Small RNA Viruses Research Articles

The RNA Interference Effector Protein Argonaute 2 Functions as a Restriction Factor Against SARS-CoV-2

Argonaute 2 (Ago2) is a key component of the RNA interference (RNAi) pathway, a gene-regulatory system that is present in most eukaryotes. Ago2 uses microRNAs (miRNAs) and small interfering RNAs (siRNAs) for targeting to homologous mRNAs which are then degraded or translationally suppressed. In plants and invertebrates, the RNAi pathway has well-described roles in antiviral defense, but its function in limiting viral infections in mammalian cells is less well understood. Here, we examined the role of Ago2 in replication of the betacoronavirus SARS-CoV-2, the etiologic agent of COVID-19. Microscopic analyses of infected cells revealed that a pool of Ago2 closely associates with viral replication sites and gene ablation studies showed that loss of Ago2 resulted in over 1,000-fold increase in peak viral titers. Replication of the alphacoronavirus 229E was also significantly increased in cells lacking Ago2. The antiviral activity of Ago2 was dependent on both its ability to bind small RNAs and its endonuclease function. Interestingly, in cells lacking Dicer, an upstream component of the RNAi pathway, viral replication was the same as in parental cells. This suggests that the antiviral activity of Ago2 is independent of Dicer processed miRNAs. Deep sequencing of infected cells by other groups identified several SARS-CoV-2-derived small RNAs that bind to Ago2. A mutant virus lacking the most abundant ORF7A-derived viral miRNA was found to be significantly less sensitive to Ago2-mediated restriction. This combined with our findings that endonuclease and small RNA-binding functions of Ago2 are required for its antiviral function, suggests that Ago2-small viral RNA complexes target nascent viral RNA produced at replication sites for cleavage. Further studies are required to elucidate the processing mechanism of the viral small RNAs that are used by Ago2 to limit coronavirus replication.

IFITM1 enhances nonenveloped viral RNA replication by facilitating cholesterol transport to the Golgi.

Aichi virus (AiV), a small non-enveloped RNA virus, hijacks the endoplasmic reticulum (ER)-Golgi cholesterol transport machinery to form cholesterol-rich replication sites originating from Golgi membranes. Interferon-induced transmembrane proteins (IFITMs) are antiviral restriction factors, whose involvement in intracellular cholesterol transport is suggested. Here, we describe the roles of IFITM1 in cholesterol transport that affect AiV RNA replication. IFITM1 stimulated AiV RNA replication and its knockdown significantly reduced the replication. In replicon RNA-transfected or infected cells, endogenous IFITM1 localized to the viral RNA replication sites. Further, IFITM1 interacted with viral proteins and host Golgi proteins, ACBD3, PI4KB, OSBP, which constitute the replication sites. When overexpressed, IFITM1 localized to the Golgi as well as endosomes, and this phenotype was also observed for endogenous IFITM1 early in AiV RNA replication, leading to the distribution of cholesterol at the Golgi-derived replication sites. The pharmacological inhibition of ER-Golgi cholesterol transport or endosomal cholesterol export impaired AiV RNA replication and cholesterol accumulation at the replication sites. Such defects were corrected by expression of IFITM1. Overexpressed IFITM1 facilitated late endosome-Golgi cholesterol transport without any viral proteins. In summary, we propose a model in which IFITM1 enhances cholesterol transport to the Golgi to accumulate cholesterol at Golgi-derived replication sites, providing a novel mechanism by which IFITM1 enables efficient genome replication of non-enveloped RNA virus.

Identification and Profiling of a Novel Bombyx mori latent virus Variant Acutely Infecting Helicoverpa armigera and Trichoplusia ni.

Insect cell expression systems are increasingly being used in the medical industry to develop vaccines against diseases such as COVID-19. However, viral infections are common in these systems, making it necessary to thoroughly characterize the viruses present. One such virus is Bombyx mori latent virus (BmLV), which is known to be specific to Bombyx mori and to have low pathogenicity. However, there has been little research on the tropism and virulence of BmLV. In this study, we examined the genomic diversity of BmLV and identified a variant that persistently infects Trichoplusia ni-derived High Five cells. We also assessed the pathogenicity of this variant and its effects on host responses using both in vivo and in vitro systems. Our results showed that this BmLV variant causes acute infections with strong cytopathic effects in both systems. Furthermore, we characterized the RNAi-based immune response in the T. ni cell line and in Helicoverpa armigera animals by assessing the regulation of RNAi-related genes and profiling the generated viral small RNAs. Overall, our findings shed light on the prevalence and infectious properties of BmLV. We also discuss the potential impact of virus genomic diversity on experimental outcomes, which can help interpret past and future research results.

