The effects of pneumolysin and hydrogen peroxide, alone and in combination, on human ciliated epithelium in vitro

We have investigated the effects of pneumolysin and H2O2, putative virulence factors of Streptococcus pneumoniae, on the ciliary beat frequency and structural integrity of human ciliated epithelium in vitro. Human ciliated epithelium was obtained by brushing the inferior nasal turbinate of healthy human volunteers. Ciliary slowing (CS) was measured using a photo-transistor technique and epithelial damage (ED) was documented using a visual scoring index. Effects of recombinant pneumolysin (100 ng/ml), a mutant pneumolysin preparation with markedly reduced haemolytic activity (100 ng/ml) and reagent H2O2 (100 microM) were measured alone and in combination, in the absence and presence of catalase (1000 units/ml). When used individually, both recombinant pneumolysin and H2O2 caused significant (P < 0.05) CS and ED. The effects of H2O2 but not those of pneumolysin were almost completely attenuated by catalase, while the mutant pneumolysin preparation did not cause significant CS or ED. When used in combination, the effects of pneumolysin and H2O2 on CS and ED were additive as opposed to synergistic. These actions of pneumolysin and H2O2 may contribute to the pathogenesis of respiratory tract infections caused by the pneumococcus.