Journal of Virology最新文献

Seneca Valley virus (SVV) infection gives rise to severe vesicular diseases in pigs, presenting a substantial threat to the global swine industry. The redox imbalance resulting from oxidative stress is an essential pathogenic mechanism during viral infections. Nevertheless, the regulatory mechanisms of oxidative stress by viral and host factors during SVV infection remain elusive. In this study, we discovered that SVV elicited cellular oxidative stress through the induction of reactive oxygen species production and the suppression of the nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathway. Our findings indicated that the overexpression of Nrf2/HO-1 exerted a remarkable anti-SVV effect. Conversely, the inhibition of Nrf2/HO-1 expression facilitated the proliferation of SVV. HO-1 metabolic products carbon monoxide and biliverdin inhibit SVV replication. HO-1 promotes type I interferon response and interferon-stimulated gene expressions, which contribute to its antiviral mechanism. Furthermore, our findings reveal that the SVV 3C proteinase targets the Nrf2/HO-1 axis for degradation via caspase pathway, thereby promoting viral replication. Collectively, these results clarify the convoluted molecular mechanisms by which SVV weakens the host's antioxidant defense system and suggest potential targets for therapeutic interventions regarding SVV infections.

Importance: Nrf2 is a crucial redox regulator responsible for initiating the expression of downstream antioxidant genes, including HO-1 and superoxide dismutase. HO-1, an enzyme induced by stress, performs protective roles through the conversion of heme into carbon monoxide, biliverdin, and iron. Nevertheless, the function of Nrf2/HO-1 during Seneca Valley virus (SVV) infection is yet to be clearly defined. In this study, we showed that SVV infection led to a reduction in the expression of Nrf2/HO-1, and the overexpression of Nrf2/HO-1 induced a potent anti-SVV effect. SVV 3C proteinase promoted the caspase-dependent degradation of Nrf2/HO-1. As a result, it attenuated the cell's ability to resist oxidative stress and counteracted the antiviral function of Nrf2/HO-1. Our research further uncovered a novel mechanism through which SVV eludes the host's antiviral effects by disrupting cellular redox balance, offering important targets for preventing and controlling SVV infection.

Avian influenza virus cross-species infection in humans poses a major threat to global public health. Species-specific differences between avian ANP32A and mammalian ANP32 proteins create a natural barrier against viral cross-species infection by directly impairing the functional interaction between the avian-origin viral RNA polymerase and mammalian ANP32 proteins, thereby restricting viral genome replication. The key to overcoming this barrier lies in the adaptation of viral RNA polymerase to host ANP32 family proteins. This mini-review summarizes the mechanisms and variations in influenza virus adaptation to ANP32 proteins across different species. Influenza viruses adapt to species-specific ANP32 proteins through various mutations and display distinct preferences for specific ANP32 family members within the same host. Additionally, alternative splicing variants of ANP32A within a single species further modulate viral RNA polymerase adaptability. Despite this diversity, the underlying interaction mechanism remains conserved: ANP32-polymerase binding is necessary but not sufficient for optimal polymerase activity. This interaction facilitates the formation of asymmetric polymerase dimers and specifically supports viral genome replication, while the step from cRNA to vRNA remains subject to species-specific restrictions. This explains the classic adaptive mechanism of the PB2 E627K mutation, which restores efficient viral genome replication through acid-base pairing with ANP32A. Furthermore, adaptive mutations in emerging strains such as H3N2 canine influenza virus and recent cases of H5N1 in dairy cows underscore the need for continuous viral surveillance and deeper mechanistic studies on virus-ANP32 interactions. Such research is strategically critical for advancing the One Health approach and mitigating future influenza pandemics.

Unlike most enveloped viruses, Herpesviridae distribute cell entry functions across several viral envelope proteins. The prevailing model posits that, upon interaction with the target cell, the activating signal is transmitted from the receptor-binding to the fusion-mediating component in a signaling cascade that involves sequential interactions. However, herpesvirus entry proteins may form complexes throughout fusion. Here, we propose that-by analogy with certain eukaryotic signaling cascades-transmission of the activating signal involves pre-assembled complexes and allosteric effects.

