Journal of Virology最新文献

SARS-CoV-2 poses an ongoing threat to human health as variants continue to emerge. Several effective vaccines are available, but a diminishing number of Americans receive the updated vaccines (only 22% received the 2023 update). Public hesitancy towards vaccines and common occurrence of "breakthrough" infections (i.e., infections of vaccinated individuals) highlight the need for alternative methods to reduce viral transmission. SARS-CoV-2 enters cells by fusing its envelope with the target cell membrane in a process mediated by the viral spike protein, S. The S protein operates via a Class I fusion mechanism in which fusion between the viral envelope and host cell membrane is mediated by structural rearrangements of the S trimer. We previously reported lipopeptides derived from the C-terminal heptad repeat (HRC) domain of SARS-CoV-2 S that potently inhibit fusion by SARS-CoV-2, both in vitro and in vivo. These lipopeptides bear an attached cholesterol unit to anchor them in the membrane. Here, to improve prospects for experimental development and future clinical utility, we employed structure-guided design to incorporate charged residues at specific sites in the peptide to enhance aqueous solubility. This effort resulted in two new, potent lipopeptide inhibitors.

Importance: Despite the existence of vaccines for SARS-CoV-2, the constant evolution of new variants and the occurrence of breakthrough infections highlight the need for new and effective antiviral approaches. We have shown that lipopeptides designed to bind a conserved region on the SARS-CoV-2 spike protein can effectively block viral entry into cells and thereby block infection. To support the feasibility of using this approach in humans, we re-designed these lipopeptides to be more soluble, using information about the structure of the spike protein interacting with the peptides to modify the peptide chain. The new peptides are effective against both SARS-CoV-2 and MERS. The lipopeptides described here could serve as treatment for people who are unvaccinated or who experience breakthrough infections, and the approach to increasing solubility can be applied in a broad spectrum approach to treating infections with emerging viruses.

Porcine epidemic diarrhea, as a porcine epidemic diarrhea virus (PEDV)-induced infectious intestinal condition typified by diarrhea, emesis, dehydration, and anorexia, leads to death rates as high as 100% among suckling piglets. Given the existing commercial vaccines, it is essential to study host-virus interactions and formulate efficient anti-viral regimes. This study concerned a host factor POLM (a DNA polymerase family member) that exerts an anti-viral effect against PEDV proliferation. Our results indicated that POLM expression was increased following PEDV infection and was regulated by the transcription factor FOXA1. In addition, our findings indicated that POLM targeted and degraded PEDV structural proteins (N, S2, and M) by the autophagy pathway to inhibit PEDV proliferation. POLM could recruit the E3 ubiquitination ligase MARCH8 for N, S2, and M protein ubiquitination, which was subsequently recognized by p62, a cargo receptor, for translocation to the autophagic lysosome, therefore degrading the N, S2, and M proteins and preventing PEDV proliferation. In summary, we showed a novel therapeutic target for combating PEDV, i.e., using the POLM-MARCH8-p62-autophagosome pathway to degrade the PEDV N, S2, and M proteins.IMPORTANCEPEDV is a coronavirus that causes high mortality in piglets, which poses significant economic damage to swine farming. During PEDV infection, the host cells may promote the natural anti-viral immune response to suppress viral replication through a variety of potential host factors. In this study, we found upregulation of a host factor POLM by FOXA1 (a transcription factor) during PEDV infection. It was indicated that POLM could be a new anti-viral protein against the PEDV replication, which interacted with MARCH8 (an E3 ubiquitin ligase) and p62 (a cargo receptor) to facilitate the PEDV N, S2, and M protein degradation via the autophagy process. Apart from elucidating a previously unidentified anti-viral function of POLM, this study also provides a novel perspective for studying host anti-viral factors that act as regulators of anti-PEDV protein degrading pathways.

