In a previous outbreak of the human respiratory syncytial virus (HRSV), we identified a variant strain of genotype BA9 with a seven-amino-acid extension (Q-R-L-Q-S-Y-A) at the C-terminus of the attachment protein (G). To assess the impact of this extension on the virulence of HRSV, two full-length infectious clones using the wild strain of genotype BA9 as a backbone, one containing the seven-amino-acid extension (rRSV BA9 WT), and the other deleting this extension (rRSV BA9 Δ7AA), were successfully rescued using a reverse genetics system. The biological properties and virulence of the two rescued viruses were then compared and analyzed in vitro and in vivo. Compared to the rRSV BA9 Δ7AA, the rRSV BA9 WT exhibited a larger plaque size and a more pronounced suppression of the host cell innate immune response in vitro (IFN-β levels: 154.33 pg/mL vs. 11.27 pg/mL). The rRSV BA9 WT demonstrated increased adaptability in mice, with a 10-fold higher lung viral load and a stronger inflammatory response following intranasal exposure. Our study primarily demonstrated that the C-terminal extension of the G protein of the HRSV can enhance viral virulence, underscoring the importance of virological surveillance in the prevention and treatment of severe HRSV-related disease.

The emergence of new variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has generated recurring worldwide infection outbreaks. These highly mutated variants reduce the effectiveness of current coronavirus disease 2019 (COVID-19) vaccines, which are designed to target only the spike (S) protein of the original virus. Except for the S of SARS-CoV-2, the immunoprotective potential of other structural proteins (nucleocapsid, N; envelope, E; membrane, M) as vaccine target antigens is still unclear and worthy of investigation. In this study, synthetic DNA vaccines encoding four SARS-CoV-2 structural proteins (pS, pN, pE, and pM) were developed, and mice were immunized with three doses via intramuscular injection and electroporation. Notably, co-immunization with two DNA vaccines that expressed the S and N proteins induced higher neutralizing antibodies and was more effective in reducing the SARS-CoV-2 viral load than the S protein alone in mice. In addition, pS co-immunization with either pN or pE + pM induced a higher S protein-specific cellular immunity after three immunizations and caused milder histopathological changes than pS alone post-challenge. The role of the conserved structural proteins of SARS-CoV-2, including the N/E/M proteins, should be investigated further for their applications in vaccine design, such as mRNA vaccines.

Current respiratory pathogen surveillance is largely based on case reporting, sentinel surveillance, and environmental sampling. This study developed an autonomous pathogen detection system (APDS) integrating real-time bioaerosol sensing, intelligent triggering, aerosol collection, nucleic acid extraction, real-time PCR, and automated data reporting for respiratory pathogen surveillance. System performance was evaluated in a 20 m³ aerosol chamber and through 52 weeks of continuous monitoring in a hospital outpatient hall in Beijing. Laboratory experiments showed that the developed platform enables the detection of airborne influenza A virus at concentrations as low as 3.75 × 10⁴ 50% tissue culture infectious dose/m³ and can detect airborne Pseudomonas aeruginosa at concentrations as low as 1.80 × 10⁴ copies/m³. The platform can detect low concentrations of airborne pathogen nucleic acids that are undetectable by surface sampling. During field monitoring, APDS autonomously triggered 381 tests and recorded 46 pathogen-positive detections. Respiratory syncytial virus showed significant correlations when APDS signals preceded national surveillance data by 1–3 weeks, with the strongest correlation at a 3-week lead (ρ = 0.487). Given the spatial mismatch between single-site APDS monitoring and national surveillance data, this association should be considered exploratory. These findings demonstrate the feasibility of APDS for long-term automated aerosol surveillance and suggest its potential as a complementary tool for respiratory pathogen monitoring.