherine Snow Gene: abo has been classified as Amber List (Moderate Evidence).
COVID-19 research v0.176 CYP2B6 Sarah Leigh reviewed gene: CYP2B6: Rating: RED; Mode of pathogenicity: ; Publications: 15622315, 20860463, 15194512, 23418033; Phenotypes: {Efavirenz central nervous system toxicity, susceptibility to} 614546, Efavirenz, poor metabolism of 614546; Mode of inheritance: BIALLELIC, autosomal or pseudoautosomal
COVID-19 research v0.160 ABO Owen Siggs gene: ABO was added
gene: ABO was added to Viral susceptibility. Sources: Literature
Mode of inheritance for gene: ABO was set to Other
Publications for gene: ABO were set to 15784866
Review for gene: ABO was set to AMBER
Added comment: Preliminary suggestion from preprints (https://www.medrxiv.org/content/10.1101/2020.03.11.20031096v2 & https://www.preprints.org/manuscript/202003.0356/v1) that ABO blood group may influence susceptibility to SARS-CoV-2 infection. Other preliminary evidence that ABO blood group may also influence susceptibility to SARS-CoV infection (PMID: 15784866). Both yet to be replicated, but suggest individuals of blood group O to be at lower risk of infection.
Sources: Literature
COVID-19 research v0.160 TLR3 Abdelazeem Elhabyan changed review comment from: These studies demonstrate the deleterious effect of some TLR3 mutations and predisposition to Herpes simplex encephalitis in 4 separate studies on unrelated patients from different countries. TLR3 mutations in 3 children were associated with severe influenza pneumonitis. Finally, 2 other studies evaluate the protective effect of a common polymorphism of TLR3 against HIV infection in repetitively exposed individuals. Accordingly, we might find protective or deleterious effects in COVID19 patients due to different mutations of TLR3.

TLR3 is a receptor for dsRNA (intermediate in the replication of many viruses including HSV) which induces IFN response to prevent the cytopathic effects of different viruses. A heterozygous dominant-negative mutation of TLR3 was discovered in 2 unrelated children with HSE. TLR3 mutant fibroblasts from the 2 patients were infected by HSV-1 and vesicular stomatitis virus(VSV).IFNB and IFNL production were impaired in those cells, viral replication was higher and cell survival was lower in the 2 patients' cells when compared with the controls. Blood leukocyte response normally with to poly (I:C) which explains why the disease is not disseminated and also explains the redundant role of TLR3 in blood cells(13).
Similar findings were reported in a polish child in 2011, however, the patient here was compound heterozygous for a missense mutation leading to autosomal recessive inheritance of TLR3 deficiency(14).
Treatment with IFN alpha and beta canceled the effect of the dominant-negative mutation increasing the causality relationship between TLR3 mutants and viral immune response(13).
Relatives of the 2 patients with the same mutation did not show decreased interferon response nor they showed HSE as a complication of HSV which means that this mutation does not have full penetrance(13).

In another study, 110 patients with HSE were sequenced (exons of TLR3) to establish a new association of TLR3 mutations and HSE. The study reported 5 novel variants other than those previously described in the literature. 2 of them were not pathogenically demonstrated by in vitro studies while 3 of them were pathogenic with similar findings to those described above. Additionally, they found 3 patients with the same mutations previously described in the literature so the total of patients with deleterious TLR3 mutations would be 6 out of 110. 4 of those 6 patients(66%) with TLR6 mutations had a relapse In contrast to 12 out of 120(total cohort) (10%)(15).

