Dual Role of PM2.5 Water-Soluble Constituents in Respiratory Viral Infection: Enhanced Cellular Susceptibility and Reduced Virion Infectivity

Fine particulate matter (PM2.5), recognized as a critical risk factor for respiratory viral infection, frequently co-exists with respiratory viruses and elicits diverse toxic effects within host microenvironment. However, the specific PM2.5 constituents that affect viral infection and the respective roles of host-mediated processes versus direct virion interactions have not been fully elucidated. This study investigated the impacts of water-soluble matters (WSM) from PM2.5 collected in Guangzhou on human influenza A virus (H1N1) infection, focusing on its dual role in modulating bronchial epithelial cells (BEAS-2B) susceptibility and altering viral activity. The results demonstrated that WSM exposure potentiated cellular H1N1 infection level by 1.5- to 3.5-fold, accompanied by 30–40% defense-related signaling (e.g., MxA) reduction. It also perturbed the inflammatory response, including increased IL-6 and IL-8 (20–40%) and 50% reduction in TNF-α. Spearman analysis showed viral infectivity was associated with MxA, IL-6, and TNF-α levels, among which only MxA displayed a dose-dependent inhibitory trend. These results suggested that WSM primarily enhanced infection by suppressing antiviral defenses. Interestingly, WSM also exhibited direct viricidal effect by reducing 25% infectious H1N1 virions after short-term co-incubation and thereby partially modulated the overall viral infectivity in BEAS-2B cells. Further analysis implicated heterogeneous constituents in viral infection outcomes, with heavy metals (e.g., As, Cd) and Na+ exerting dual effects, both enhancing cellular viral infection and directly reducing virion infectivity. These findings establish a link between prevalence of respiratory viral infection and PM2.5 chemical constituents, highlighting the need for public health-guided mitigation strategies.