Venezuelan, western, and eastern equine encephalitis virus (VEEV, WEEV, and EEEV) cause a febrile illness that may result in fatal neurological disease in humans and equines. Human infections are typically from mosquito bites, although cases from respiratory exposure in laboratory accidents have been documented. In addition to natural mosquito-borne infection, the potential biothreat inherent in the ability to disseminate these viruses via the respiratory route has driven the development of antiviral drugs for this route of exposure. To address this gap, we tested the prophylactic administration of a novel brain-penetrant, antiviral, BDGR-49, against a lethal intranasal challenge of VEEV, WEEV, or EEEV in BALB/c mouse model. BDGR-49 conferred 100% protection with 6 mg kg^-1 twice per day for 6 days for VEEV, but not EEEV or WEEV. By 8 days post-infection (dpi), infectious virus, viral RNA, and viral antigen in the brain of BDGR-49-treated mice were significantly reduced. Brains of VEEV TrD-infected, BDGR-49-treated mice showed a significant reduction in the expression of genes associated with inflammation (IFNB1, TNF, IL6, and CCL5) and cell death (CASP4, GSDMD, PYCARD, and ZBP1). At dpi 14, histopathology showed that neuronal lesions and inflammatory cell infiltrates were essentially absent, and viral antigen was not detected in the brains of VEEV TrD-infected, BDGR-49-treated mice. In summary, although BDGR-49 treatment showed significant promise for the treatment of mice exposed intranasally to VEEV, the more rapid and efficient entry of EEEV and WEEV by this route into the central nervous system will require additional optimization of the dosing regimen.IMPORTANCEProphylactic and therapeutic treatment of viruses that cause encephalitis requires fast-acting drugs that rapidly penetrate the blood-brain barrier. Currently, clinicians have only a limited set of antivirals for the treatment of neurotropic infections such as herpesviruses or HIV-1, and none for alphaviruses, and treatment outcomes remain poor. New medical countermeasures will address the gap in treatment of viral encephalitis such as those caused by the neurotropic alphaviruses and others.

RIG-I and MDA5, known as the RIG-I-like receptors (RLRs), play a pivotal role in inducing antiviral responses to RNA viral infections. While chickens lack RIG-I, they possess a functionally enhanced MDA5 that recognizes pathogens and regulates immunity, underscoring the critical role of MDA5 in maintaining immune homeostasis in chickens. However, the precise mechanisms governing the expression and optimal activation of MDA5 remain unclear. Here, we reveal that the chicken E3 ubiquitin ligase RNF20 is essential for modulating MDA5-mediated innate immune homeostasis. Transcriptome sequencing analysis revealed that RNA viral infection of DF-1 cells significantly upregulated the expression of chicken RNF20. Overexpression of RNF20 markedly suppresses the expression of chicken innate immunity-related genes, while RNF20 knockout leads to immune deficiency both in vivo and in vitro. Mechanistically, RNF20 is located in the nucleus, where it maintains the basic expression and regulates the inducible expression of MDA5 to establish immune defense during the early infection phase. In the late phase, RNF20 translocates to the cytoplasm, where it facilitates the K27- and K48-linked polyubiquitination and subsequent degradation of MDA5, thereby preventing immune overstimulation. Overall, this study establishes RNF20 as an important E3 ubiquitin ligase that maintains chicken innate immune homeostasis.

Importance: Chicken MDA5 is an important RNA viral sensor for initiating the antiviral innate immune response. The protein level of MDA5 must be tightly regulated to maintain antiviral innate immune homeostasis. In this study, we demonstrate that the E3 ubiquitin ligase RNF20 precisely regulates MDA5 protein stabilization through nucleoplasmic translocation. Specifically, in uninfected and during early infection, RNF20 regulates MDA5 transcription in the nucleus. While in the late stages of infection, RNF20 translocates out of the nucleus and catalyzes the ubiquitinated degradation of MDA5. Thus, RNF20 is important in regulating chicken antiviral innate immune homeostasis.

Human immunodeficiency virus type 1 (HIV-1) genome diversification is a key determinant of viral evolution and the pathogenesis of HIV/AIDS. Antiretroviral therapy is non-curative, and in the context of monitoring the latent reservoir, precision tools are needed to detect and enumerate HIV-1 genomes as well as to assess their heterogeneity, replication potential, and predict responses to therapy. Current sequencing-based methodologies are often unable to confirm intact genomes and most cell-based reporters provide limited information pertaining to viral fitness. In this study, we describe dual reporter sensor cells (DRSCs), an imaging-based reporter system designed to detect HIV-1 infection and measure several independent attributes of the virus in a single-cell high-content assay. We show that the DRSC assay can be used to measure infection, viral gene activation kinetics, and quantify viral circumvention of host antiviral responses. Using the DRSCs, we confirmed markedly different functional heterogeneity for vif alleles derived from diverse HIV-1 strains and subtypes affecting both rates of APOBEC3G degradation and the cell cycle. Furthermore, the assay allowed for the delineation of virus co-receptor preference (X4- vs R5-tropism) and visualization of virion assembly. Overall, our study illustrates proof-of-principle for a multivariate imaging-based cell-based system capable of detecting HIV-1 and studying viral genetic variability with greater data richness relative to prior available modalities.

Importance: Human immunodeficiency virus type 1 (HIV-1) is highly heterogeneous and constantly mutating. These changes drive immune evasion and can cause treatment efforts to fail. Here, we describe the "dual reporter sensor cell" (DRSC) assay; a novel imaging-based approach that allows for the detection of HIV-1 infection coupled with a multivariate definition of several independent phenotypic aspects of viral genome activity in a single integrated assay. We validate the DRSC system by studying lab-adapted and patient isolate-derived versions of the viral Vif accessory protein, confirming marked differences in the capacity of diverse vif alleles to mediate downregulation of antiviral APOBEC3G proteins and dysregulate the cell cycle.

