Virologica Sinica最新文献

With an unexpected increase of human metapneumovirus (hMPV) cases in northern China since late 2024, concerns arose whether novel hMPV variants triggered this epidemic. Utilizing the Beijing Respiratory Pathogen Surveillance System (RPSS), we conducted a genomic evolutionary analysis spanning 2014-2024 and revealed genetic information for the strains that caused the high rates of hMPV outbreaks during this period. To clarify the epidemic drivers and evolutionary characteristics of the hMPV strains circulating in Beijing, phylogenetic, population dynamic and mutation analyses were performed using high-quality complete sequences from both this study and publicly available data. A total of 348 high-quality hMPV genomes were obtained by next-generation sequencing (NGS), all of which belonged to four known clades: A2b1, A2b2, B1, and B2. Before 2024, A2b2 predominated in Beijing; however, a shift to clade B2 was observed starting in late 2024. In addition, a phylogenetically independent lineage Ⅰ was identified in this study, accounting for 93.1% of B2 genomes collected since late 2024. Furthermore, we identified several unique nonsynonymous mutations in viruses within lineage I that may have phenotypic implications. Our findings indicate that lineage I of clade B2 was the major cause of the unusual increase in hMPV outbreaks in Beijing in late 2024, with no evidence of an emerging novel variant. Although our data were only restricted to samples from Beijing, the findings are likely representative of the hMPV surge across northern China in 2024, given city's high population density and mobility.

Influenza A virus (IAV) is one of the most important zoonotic pathogens and can cause global influenza pandemics and seasonal influenza outbreaks. Generation of recombinant IAV expressing a fluorescent protein will allow the infection to be easily monitored. In this study, we initially constructed a replication-defective H1N1/ΔPB2-GFP and a replication-competent H1N1/NS-GFP. However, these two reporter IAVs exhibited genetic instability. To stabilize the recombinant viral genome, we recoded the gfp sequence (rGFP) using synonymous codons to mimic the high-NP-binding regions involved in NP-vRNA interaction. This approach resulted in the development of replication-defective H1N1/ΔPB2(300)-rGFP and replication-competent H1N1/NS-rGFP, both of which exhibited enhanced stability in GFP expression. By replacing the HA segment from strain A/mink/China/CY 2017 (H5N1), we also generated a replication-defective H5N1/ΔPB2(300)-rGFP, which showed excellent genetic stability. Using these reporter IAVs, the blocking of virus infection by neutralizing antibodies and antivirals can be rapidly detected by the loss of fluorescent reporter expression. Replication-defective reporter IAVs constructed in this study can only infect and replicate in cells expressing PB2, allowing the possibility of manipulation of highly pathogenic IAV and their related reassortant strains in biosafety level-2 laboratories. Our data highlight the importance of NP-vRNA interaction for the stability of IAV genome, and the reporter IAVs generated using this strategy could be powerful tools for both basic and applied influenza virus research.

Pseudorabies virus (PRV), a member of the Alphaherpesvirinae subfamily, is the causative agent of Aujeszky's disease, which severely affects swine health and poses a potential zoonotic risk. PRV can evade the type I interferon (IFN-I)-mediated antiviral response, thus enabling persistent infection, yet the molecular basis for this immune evasion remains unclear. Here, we identify a novel role for thymidine kinase (TK), a key PRV virulence factor, in suppressing IFN-I signaling. Ectopic expression of TK markedly inhibited IFNα-induced transcription and expression of interferon-stimulated genes (ISGs), whereas TK-deficient PRV (PRV-ΔTK) showed increased sensitivity to IFN-I, elevated ISG expression, and reduced replication following IFNα treatment. Mechanistic analyses revealed that TK interacts with both Janus kinase 1 (JAK1) and signal transducer and activator of transcription 1 (STAT1), disrupting the JAK1-STAT1 complex formation and impairing STAT1 phosphorylation and downstream ISG induction. This inhibition is mediated by amino acids 107-212 of TK, a region independent of its catalytic site, and is essential for its immunosuppressive activity. These findings uncover a previously unrecognized function of TK in antagonizing the IFN-I response through interference with JAK1-STAT1 signaling. Beyond its established role in nucleotide metabolism and virulence, this immune evasion function may account for the strong conservation of TK among PRV strains. Collectively, our results expand the understanding of PRV pathogenesis and identify TK as a potential target for antiviral intervention.