As the most abundant biological entities in the ocean, viruses of microbes play important roles in regulating host population dynamics and influencing biogeochemical cycles. Metagenomic surveys have revealed an astounding reservoir of viral genetic diversity in single-celled marine eukaryotes known as protists, but the vast majority of these viruses have not been directly observed, and information about their protist hosts remains fragmentary. The 2023 discovery of mirusviruses provides a striking example, whereby metagenomic surveys of samples collected by the Tara Oceans expedition led to the discovery of a new phylum of viruses, the Mirusviricota, with remarkable chimeric genomes encoding structural proteins from herpesviruses and enzymes from giant eukaryotic viruses. However, because mirusviruses were detected indirectly by metagenomics, their host range remained unclear, and their biological properties unexplored. Here, we provide new insights into research approaches to identify bona fide protist hosts for marine viruses and characterize virus-host interactions. A greater understanding of these viruses and their natural hosts will unlock opportunities to understand the roles that they play in regulating biogeochemical processes in marine habitats.

Recombination facilitates the generation of defective viral genomes (DVGs), truncated derivatives of the parental genome that require a helper virus to replicate. Recombination mechanisms are poorly understood for viruses with double-stranded RNA (dsRNA) genomes. Two strains of the dsRNA virus reovirus differ in the pattern of packaged DVGs during serial passage. To determine whether the polymerase complex or gene segment sequence contributes to these differences, we exchanged polymerase complexes between the two reovirus strains. We identified DVG patterns using RT-PCR and recombination junction profiles using ClickSeq. Reoviruses synthesized DVGs that maintained the 5' and 3' termini and contained large central deletions. The polymerase complex did not detectably affect DVG pattern following reovirus serial passage or viral recombination junction profiles. Instead, recombination junction profiles correlated with the identity of viral RNA gene segments, even in the presence of a non-native polymerase complex or virus background. Reovirus recombination junction start and stop sites often occur in regions of sequence microhomology. While we observed many instances of short stretches of identical nucleotides within a viral gene segment, only a select few positions were incorporated into recombination junctions. Overall, these data suggest that recombination events that can mediate reovirus DVG formation are highly selective, and properties of viral gene segments primarily dictate where recombination occurs. These observations suggest a model for dsRNA virus recombination in which the polymerase pauses RNA synthesis and reinitiates further along the same template at a specific junction stop site that has sequence homology to the junction start site.IMPORTANCEViral infection gives rise to defective viral genomes (DVGs), which cannot complete a full replication cycle. Recombination facilitates DVG generation but is understudied for RNA viruses with double-stranded genomes. We found that for a double-stranded RNA (dsRNA) virus, reovirus, recombination occurs preferentially at specific sites in the genome that correspond with the identity of the gene segment. Recombination tends to initiate and terminate at sites sharing identical sequences. However, even if these short nucleotide sequences appear multiple times in a gene segment, only specific sites are used for recombination. Our results indicate that reovirus recombination is a highly orchestrated event in which individual gene segments contain the characteristics that drive recombination. These findings suggest that RNA properties, such as sequence and structure, drive recombination for dsRNA viruses, likely through reinitiation after re-hybridization of the newly formed RNA product with the same RNA template molecule at a different location.

Herpesviruses encode multiple factors that disarm innate immune signaling to evade host anti-viral responses. Several viral microRNAs expressed by Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV) disrupt the induction of type I interferons (IFN) and/or the subsequent signaling events activated through type I IFN receptors. Here, we aimed to determine whether non-human primate (NHP) γ-herpesviruses (rhesus lymphocryptovirus [rLCV], rhesus rhadinovirus [RRV], and Japanese macaque rhadinovirus [JMRV]), closely related to EBV and KSHV, use similar microRNA (miRNA)-mediated strategies to regulate IFN responses. Through functional screens, we identified multiple viral miRNAs that attenuated type I IFN-mediated activation of an IFN-stimulated response element reporter and diminished expression of interferon-stimulated genes (ISGs). Infection of primary cells with miRNA-deficient rLCVs resulted in augmented expression of ISGs. Abrogation of EBV BART miRNA homologs from rLCV, in particular, led to heightened sensitivity of latently infected cells to exogenous type I IFN. Through sequence analysis and reporter assays, we show that targets of these viral miRNAs include transcripts encoding the type I IFN receptors (IFNAR1, IFNAR2) and core components of JAK/STAT signaling pathways (JAK1, IRF9). Taken together, these data demonstrate that suppression of type I IFN responses is a conserved function for NHP γ-herpesvirus miRNAs and provide important mechanistic insight into how these viral miRNAs regulate type I IFN signaling pathways.IMPORTANCEGamma-herpesviruses establish life-long infections in their hosts. Evading anti-viral responses is a key component of long-term viral persistence. In this work, we show that small noncoding RNAs expressed by multiple non-human primate γ-herpesviruses regulate anti-viral responses by directly targeting components of the type I interferon (IFN) signaling pathway.

