The proposed research project will identify outer membrane proteins of Haemophilus influenzae type b (Hib) that have potential for use as vaccinogens to protect human infants against systemic Hib disease. Three different groups of Hib proteins which have been shown to be both immunogenic in infant rats and accessible to antibody on the cell surface of Hib will be investigated for their vaccinogenic potential. These are: the major outer membrane protein with an apparent molecular weight of 39,000, several proteins with molecular weights greater than 100,000, and two soluble Hib proteins found in cell-free culture supernatants. These proteins will be purified through the use of monoclonal antibody-based affinity chromatography and then will be injected into infant rats in order to determine if these purified proteins can induce the synthesis of antibodies protective against systemic Hib disease in the infant rat model system. For any protein shown to be capable of inducing protective immunity in infant rats, it will be necessary to identify a protein)s) of this type that bears cell surface-exposed antigenic determinants which are common to, or cross-reactive with, most or all Hib strains. Monoclonal antibody technology will be used in conjunction with a colony blot-radioimmunoassay system to identify the cross-reactive protein(s). The relevance of these findings to the human situation will be established by investigation of the antibody response of human situation will be established by investigation of the antibody response of human infants to Hib disease. Acute and convalescent sera from human infants with Hib disease will be analyzed in a radioimmunoprecipitation system for the presence of antibodies directed against cell surface-exposed proteins of the infecting Hib strain. Murine monoclonal antibodies specific for the different human antibody subclasses will be employed to identify Hib cell surface-exposed proteins which consistently induce a significant IgG antibody response in human infants.
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