Contribution of ambient airborne particles on the susceptibility to respiratory viral infections

The respiratory tract is the primary entry point for inhaled particles from anthropogenic or biological origin such as respiratory viruses. Ambient particulate matter (PM) has adverse effects on the respiratory tract through mechanisms eliciting inflammatory responses, oxidative stress, and other pathophysiological effects. At the same time, respiratory viruses cause a range of infections. By compromising the integrity of the respiratory barrier and by modulating the host immune response, PM may facilitate viral entry and replication, thereby enhancing the pathogenicity of respiratory viruses. While epidemiological studies suggest that PM exposure may influence susceptibility to and severity of viral infection, the underlying mechanisms are not fully understood. This review aims to synthesise experimental studies that investigate how PM exposure may modulate virus infection and antiviral defence. These findings will be contextualised by an overview of the characteristics and effects of PM, the major respiratory viruses, and innate lung immunity.