Anisomycin inhibits Coxsackievirus B replication by promoting the lysosomal degradation of eEF1A1

Group B Coxsackieviruses (CVB) are non-enveloped small RNA viruses in the genus Enterovirus, family Picornaviridae. CVB infection causes diverse conditions from common cold to myocarditis, encephalitis, and pancreatitis. No specific antiviral is available for the treatment of CVB infection. Anisomycin, a pyrrolidine-containing antibiotic and translation inhibitor, was reported to inhibit the replication of some picornaviruses. However, it is unknown if anisomycin can act as an antiviral against CVB infection. Here we observed that anisomycin showed potent inhibition on CVB type 3 (CVB3) infection with negligible cytotoxicity when applied at the early stage of virus infection. Mice infected with CVB3 showed markedly alleviated myocarditis with reduced viral replication. We found that CVB3 infection significantly increased the transcription of eukaryotic translation elongation factor 1 alpha 1 (eEF1A1). CVB3 replication was suppressed by EEF1A1 knockdown, while elevated by EEF1A1 overexpression. Similar to the effect of CVB3 infection, EEF1A1 transcription was increased in response to anisomycin treatment. However, eEF1A1 protein level was decreased with anisomycin treatment in a dose-dependent manner in CVB3-infected cells. Moreover, anisomycin promoted eEF1A1 degradation, which was inhibited by the treatment of chloroquine but not MG132. We demonstrated that eEF1A1 interacted with the heat shock cognate protein 70 (HSP70), and eEF1A1 degradation was inhibited by LAMP2A knockdown, implicating that eEF1A1 is degraded through chaperone-mediated autophagy. Taken together, we demonstrated that anisomycin, which inhibits CVB replication through promoting the lysosomal degradation of eEF1A1, could be a potential antiviral candidate for the treatment of CVB infection.

Soluble ORF2 protein enhances HEV replication and induces long-lasting antibody response and protective immunity in vivo.

The HEV is a small positive-sense RNA virus that encodes a cytoplasmic form of the capsid protein (ORF2c), essential for virion structure, and a secreted glycosylated form (ORF2s) that accumulates at high titer in serum and can mask neutralizing epitopes. We explored the contribution of ORF2s to HEV replication and its role in generating antibodies against ORF2 in a nonhuman primate model. We used a recombinant HEV genotype 3 variant that does not express ORF2s due to the introduction of stop codons (ORF2s mut ). Rhesus macaques (RMs) were given intrahepatic injections of infectious wildtype HEV (ORF2s wt ) RNA or a variant lacking ORF2s expression (ORF2s mut ). The replication of the ORF2s mut virus was delayed by ~2 weeks compared with ORF2s wt , and peak titers were nearly tenfold lower. Reversions of the 3 mutations that blocked ORF2s expression were not detected in the ORF2s mut genomes, indicating genetic stability. However, serum antibodies against ORF2 were transiently detected in RMs infected with ORF2s mut , whereas they were long-lasting in RMs infected with ORF2s wt . Moreover, RMs infected with ORF2s mut were more susceptible to reinfection, as evidenced by the viral RNA detected in fecal samples and the expansion of HEV-specific CD8 + T cells. These findings indicate that ORF2s may be dispensable for viral replication in vivo but is required for long-lived antibody-mediated responses that protect against HEV re-exposure.

Bi-allelic variants in INTS11 are associated with a complex neurological disorder

The Integrator complex is a multi-subunit protein complex that regulates the processing of nascent RNAs transcribed by RNA polymerase II (RNAPII), including small nuclear RNAs, enhancer RNAs, telomeric RNAs, viral RNAs, and protein-coding mRNAs. Integrator subunit 11 (INTS11) is the catalytic subunit that cleaves nascent RNAs, but, to date, mutations in this subunit have not been linked to human disease. Here, we describe 15 individuals from 10 unrelated families with bi-allelic variants in INTS11 who present with global developmental and language delay, intellectual disability, impaired motor development, and brain atrophy. Consistent with human observations, we find that the fly ortholog of INTS11, dIntS11, is essential and expressed in the central nervous systems in a subset of neurons and most glia in larval and adult stages. Using Drosophila as a model, we investigated the effect of seven variants. We found that two (p.Arg17Leu and p.His414Tyr) fail to rescue the lethality of null mutants, indicating that they are strong loss-of-function variants. Furthermore, we found that five variants (p.Gly55Ser, p.Leu138Phe, p.Lys396Glu, p.Val517Met, and p.Ile553Glu) rescue lethality but cause a shortened lifespan and bang sensitivity and affect locomotor activity, indicating that they are partial loss-of-function variants. Altogether, our results provide compelling evidence that integrity of the Integrator RNA endonuclease is critical for brain development.

