Journal of Virology最新文献

Bovine viral diarrhea virus (BVDV) is a major animal pathogen with a broad host range, causing gastrointestinal, respiratory, and reproductive diseases in cattle worldwide. BVDV exists as two biotypes: cytopathic (cp) and non-cytopathic (ncp). Although both cpBVDV and ncpBVDV have developed sophisticated strategies to evade or subvert host antiviral innate immune response, the underlying mechanisms remain incompletely understood. Autophagy, a process essential for maintaining cellular homeostasis, plays an important role in regulating viral replication and antiviral immunity. In this study, we demonstrated that the induction of autophagy with rapamycin enhanced the production of infectious progeny for both cpBVDV and ncpBVDV, whereas pharmacological inhibition of autophagy with 3-MA reduced viral yields. We further showed that modulating autophagy significantly influenced the early stages of the viral life cycle and the production of type I IFN (IFN-I). Notably, overexpression of BECN1 suppressed the synthesis of IFN-α and IFN-β, thereby promoting the replication of both cpBVDV and ncpBVDV. Conversely, RNA interference-mediated knockdown of BECN1 potentiated the antiviral innate immune response and restricted viral replication. Mechanistically, BECN1 was found to inhibit RIG-I-MAVS pathway activation by promoting ubiquitination and subsequent degradation of mitochondrial antiviral signaling (MAVS) protein, leading to suppression of IFN-I production. Additionally, both cpBVDV and ncpBVDV were shown to induce autophagy via the ROS-endoplasmic reticulum stress axis. These findings deepen our understanding of how BVDV evades host immunity and may inform the development of preventive strategies against BVDV infection.

Importance: Bovine viral diarrhea virus (BVDV), the causative agent of bovine viral diarrhea-mucosal disease, is a major global threat to cattle health. BVDV employs sophisticated strategies to evade host defense and facilitate its replication. Understanding these mechanisms is crucial for developing effective vaccines and antiviral agents. Our study elucidates how cytopathic BVDV and non-cytopathic BVDV subvert the host's antiviral innate immune response by exploiting autophagy to inhibit the RIG-I-MAVS pathway. A key finding is that BECN1-mediated autophagy directly targets MAVS protein for degradation via a specific BECN1 and MAVS interaction. Furthermore, we demonstrate that BVDV activates autophagy through ROS-ER stress axis to promote its replication. These insights reveal a novel immune evasion mechanism of BVDV and highlight the therapeutic potential of autophagy inhibition in treating BVDV-related diseases.

Introduced mammalian species in Aotearoa New Zealand pose significant ecological risks and may serve as reservoirs for novel or emerging infectious diseases. In this study, we present the first metatranscriptomic survey of viruses in five introduced mammals: ferrets (Mustela furo), stoats (Mustela erminea), weasels (Mustela nivalis), brushtail possums (Trichosurus vulpecula), and European hedgehogs (Erinaceus europaeus), sampled across both the North and South Islands. Through total RNA sequencing, we identified 11 mammalian-infecting viruses spanning eight viral families, including four novel virus species: Ferret mastadenovirus, Possum astrovirus, Ferret pestivirus, and Weasel jeilongvirus. Whole genomes were recovered for six of these viruses, enabling detailed phylogenetic analysis. Notably, we observed strong global geographic clustering in both Wobbly possum disease virus and Ferret hepatitis E virus, suggesting localized viral evolution following the introduction of their hosts into New Zealand. In addition, the detection of Human rotavirus A in hedgehogs highlights the possibility of reverse zoonotic transmission. Together, these findings broaden our understanding of the viral diversity harbored by New Zealand's introduced mammals and provide a critical foundation for future biocontrol and disease surveillance efforts.IMPORTANCEIntroduced mammals in Aotearoa New Zealand not only threaten native biodiversity through predation and competition, but also represent a largely overlooked source of infectious disease risk. Viruses circulating in these species may spill over into native wildlife, livestock, or even humans, while human viruses can also establish in introduced animals and create new reservoirs. Understanding which viruses are present, and how they evolve in isolated host populations, is critical for anticipating future disease outbreaks, improving biosecurity, and guiding wildlife management strategies. This work provides foundational knowledge that links ecology, conservation, and health, highlighting the need to consider pathogens as part of the broader impact of invasive species.

