Otitis media and other illnesses caused by nontypable Haemophilus influenzae (NTHI) remain significant health problems for children in this country and elsewhere in the world. Efforts to develop vaccines for the prevention of disease are being made by a number of investigators. We have identified a family of high molecular weight outer membrane proteins nontypable Haemophilus influenzae which are major targets of host antibody both in children convalescing from nontypable Haemophilus acute otitis media and in normal adults who are naturally immune to disease. In an effort to further characterize these proteins, we have cloned, expressed, and sequenced two genes from a prototype NTHI strain which encode high molecular weight proteins identical to those recognized by the human sera. The nucleotide sequence data from these two cloned genes and additional immunologic and morphologic data suggest that the NTHI high, molecular weight proteins are structural and possibly functional analogues of the filamentous hemagglutinin protein of Bordetella Pertussis. Filamentous hemagglutinin is an important adherence factor and protective antigen of Bordetella pertussis. Our hypothesis is that the high molecular weight serve a similar functional role for NTHI. We will use several in vitro and in vivo techniques to further characterize these high molecular weight proteins and define their role in bacterial adhesion and the role of antibody directed against them in host protection. Specifically, we will perform absorption experiments to determine the contribution of antibody directed against the high molecular weight proteins to the bactericidal activity present in human sera. We will prepare antisera against purified high molecular weight proteins and assay the resulting antisera in functional assays which include bactericidal assays in vitro and animal protection experiments in the chinchilla otitis media in vivo. Active immunization experiments with purified proteins will also be performed in the animal model. We will assess the contribution of these high molecular weight proteins to the adherence of NTHI using an adenoidal organ culture model. Finally, we will further examine the relationship between the NTHI high molecular weight proteins and the filamentous hemagglutinin protein of Bordetella pertussis using several Bordetella pertussis specific adherence assays. The resulting information should be of value not only for enhancing our understanding of the biology of NTHI and but also may be of importance in efforts to develop vaccines protective against infection caused by these organisms.
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