Systematic identification and characterization of viral small RNAs from small RNA-Seq data.

Virus-encoded small RNAs (vsRNAs) have been reported to play an important role in viral infections. Unfortunately, there is still a lack of a systematic characterization and resource of vsRNAs. Herein, we identified a total of 19 734 high-confidence vsRNAs including 2746 microRNAs (miRNAs) in 64 viral species from more than 800 samples of public small RNA-Seq data. The number of vsRNAs identified in viruses varied from 1 to 2489 with a median of 170. The length distribution of vsRNAs peaked at 21 and 22 nt. Plant viruses were found to express larger number and higher levels of vsRNAs than those of animal viruses. Besides, the number of vsRNAs identified increased as the viral infection persisted. Interestingly, the vsRNA showed strong expression specificity as little overlap was observed among vsRNAs identified in different strains of a virus, or in different hosts, cells, or tissues infected by the same virus. Little conservation was observed among vsRNAs of different viruses. The viral miRNAs were found to interact with host genes involved in multiple biological processes related to organization, development, action potential, polarity establishment, methylation, immune response, gene regulation, localization, and so on. To facilitate the usage of vsRNAs, a database named vsRNAdb was built for organizing and storing vsRNAs which is available at http://www.computationalbiology.cn/vsRNAdb/#/vsRNAdb/#/. Overall, the study deepens our understanding about the diversity and complexity of vsRNAs and provides a rich resource for further studies of vsRNAs.

Discovery and Genome Characterization of a Closterovirus from Wheat Plants with Yellowing Leaf Symptoms in Japan.

Many aphid-borne viruses are important pathogens that affect wheat crops worldwide. An aphid-transmitted closterovirus named wheat yellow leaf virus (WYLV) was found to have infected wheat plants in Japan in the 1970s; however, since then, its viral genome sequence and occurrence in the field have not been investigated. We observed yellowing leaves in the 2018/2019 winter wheat-growing season in an experimental field in Japan where WYLV was detected five decades ago. A virome analysis of those yellow leaf samples lead to the discovery of a closterovirus together with a luteovirus (barley yellow dwarf virus PAV variant IIIa). The complete genomic sequence of this closterovirus, named wheat closterovirus 1 isolate WL19a (WhCV1-WL19a), consisted of 15,452 nucleotides harboring nine open reading frames. Additionally, we identified another WhCV1 isolate, WL20, in a wheat sample from the winter wheat-growing season of 2019/2020. A transmission test indicated that WhCV1-WL20 was able to form typical filamentous particles and transmissible by oat bird-cherry aphid (Rhopalosiphum pad). Sequence and phylogenetic analyses showed that WhCV1 was distantly related to members of the genus Closterovirus (family Closteroviridae), suggesting that the virus represents a novel species in the genus. Furthermore, the characterization of WhCV1-WL19a-derived small RNAs using high-throughput sequencing revealed highly abundant 22-nt-class small RNAs potentially derived from the 3'-terminal end of the WhCV1 negative-strand genomic RNA, indicating that this terminal end of the WhCV1 genome is likely particularly targeted for the synthesis of viral small RNAs in wheat plants. Our results provide further knowledge on closterovirus diversity and pathogenicity and suggest that the impact of WhCV1 on wheat production warrants further investigations.

Identification of Non-Polio Enterovirus in an Infant with Impaired Immunity in Sri Lanka

Enteroviruses are a group of small RNA viruses. With their ubiquitous nature, they cause a wide spectrum of diseases worldwide.

SARS-CoV-2-encoded small RNAs are able to repress the host expression of SERINC5 to facilitate viral replication.