N6-methyladenosine (m⁶A) is the most abundant internal modification in eukaryotic RNA and plays diverse roles in RNA metabolism. Increasing evidence indicates that m⁶A is also present in viral RNAs, where it exerts virus-specific effects. While several studies have shown that m⁶A can facilitate viral replication, its antiviral mechanisms remain less understood. In this study, we used transmissible gastroenteritis virus (TGEV) as a model to investigate the inhibitory role of m⁶A in viral infection. We demonstrated that m⁶A modification is present in the TGEV genome and suppresses viral replication. The m⁶A reader proteins bind to viral RNA and reduce the stability of m⁶A-modified transcripts. Notably, TGEV infection increased global m⁶A levels in host RNA, particularly in interferon (IFN)-associated genes. Inhibition of m⁶A methylation significantly diminished IFN gene expression. Furthermore, compared to other viruses, TGEV genomic RNA displayed an abnormally higher m⁶A ratio, which can be distinguished by RIG-I to promote an immune response. Collectively, our findings reveal that high m⁶A modification enhances RIG-I-mediated sensing of TGEV RNA, leading to the activation of IFN responses and inhibition of viral replication. This study provides new insights into the complex regulatory functions of m⁶A during viral infection and host antiviral defense.IMPORTANCEN6-methyladenosine (m⁶A) is one of the most prevalent RNA modifications in viral genomes, but its functional impact varies widely across viruses. While m⁶A often promotes viral replication, it can exert inhibitory effects in certain viruses, particularly within the Flaviviridae and Coronaviridae families. Despite growing evidence of this antiviral role, the underlying mechanisms remain largely unclear. Here, we used transmissible gastroenteritis virus (TGEV), a swine coronavirus, as a model to explore the inhibitory function of m⁶A. We show that the TGEV genome harbors a relatively high density of m⁶A modification compared to other viruses and host mRNA, which are efficiently detected by the host pattern recognition receptor RIG-I. This interaction enhances innate immune activation and restricts viral replication. Our findings uncover the mechanism by which abnormal m⁶A modification can be sensed to activate antiviral immunity and provide deeper insight into the multifaceted role of m⁶A in host-virus interactions.

A prevailing model holds that human cytomegalovirus (HCMV) spreads cell-to-cell spread upon initial culturing from clinical specimens and that de novo mutations in the UL128-131 genes reduce expression of glycoprotein complex gH/gL/UL128-131 (pentamer) relative to gH/gL/gO (trimer), which in turn enhances virion infectivity and favors cell-free spread. The clone Merlin-BAC (ME) expresses far more pentamer than trimer and is highly cell-associated, whereas clone TB40-BAC4 (TB) expresses mostly trimer and spreads predominantly cell-free. A single G>T polymorphism in TB relative to ME was shown to impair UL128 mRNA splicing, reducing pentamer expression and enhancing infectivity and cell-free spread. However, enhanced cell-free spread of ME due to pentamer suppression did not come at the expense of efficient cell-to-cell spread, and cell-to-cell spread of TB was especially poor despite highly infectious intracellular virus. Most of the nucleotide diversity in the HCMV genome is due to 17 genes that have up to 14 alleles each, and TB and ME match at only two of the 17. Here, we report a set of recombinant HCMV generated by coinfecting cells with TB and ME. Trimer:pentamer ratio and virion infectivity largely aligned with the TB or ME UL128, with "TB-like" recombinants displaying more trimer and higher infectivity and "ME-like" recombinants displaying more pentamer and lower infectivity. Strikingly, some recombinants had shifts in preference for cell-free vs cell-to-cell spread without predicted changes to trimer:pentamer ratio or virion infectivity, demonstrating uncoupling of these phenotypes.IMPORTANCEThe emerging picture of HCMV genetic diversity in vivo prompts a reevaluation of how in vitro-characterized phenotypes, such as the abundance of different viral envelope glycoproteins, virion infectivity, and tendency toward cell-free or direct cell-to-cell spread, reflect viral characteristics in vivo. Laboratory examination of HCMV phenotypes has included a limited sampling of the apparent in vivo genetic diversity. A widely held model that directly links cell-free and cell-to-cell spread characteristics to glycoprotein display and virion infectivity also presumes that HCMV is predominantly cell-associated in vivo. These have implications for intervention strategies, such as calling into question the therapeutic benefit of neutralizing antibodies. Our finding that spread characteristics can be uncoupled from glycoprotein display and virion infectivity suggests a model that includes both cell-free and cell-associated spread as bona fide wild-type phenotypes for different allelic haplotypes. This model would allow a broader examination of neutralizing antibodies as correlates of protection.