Due to inherent immune deficiency, the characteristics of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific immune responses in people living with HIV (PLWH) following breakthrough infection with remain incompletely elucidated. A large-sample real-world study was conducted from December 2022 to January 2023, which systematically analyzed immune responses in 1,367 PLWH and 219 people without HIV (PWOH) by evaluating serum IgG antibody levels against SARS-CoV-2 wild-type strain and Omicron variants, neutralizing antibody titers, as well as the features of SARS-CoV-2-specific T-cell responses in this population. The results demonstrated that the breakthrough Omicron infection rate in PLWH (60.6%) was significantly lower than that in PWOH. Meanwhile, PLWH exhibited notably reduced IgG antibody levels against both the wild-type strain and Omicron BF.7 variant, with a concurrent decline in neutralizing antibody titers. However, fully vaccinated PLWH with CD4⁺ T-cell counts ≥ 200 cells/μL achieved post-infection antibody levels comparable to those of PWOH. Notably, PLWH with CD4⁺ T-cell counts < 200 cells/μL or unvaccinated PLWH showed obvious impairment in both humoral and cellular immunity. Although PLWH could maintain relatively high levels of SARS-CoV-2-specific antibodies and T-cell responses within six months after infection, the overall intensity of their immune responses remained lower than that of PWOH. Furthermore, while wild-type SARS-CoV-2 vaccines could effectively elevate antibody levels in PLWH, their protective efficacy against Omicron variants was relatively limited. These findings provide important experimental and clinical evidence for formulating exclusive and targeted SARS-CoV-2 vaccination strategies for the PLWH.

Herpes simplex virus type 1 (HSV-1) causes lifelong latent infection and is associated with severe diseases, including herpes simplex encephalitis, neonatal herpes, and no licensed vaccine is currently available for this pathogen. Here, we systematically evaluated an attenuated HSV-1 platform with deletions in ICP34.5 and ICP47 genes (HSV-1 Δ34.5Δ47) for application as a dual-function vaccine. This construct, generated by BAC-galK recombination, showed attenuated replication in vitro. Notably, it elicited robust humoral and cellular immune responses in mice, and provided complete protection against lethal challenge with virulent HSV-1 McKrae strain through both corneal and genital tract infection routes. To assess its utility for heterologous antigen delivery, we engineered a recombinant HSV-1 Δ34.5Δ47-N, which expresses the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleocapsid (N) protein. This recombinant virus retained the protective efficacy against HSV-1 and induced robust N-specific immune responses. Passive serum transfer and in vivo T-cell depletion studies demonstrated that humoral immunity was sufficient to mediate protective immunity against HSV-1 challenge. Safety assessment revealed no detectable viral mRNA or pathological lesions in the brains of immunized animals. These findings support HSV-1 Δ34.5Δ47 as a safe and versatile platform for both HSV-1 prophylaxis and heterologous antigen delivery.

Dengue fever, an acute mosquito-borne infectious disease caused by dengue virus (DENV), is primarily endemic in tropical and subtropical regions. In recent years, the global incidence of dengue has increased dramatically. Since 2023, widespread outbreaks have been reported across numerous countries in the Americas, Asia and Africa. According to the World Health Organization, more than 5 million dengue cases were reported globally in 2023, while the number surged to over 14 million cases with more than 10,000 deaths in 2024-marking the highest global burden ever recorded. A similar upward trend has been observed in China, which experienced its largest dengue outbreak in a decade in 2024, with Guangdong Province accounting for the majority of domestically reported cases. These epidemiological patterns highlight the rapid expansion of dengue transmission, driven by climate change, accelerated urbanization and increased human mobility. In this context, vaccine development has become a public health priority. To date, two vaccines-Dengvaxia and Qdenga-have been licensed for clinical use. Six other vaccine candidates are currently in clinical trials, among which the tetravalent live-attenuated vaccines TV003/TV005 are considered the most promising. Despite considerable advances in dengue vaccine research, significant challenges remain, including the need to elicit balanced immune responses against the four serotypes and to reduce the risk of antibody-dependent enhancement (ADE). Taken together, this review systematically summarizes recent global and regional trends in dengue fever and the current progress in dengue vaccine development, collectively offering a valuable resource for informing prevention and control strategies.