In a recent study done on 16 patients with adult-onset HSE using whole-exome sequencing(WES), 1 patient was discovered to have TLR3 deficiency, while 8 other patients had mutations in other genes in the TLR3 pathway(2 patients with a mutation in IRF3, 2 patients with mutations in STAT1, 2 patients with mutations in TRIF, 1 patient with a mutation in TYK2,1 patients with a mutation in MAVS, and finally 1 patient with a mutation in TBK1)(16)

A common polymorphism in TLR3(rs3775291) was linked to increased resistance to HIV1 infection by the genotyping study of Spanish and Italian cohorts with a P value of .023 and .029 respectively. The study compared HIV exposed seronegative cohort(IV drug abuse and sexually active ) with controls. Repetitive HIV exposure in the cohort was evidenced by HCV seropositivity. In vitro infection of PBMCs with HIV showed increased resistance in cells carrying the allele and also TLR3 stimulation by TLR3 agonists showed an increased level of expression of CD69, IL-6, and CCL3(17).

A similar study was conducted on the Caucasian population showing the protective effect of the allele against HIV infection(18).

Autosomal recessive IRF7 and IRF9 deficiencies impair type I and III IFN immunity and underlie severe influenza pneumonitis. We report three unrelated children with influenza A virus (IAV) infection manifesting as acute respiratory distress syndrome (IAV-ARDS), heterozygous for rare TLR3 variants (P554S in two patients and P680L in the third) causing autosomal dominant (AD) TLR3 deficiency. AD TLR3 deficiency can underlie herpes simplex virus-1 (HSV-1) encephalitis (HSE) by impairing cortical neuron-intrinsic type I IFN immunity to HSV-1. TLR3-mutated leukocytes produce normal levels of IFNs in response to IAV. In contrast, TLR3-mutated fibroblasts produce lower levels of IFN-β and -λ, and display enhanced viral susceptibility, upon IAV infection. Moreover, the patients’ iPSC-derived pulmonary epithelial cells (PECs) are susceptible to IAV. Treatment with IFN-α2b or IFN-λ1 rescues this phenotype. AD TLR3 deficiency may thus underlie IAV-ARDS by impairing TLR3-dependent, type I, and/or III IFN–mediated, PEC-intrinsic immunity. Its clinical penetrance is incomplete for both IAV-ARDS and HSE, consistent with their typically sporadic nature(PMID: 31217193
)




13.Zhang SY, Jouanguy E, Ugolini S, et al. TLR3 deficiency in patients with herpes simplex encephalitis. Science. 2007;317(5844):1522–1527. doi:10.1126/science.1139522

14.Guo Y, Audry M, Ciancanelli M, et al. Herpes simplex virus encephalitis in a patient with complete TLR3 deficiency: TLR3 is otherwise redundant in protective immunity. J Exp Med. 2011;208(10):2083–2098. doi:10.1084/jem.20101568

15.Lim HK, Seppänen M, Hautala T, et al. TLR3 deficiency in herpes simplex encephalitis: high allelic heterogeneity and recurrence risk. Neurology. 2014;83(21):1888–1897. doi:10.1212/WNL.0000000000000999

16.Mørk N, Kofod-Olsen E, Sørensen KB, et al. Mutations in the TLR3 signaling pathway and beyond in adult patients with herpes simplex encephalitis. Genes Immun. 2015;16(8):552–566. doi:10.1038/gene.2015.46

17.Sironi M, Biasin M, Cagliani R, et al. A common polymorphism in TLR3 confers natural resistance to HIV-1 infection. J Immunol. 2012;188(2):818–823. doi:10.4049/jimmunol.1102179

18.Huik K, Avi R, Pauskar M, et al. Association between TLR3 rs3775291 and resistance to HIV among highly exposed Caucasian intravenous drug users. Infect Genet Evol. 2013;20:78–82. doi:10.1016/j.meegid.2013.08.008

19.Lim HK, Huang SXL, Chen J, et al. Severe influenza pneumonitis in children with inherited TLR3 deficiency. J Exp Med. 2019;216(9):2038–2056. doi:10.1084/jem.20181621; to: These studies demonstrate the deleterious effect of some TLR3 mutations and predisposition to Herpes simplex encephalitis in 4 separate studies on unrelated patients from different countries. TLR3 mutations in 3 children were associated with severe influenza pneumonitis. Finally, 2 other studies evaluate the protective effect of a common polymorphism of TLR3 against HIV infection in repetitively exposed individuals. Accordingly, we might find protective or deleterious effects in COVID19 patients due to different mutations of TLR3.

