Cell vacuolation induced by Haemophilus influenzae supernatants in HEp-2 cells

Haemophilus influenzae belongs to respiratory tract microbiota. Weobserved vacuoles formation in previous studies with H. influenzaeculture supernatants, so in this work we characterised that cytotoxic effect. Weobserved an abundant production of acidic cytoplasmic vacuoles due to the presence ofa “vacuolating factor” in H. influenzae supernatants which was characterised asthermolabile. Greatest vacuolating activity was observed when utilizing the fraction> 50 kDa. The presence of a large number of vacuoles in HEp-2 cells was verifiedby transmission electron microscopy and some vacuoles were identified with a doublemembrane and/or being surrounded by ribosomes. These results suggest similarbehaviour to that of vacuolating effects described by autotransporter proteins anundescribed cytotoxic effect induced by H. influenzae .