Serine incorporator protein 5 (SERINC5) is a key innate immunity factor that operates in the cell to restrict the infectivity of certain viruses. Different viruses have developed strategies to antagonize SERINC5 function but, how SERINC5 is controlled during viral infection is poorly understood. Here, we report that SERINC5 levels are reduced in COVID-19 patients during the infection by SARS-CoV-2 and, since no viral protein capable of repressing the expression of SERINC5 has been identified, we hypothesized that SARS-CoV-2 non-coding small viral RNAs (svRNAs) could be responsible for this repression. Two newly identified svRNAs with predicted binding sites in the 3'-untranslated region (3'-UTR) of the SERINC5 gene were characterized and we found that the expression of both svRNAs during the infection was not dependent on the miRNA pathway proteins Dicer and Argonaute-2. By using svRNAs mimic oligonucleotides, we demonstrated that both viral svRNAs can bind the 3'UTR of SERINC5 mRNA, reducing SERINC5 expression in vitro. Moreover, we found that an anti-svRNA treatment to Vero E6 cells before SARS-CoV-2 infection recovered the levels of SERINC5 and reduced the levels of N and S viral proteins. Finally, we showed that SERINC5 positively controls the levels of Mitochondrial Antiviral Signalling (MAVS) protein in Vero E6. These results highlight the therapeutic potential of targeting svRNAs based on their action on key proteins of the innate immune response during SARS-CoV-2 viral infection.

Beyond bulevirtide: Alternative therapeutic options for the management of hepatitis delta virus.

Hepatitis delta virus (HDV) is a small RNA virus which needs Hepatitis B Surface Antigen for its envelope, for entry into hepatocytes and secretion. HDV chronic infection affects around 12million people worldwide. HDV infection is believed to be the most severe form of viral hepatitis, with a high risk of developing cirrhosis and hepatocellular carcinoma. Pegylated interferons has been used and recommended by guidelines, although not approved, with low efficacy and poor tolerability. Bulevirtide (entry inhibitor) has been recently conditionally approved by the European Medicines Agency. These treatments have many advantages, but they have also limitations since there are non-responders to these previous therapies. There is an urgent need to develop new drugs. In this article, we review antiviral treatments under development for HDV chronic infection (except bulevirtide reviewed in a specific article), including those in the HBV cure programme, outlining their respective mechanisms-of-action.

A potential role for SARS-CoV-2 small viral RNAs in targeting host microRNAs and modulating gene expression

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes coronavirus disease (COVID-19) in humans, with symptoms ranging from mild to severe, including fatality. The molecular mechanisms surrounding the effects of viral infection on the host RNA machinery remain poorly characterized. We used a comparative transcriptomics approach to investigate the effects of SARS-CoV-2 infection on the host mRNA and sRNA expression machinery in a human lung epithelial cell line (Calu-3) and an African green monkey kidney cell line (Vero-E6). Upon infection, we observed global changes in host gene expression and differential expression of dozens of host miRNAs, many with known links to viral infection and immune response. Additionally, we discovered an expanded landscape of more than a hundred SARS-CoV-2-derived small viral RNAs (svRNAs) predicted to interact with differentially expressed host mRNAs and miRNAs. svRNAs are derived from distinct regions of the viral genome and sequence signatures suggest they are produced by a non-canonical biogenesis pathway. 52 of the 67 svRNAs identified in Calu-3 cells are predicted to interact with differentially expressed miRNAs, with many svRNAs having multiple targets. Accordingly, we speculate that these svRNAs may play a role in SARS-CoV-2 propagation by modulating post-transcriptional gene regulation, and that methods for antagonizing them may have therapeutic value.

Cardiovirus leader proteins retarget RSK kinases toward alternative substrates to perturb nucleocytoplasmic traffic.

Proteins from some unrelated pathogens, including small RNA viruses of the family Picornaviridae, large DNA viruses such as Kaposi sarcoma-associated herpesvirus and even bacteria of the genus Yersinia can recruit cellular p90-ribosomal protein S6 kinases (RSKs) through a common linear motif and maintain the kinases in an active state. On the one hand, pathogens' proteins might hijack RSKs to promote their own phosphorylation (direct target model). On the other hand, some data suggested that pathogens' proteins might dock the hijacked RSKs toward a third interacting partner, thus redirecting the kinase toward a specific substrate. We explored the second hypothesis using the Cardiovirus leader protein (L) as a paradigm. The L protein is known to trigger nucleocytoplasmic trafficking perturbation, which correlates with hyperphosphorylation of phenylalanine-glycine (FG)-nucleoporins (FG-NUPs) such as NUP98. Using a biotin ligase fused to either RSK or L, we identified FG-NUPs as primary partners of the L-RSK complex in infected cells. An L protein mutated in the central RSK-interaction motif was readily targeted to the nuclear envelope whereas an L protein mutated in the C-terminal domain still interacted with RSK but failed to interact with the nuclear envelope. Thus, L uses distinct motifs to recruit RSK and to dock the L-RSK complex toward the FG-NUPs. Using an analog-sensitive RSK2 mutant kinase, we show that, in infected cells, L can trigger RSK to use NUP98 and NUP214 as direct substrates. Our data therefore illustrate a novel virulence mechanism where pathogens' proteins hijack and retarget cellular protein kinases toward specific substrates, to promote their replication or to escape immunity.