Zika virus (ZIKV) infection is associated with severe neurological complications such as congenital microcephaly, yet no safe and effective vaccine is currently available. A critical challenge in ZIKV vaccine development arises from cross-reactive, non- or sub-neutralizing antibodies, which may enhance dengue virus (DENV) infection through antibody-dependent enhancement (ADE). Herein, we report a vaccine strategy utilizing Mi3 nanoparticles to display the Envelope (E) protein domain III (EDIII) of ZIKV, which induces protective immunity against ZIKV infection in murine models. Compared to an EDIII subunit vaccine, the Mi3-EDIII nanoparticle vaccine elicited significantly higher antibody responses and stronger cell-mediated immune responses. In C57BL/6 mice, maternal immunization with Mi3-EDIII protected the neonates against ZIKV-caused symptoms, including body weight loss, neurological abnormalities, retardation of brain development, and mortality. In interferon-α/β receptor knockout (Ifnar1^-/-) C57BL/6 mice, Mi3-EDIII immunization conferred effective protection against lethal ZIKV challenge. Notably, unlike ZIKV convalescent sera, Mi3-EDIII immune sera did not enhance DENV infection in human chronic myelogenous leukemia K562 cells, suggesting the absence of ADE-prone antibody induction. Our results demonstrate that Mi3-EDIII is a promising vaccine candidate against ZIKV infection and warrants further development.

Viral hemorrhagic septicemia virus (VHSV) is a major pathogen affecting freshwater and marine fish species, posing a significant threat to global aquaculture. Reverse genetics systems are essential for studying viral replication, and host interactions, as well as developing vaccines and therapeutics. In this study, we developed a reverse genetics platform for VHSVLB2018 strain, a genetically distinct VHSV genotype IVa strain which exhibits low genomic identity with other Asian isolates, using a dual RNA polymerase I/II transcription vector. We successfully rescued recombinant VHSV in mammalian (B7GG) and fish (FHM and EPC) cell lines, and engineered recombinant VHSV strains expressing EGFP (rVHSV-EGFP) and cherry (rVHSV-Cherry) fluorescent proteins. Phenotypic analysis revealed that unmodified recombinant VHSV (rVHSV) exhibited growth kinetics and virulence similar to the wild-type VHSV, while fluorescent protein-expressing variants showed attenuated replication and virulence, with the rVHSV-EGFP strain displaying the greatest attenuation. Utilizing the rVHSV-EGFP strain, we conducted antiviral compound screening and identified three promising inhibitors-xanthohumol, octyl gallate, and rottlerin that effectively inhibit VHSV replication. Time-of-addition assays further revealed that xanthohumol and rottlerin targeted the viral replication stage, while octyl gallate interfered with viral internalization. This reverse genetics system provides a versatile platform for studying VHSV pathogenesis, developing live-attenuated vaccines, and screening antiviral compounds, enhancing our understanding of this pathogen and offering new tools for aquaculture disease management.

Emerging zoonotic infectious diseases, predominantly caused by viruses, pose increasing public health threats globally. Rodents and shrews are natural hosts for a variety of zoonotic viruses. Guangzhou is one of China's most densely populated cities and experiences frequent international and domestic population movements, making it a hotspot for infectious diseases. This study reports the metatranscriptomics virome of 208 rodents and shrews collected between June 2023 and December 2024 from four main urban areas (Tianhe, Baiyun, Liwan, Yuexiu) and five non-main urban areas (Zengcheng, Huadu, Conghua, Panyu, Nansha) in Guangzhou. Individual libraries were constructed from mixed tissue samples (liver, spleen, lung, and kidney) of each animal. Metatranscriptomics sequencing revealed diverse viral communities, identifying 24 viral strains across eight mammalian-associated viral families. Notably, we identified 17 known viruses and seven potentially novel viruses, including Seoul virus (5.2% prevalence in Rattus norvegicus from Panyu), Wenzhou mammarenavirus (13.2% in Rattus norvegicus from Conghua and Huadu), Jeilongvirus (29.4% in Rattus andamanensis from Panyu), and a divergent lineage of arteriviruses that may represent a new genus (maximum positivity rates of 2.9% in Rattus norvegicus and 5.7% in Rattus tanezumi). Phylogenetic analysis elucidated evolutionary relationships within key families such as Hantaviridae, Arenaviridae, Flaviviridae, and Parvoviridae, revealing distinct viral carriage patterns in Guangzhou City that are shaped by host species and geographical location. This is the first macro-level study of rodent and shrew viromes in Guangzhou and provides a scientific basis for strengthening surveillance of mammalian-associated viruses and preventing emerging zoonotic infectious diseases in the region.