Journal of Virology最新文献

{"title":"Murine norovirus allosteric escape mutants mimic gut activation.","authors":"Michael B Sherman, Hong Q Smith, Faith Cox, Christiane E Wobus, Gillian C Lynch, B Montgomery Pettitt, Thomas J Smith","doi":"10.1128/jvi.00219-25","DOIUrl":"https://doi.org/10.1128/jvi.00219-25","url":null,"abstract":"<p><p>Murine norovirus (MNV) undergoes large conformational changes in response to the environment. The T=3 icosahedral capsid is composed of 180 copies of ~58 kDa VP1 that has N-terminal (N), shell (S), and C-terminal protruding (P) domains. In phosphate-buffered saline, the P domains are loosely tethered to the shell and float ~15 Å above the surface. At conditions found in the gut (i.e., low pH with high metal ion and bile salt concentrations), the P domain rotates and drops onto the shell with intra P domain changes that enhance receptor interactions while blocking antibody binding. Two of our monoclonal antibodies (2D3 and 4F9) have broad strain recognition, and the only escape mutants, V339I and D348E, are located on the C'D' loop and ~20 Å from the epitope. Here, we determined the cryo-EM structures of V339I and D348E at neutral pH +/-metal ions and bile salts. These allosteric escape mutants have the activated conformation in the absence of gut triggers. Since this conformation is not recognized by antibodies, it explains how these mutants evade antibody recognition. Dynamic simulations of the P domain further suggest that movement of the C'D' loop may be the rate-limiting step in the conformational change and that V339I increases the motion of the A'B'/E'F' loops compared to the wild-type (WT), facilitating the transition to the activated state. These findings have important implications for norovirus vaccine design since they uncover a form of the viral capsid that should lend superior immune protection against subsequent challenge by wild-type virus.IMPORTANCEImmune protection from norovirus infection is notoriously transient in both humans and mice. Our results strongly suggest that this is likely because the \"activated\" form of the virus found in gut conditions is not recognized by antibodies created in the circulation. By reversibly presenting one structure in the gut and a completely different antigenic structure in circulation, the gut tissue can be infected in subsequent challenges, while extraintestinal organs are protected. We find here that allosteric escape mutants to the most broadly neutralizing antibodies thwart recognition by transitioning to the activated state without the need for gut triggers (i.e., bile, low pH, or metal ions). These findings are significant because it is now feasible to present the activated form of the virus to the immune system (for example, as a vaccine) to better protect the gut tissue for longer periods of time.</p>","PeriodicalId":17583,"journal":{"name":"Journal of Virology","volume":" ","pages":"e0021925"},"PeriodicalIF":4.0,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144002476","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Advances in African swine fever virus molecular biology and host interactions contributing to new tools for control.","authors":"Linda K Dixon","doi":"10.1128/jvi.00932-24","DOIUrl":"https://doi.org/10.1128/jvi.00932-24","url":null,"abstract":"<p><p>African swine fever virus (ASFV) causes a frequently fatal hemorrhagic disease in domestic pigs and wild boar. The spread from Africa to Georgia in 2007 initiated a pandemic affecting many European and most Asian countries. This has had a very high socio-economic impact and threatens global food security. The virus is a large, complex, cytoplasmic DNA virus, the only member of the <i>Asfarviridae</i> family and codes for 170-190 proteins. Many of these have unknown functions and do not resemble other viruses or host proteins. This complexity has hindered the development of vaccines and other tools for control. The intensity of research has increased since the spread of ASFV in Europe and Asia, leading to rapid advances in knowledge. This review summarizes recent research, including the determination by cryogenic electron microscopy of the virus capsid structure and virion proteome. Novel information on the virus replication cycle, including mechanisms of virus entry into cells and the identification of host endosomal proteins important for entry, is summarized. Multiple, novel virus immune evasion proteins and their targets in the type I interferon response and inflammation pathways have been identified. The potential for the application of this knowledge to developing novel control tools, including modified live vaccines and other interventions targeting critical virus processes or host interactions, is discussed.