Glycoprotein M (gM) of human cytomegalovirus (HCMV) forms a conserved protein complex with glycoprotein N (gN), whose precise function in viral morphogenesis is poorly understood. To elucidate the function of the gM/gN complex in secondary envelopment, we employed a combination of viral mutants, siRNA knockdown, and ultrastructural analyses. Ultrastructural examination of a mutant virus with a cysteine-to-serine mutation in the cytoplasmic tail of gN (TB-gN-C123S) showed a defect in the initiation of secondary envelopment as most capsids in TB-gN-C123S-infected cells were either not in contact with cytoplasmic membranes or, when near membranes, lacked signs of budding. The defect in secondary envelopment was associated with an accumulation of partially tegumented capsids in the peripheral region of the cytoplasmic viral assembly compartment (cVAC). Additionally, large protein aggregates were observed within and near the cVAC, often associated with non-enveloped capsids. A comparable ultrastructural phenotype was observed in wild-type virus-infected cells treated with siRNA against gM. Further evidence underscoring the role of the gM/gN glycoprotein complex in viral morphogenesis was obtained by investigating gM- and gN-null mutants, which displayed the same altered capsid distribution observed in TB-gN-C123S infections and after siRNA knockdown of gM. Finally, the inhibition of palmitoylation in wild-type virus-infected cells resulted in analogous defects, including an accumulation of partially tegumented capsids in the periphery of the cVAC and protein aggregates associated with capsids. In summary, our findings indicate a crucial role for the gM/gN complex in initiating secondary envelopment and highlight the involvement of palmitoylation in this process.IMPORTANCEHuman cytomegalovirus (HCMV) is a widespread herpesvirus that can cause severe illness in newborns and immunocompromised individuals. Like other herpesviruses, HCMV assembles its infectious particles through a complex process where the virus acquires its envelope through secondary envelopment. In this study, we investigated the role of glycoprotein M (gM) and glycoprotein N (gN), which form a conserved complex across herpesviruses. Using genetic mutants, RNA interference, and electron microscopy, we found that the gM/gN complex is crucial for initiating secondary envelopment. Disruption of gM or gN function, or palmitoylation inhibition, prevents capsids from budding into membranes, resulting in partially tegumented capsids that accumulated at the periphery of the cytoplasmic viral assembly compartment (cVAC). Our findings highlight the important role of the gM/gN complex and palmitoylation in HCMV assembly and suggest that the assembly occurs in a spatially organized manner within the cVAC, providing new insights into how herpesviruses produce infectious particles.

Venezuelan equine encephalitis virus (VEEV) is an arbovirus that causes a disease in which 4%-14% of individuals can develop neurological symptoms. Prior to 1970, VEEV was developed as a biological threat agent due to its stability and high morbidity when administered by aerosol. Currently, no FDA-licensed vaccines nor therapeutics for VEEV exist. Single-domain antibodies (sdAbs) may provide a therapeutic option due to their small size and ability to bind recessed epitopes not recognized by conventional antibodies. This study identified two bivalent sdAbs that were able to protect mice from a lethal challenge against both epizootic and enzootic subtypes of VEEV. Cryo-EM structures of sdAb-VEEV complexes revealed the sdAbs that comprised the bivalent sdAbs to recognize a mixture of conserved and non-conserved regions of the VEEV envelope proteins. While all three of the cryo-EM-characterized epitopes were unique in terms of their recognized VEEV residues, two sdAbs, V2B3 and V2C3, overlapped sterically, explaining why only their combinations with the non-sterically overlapping sdAb V3A8f, which composed the bivalent sdAbs described here, were so particularly effective. Binding and neutralization studies found that the bivalent sdAbs have the potential to be broad-spectrum anti-alphavirus therapeutics as they cross-neutralize multiple alphaviruses.IMPORTANCEAlphaviruses are no longer geographically constrained to one region of the world but are expanding to be of global concern. In many regions of the world, multiple alphaviruses co-circulate; therefore, having a therapeutic that is pan-alphavirus is important. A cocktail of multiple pan-alphavirus binding/neutralizing antibodies (Abs) may provide optimal coverage against alphaviruses while decreasing the prevalence of viral escape mutants, which could cause the therapeutic to no longer be efficacious. Structures of these Abs, defining their recognition, could assist in identifying optimal combinations. A bivalent pan-alphavirus single-domain antibody could be used in a cocktail with already identified alphavirus IgG antibodies.

