Emerging Microbes & Infections最新文献

The H1N1pdm09 influenza virus, which emerged in 2009 following a unique reassortment of swine-origin gene segments, rapidly replaced the seasonal H1N1 strain and triggered the first influenza pandemic of the twenty-first century. In Brazil, the virus initially spread through intense community transmission before establishing a pattern of seasonal circulation. However, its long-term evolutionary dynamics in the country remain insufficiently characterized. To address this gap, we conducted a coordinated national genomic surveillance effort focused on the period from 2014 onward, when Brazil began systematic whole-genome sequencing of circulating H1N1pdm09 viruses. Through collaborative sequencing across all five Brazilian macroregions, we generated 597 complete genomes collected between 2014 and 2024. Using phylodynamic approaches, we reconstructed the spatiotemporal spread of H1N1pdm09, identified major circulating lineages, and integrated epidemiological data to assess patterns of persistence and regional transmission. Our findings reveal sustained circulation and multiple independent viral introductions over the past decade, with evidence of localized lineage maintenance, particularly in the Southeast and South regions. Phylogenetic analyses also indicate repeated seeding from international sources, underscoring the continued impact of global viral movement. In addition, genome-wide comparisons revealed reassortment events involving internal segments, which may have contributed to the persistence and adaptation of dominant lineages following the COVID-19 pandemic. This study presents the most comprehensive reconstruction of H1N1pdm09 evolutionary dynamics in Brazil to date, highlighting the critical role of integrated, nationwide genomic surveillance in enhancing public health preparedness in tropical and subtropical regions.

Dengue, transmitted by Aedes mosquitoes, can progress to severe symptoms like hemorrhagic fever and shock syndrome. While the virus and host immune response contribute to severity, other factors, such as small extracellular vesicles (sEVs), may play a role. sEVs mediate intercellular communication by transferring cellular components; however, their role in vivo infection remains unclear. We isolated and characterized sEVs from DENV-infected C6/36 mosquito cells, finding that they interact with mammalian cells and internalize the content. Using sEVs populations (with a size between 100 and 200 nm), we demonstrated enhanced infection in in vitro and in vivo murine models, including immunocompetent and immunosuppressed mice, which developed severe dengue-like symptoms. Our study reveals that sEVs from DENV-infected mosquito cells contribute to dengue pathogenesis, inducing severe symptoms in in vivo models, highlighting their potential role in disease progression and severe outcomes.

The persistent emergence of SARS-CoV-2 variants continues to compromise current vaccine efficacy, driving the development of broad-spectrum coronavirus vaccines to address variant evasion and future outbreaks. To develop a pan-coronavirus vaccine, we identified some conserved T/B epitopes across spike proteins of human-infecting coronaviruses, focusing on two conserved long peptides, VV and VS, which demonstrated broad immunogenicity in PBMCs from COVID-19 convalescent patients. By structurally fusing the VV and VS long peptides with heptad repeat 1/2 (HR1/2) domains from the S2 subunit, we engineered a trimeric immunogen HR1-VV-HR2-VS. This design induced superior cellular and humoral immune responses compared to individual peptide components in immunized mice. The vaccine also significantly reduced viral loads and attenuated lung pathology in mice challenged with HCoV-229E, SARS-CoV-2 prototype strain, and the KP.2 variant, demonstrating cross-protective immunity. Therefore, these results indicated that HR1-VV-HR2-VS vaccine elicits cross-protective immunity, highlighting its potential as a universal coronavirus vaccine. In addition, we developed an innovative peptide vaccine platform based on the HR1-HR2 trimeric structural protein, which serves as a potent polypeptide fusion scaffold to significantly enhance peptide immunogenicity.

Commonly used abbreviations: AT, IT, and CT: Acute, intermediate, and chronic stages of T. cruzi infection, respectively; APTT: Activated partial thromboplastin time; BCV: Bicistronic immunogen; BCVR: BCV adjuvanted with RIG-I agonist; CD: Chagas disease; EC: Endothelial cells; INR: International normalized ratio; LV: Left ventricle; PT: Prothrombin time; SMC: Smooth muscle cell; TF: Tissue factor; Tc: Trypanosoma cruzi; uPA: Urokinase plasminogen activator; VCAM1: Vascular Cell adhesion molecule 1; VEGF: Vascular endothelial growth factor.

