Hyaluronidase augments pneumolysin-mediated injury to human ciliated epithelium

SummaryObjectivesThe main objective of this study was to investigate the effects of pneumococcal hyaluronidase (0.1–10 μg/ml), alone and in combination with pneumolysin (50 and 100 ng/ml), on human ciliated epithelium.MethodsCiliary beat frequency (CBF) and structural integrity of human ciliated respiratory epithelium in vitro were studied using a phototransistor technique and a visual scoring index, respectively.ResultsHyaluronidase per se did not affect either CBF or the structural integrity of the epithelium. However, preincubation of the epithelial strips with hyaluronidase (10 μg/ml) for 30 min at 37 °C significantly potentiated pneumolysin-mediated ciliary slowing and epithelial damage. Hyaluronan, a substrate of hyaluronidase, had no effects on the ciliated respiratory epithelium in concentrations up to 100 μg/ml and did not antagonize the injurious effects of pneumolysin on the epithelium. However, preincubation of the epithelial strips with hyaluronan (100 μg/ml) was associated with attenuation of the ciliary slowing and epithelial damage induced by incubation of the strips with hyaluronidase (10 μg/ml) for 30 min at 37 °C followed by addition of pneumolysin (50 ng/ml).ConclusionsAlthough having no direct effects alone, hyaluronidase may contribute to pneumolysin-mediated damage and dysfunction to respiratory epithelium, thereby favoring colonization and subsequently extra-pulmonary dissemination of the pneumococcus.