Virus emergence is often due to cross-species transmission and adaptation to the new host. We studied the effect of innate immune responses on shaping virus populations in native and nonnative virus-host combinations, using as a model system Drosophila melanogaster infected with either Drosophila C virus (DCV) or cricket paralysis virus (CrPV). In this host, the cGAS-like receptor 1 senses viral double-stranded RNA and produces cyclic dinucleotides (CDNs) to activate the STING protein and induce an antiviral response. Both viruses were serially passaged in three host conditions differing in their cGAS-STING response: wild-type (WT) flies, Sting knock-out (KO) flies, and flies with a primed immune response by CDN injection. We found no immune-related effects on virus evolution, but we uncovered the CrPV nonstructural 2B protein as a key regulator of cross-species transmission. Nucleotide diversity specifically accumulated in the 2B gene during passage of CrPV in its nonnative Drosophila host, while 2B of the fly-adapted DCV displayed markedly lower and constant nucleotide diversity. In particular, the CrPV 2B D29N variant was selected in all six virus lineages evolved in WT and Sting KO flies, with an estimated selection coefficient greater than 0.2. This variant replicated faster and was more lethal than the parental virus in all three host backgrounds. 2B is a predicted transmembrane protein, which we found to be associated with cellular endomembranes and may be involved in replication organelle formation. Our findings suggest a role for the 2B protein in adaptation to a new host independent of the cGAS-STING pathway.

Importance: The forces driving virus evolution are central to understanding cross-species transmission and virus emergence. It is well established that the adaptive immune system drives virus evolution in mammals, but whether innate responses likewise drive virus evolution upon host shifts is less well understood. In this manuscript, we used Drosophila melanogaster as a model to study the evolution of a native and a nonnative pathogen under conditions in which innate antiviral immunity is either abolished or enhanced. Using an experimental evolution approach, we find little evidence for adaptive evolution of the natural pathogen Drosophila C virus. In contrast, we observed a recurrent adaptive mutation in the viral nonstructural 2B protein in the nonnative cricket paralysis virus, independent of the antiviral cGAS/STING pathway. Our work provides insights into viral adaptation to new hosts and the characteristics of the 2B protein of dicistroviruses, a family comprising important model insect viruses.

Hepatitis E virus (HEV) is a viral hepatitis pathogen that poses a significant threat to global human health, representing a serious yet long-overlooked public health concern. In this study, we identified glucose-regulated protein 75 (GRP75) as an interaction partner of HEV-ORF2 using recombinant ORF2 truncation as bait. The substrate-binding domain of GRP75 interacted with HEV-ORF2 and inhibited HEV replication by facilitating HEV-ORF2 degradation. Further analysis revealed that HEV-ORF2 contains three KFERQ-like motifs, the key signature sequence required for chaperone-mediated autophagy (CMA). Our data demonstrated that GRP75-mediated degradation of HEV-ORF2 was heat-shock cognate protein 70 (HSC70)-dependent, although no direct interaction between HSC70 and ORF2 was detected. Instead, GRP75, together with HEV-ORF2 and HSC70, formed a complex that mediated CMA-dependent degradation of HEV-ORF2, whereas deletion of all three KFERQ-like motifs from ORF2 conferred resistance to such processes. Additionally, GRP75 blocked mitochondrial transport of HEV-ORF2, potentially mitigating ORF2's function as an interferon (IFN) induction antagonist. Furthermore, GRP75 enhanced the interaction between mitochondrial antiviral signaling protein (MAVS) and TANK-binding kinase 1 (TBK1), promoting IFN-β production and ultimately inhibiting HEV infection. In conclusion, our findings identify GRP75 as a novel restriction factor for HEV infection and provide new insights into its role in CMA and antiviral innate immunity.

Importance: Due to the lack of an effective in vitro model, the viral-host interaction of HEV remains largely elusive. This study uncovers a novel mechanism by which GRP75 inhibits HEV infection. On one hand, the GRP75 protein facilitates the degradation of HEV-ORF2 through the lysosome-associated, chaperone-mediated autophagy by recognizing KFERQ-like motif presented on HEV-ORF2. On the other hand, GRP75 enhances the production of IFN-β by promoting interaction between MAVS and TBK1, thereby establishing an antiviral state and suppressing HEV infection. This research expands our current understanding of host resistance to HEV and provides a new function of GRP75, suggesting that GRP75 might be a novel antiviral factor against virus infection.

