Cleavage of chimpanzee secretory immunoglobulin A by Haemophilus influenzae IgA1 protease.

Immunoglobulin (Ig)A proteases synthesized by human mucosal pathogens have a unique specificity for human IgA and will not cleave IgA from other species. In contrast, animal pathogens have not reliably been shown to cleave IgA of the animals they infect. This lack of an animal model has prevented an understanding of the importance of IgA1 proteases as virulence factors. One strategy to develop an animal model would be to identify a species capable of infection by a human IgA-producing pathogen whose IgA was susceptible to cleavage by IgA1 protease of that bacterium. The chimpanzee can be infected with Haemophilus influenzae and is closely related immunologically to man. For these reasons it was sought to determine whether chimpanzee secretory IgA (SIgA) is susceptible to cleavage by IgA1 protease of H. influenzae. This report shows that chimpanzee SIgA can indeed be cleaved at the hinge region by H. influenzae IgA1 protease into Fab alpha and (Fc alpha)2.SC fragments. The susceptibility of chimpanzee SIgA to IgA1 protease of a human pathogen could serve as the basis of an animal model to determine the importance of IgA1 protease in pathogenesis.