IMMUNIZATION WITH HIGH-MOLECULAR-WEIGHT ADHESION PROTEINS OF NONTYPABLE HAEMOPHILUS-INFLUENZAE MODIFIES EXPERIMENTAL OTITIS-MEDIA IN CHINCHILLAS

Prevention of nontypeable Haemophilus influenzae otitis media by vacci nation is an important health care goal. Proteins important in bacteri al adherence deserve consideration as potential vaccine candidates. Tw o colleagues and I previously identified a family of immunogenic high- molecular-weight proteins important in adherence of nontypeable H. inf luenzae to human epithelial cells (J. W. St. Geme III, S. Falkow, and S. J. Barenkamp, Proc. Natl. Acad. Sci. USA,. 90:2875-2879, 1993). In the work described here, I determined whether immunization with two su ch adherence proteins, HMW1 and HMW2, purified from prototype nontypea ble Haemophilus strain 12, would modify the course of experimental oti tis media caused by the homologous strain. Chinchillas received three monthly subcutaneous injections with 40 Ecg of an HMW1/HMW2 protein mi xture in Freund's adjuvant. One month after the last injection, animal s were challenged by intrabullar inoculation with 300 CFU of nontypeab le H. influenzae 12. Infection developed in five of five central anima ls versus 5 of 10 immunized animals (P = 0.08, Fisher exact, one-taile d). Among infected animals, bacterial counts in middle ear fluid speci mens 7 days postchallenge were significantly greater in control animal s than in immunized animals (P = 0.014, Mann-Whitney U test). Serum an tibody titers following immunization were comparable in uninfected and infected animals. However, infection in immunized animals was uniform ly associated with the appearance of bacteria downregulated in express ion of the high-molecular-weight proteins, suggesting bacterial select ion in response to immunologic pressure. Although protection following immunization was incomplete, these data suggest that the high-molecul ar-weight adhesion proteins are potentially important protective antig ens which might represent one component of a multicomponent nontypeabl e Haemophilus vaccine.