Immune checkpoints are critical regulators of T-cell exhaustion, impairing their ability to eliminate antigens present during chronic viral infections. Current immune checkpoint inhibitors (ICIs) used in the clinic aim to reinvigorate exhausted T cells; yet, most patients fail to respond or develop resistance to these therapies, underscoring the need to better understand these immunosuppressive pathways. PSGL-1 (Selplg), a recently discovered immune checkpoint, negatively regulates T-cell function. We investigated the cell-intrinsic effects of PSGL-1, PD-1, and combined deletion on CD8⁺ T cells during chronic viral infection. We found that combined PSGL-1 and PD-1 (Selplg^-/-Pdcd1^-/-) deficiency in CD8⁺ T cells increased their frequencies and numbers throughout chronic infection compared to the wild type. This phenotype was primarily driven by PD-1 deficiency. Furthermore, while PD-1 deletion increased virus-specific T-cell frequencies, it was detrimental to their function. Conversely, PSGL-1 deletion improved T-cell function but resulted in lower frequencies and numbers. The primary mechanism behind these differences in cell maintenance was driven by proliferation rather than survival. Combined PSGL-1 and PD-1 deletion resulted in defective T-cell differentiation, driving cells from a progenitor self-renewal state to a more terminal dysfunctional state. These findings suggest that PD-1 and PSGL-1 have distinct, yet complementary, roles in regulating T-cell exhaustion and differentiation during chronic viral infection. Overall, this study provides novel insights into the individual and combined roles of PSGL-1 and PD-1 in CD8⁺ T-cell exhaustion. It underscores the potential of targeting these checkpoints in a more dynamic and sequential manner to optimize virus-specific T-cell responses, offering critical perspectives for improving therapeutic strategies aimed at reinvigorating exhausted CD8⁺ T cells.IMPORTANCEOur findings provide a comprehensive analysis of how the dual deletion of PD-1 and PSGL-1 impacts the response and function of virus-specific CD8⁺ T cells, revealing novel insights into their roles in chronic infection. Notably, our findings show that while PD-1 deletion enhances T-cell frequencies, it paradoxically reduces T-cell functionality. Conversely, PSGL-1 deletion improves T-cell function but reduces their survival. Whereas the combined deletion of PSGL-1 and PD-1 in CD8⁺ T cells improved their survival but decreased their function and progenitor-exhausted phenotypes during infection. We believe our study advances the understanding of immune checkpoint regulation in chronic infections and has significant implications for developing more effective immune checkpoint inhibitor (ICI) therapies.

Lymph node T follicular helper (Tfh) cells and germinal center (GC) B cells are critical to generate potent antibodies but are rarely possible to study in humans. To understand how Tfh/GC B-cell interactions during acute HIV-1 infection (AHI) impact the generation of HIV-specific antibodies, we performed a unique cross-sectional analysis of inguinal lymph node biopsies taken prior to antiretroviral therapy (ART) initiation in AHI. Although total Tfh and GC B cell frequencies did not change during AHI, increased frequencies of proliferating Th1-like CXCR3⁺ Tfh, CXCR3⁺ non-GC B cells, and total CXCR3⁺ GC B cells correlated with gp120-specific IgG antibody levels in AHI. Frequencies of proliferating CXCR3⁺ Tfh in AHI also correlated with gp120-specific IgG antibody levels after 48 weeks of ART, antibody-dependent cellular cytotoxicity, antibody-dependent cellular phagocytosis, and increased antibody binding to infected cells after ART. Importantly, while beneficial for antibody development, CXCR3⁺ Tfh cells were also infected by HIV-1 at higher frequencies than their CXCR3^- counterparts and may contribute to the initial dissemination of HIV-1 in follicles. Together, these data suggest that activation of CXCR3⁺ Tfh cells is associated with induction of the germinal center response and subsequent antibody development, making these cells an important target for future therapeutic interventions.

Importance: Early initiation of antiretroviral therapy (ART) is important to limit the seeding of the long-lasting HIV-1 reservoir; however, it also precludes the development of HIV-specific antibodies that can help control the virus if ART is stopped. Antibody development occurs within germinal centers in the lymph node and requires activation of both antigen-specific B cells and T follicular helper cells (Tfh), a specialized CD4⁺ cell that provides B cell help. To understand how early ART initiation may prohibit antibody development, we analyzed the frequencies and activation status of Tfh and B cells in lymph node biopsies collected in the different stages of acute HIV-1 infection. Our data suggest that decreased antibody development after early ART initiation may be due to limited germinal center development at the time of treatment and that new interventions that target activation of CXCR3⁺ Tfh may be beneficial to increase long-term HIV-specific antibody levels.