Porcine epidemic diarrhea virus (PEDV) is a highly pathogenic alphacoronavirus that causes severe diarrhea. It has a high fatality rate among newborn piglets, posing a considerable economic burden to the swine industry. Therefore, elucidating the host-pathogen interaction is warranted to advance precision antiviral therapies. Herein, for the first time, we noted a marked upregulation of aldehyde dehydrogenase 1 family member L1 (ALDH1L1) during PEDV infection. Furthermore, ALDH1L1 exerts its antiviral effects by specifically binding to the viral nucleocapsid (N) and envelope (E) proteins and mediating their degradation via the autophagosome-lysosomal degradation pathway. Additional experiments revealed that this degradation process is mediated via the interactions of ALDH1L1 with the E3 ubiquitin ligase STUB1 and the cargo receptor TOLLIP, eliminating the N and E structural glycoproteins via the autophagolysosomal pathway. Our study findings suggest the ALDH1L1-STUB1-TOLLIP axis as a novel antiviral target and propose a new strategy for viral clearance based on the degradation of host protein. Furthermore, our research provides valuable information on how host antiviral factors impede PEDV replication as a regulator of the protein degradation pathway.IMPORTANCEPorcine epidemic diarrhea virus (PEDV) is a highly pathogenic alphacoronavirus that causes fatal hemorrhagic gastroenteritis among neonatal piglets. This causes significant financial losses. During infection, certain host factors can activate the innate immune regulatory network to antagonize the viral replication cycle, interfere with the virus invasion, inhibit virus replication, prevent virus assembly and release, and enhance the host's immune response. Our study revealed that the host metabolic enzyme ALDH1L1 acts as a novel antiviral restriction factor that mediates the autophagy-lysosome-targeted degradation of viral structural proteins (N/E) via the STUB1 (E3 ubiquitin ligase)-TOLLIP (autophagy adaptor protein) axis. Our study findings offer new perspectives on the mechanism by which host antiviral factors inhibit PEDV by regulating the protein degradation pathway.

As a unique antigenic variant of Newcastle disease virus (NDV) in pigeons, genotype VI NDVs cause serious disease in pigeons and pose a potential threat to domestic poultry. In this study, analyses of genetic variation and evolution of global genotype VI NDVs revealed the worldwide distribution and continuous evolution of genotype VI NDVs. Of importance, VI.2.1.1.2.1 and VI.2.1.1.2.2 are the two prevalent sub-genotypes worldwide. The virulence, replication capacity, and pathogenesis in chickens of representative strains from VI.2.1.1.2.1 and different clusters in VI.2.1.1.2.2 were further evaluated. Compared with the VI.2.1.1.2.1 strain, increased replication capacity and virulence in chickens were observed in strains of VI.2.1.1.2.2. VI.2.1.1.2.2 strains showed preferential binding for α-2,3-linked sialic acids and superior performance in viral entry, cell-cell fusion, and release of progeny virions. Evaluation with recombinant viruses demonstrated that residues at positions 365 and 497 in the HN protein contributed to the differences in biological characteristics of VI.2.1.1.2.2 strains, and residue 365 was a key determinant. Moreover, our results showed that the activity of the viral replication complex contributed to the differences in replication capacity among these viruses, with the P protein being the major individual contributor. The optimal effect was achieved when the NP and L proteins were homologous. Moreover, the 5' terminal trailer region was also found to be involved in the replication capacity of genotype VI NDVs; however, the viral V protein was not related to the replication and virulence of these viruses. Our findings highlight the potential risk of VI.2.1.1.2.2 NDVs due to their persistent circulation and evolution.

Importance: Genotype VI is the most diverse group of Newcastle disease viruses (NDVs). In addition to infectious disease in pigeons, the potential threat to chicken flocks and the public health implications associated with genotype VI NDVs also need to be addressed. Herein, comprehensive genetic evolution analysis revealed a global distribution pattern and continuous evolution of genotype VI NDVs worldwide. The biological characteristics of genotype VI NDVs belonging to different sub-genotypes were also evaluated. In particular, the widespread transmission, circulation, and constant evolution of currently prevalent sub-genotype VI.2.1.1.2.2 have led to the alteration of receptor binding preference, an increase in replication capacity, and a resultant increase in virulence in chickens. These findings expand our current understanding of the evolution and pathogenesis of genotype VI NDVs.