Multiple influenza virus subtypes actively circulate in nature, and assessing their transmissibility provides crucial information for predicting their pandemic potential and for pandemic preparedness. Here, we evaluated the receptor-binding preferences, replication, and transmission of five different influenza viruses (i.e., CA/07-H1N1, GX/18-H1N1, CK/S2283-H3N8, CK/SD007-H9N2, and DK/35-H5N1) in Syrian hamsters. Receptor-binding analysis using biolayer interferometry revealed that four of these viruses preferentially bound α2,6-linked sialic acid receptors, whereas the H5N1 virus bound to α2,3-linked and α2,6-linked sialic acid receptors similarly. All five viruses replicated well in the respiratory tissues of Syrian hamsters, but did not cause obvious symptoms or death, indicating that Syrian hamsters can tolerate influenza virus infection and are not suitable for influenza virus pathogenicity studies. The four viruses that bound to α2,6-linked sialic acid receptors with higher affinity than to α2,3-linked sialic acid receptors were transmissible between Syrian hamsters via direct contact or respiratory droplets; however, the H5N1 virus was not transmissible through respiratory droplets, consistent with previously reported transmission characteristics observed for these viruses in guinea pigs and ferrets. Given that Syrian hamsters and humans have similar receptor expression patterns in their nasal mucosa, our findings suggests that Syrian hamsters can be used as a suitable animal model for evaluating the transmissibility of influenza viruses that preferentially bind to α2,6-linked sialic acid receptors.

Linezolid-resistant Clostridioides difficile, conferred by the acquisition of cfr-like genes, has been reported in Europe and America. However, the emergence of linezolid resistance in C. difficile in the Asia-Pacific region and its impacts on C. difficile pathogenicity remain unclear. In this study, 881 C. difficile isolates from the Asia-Pacific region were screened for cfr-like genes. Whole genome sequencing was performed on 16 cfr-like gene-positive isolates from four countries. Thirteen isolates possessed cfr(B), which was located within Tn6218, while three isolates possessed cfr(C), which was located within the integrative and conjugative elements (ICE) F548 and DA275. Fourteen (87.5%, 14/16) of the cfr-like gene-positive isolates were resistant to linezolid. In comparison to the two isolates susceptible to linezolid, these 14 isolates exhibited significantly higher mRNA expression levels of cfr(B) and cfr(C), along with significantly higher bacterial density at 12 h. Conversely, they demonstrated reduced abilities for sporulation and biofilm formation. After the cfr(B) gene was knocked down by the CRISPR interference, the C. difficile strain presented lower bacterial density at 12 h, higher toxin production and stronger sporulation and biofilm formation abilities. Our findings reveal the emergence of cfr-like genes C. difficile isolates in the Asia-Pacific region, highlighting that cfr-like genes not only mediate linezolid resistance but also contribute to regulating pathogenic potential. Linezolid resistance in CDI should be closely monitored in specific patients.

Current anti-tuberculosis treatments primarily target extracellular Mycobacterium tuberculosis (Mtb), but exhibit limited efficacy against intracellular Mtb, leading to incomplete clearance of pathogens and an increased risk of recurrence. Antimicrobial peptides (AMPs) possess broad-spectrum antimicrobial activity and low potential for resistance development. Here we developed an in vitro mRNA expression platform which not only facilitates intracellular AMPs expression within macrophages, but also significantly enhances their bactericidal activity against Mtb post-infection. Notably, the combination of AMPs trimers demonstrated superior anti-Mtb activity compared to individual AMPs or other combinations. Furthermore, fusion of this AMP complex with either the minor tail protein Gp6 or lysin Gp10 from Mycobacterium phage L5 substantially improved macrophage-specific targeting and intracellular Mtb elimination. Thus, our current study provides novel insights and innovative strategies for the treatment of tuberculosis or other intracellular bacterial pathogens.

