Formation of a Stable Mimic of Ambient Particulate Matter Containing Viable Infectious Respiratory Syncytial Virus and Its Dry-Deposition Directly onto Cell Cultures

Epidemiological associations of worse respiratory outcomes from combined exposure to ambient particulate matter (PM) and respiratory viral infection suggest possible interactions between PM and viruses. To characterize outcomes of such exposures, we developed an <i>in vitro</i> mimic of the <i>in vivo</i> event of exposure to PM contaminated with respiratory syncytial virus (RSV). Concentration of infectious RSV stocks and a particle levitation apparatus were the foundations of the methodology developed to generate specific numbers of PM mimics (PM_Mimics) of known composition for dry, direct deposition onto airway epithelial cell cultures. Three types of PM_Mimics were generated for this study: (i) carbon alone (P_C), (ii) carbon and infectious RSV (P_C+RSV), and (iii) aerosols consisting of RSV (A_RSV). P_C+RSV were stable in solution and harbored infectious RSV for up to 6 months. Unlike A_RSV infection, P_C+RSV infection was found to be dynamin dependent and to cause lysosomal rupture. Cells dosed with PM_Mimics comprised of RSV (A_RSV), carbon (P_C), or RSV and carbon (P_C+RSV) responded differentially as exemplified by the secretion patterns of IL-6 and IL-8. Upon infection, and prior to lung cell death due to viral infection, regression analysis of these two mediators in response to incubation with A_RSV, P_C, or P_C+RSV yielded higher concentrations upon infection with the latter and at earlier time points than the other PM_Mimics. In conclusion, this experimental platform provides an approach to study the combined effects of PM–viral interactions and airway epithelial exposures in the pathogenesis of respiratory diseases involving inhalation of environmental agents