TLR3 is a receptor for dsRNA (intermediate in the replication of many viruses including HSV) which induces IFN response to prevent the cytopathic effects of different viruses. A heterozygous dominant-negative mutation of TLR3 was discovered in 2 unrelated children with HSE. TLR3 mutant fibroblasts from the 2 patients were infected by HSV-1 and vesicular stomatitis virus(VSV).IFNB and IFNL production were impaired in those cells, viral replication was higher and cell survival was lower in the 2 patients' cells when compared with the controls. Blood leukocyte response normally with to poly (I:C) which explains why the disease is not disseminated and also explains the redundant role of TLR3 in blood cells(13).
Similar findings were reported in a polish child in 2011, however, the patient here was compound heterozygous for a missense mutation leading to autosomal recessive inheritance of TLR3 deficiency(14).
Treatment with IFN alpha and beta canceled the effect of the dominant-negative mutation increasing the causality relationship between TLR3 mutants and viral immune response(13).
Relatives of the 2 patients with the same mutation did not show decreased interferon response nor they showed HSE as a complication of HSV which means that this mutation does not have full penetrance(13).

In another study, 110 patients with HSE were sequenced (exons of TLR3) to establish a new association of TLR3 mutations and HSE. The study reported 5 novel variants other than those previously described in the literature. 2 of them were not pathogenically demonstrated by in vitro studies while 3 of them were pathogenic with similar findings to those described above. Additionally, they found 3 patients with the same mutations previously described in the literature so the total of patients with deleterious TLR3 mutations would be 6 out of 110. 4 of those 6 patients(66%) with TLR6 mutations had a relapse In contrast to 12 out of 120(total cohort) (10%)(15).

In a recent study done on 16 patients with adult-onset HSE using whole-exome sequencing(WES), 1 patient was discovered to have TLR3 deficiency, while 8 other patients had mutations in other genes in the TLR3 pathway(2 patients with a mutation in IRF3, 2 patients with mutations in STAT1, 2 patients with mutations in TRIF, 1 patient with a mutation in TYK2,1 patients with a mutation in MAVS, and finally 1 patient with a mutation in TBK1)(16)

A common polymorphism in TLR3(rs3775291) was linked to increased resistance to HIV1 infection by the genotyping study of Spanish and Italian cohorts with a P value of .023 and .029 respectively. The study compared HIV exposed seronegative cohort(IV drug abuse and sexually active ) with controls. Repetitive HIV exposure in the cohort was evidenced by HCV seropositivity. In vitro infection of PBMCs with HIV showed increased resistance in cells carrying the allele and also TLR3 stimulation by TLR3 agonists showed an increased level of expression of CD69, IL-6, and CCL3(17).

A similar study was conducted on the Caucasian population showing the protective effect of the allele against HIV infection(18).

Autosomal recessive IRF7 and IRF9 deficiencies impair type I and III IFN immunity and underlie severe influenza pneumonitis. We report three unrelated children with influenza A virus (IAV) infection manifesting as acute respiratory distress syndrome (IAV-ARDS), heterozygous for rare TLR3 variants (P554S in two patients and P680L in the third) causing autosomal dominant (AD) TLR3 deficiency. AD TLR3 deficiency can underlie herpes simplex virus-1 (HSV-1) encephalitis (HSE) by impairing cortical neuron-intrinsic type I IFN immunity to HSV-1. TLR3-mutated leukocytes produce normal levels of IFNs in response to IAV. In contrast, TLR3-mutated fibroblasts produce lower levels of IFN-β and -λ, and display enhanced viral susceptibility, upon IAV infection. Moreover, the patients’ iPSC-derived pulmonary epithelial cells (PECs) are susceptible to IAV. Treatment with IFN-α2b or IFN-λ1 rescues this phenotype. AD TLR3 deficiency may thus underlie IAV-ARDS by impairing TLR3-dependent, type I, and/or III IFN–mediated, PEC-intrinsic immunity. Its clinical penetrance is incomplete for both IAV-ARDS and HSE, consistent with their typically sporadic nature(PMID: 31217193
)