</p>","PeriodicalId":17583,"journal":{"name":"Journal of Virology","volume":" ","pages":"e0093224"},"PeriodicalIF":4.0,"publicationDate":"2025-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143975413","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dexamethasone disrupts intracellular pH homeostasis to delay coronavirus infectious bronchitis virus cell entry via sodium hydrogen exchanger 3 activation.","authors":"Jun Dai, Yiyi Feng, Hong Long, Ying Liao, Lei Tan, Yingjie Sun, Cuiping Song, Xusheng Qiu, Chan Ding","doi":"10.1128/jvi.01894-24","DOIUrl":"https://doi.org/10.1128/jvi.01894-24","url":null,"abstract":"<p><p>Coronavirus entry into host cells enables the virus to initiate its replication cycle efficiently while evading host immune response. Cell entry is intricately associated with pH levels in the cytoplasm or endosomes. In this study, we observed that the sodium hydrogen exchanger 3 (Na⁺/H⁺ exchanger 3 or NHE3), which is strongly activated by dexamethasone (Dex) to promote cell membrane Na⁺/H⁺ exchange, was critical for cytoplasmic and endosomal acidification. Dex activates NHE3, which increases intracellular pH and blocks the initiation of coronavirus infectious bronchitis virus (IBV) negative-stranded genomic RNA synthesis. Also, Dex antiviral effects are relieved by the glucocorticoid receptor (GR) antagonist RU486 and the NHE3 selective inhibitor tenapanor. These results show that Dex antiviral effects depend on GR and NHE3 activities. Furthermore, Dex exhibits remarkable dose-dependent inhibition of IBV replication, although its antiviral effects are constrained by specific virus and cell types. To our knowledge, this is the first report to show that Dex helps suppress the entry of coronavirus IBV into cells by promoting proton leak pathways, as well as by precisely tuning luminal pH levels mediated by NHE3. Disrupted cytoplasmic pH homeostasis, triggered by Dex and NHE3, plays a crucial role in impeding coronavirus IBV replication. Therefore, cytoplasmic pH plays an essential role during IBV cell entry, probably assisting viruses at the fusion and/or uncoating stages. The strategic modulation of NHE3 activity to regulate intracellular pH could provide a compelling mechanism when developing potent anti-coronavirus drugs.IMPORTANCESince the outbreak of coronavirus disease 2019, dexamethasone (Dex) has been proven to be the first drug that can reduce the mortality rate of coronavirus patients to a certain extent, but its antiviral effect is limited and its underlying mechanism has not been fully clarified. Here, we comprehensively evaluated the effect of Dex on coronavirus infectious bronchitis virus (IBV) replication and found that the antiviral effect of Dex is achieved by regulating sodium hydrogen exchanger 3 (NHE3) activity through the influence of glucocorticoid receptor on cytoplasmic pH or endosome pH. Dex activates NHE3, leading to an increase in intracellular pH and blocking the initiation of negative-stranded genomic RNA synthesis of coronavirus IBV. In this study, we identified the mechanism by which glucocorticoids counteract coronaviruses in cell models, laying the foundation for the development of novel antiviral drugs.</p>","PeriodicalId":17583,"journal":{"name":"Journal of Virology","volume":" ","pages":"e0189424"},"PeriodicalIF":4.0,"publicationDate":"2025-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144008782","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"DEAD-box RNA helicase 10 inhibits porcine circovirus type 3 replication by interacting with the viral capsid protein and activating interferon responses.","authors":"Jianwei Zhou, Ning Zhu, Qianhong Dai, Haoyu Sun, Jie Zhao, Yonghui Qiu, Beiyi Zhou, Dedong Wang, Yongqiu Cui, Jinshuo Guo, Xufei Feng, Lei Hou, Jue Liu","doi":"10.1128/jvi.00576-25","DOIUrl":"https://doi.org/10.1128/jvi.00576-25","url":null,"abstract":"<p><p>Porcine circovirus type 3 (PCV3) is an emerging pathogen that causes porcine dermatitis and nephropathy syndrome-like symptoms, multisystemic inflammation, and reproductive failure. The PCV3 capsid (Cap) protein interacts with DEAD-box RNA helicase 10 (DDX10), a protein that functions primarily through regulating interferon (IFN)-β production to exert its antiviral activity. However, how the interaction between DDX10 and PCV3 Cap regulates viral replication remains unknown. We used Western blotting, interaction assays, and knockdown analyses to observe impaired PCV3 proliferation in transiently DDX10-overexpressing cells, as indicated by decreased viral protein expression levels and virus production. In contrast, PCV3 replication increased upon small interfering RNA-mediated <i>DDX10</i> depletion. Furthermore, DDX10 positively regulated IFN-β production and interferon-stimulated gene expression, inhibiting PCV3 replication. Mechanistically, PCV3 Cap co-localized and interacted with DDX10, and the N-terminal nuclear localization signal of PCV3 Cap and the helicase domain of DDX10 were essential for the Cap-DDX10 