AbstractMultiple mechanisms underpinning biofilm antimicrobial resistance (AMR) have been studied individually. This study aimed to integrate these mechanisms, to understand their contributions to staphylococcal biofilm AMR, as a part of a whole, and to elucidate key hurdles hindering effective biofilm eradication by antimicrobial agents.Nine antibiotics were selected against microplate-based biofilms formed by Staphylococcus aureus ATCC 25923 and Staphylococcus epidermidis RP62A. Four mechanisms, including repressed bacterial metabolism, the barrier effect of the biofilm extracellular polymeric substances (EPS) matrix, the acidic inner-biofilm pH, and inoculum effects associated with high-cell-density biofilm growth were studied. The impact of individual mechanism on biofilm AMR was quantitated by determining the fold increase of concentration that allows antibiotics to overcome the mechanism. Antibiotic concentrations were then incrementally increased from minimum bactericidal concentration (MBC) to sequentially address all four mechanisms, ultimately aiming to kill at least 99.9% of biofilm cells.A simplified method was developed to evaluate the dependence of antibiotics on bacterial metabolic states for the lethality. Gentamicin, tobramycin and ciprofloxacin at 1,024 µg/mL overcame all four mechanisms and successfully killed S. aureus ATCC 25923 biofilms by at least 3 log units. Ciprofloxacin at 1,024 µg/mL effectively killed S. epidermidis RP62A biofilms. The contribution of each mechanism to biofilm AMR was strain- and drug- dependent, with low-cell-metabolism being the most important factor.This study underscores the individual contributions of each mechanism to staphylococcal biofilm AMR and highlights the necessity of targeting all four mechanisms to achieve effective biofilm eradication.

Understanding the mechanisms underlying the emergence and spread of high pathogenicity avian influenza virus (HPAIV) is critical for tracking its global dissemination, particularly via migratory seabirds, given their role in transmission over long distances. Scavenging seabirds, such as skuas, may act as both reservoirs and vectors, and have been linked to multiple outbreaks since 2021. Here, we report the detection of HPAIV H5N1 clade 2.3.4.4b in three Tristan skua (Stercorarius antarcticus hamiltoni) carcasses on Gough Island in the central South Atlantic Ocean. To investigate potential incursion routes, we combined genomic analyses with year-round tracking data from global location sensors. Although migratory movement patterns suggested southern Africa as the most obvious pathway, the strain detected on Gough Island was more closely related to that identified in South Georgia, indicating that infection may have occurred during the pre-laying exodus, when skuas disperse into frontal waters south of the island. No further cases have been confirmed for Gough, but more systematic monitoring is needed to understand the dynamics of virus infection. The detection of HPAIV H5N1 in skuas on Gough Island highlights the importance of continued vigilance, proactive and geographically inclusive surveillance strategies, and biosecurity measures globally, alongside efforts to reduce other pressures on globally important seabird populations to help strengthen their resilience.

Older adults remain highly vulnerable to severe SARS-CoV-2 outcomes despite multiple vaccinations, yet age-associated differences in immune responses to updated COVID-19 booster vaccines remain incompletely characterized. Here, we administered an XBB.1.5 trivalent recombinant protein booster (WSK-V102C) to 22 individuals (<38 years) and 20 individuals (≥73 years), all of whom had previously received 2-3 doses of inactivated COVID-19 vaccines. Neutralizing antibody responses against multiple SARS-CoV-2 variants were quantified and compared between age groups. Meanwhile, single-cell RNA sequencing was also performed on peripheral blood mononuclear cells (PBMCs) collected at baseline and 28 days post-vaccination to profile age-associated immune features following boosting. Following booster immunization, both age groups achieved significantly elevated antibody titers against all tested strains. Nevertheless, the magnitude of antibody fold increase was consistently lower in elderly individuals than in younger adults. Single-cell analyses revealed age-associated differences in post-vaccination immune organization. In elderly individuals, B-cell state transitions were characterized by transcriptional signatures consistent with memory B cell-to-plasmablast differentiation, whereas younger individuals predominantly exhibited transitions from naïve B cells. CD4+ T cells from elderly individuals displayed altered transcriptional trajectories and reduced T-cell receptor diversity relative to younger adults. In contrast, younger individuals showed coordinated B- and T-cell-associated transcriptional programs, including enrichment of transcription factors such as KLF7, CEBPB, CEBPD, and MAFB. Collectively, our study describes age-associated differences in immune coordination and cellular response patterns following XBB.1.5 booster vaccination. Further longitudinal and functional studies will be required to clarify the mechanistic basis and clinical implications of these observations.