Polyinosine-polycytidylic acid enhances cellular adherence of Streptococcus pneumoniae.

OBJECTIVES/HYPOTHESIS Viral upper respiratory tract infections (URIs) are often followed by secondary bacterial infections. To better understand this phenomenon, we examined the impact of the viral agent polyinosine-polycytidylic acid [Poly (I:C)] on the adherence of Streptococcus pneumoniae (Spn) to pharyngeal epithelial cells. STUDY DESIGN In vitro model of cultured human pharyngeal epithelial cells. METHODS Detroit 562 cells, a human pharyngeal carcinoma cell line, were pretreated with Poly (I:C). Poly (I:C)-induced expression of platelet-activating factor receptor (PAF-R) was assayed using real-time polymerase chain reaction, flow cytometry, and immunofluorescence microscopy. Bacterial adhesion to these epithelial cells was assessed using immunofluorescence microscopy and colony formation assays. RESULTS Pretreatment with Poly (I:C) increased mRNA and protein expression of PAF-R in Detroit 562 cells and enhanced the adherence of Spn to these epithelial cells. CONCLUSIONS RNA viral infection can enhance PAF-R expression in epithelial cells and increase the adherence of Spn. These findings might explain in part the mechanisms that underlie the increase in bacterial infection following URIs.