13.Zhang SY, Jouanguy E, Ugolini S, et al. TLR3 deficiency in patients with herpes simplex encephalitis. Science. 2007;317(5844):1522–1527. doi:10.1126/science.1139522

14.Guo Y, Audry M, Ciancanelli M, et al. Herpes simplex virus encephalitis in a patient with complete TLR3 deficiency: TLR3 is otherwise redundant in protective immunity. J Exp Med. 2011;208(10):2083–2098. doi:10.1084/jem.20101568

15.Lim HK, Seppänen M, Hautala T, et al. TLR3 deficiency in herpes simplex encephalitis: high allelic heterogeneity and recurrence risk. Neurology. 2014;83(21):1888–1897. doi:10.1212/WNL.0000000000000999

16.Mørk N, Kofod-Olsen E, Sørensen KB, et al. Mutations in the TLR3 signaling pathway and beyond in adult patients with herpes simplex encephalitis. Genes Immun. 2015;16(8):552–566. doi:10.1038/gene.2015.46

17.Sironi M, Biasin M, Cagliani R, et al. A common polymorphism in TLR3 confers natural resistance to HIV-1 infection. J Immunol. 2012;188(2):818–823. doi:10.4049/jimmunol.1102179

18.Huik K, Avi R, Pauskar M, et al. Association between TLR3 rs3775291 and resistance to HIV among highly exposed Caucasian intravenous drug users. Infect Genet Evol. 2013;20:78–82. doi:10.1016/j.meegid.2013.08.008

19.Lim HK, Huang SXL, Chen J, et al. Severe influenza pneumonitis in children with inherited TLR3 deficiency. J Exp Med. 2019;216(9):2038–2056. doi:10.1084/jem.20181621
COVID-19 research v0.126 NOS2 Ivone Leong gene: NOS2 was added
gene: NOS2 was added to Viral susceptibility. Sources: Expert list
Mode of inheritance for gene: NOS2 was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: NOS2 were set to 31995689; 11207313
Review for gene: NOS2 was set to GREEN
Added comment: NOS2 is part of the list of genes that confer susceptibility to viral infections on the COVID Human Genetic Effort website (https://www.covidhge.com/).

PMID: 31995689 describes a 51 year old man from Iran who had an acute cytomegalovirus (CMV) infection which progressed to CMV disease and later died from it. The researchers found a homozygous variant that causes a frameshift mutation in NOS2 that caused NOS2 deficiency, which might cause the patient to be more susceptible to lethal CMV infection. It is rare for CMV to cause fatality in healthy people; however, Nos2 knockout mice are susceptible to lethal infection with murine CMV (PMID: 11207313).