interaction. Furthermore, PCV3 infection decreases DDX10 expression to antagonize its antiviral activity. These results show that DDX10 antagonizes PCV3 replication by interacting with the PCV3 Cap protein and activating IFN-β responses, which provides important insight into the prevention and control of PCV3 infection.IMPORTANCEClarifying how host factors contribute to infection with PCV3, a newly discovered pathogen associated with multiple clinicopathological signs in swine, helps elucidate viral pathogenesis. The PCV3 Cap protein has been shown to interact with DDX10, a crucial protein that regulates RNA virus replication. Herein, we further demonstrated that DDX10 expression is downregulated in PCV3-infected cells and antagonizes the replication of PCV3 and that DDX10 increases interferon-β and interferon-stimulated gene levels to inhibit PCV3 replication by binding to the PCV3 Cap. In addition, PCV3 infection decreases DDX10 expression to antagonize its antiviral activity. These results reveal a molecular mechanism by which DDX10 antagonizes PCV3 replication by binding to the PCV3 Cap protein and activating IFN signals, thereby providing important targets for preventing and controlling PCV3 infection.</p>","PeriodicalId":17583,"journal":{"name":"Journal of Virology","volume":" ","pages":"e0057625"},"PeriodicalIF":4.0,"publicationDate":"2025-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144032865","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Clade 2.3.4.4b highly pathogenic avian influenza H5N1 viruses: knowns, unknowns, and challenges.","authors":"Zimin Xie, Jiayun Yang, Wanlin Jiao, Xueqing Li, Munir Iqbal, Ming Liao, Manman Dai","doi":"10.1128/jvi.00424-25","DOIUrl":"https://doi.org/10.1128/jvi.00424-25","url":null,"abstract":"<p><p>Since 2020, the clade 2.3.4.4b highly pathogenic avian influenza (HPAI) H5N1 viruses have caused unprecedented outbreaks in wild birds and domestic poultry globally, resulting in significant ecological damage and economic losses due to the disease and enforced stamp-out control. In addition to the avian hosts, the H5N1 viruses have expanded their host range to infect many mammalian species, potentially increasing the zoonotic risk. Here, we review the current knowns and unknowns of clade 2.3.4.4b HPAI H5N1 viruses, and we highlight common challenges in prevention. By integrating our knowledge of viral evolution and ecology, we aim to identify discrepancies and knowledge gaps for a more comprehensive understanding of the virus. Ultimately, this review will serve as a theoretical foundation for researchers involved in related avian influenza virus studies, aiding in improved control and prevention of H5N1 viruses.</p>","PeriodicalId":17583,"journal":{"name":"Journal of Virology","volume":" ","pages":"e0042425"},"PeriodicalIF":4.0,"publicationDate":"2025-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143999744","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A human cytomegalovirus prefusion-like glycoprotein B subunit vaccine elicits humoral immunity similar to that of postfusion gB in mice.","authors":"Krithika P Karthigeyan, Megan Connors, Christian R Binuya, Mackensie Gross, Adelaide S Fuller, Chelsea M Crooks, Hsuan-Yuan Wang, Madeline R Sponholtz, Patrick O Byrne, Savannah Herbek, Caroline Andy, Linda M Gerber, John D Campbell, Caitlin A Williams, Elizabeth Mitchell, Lara van der Maas, Itzayana Miller, Dong Yu, Matthew J Bottomley, Jason S McLellan, Sallie R Permar","doi":"10.1128/jvi.02178-24","DOIUrl":"https://doi.org/10.1128/jvi.02178-24","url":null,"abstract":"<p><p>Human cytomegalovirus (HCMV) is the leading infectious cause of birth defects. Despite the global disease burden, there is no Food and Drug Administration (FDA)-approved HCMV vaccine. The most efficacious HCMV vaccine candidates to date have used glycoprotein B (gB), a class III viral fusion protein, in its postfusion form. While some viral fusion proteins have been shown to elicit stronger neutralizing responses in their prefusion conformation, HCMV prefusion-like and postfusion gB were recently shown to elicit antibodies with similar fibroblast neutralization titers in mice. We aimed to define and compare the specificity and functionality of plasma IgG elicited by distinct prefusion-like and postfusion gB constructs. Prefusion-like and postfusion gB elicited comparable IgG responses that predominantly mapped to the AD-5 antigenic domain known to elicit neutralizing antibodies. Interestingly, postfusion gB elicited significantly higher plasma IgG binding to cell-associated gB and antibody-dependent cellular phagocytosis than that of prefusion-like gB. The vaccines elicited comparable neutralization titers of heterologous HCMV strain AD169r in fibroblasts; however, neither elicited neutralizing titers against the vaccine-matched strain Towne in fibroblasts. Our data indicate that gB in