Evidence from both field and experimental studies suggests that recombination is a common feature in the evolution of foot-and-mouth disease virus (FMDV). Recent studies have demonstrated that heterologous superinfection of cattle persistently infected with FMDV leads to rapid generation of inter-serotypic recombinant viruses in the upper respiratory tract mucosa. The current study demonstrates that the order of exposure to FMDV strains A24 Cruzeiro and O1 Manisa substantially influenced the patterns of mosaicism of resultant recombinants. FMDV recombinants were isolated from oropharyngeal fluid samples from 7 of 12 cattle following heterologous superinfection at 21 days post-initial infection. There was no apparent competitive advantage of either parental virus. However, recombinant viruses recovered from six of seven animals had gained, or regained through multiple recombination events, the capsid-coding sequence of FMDV O1 Manisa despite the presence of high titers of neutralizing antibodies against that virus. Additionally, a sub-genomic region of high amino acid diversity, spanning the 3' portion of 3A through 3B, was derived from FMDV A24 in most of the recovered recombinants. Despite the frequent recovery of FMDV recombinants from the upper respiratory tract of superinfected animals, there was no detection of recombinant viruses in blood or lesions in the subset of animals that developed clinical foot-and-mouth disease during superinfection. Overall, these findings confirm the high frequency at which FMDV recombination occurs when persistently infected carrier cattle are exposed to a heterologous virus and reaffirm that superinfection of carriers should be considered as a source of FMDV genetic diversity in endemic regions.IMPORTANCEFoot-and-mouth disease virus (FMDV) is a pathogen of domestic livestock with profound global socioeconomic impacts. FMDV causes a subclinical persistent infection in ruminant hosts, such as cattle, during which the animals may become sequentially infected by heterologous variants of the virus. Our previous works have demonstrated that such superinfections frequently lead to emergence of novel recombinant virus variants in the upper respiratory tracts of infected animals. This current investigation demonstrates that the order in which the animals are exposed to two different viruses substantially influences the structure of resultant recombinant genomes and confirms the frequency at which FMDV recombination occurs following heterologous superinfection of persistently infected FMDV carriers.

Rhesus macaque rhadinovirus (RRV) is a primate gamma-2 herpesvirus (rhadinovirus) closely related to Kaposi sarcoma-associated herpesvirus (KSHV), the human oncovirus that causes Kaposi sarcoma. Like other herpesviruses, KSHV and RRV encode numerous envelope glycoproteins involved in cell attachment, entry, as well as assembly and release of progeny virions from infected cells. Two glycoproteins postulated to form a complex and reported to be virus-neutralizing targets are glycoproteins M (gM) and N (gN). To investigate gM and gN in rhadinovirus infection, we utilized infectious and pathogenic bacterial artificial chromosomes (BAC). RRV BACmids with nonsense mutations introduced into gM or gN did not yield an infectious virus. However, when gM or gN of RRV were exchanged for gM or gN from KSHV, each of the KSHV-chimeric RRV BACmids restored virus replication and infectious spread. Interestingly, we also discovered that the substitution of KSHVgM into the RRV BACmid was associated with attenuation in viral spread, an effect that was not countered by a double-chimeric virus. In contrast, the substitution of RRV gN into a KSHV BACmid negatively affected the assembly of KSHV, independent of gM/gN complex formation. Therefore, here, we revealed that in KSHV and RRV, gM and gN are interchangeable, contribute to crucial functions for viral assembly and spread, and have evolved in a virus-specific manner. Although more research is needed to define the roles of gM and gN, our work establishes the first glycoprotein-chimeric viruses for KSHV and RRV, which can now be used to corroborate gM/gN as targets for a cancer vaccine.IMPORTANCEKaposi sarcoma (KS) is a human cancer caused by KSHV and is one of the most frequently occurring cancers in HIV/AIDS patients, as well as in regions where KSHV is endemic. In this report, we have constructed and authenticated the first KSHV glycoprotein-encoding chimeric viruses for evaluations in the RRV/rhesus macaque model and have also uncovered fundamental roles for the glycoproteins gM and gN. Our work is significant by successfully bridging the human-specific, species barrier that has previously restricted preclinical evaluations of the KSHV glycoproteins as vaccine targets in vivo. Although there is no KSHV-specific animal model that is widely used, these KSHV-chimeric viruses may be useful as tools to guide future vaccine design and strategy as vaccine candidates progress toward clinical trials.