Based on the above evidence NOS2 has been given Green gene status.
Sources: Expert list
COVID-19 research v0.62 FCGR1A Catherine Snow Added comment: Comment on list classification: FCGR1 is on the Immunoplex Panel offered by the University of Washington Department of Laboratory Medicine however there is currently no link to alleles and disease (PMID: 31057544)
COVID-19 research v0.36 LIG1 Ellen McDonagh gene: LIG1 was added
gene: LIG1 was added to Viral susceptibility. Sources: Emory Genetics Laboratory,Expert Review,Other,IUIS Classification December 2019,Expert Review Red,Literature,IUIS Classification February 2018
Mode of inheritance for gene: LIG1 was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: LIG1 were set to 30395541; 1581963; 32086639; 32048120
Phenotypes for gene: LIG1 were set to DNA ligase I deficiency; Combined immunodeficiencies with associated or syndromic features; DNA-ligase 1 ATP-dependent deficiency (LIG1); Recurrent respiratory infections, growth retardation, sun sensitivity, lymphoma, radiation sensitivity
COVID-19 research v0.36 TCN2 Ellen McDonagh gene: TCN2 was added
gene: TCN2 was added to Viral susceptibility. Sources: Expert Review Green,Agranulocytosis v1.3,Combined B and T cell defect v1.12,ESID Registry 20171117,North West GLH,Victorian Clinical Genetics Services,Congenital neutropaenia v1.22,GRID V2.0,NHS GMS,London North GLH,A- or hypo-gammaglobulinaemia v1.25,SCID v1.6,IUIS Classification February 2018
Mode of inheritance for gene: TCN2 was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: TCN2 were set to 20352340; 24305960; 7849710; 7980584; 18956254
Phenotypes for gene: TCN2 were set to Transcobalamin-2 precursor; Transcobalamin II deficiency; Agammaglobulinemia; Megaloblastic anemia, pancytopenia, if untreated for prolonged periods results in intellectual disability; pancytopenia; Transcobalamin II deficiency, 275350; neutropenic colitis; Defects of Vitamin B12 and Folate metabolism; megaloblastic bone; can have a presentation similar to severe combined immunodeficiency; Combined immunodeficiencies with associated or syndromic features
COVID-19 research v0.36 SLC46A1 Ellen McDonagh gene: SLC46A1 was added
gene: SLC46A1 was added to Viral susceptibility. Sources: Expert Review Green,ESID Registry 20171117,North West GLH,Victorian Clinical Genetics Services,GRID V2.0,NHS GMS,London North GLH,IUIS Classification February 2018
Mode of inheritance for gene: SLC46A1 was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: SLC46A1 were set to 17446347; 17129779; 27664775
Phenotypes for gene: SLC46A1 were set to Folate malabsorption, hereditary 229050; Congenital defect of folate absorption; Megaloblastic anemia, failure to thrive, if untreated for prolonged periods results in intellectual disability; Defects of Vitamin B12 and Folate metabolism; Combined immunodeficiencies with associated or syndromic features
COVID-19 research v0.36 MTHFD1 Ellen McDonagh gene: MTHFD1 was added
gene: MTHFD1 was added to Viral susceptibility. Sources: Expert Review Green,ESID Registry 20171117,North West GLH,Victorian Clinical Genetics Services,GRID V2.0,NHS GMS,London North GLH,IUIS Classification February 2018
Mode of inheritance for gene: MTHFD1 was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: MTHFD1 were set to 25633902; 27707659
Phenotypes for gene: MTHFD1 were set to Recurrent bacterial infection, Pneumocystis jirovecii, megaloblastic anemia, failure to thrive, neutropenia, seizures, intellectual disability, folate-responsive; Combined immunodeficiency and megaloblastic anemia with or without hyperhomocysteinemia 617780; Combined immunodeficiencies with associated or syndromic features; Defects of Vitamin B12 and Folate metabolism
COVID-19 research v0.36 CSF2RB Ellen McDonagh gene: CSF2RB was added
gene: CSF2RB was added to Viral susceptibility. Sources: Expert Review Green,North West GLH,NHS GMS,London North GLH,IUIS Classification February 2018
Mode of inheritance for gene: CSF2RB was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: CSF2RB were set to 21205713; 21075760; 9410898
Phenotypes for gene: CSF2RB were set to Surfactant metabolism dysfunction, pulmonary, 5, 614370; Congenital defects of phagocyte number or function; Alveolar proteinosis
COVID-19 research v0.36 CSF2RA Ellen McDonagh gene: CSF2RA was added
gene: CSF2RA was added to Viral susceptibility. Sources: Expert Review Green,ESID Registry 20171117,North West GLH,Victorian Clinical Genetics Services,GRID V2.0,NHS GMS,London North GLH,IUIS Classification February 2018
Mode of inheritance for gene: CSF2RA was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: CSF2RA were set to 1972780; 18955570; 23632888; 18955567
Phenotypes for gene: CSF2RA were set to Congenital pulmonary alveolar proteinosis; Alveolar proteinosis; Congenital defects of phagocyte number or function; Pulmonary alveolar proteinosis; hypersensitivity; Surfactant metabolism dysfunction, pulmonary 4, 300770