Virologica Sinica最新文献

Influenza virus infections cause significant illness or death every year, becoming a serious health risk. Currently, influenza vaccines mainly induce responses to antibodies against specific strains, but they do not effectively induce effective T cell-mediated immunity. Humoral immunity relies on the production of antibodies that bind to surface proteins (such as hemagglutinin and neuraminidase) to combat the virus. These antibodies envelope the virus to prevent it from invading cells and also label the virus for phagocytic cells to clear. T cell-mediated immunity relies on cytotoxic cells to kill infected cells to combat the virus. Cytotoxic T cells rely on viral proteins on the surface of infected cell to recognize them. This enables the detection of more viral proteins, such as internal proteins like nucleoproteins. A better understanding of the mechanism by which T cells combat influenza is helpful for vaccine development. In this review, we elaborate on the role of T cells in enhancing anti-influenza immune defense. In addition, we explore the possibility that new influenza vaccines can induce such T cell responses.

Despite widespread use of multiple PCR, a substantial proportion of pediatric acute respiratory tract infections (ARTIs) lack identifiable pathogens and are classified as unknown etiology. The microbial characteristics and clinical relevance of these cases remain unclear. In this study, we compared the airway microbiomes of PCR-positive and PCR-negative ARTIs and examined their relationships with sampling site and disease severity. A total of 514 hospitalized children with ARTIs were enrolled. Nasopharyngeal swabs (NS) and bronchoalveolar lavage fluid (BALF) samples were tested using a 22-target multiplex PCR panel and subsequently stratified by pathogen status for pooled metatranscriptomic sequencing to profile active microbial communities, viral genotypes, and antibiotic resistance genes. PCR identified common respiratory pathogens in 77.0% of NS and 54.1% of BALF samples. Metatranscriptomic analysis showed that PCR-negative pools displayed markedly lower viral activity and comparatively higher bacterial transcript abundance, with notable enrichment of Pseudomonas. Microbial signatures differed between upper and lower airway samples and across clinical severity, with severe cases demonstrating increased bacterial burden and Pseudomonas enrichment, whereas mild infections exhibited relatively stronger viral signals. Under current thresholds, antibiotic resistance genes were detected in patient pools but not in healthy controls. Overall, PCR-negative pediatric ARTIs exhibited distinct, bacteria-enriched microbial profiles. Integrating metatranscriptomics with PCR enhances pathogen characterization and reveals site- and severity-related microbial patterns that may support diagnostic evaluation and clinical management.

Sp100 (Speckled protein 100 kDa), a key component of promyelocytic leukemia (PML) nuclear bodies, plays a pivotal role in intrinsic and innate immunity. The predominant isoform, Sp100A, has been shown by our previous studies to shuttle between subcellular compartments to enhance innate immunity against RNA viruses and to circulate between cells via extracellular vesicles (EVs) to restrict herpes simplex virus 1 (HSV-1) spread. This study investigates the biological significance of the cyto-nuclear shuttling of Sp100A, a key component of PML nuclear bodies, in antiviral defense against DNA viruses, particularly herpes simplex virus 1 (HSV-1). We demonstrate that Sp100A effectively inhibits multiple DNA viruses in vitro, with its antiviral activity being critically regulated by phosphorylation at the S188 site (a nuclear import-mimicking mutant, S188D, is active, while the S188A mutant is not). Furthermore, DNA virus infection and type I IFN significantly induce Sp100A secretion via extracellular vesicles (EVs), which confers broad, non-IFN-mediated antiviral protection between cells. In a murine model, Sp100A expression significantly reduced HSV-1 lytic replication and clinical signs, but did not impair latency establishment or reactivation potential. These findings underscore the critical role of Sp100A's dynamic shuttling in antiviral defense, showing its activity is specifically restricted to the lytic phase of HSV-1. Sp100A's multifaceted antiviral properties highlight its potential as a novel therapeutic target for combating DNA virus infections.

Coronavirus Disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), affects multiple organ systems, with the respiratory system being the primary target. Respiratory organoids, which closely mimic the structure and function of the human respiratory tract, have emerged as essential tools for studying SARS-CoV-2 infection. This review summarizes current methods for generating various respiratory organoids, including nasal, tonsil, airway, bronchial, and alveolar organoids, and highlights their application in investigating the mechanism of SARS-CoV-2 infection and evaluating potential therapeutic agents. Meanwhile, this review also introduces respiratory organoid-on-a-chip technology, which can precisely regulate culture conditions and incorporate vascularization and immune cells to enhance physiological complexity, thereby providing crucial support for investigating SARS-CoV-2-induced lung injury, immune responses, and conducting high-throughput drug screening. The aim of this review is to provide valuable insights for further research into the pathogenesis and intervention strategies of COVID-19.

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.