this prefusion-like conformation elicits similar specificity and functional humoral immunity to that of postfusion gB, unlike certain class I viral fusion proteins that have been used as vaccine antigens. These findings deepen our understanding of the immune response elicited by class III fusion proteins and may inform further design and testing of conformationally dependent herpesvirus glycoprotein vaccine candidates.IMPORTANCEVaccines against human cytomegalovirus (HCMV) still remain elusive in spite of the high disease burden of the virus, especially in pre-term infants and immunocompromised individuals. While vaccine efforts have focused on vaccine-induced antibodies to neutralize the virus, studies have increasingly shown the importance of other antibody functions in protection against cytomegalovirus (CMV) transmission. In this study, we comprehensively evaluated immune responses elicited by the prefusion state of an important HCMV protein called glycoprotein B (gB) in mice. Our results indicate that prefusion gB elicits immune responses similar to that of postfusion gB in mice and reveals areas for further redesign and testing for prefusion vaccine antigens against CMV and other herpesviruses, which could help in furthering vaccine development against HCMV.</p>","PeriodicalId":17583,"journal":{"name":"Journal of Virology","volume":" ","pages":"e0217824"},"PeriodicalIF":4.0,"publicationDate":"2025-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144008767","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Adaptive selection of quasispecies during <i>in vivo</i> passaging in chickens, mice, and ferrets results in host-specific strains for the H9N2 avian influenza virus.","authors":"Yiliang Li, Xi Quan, Rujian Chen, Xiao Wang, Yiting Chen, Yingde Gan, David M Irwin, Yongyi Shen","doi":"10.1128/jvi.00151-25","DOIUrl":"https://doi.org/10.1128/jvi.00151-25","url":null,"abstract":"<p><p>Sporadic human infections of avian influenza virus (AIV) raise significant public health concerns. A critical factor limiting the transmission of AIVs is the shift in receptor-binding preference from Siaα2,3 to Siaα2,6. To reveal the adaptive selection dynamics during the host adaptation process of AIVs, this study generated a viral library with random mutations in the HA gene of the H9N2 strain. Upon passaging the viral library in chickens and mice, the predominantly selected variants exhibited a preference for Siaα2,3 receptors. Notably, the wild-type strain remained dominant in both inoculated and direct-contact chickens, while variants with the ΔL226/R229I substitutions were preferentially selected in mice. Ferrets have a predominance of Siaα2,6 in their respiratory tract. As expected, the variant harboring the N289D mutation, which prefers Siaα2,6 binding, was enriched during <i>in vivo</i> passaging in ferrets. The mice-adapted variant with the ΔL226/R229I mutations causes reduced levels of TNF-α in the early days post-infection in mice, which correlated with an increase in its viral titers. Conversely, elevated levels of IL-6 and IL-1β at five dpi may contribute to the development of the cytokine release syndrome, potentially elucidating the higher fatality rate observed. In conclusion, based on the mutant spectra of the HA gene, this study elucidates the distinct quasispecies dynamics during the adaptation of H9N2 to different hosts, with receptor availability serving as one of the driving factors. Furthermore, a series of critical substitutions that influence the interspecific transmission potential of H9N2 AIVs were identified.IMPORTANCEThe mutation of viruses creates a quasispecies reservoir. In this study, we aimed to investigate the dynamics of quasispecies during the host adaptation of AIVs. We generated a viral library with random mutations in the HA gene of H9N2 and conducted serial passaging in chickens, mice, and ferrets for five generations, respectively. The wild-type strain was dominant in chickens, while mice selected viruses with the ΔL226/R229I substitutions. Both variants showed a preference for binding to Siaα2,3, which aligned with the abundance of Siaα2,3 found in the respiratory tract epithelial cells of chickens and mice. In ferrets, where Siaα2,6 is more prevalent, the variant with the N289D mutation, which prefers Siaα2,6, was found to be enriched. In summary, this study revealed the adaptive selection of H9N2 quasispecies in various hosts, contributing to our understanding of AIV host adaptation.