Rotavirus (RV) infection remains a leading cause of hospitalization and mortality among infants and young children. Despite global implementation of RV vaccines, hundreds of thousands of infants and young children still succumb to this disease each year due to ineffective treatment. In this study, we demonstrated that NVP-HSP990, a novel small-molecule heat shock protein 90 (HSP90) inhibitor, inhibited RV infection with a fascinatingly higher selectivity index compared to conventional HSP90 inhibitors like geldanamycin and its derivative tanespimycin (17-allylamino-17-demethoxygeldanamycin [17-AAG]). NVP-HSP990 effectively inhibited RV replication in vitro without blocking the initial establishment of infection. NVP-HSP990 restored host gene expression in most KEGG pathways disrupted by RV infection in Caco-2 cells, except some inflammatory pathways (such as IL-17 and TNF pathways). NVP-HSP990 significantly inhibited RV-induced activation of the MAPK pathway and prevented the disruption of tight junctions in Caco-2 cells. More importantly, NVP-HSP990 effectively suppressed RV infection in BALB/c suckling mice and significantly alleviated RV-induced diarrhea.IMPORTANCERotavirus (RV) infection poses a global health threat with an urgent need for targeted antiviral therapies. Here, we identified NVP-HSP990 as a next-generation HSP90 inhibitor with exceptional translational potential against RV infection. Compared to conventional HSP90 inhibitors, NVP-HSP990 demonstrated markedly enhanced anti-RV selectivity. NVP-HSP990 effectively reversed dysregulation of key host pathways in RV infection while selectively modulating pro-inflammatory responses, thereby balancing antiviral and immunopathological outcomes. NVP-HSP990 also blocked MAPK-driven tight junction disruption to preserve intestinal barrier integrity. As a result, NVP-HSP990 significantly alleviated the severity of RV-induced diarrhea. Given its excellent oral efficacy and systemic penetration previously reported, NVP-HSP990 emerges as a promising HSP90-targeted candidate capable of addressing both intestinal and possible extraintestinal RV infections, which also repositions HSP90 inhibition as a viable strategy in RV management.

Canine distemper virus (CDV, species Morbillivirus canis) is a highly contagious pathogen with a broad host range among carnivores. In common with measles virus, alveolar macrophages (AMs) are among the first target cells of infection in the respiratory tract. Therefore, in vitro infections of primary canine AMs were performed with the attenuated Onderstepoort (Ond) and field R252 strain of CDV over a period of 6 days. This showed that AMs are permissive to CDV infection and that such infections are productive with respect to the release of new virus particles. Phenotypic differences were observed over the entire course of the experiment, as higher levels of infection and virus production were observed in CDV R252-infected AMs, while infection with CDV Ond resulted in more prominent cytopathic effects, including syncytium formation. Transcriptome analyses of samples from 1 day post-infection via total RNA sequencing demonstrated further marked differences with respect to the pro-inflammatory response and cell death pathways. CDV Ond-infected AMs exhibited robust induction of pro-inflammatory mediators including type I interferon-related signaling pathways, whereas CDV R252-infected cells showed much weaker expression of these pathways. These transcriptomic differences were further highlighted by the detection of the highest rates of cell apoptosis and lactate dehydrogenase activity in the supernatants of CDV Ond-infected AM cultures over the entire course of the experiment. In addition, transcriptome differences indicate disturbances of homeostatic AM functions associated with CDV infection. These results provide insights into early events in the pathogenesis of CDV infection and mechanisms underlying vaccine strain attenuation.IMPORTANCEMorbilliviruses, including canine distemper virus (CDV) and human measles virus, cause severe systemic disease with respiratory distress, immunosuppression, and neurologic signs. While natural infection in dogs has become rare due to efficient vaccination, outbreaks in wildlife populations can be devastating, and concerns about zoonotic potential of CDV have been raised. The impact of CDV infection on the transcriptome of alveolar macrophages has not been elucidated thus far. Knowledge about early events in CDV pathogenesis and phenotypic consequences of vaccine attenuation is therefore necessary to protect endangered wildlife populations and might furthermore serve as a model for human measles. This study presents the first transcriptomic analyses of primary AMs during the initial phase of morbillivirus infection. These results provide insights into early events in the pathogenesis of CDV infection and mechanisms serving to restrict the spread of an attenuated virus strain.