This project explores the nature of antibody responses to CD4 and to gp120 of HIV. In order to develop appropriate vaccine antigens, responses to different forms of antigens must be better understood. Specific projects: 1) Little is known about the comparative immunogenicity of epitopes on recombinant proteins vs native forms present in cells or on organisms. We analyzed antibody responses of mice to human CD4 when presented in recombinant or in cellular form. Mice immunized with rCD4 generate a large response to rCD4, but a lower response to the cell surface form, implying that additional sites are recognized on the recombinant form that are absent in the cellular form. Mice immunized with CD4+ cells had high titers of antibody reactive with whole cells, of which only a small portion was reactive with CD4. Titers on rCD4 are much lower for these mice than in rCD4-immunized mice. Either form of CD4 induced antibodies to the gp120 binding site with comparable efficiency. For another site in domain 3 or 4 of CD4, cellular CD4 induced antibodies more frequently than the recombinant form. Immune response gene differences did not play a detectable role in the anti-CD4 response. 2) In collaboration with Dr. Norcross, a series of monoclonal antibodies (mAbs) was derived against recombinant gp120-IIIB of HIV. The goal is to derive mAbs that might distinguish the cell surface form of gp120 from recombinant protein. 3) In collaboration with Dr. Klinman, mice were immunized sequentially with rgp120 of different HIV isolates, in an attempt to focus immunity on shared, cross-reactive sites. The mAbs derived did cross-react on multiple isolates in binding assays, but so did mAbs derived by immunization with only one rgp120 isolate. None of the mAbs neutralized.