</p>","PeriodicalId":17583,"journal":{"name":"Journal of Virology","volume":" ","pages":"e0015125"},"PeriodicalIF":4.0,"publicationDate":"2025-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144000798","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Schmallenberg virus non-structural proteins NSs and NSm are not essential for experimental infection of <i>Culicoides sonorensis</i> biting midges.","authors":"Kerstin Wernike, Ana Vasic, Susanne Amler, Franziska Sick, Cristian Răileanu, Oliver Dähn, Helge Kampen, Cornelia Silaghi, Martin Beer","doi":"10.1128/jvi.00343-25","DOIUrl":"https://doi.org/10.1128/jvi.00343-25","url":null,"abstract":"<p><p>The teratogenic orthobunyavirus Schmallenberg virus (SBV) is transmitted between its mammalian hosts by <i>Culicoides</i> biting midges. The genome of circulating SBV, i.e., variants present in viremic ruminants or insect vectors, is very stable, while variants found in malformed ruminant fetuses display a high genetic variability. It was suggested that fetal infection provides an environment that favors viral mutations that enable immune escape in the unborn but at the cost of limiting the ability of the virus to spread further. To investigate infection and dissemination rates of different SBV variants in the insect vectors, we fed laboratory-reared <i>Culicoides sonorensis</i> with blood containing the prototype strain BH80/11-4 from a viremic cow or strain D281/12, which was isolated from the brain of a sheep fetus and harbors multiple mutations in all three genome segments. Furthermore, virus variants lacking NSs, NSm, or both non-structural proteins were included. Six days after feeding, virus replication was found in about 2% of the midges exposed to wild-type strain BH80/11-4. The absence of the non-structural proteins had no obvious effect on the oral susceptibility to virus infection, as after 6 days, 2.78% of the midges fed with the NSs-deletion mutant displayed viral loads higher than the respective day-0 group, 1.92% of the midges exposed to the NSm-deletion mutant, and 1.55% of midges exposed to the NSs/NSm-deletion mutant. In contrast, strain D281/12 did not replicate at all in the midges, supporting the assumption that SBV variants arising in infected fetuses are unable to enter the normal insect-mammalian host cycle.IMPORTANCEBiting midges are responsible for the transmission of Schmallenberg virus (SBV), a pathogen of veterinary importance that primarily infects ruminants. Although SBV has been extensively studied in the mammalian host, the virus-intrinsic factors allowing infection of and replication in biting midges are largely unknown. Therefore, we infected laboratory-reared <i>Culicoides sonorensis</i> midges with SBV variants by feeding them virus-containing blood. The SBV variants differed in their genome composition, as we used the prototype wild-type strain, a strain with multiple mutations that was isolated from the brain of a malformed fetus, and recombinants lacking either NSs or NSm or both of these non-structural proteins. While the non-structural proteins had no obvious effect, the variant from the malformed fetus did not replicate at all, indicating that virus variants with characteristic genomic mutations present in fetuses lose their ability to infect the insect vector and will be excluded from the natural transmission cycle.</p>","PeriodicalId":17583,"journal":{"name":"Journal of Virology","volume":" ","pages":"e0034325"},"PeriodicalIF":4.0,"publicationDate":"2025-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144032893","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ineffectual immunity in a resurrected mouse model of persistent viremia.","authors":"Kylie Nennig, Teressa Shaw, Logan Borsinger, Adam L Bailey","doi":"10.1128/jvi.00248-25","DOIUrl":"https://doi.org/10.1128/jvi.00248-25","url":null,"abstract":"<p><p>Viruses that establish persistent (i.e., chronic) infections have evolved sophisticated strategies to avoid clearance by the host immune system. This is particularly true for viruses that infect immunocompetent mammals and sustain high infectious burdens in body sites under intense immune surveillance (i.e., the blood, a.k.a., \"viremia\"). Historically, lymphocytic choriomeningitis virus (LCMV) infection of laboratory mice has served as a powerful model to understand mechanisms of failed immunity, but other viruses may have unique and underappreciated persistence strategies. Here, we resurrect a bygone model of viral persistence-lactate dehydrogenase-elevating virus (LDV)-and use modern transgenic mouse technologies to investigate various aspects of anti-viral immunity. We find that interferons have a modest impact on LDV replication, with interferon-alpha blunting LDV viremia in the acute phase of the infection and interferon-gamma reducing LDV viral loads in the chronic phase of infection, but only when paired with an intact interferon-alpha response. Adaptive immunity, assessed in Rag-knockout mice, had only a modest impact on LDV viremia, and only during the sub-acute phase of infection. Mice lacking the critical immune checkpoint molecule PD-1 showed no signs of disease and supported LDV viral loads at levels equivalent to their wild-type counterparts. Altogether, these results point to a novel and highly effective mechanism of persistence that is minimally impacted by conventional aspects of anti-viral immunity or immune exhaustion-a rarity among persistent viruses. Given the relative paucity of chronic infection models in the laboratory mouse, LDV infection may be useful for exploring unique modes of immune system failure.