Stimulation of interferon-β responses by aberrant SARS-CoV-2 small viral RNAs acting as retinoic acid-inducible gene-I agonists

Patients with severe COVID-19 exhibit a cytokine storm characterized by greatly elevated levels of cytokines. Despite this, the interferon (IFN) response is delayed, contributing to disease progression. Here, we report that SARS-CoV-2 excessively generates small viral RNAs (svRNAs) encoding exact 5' ends of positive-sense genes in human cells invitro and exvivo, whereas endemic human coronaviruses (OC43 and 229E) produce significantly fewer similar svRNAs. SARS-CoV-2 5' end svRNAs are RIG-I agonists and induce the IFN-β response in the later stages of infection. The first 60-nt ends bearing duplex structures and 5'-triphosphates are responsible for immune-stimulation. We propose that RIG-I activation by accumulated SARS-CoV-2 5' end svRNAs may contribute to later drive over-exuberant IFN production. Additionally, the differences in the amounts of svRNAs produced and the corresponding IFN response among CoV strains suggest that lower svRNA production during replication may correlate with the weaker immune response seen in less pathogenic CoVs.

Expanding, Characterizing, and Repurposing the Invertebrate Virosphere

Modern medicine demands the capacity to deliver genetic or biological cargo to specific cell types. Past efforts to achieve this goal have relied on the retooling and re-engineering of a small subset of vertebrate viruses with limited success. Remaining challenges with regards to in vivo delivery include finding novel viral vectors that can achieve different target specificities in addition to those that are more amenable to synthesize de novo. In an attempt to address these remaining limitations, we collected and sampled diverse invertebrate species to isolate and identify RNA viruses associated with them. As the invertebrate virosphere remains largely unknown, we hypothesized that we would identify novel viruses whose components could be characterized and repurposed to build a new suite of viral-based tools. To this end, we isolated and sequenced RNA from a diverse library of invertebrates (including 42 insects) by next-generation sequencing and subsequently performed de novo genome assembly on the reads obtained. Captured reads were analyzed for signatures of RNA dependent RNA polymerases (RdRps) – a necessary component of all RNA viruses. The two putative novel virus genome assemblies discovered were named Castor and Pollux, and were characterized and independently confirmed by quantitative PCR. These small RNA viruses or their RdRps (less than 5kB) will, in the future, be synthesized and artificially launched in mammalian cells to ascertain whether they can be selected via guided evolution to function and deliver a desired genetic or biological cargo.

VsRNAfinder: a novel method for identifying high-confidence viral small RNAs from small RNA-Seq data.

Virus-encoded small RNAs (vsRNA) have been reported to play an important role in viral infection. Unfortunately, there is still a lack of an effective method for vsRNA identification. Herein, we presented vsRNAfinder, a de novo method for identifying high-confidence vsRNAs from small RNA-Seq (sRNA-Seq) data based on peak calling and Poisson distribution and is publicly available at https://github.com/ZenaCai/vsRNAfinder. vsRNAfinder outperformed two widely used methods namely miRDeep2 and ShortStack in identifying viral miRNAs with a significantly improved sensitivity. It can also be used to identify sRNAs in animals and plants with similar performance to miRDeep2 and ShortStack. vsRNAfinder would greatly facilitate effective identification of vsRNAs from sRNA-Seq data.

2'-Fucosyllactose Inhibits Coxsackievirus Class A Type 9 Infection by Blocking Virus Attachment and Internalisation.

