Opacity-associated protein a contributes to the binding of Haemophilus influenzae to Chang epithelial cells

Opacity-associated protein A (OapA), which is responsible for the transpare nt-colony phenotype of Haemophilus influenzae, has been implicated in the c olonization of the nasopharynx in an infant rat model of carriage. In this report, we show that OapA mediates attachment to Chang epithelial cells exa mined by using genetically defined type b and nontypeable H. influenzae str ains with or without OapA. We also showed that OapA was conserved among H. influenzae strains by comparing deduced amino acid sequences. Both recombin ant OapA and polyclonal anti-OapA antiserum blocked the binding of H. influ enzae to Chang epithelial cells, suggesting that the interaction of H. infl uenzae is specific to OapA. Moreover, the binding of recombinant OapA to ep ithelial cells further provided evidence that OapA can promote attachment o f H. influenzae. Expression of oapA gene in a nonadherent Escherichia coli strain significantly increased the binding to Chang epithelial cells, and d isruption of the oapA gene with kanamycin resistance cassette insertion res ulted in a significant loss of binding. These findings demonstrate that Oap A plays a role in H. influenzae binding to human conjunctival epithelial ce lls.