</p><p><strong>Importance: </strong>Viruses that infect a host over long periods of time have evolved unique strategies to evade the host immune system. Of particular interest are viruses that cause persistent infection in the laboratory mouse-the most well-developed tool for studying the mammalian immune system. Here, we resurrected a model of persistent RNA virus infection (lactate dehydrogenase-elevating virus, LDV) and applied modern tools of mouse immunology to further characterize its persistence. We found that host factors that typically have a dramatic effect on viral infections-e.g., the interferon system and lymphocytes-had very little impact on LDV infection. Removing \"checks\" on immune activation also had little effect on the virus or host health. Altogether, these findings imply that LDV uses a unique and highly effective mechanism to avoid immune clearance. Understanding this mechanism has implications for understanding ways in which the immune system fails.</p>","PeriodicalId":17583,"journal":{"name":"Journal of Virology","volume":" ","pages":"e0024825"},"PeriodicalIF":4.0,"publicationDate":"2025-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144002743","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"How to recover from a bad start: adaptation of HIV-1 transcription start site mutants during serial passaging in culture.","authors":"Olga A Nikolaitchik, Akhil Chameettachal, Saiful Islam, Zetao Cheng, Krista Delviks-Frankenberry, Brandon F Keele, Vinay K Pathak, Wei-Shau Hu","doi":"10.1128/jvi.00159-25","DOIUrl":"https://doi.org/10.1128/jvi.00159-25","url":null,"abstract":"<p><p>HIV-1 uses neighboring sequences as transcription start sites and generates multiple unspliced transcripts, including two major transcripts with three guanosines (3G) or one guanosine (1G) at the 5' end. Although only differing by 2-nt, 3G RNA and 1G RNA are functionally distinct. We have previously generated two mutants: the TTG virus mainly expresses 1G RNA, whereas the plusAC virus predominantly expresses 3G RNA. Both mutant viruses are replication-competent but exhibit fitness defects. Here, we passaged the plusAC virus in T cells and characterized the changes near the transcription start sites. We observed the rapid loss of the plusAC virus genotype and the emergence of multiple revertants. All major revertants that dominated the cultures had a 1- to 3-nt deletion that compensated for the dinucleotide insertion in the plusAC virus. These major revertants express more than one major transcript, preferentially package 1G RNA, and have improved replication kinetics compared with the plusAC virus. Most major revertants likely arose through errors during reverse transcription, including misalignments during minus-strand DNA transfer, nucleotide deletion in a homopolymer run, or deletion of a short direct repeat. Additionally, we have determined that a T-to-G substitution near transcription start sites occurs at ~5% per replication cycle by copying the guanosine cap. Converting a base to guanosine through cap copying has been observed in multiple positions, but always directly upstream of a major transcription start site. Taken together, our findings demonstrate the selection pressure for expressing functionally distinct unspliced RNA species to optimize replication fitness.IMPORTANCEHIV-1 unspliced RNA serves as the mRNA to translate Gag/Gag-Pol polyproteins and as the virion genome. HIV-1 produces two major RNA species: 1G RNA is preferentially packaged and 3G RNA is favorably translated, although each transcript can perform both functions. We have previously generated a replication-competent mutant virus that mainly expresses 3G RNA and observed that this mutant has replication fitness defects. We found that the mutant virus improved its replication kinetics after passaging, indicating adaptation. Our analyses showed that, through mutations occurring during DNA synthesis, multiple revertants arose rapidly to replace the input mutant virus. The major revertants regained the ability to generate more than one major transcript and preferentially package 1G RNA. These results highlight the importance of expressing HIV-1 RNA species that serve distinct functions and the ability of HIV-1 to adapt through mutations in the genome.</p>","PeriodicalId":17583,"journal":{"name":"Journal of Virology","volume":" ","pages":"e0015925"},"PeriodicalIF":4.0,"publicationDate":"2025-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144017304","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}