Enhanced adherence of Streptococcus pneumoniae to human epithelial cells infected with respiratory synctial virus

Abstract

In the present study, we analyzed the effect of a preceding respiratory syncytial virus (RSV) infection of human respiratory epithelial cells on the adherence of Streptococcus pneumoniae tested by means of a cytometric fluorescence assay. Adherence of clinically relevant pneumococcal serotypes 3, 9, 14, 18, 19, and 23 was studied using uninfected and RSV-infected monolayers. To this end, monolayers of both human nasopharyngeal cells (HEp-2) and pneumocyte type II cells (A549) were infected with RSV serotype A. Adherence to uninfected epithelial cells varied between pneumococcal serotypes. After RSV infection of the monolayers, all serotypes showed a strongly (2- to 10-fold) and significantly increased adherence when compared with adherence to uninfected monolayers. Enhanced adherence was observed with both cell lines. By fluorescence and scanning electron microscopy, we observed redistribution of pneumococcal adherence over the epithelial surface due to RSV infection, with dense bacterial accumulations near to epithelial syncytia.