Coxsackieviruses, a genus of enteroviruses in the small RNA virus family, cause fatal infectious diseases in humans. Thus far, there are no approved drugs to prevent these diseases. Human milk contains various biologically active components against pathogens. Currently, the potential activity of breast milk components against the coxsackievirus remains unclear. In our study, the inhibitory effect of 16 major human milk components was tested on coxsackievirus class A type 9 isolate (CV-A9), BUCT01; 2'-Fucosyllactose (2'-FL) was identified to be effective. Time-of-addition, attachment internalisation assays, and the addition of 2'-FL at different time points were applied to investigate its specific role in the viral life cycle. Molecular docking was used to predict 2'-FL's specific cellular targets. The initial screening revealed a significant inhibitory effect (99.97%) against CV-A9 with 10 mg/mL 2'-FL, with no cytotoxicity observed. Compared with the control group, 2'-FL blocked virus entry (85%) as well as inhibited viral attachment (48.4%) and internalisation (51.3%), minimising its infection in rhabdomyosarcoma (RD) cells. The cell pre-incubation with 2'-FL exhibited significant inhibition (73.2-99.9%). Extended incubation between cells with 2'-FL reduced CV-A9 infection (93.9%), suggesting that 2'-FL predominantly targets cells to block infection. Molecular docking results revealed that 2'-FL interacted with the attachment receptor αvβ6 and the internalisation receptor FCGRT and β2M with an affinity of -2.14, -1.87, and -5.43 kcal/mol, respectively. This study lays the foundation for using 2'-FL as a food additive against CV-A9 infections.

Construction of a Vero Cell Line Expressing Human ICAM1 for the Development of Rhinovirus Vaccines.

Human rhinoviruses (HRVs) are small non-enveloped RNA viruses that belong to the Enterovirus genus within the Picornaviridae family and are known for causing the common cold. Though symptoms are generally mild in healthy individuals, the economic burden associated with HRV infection is significant. A vaccine could prevent disease. The Vero-cell-based viral vaccine platform technology was considered for such vaccine development. Unfortunately, most HRV strains are unable to propagate on Vero cells due to a lack of the major receptor of HRV group A and B, intercellular adhesion molecule (ICAM1, also known as CD54). Therefore, stable human ICAM1 expressing Vero cell clones were generated by transfecting the ICAM1 gene in Vero cells and selecting clones that overexpressed ICAM1 on the cell surface. Cell banks were made and expression of ICAM1 was stable for at least 30 passages. The Vero_ICAM1 cells and parental Vero cells were infected with four HRV prototypes, B14, A16, B37 and A57. Replication of all four viruses was detected in Vero_ICAM1, but not in the parental Vero cells. Altogether, Vero cells expressing ICAM1 could efficiently propagate the tested HRV strains. Therefore, ICAM1-expressing cells could be a useful tool for the development and future production of polyvalent HRV vaccines or other viruses that use ICAM1 as a receptor.

Viral and Host Small RNA Response to SARS-CoV-2 Infection

After two years into the pandemic of the coronavirus disease 2019 (COVID-19), it remains unclear how the host RNA interference (RNAi) pathway and host miRNAs regulate severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and impact the development of COVID-19. In this study, we profiled small RNAs in SARS-CoV-2-infected human ACE2-expressing HEK293T cells and observed dysregulated host small RNA groups, including specific host miRNAs that are altered in response to SARS-CoV-2 infection. By comparing dysregulated miRNAs in different SARS-CoV-2-infected samples, we identified miRNA-210-3p, miRNA-30-5p, and miR-146a/b as key host miRNAs that may be involved in SARS-CoV-2 infection. Furthermore, by comparing virally derived small RNAs (vsmRNAs) in different SARS-CoV-2-infected samples, we observed multiple hot spots in the viral genome that are prone to generating vsmRNAs, and their biogenesis can be dependent on the antiviral isoform of Dicer. Moreover, we investigated the biogenesis of a recently identified SARS-CoV-2 viral miRNA encoded by ORF7a and found that it is differentially expressed in different infected cell lines or in the same cell line with different viral doses. Our results demonstrate the involvement of both host small RNAs and vsmRNAs in SARS-CoV-2 infection and identify these small RNAs as potential targets for anti-COVID-19 therapeutic development.

ICTV Virus Taxonomy Profile: Hepeviridae 2022.

The family Hepeviridae includes enterically transmitted small quasi-enveloped or non-enveloped positive-sense single-stranded RNA viruses infecting mammals and birds (subfamily Orthohepevirinae) or fish (Parahepevirinae). Hepatitis E virus (genus Paslahepevirus) is responsible for self-limiting acute hepatitis in humans; the infection may become chronic in immunocompromised individuals and extrahepatic manifestations have been described. Avian hepatitis E virus (genus Avihepevirus) causes hepatitis-splenomegaly syndrome in chickens. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the family Hepeviridae, which is available at www.ictv.global/report/hepeviridae.