Haemophilus influenzae is an important cause of human disease, producing both localized respiratory tract and systemic (bacteremic) infections. The initial step in the pathogenesis of disease due to this organism involves colonization of the upper respiratory tract. Despite the essential role of colonization, the determinants of this process remain poorly defined. We have developed an in vitro model for studying interactions between H. influenzae and human epithelial cells. In this model H. influenzae demonstrates efficient attachment and appreciable cell entry, properties that are likely to be important in colonization. The objective of this proposal is to define the bacterial and host cell factors involved in H. influenzae attachment and cell entry. Initially the genetic elements required for in vitro attachment and cell entry will be isolated. An attachment-deficient mutant and a recombinant strain endowed with the capacity for cell entry, both of which have already been isolated, will facilitate these efforts. Subsequently the attachment and cell entry proteins will be purified and their expression will be characterized. Following purification of these proteins, their affinity for epithelial cell surface molecules will be examined and these putative receptors will be isolated and characterized. Finally, to confirm a role for the attachment and cell entry proteins in natural colonization, H. influenzae mutants deficient in attachment and cell entry will be constructed and examined in an animal colonization model. From a practical perspective, results from these studies may form the basis for a novel approach to the universal prevention of H. influenzae disease. Perhaps more importantly, they may provide general insights into the nature of the host-microbial relationship.
