DESIGN AND SYNTHESIS OF IMMUNOMODULATORS AND VACCINE CONSTRUCTS

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Abstract

These studies are aimed at developing an effective immunotherapeutic vaccine for treating HIV-infected, immunocompromised individuals. As a model for such patients, Drs. B. Golding, H. Golding and D. E. Scott and their staff (CBER, FDA) have employed MHC class II deficient (?knockout?) mice (II-/- mice), since these mice have low CD4+ T cell numbers and are susceptible to opportunistic infections. We provided these investigators with conjugates of a synthetic peptide from the V3-loop structure of HIV-1 (MN). The conjugate carriers were heat-killed bacteria from Brucella abortus (BA). When injected into normal (WT) and II-/- mice, V3-BA induced high levels of cytokines, IL-12, IFNgamma (associated with a favorable Th1 type responses), and IL-10 mRNA. In both WT and II-/- mice, V3-BA but not V3-KLH developed serum anti-V3 antibodies of IgA and predominantly Ig2a, Ig2b and Ig3 isotypes. Sera from both WT and II-/- mice inhibited syncytia development at titers similar to those observed from a non-progressing HIV-1-infected subject. Thus, V3-BA induced potentially therapeutic antibodies in these immunodeficient mice and a cytokine profile that supports a good cellular immunity. We have designed and prepared a number of antibody-dextran conjugates that have been employed by Dr. Patricia Mongini at NY University in experiments aimed at exploring how the manner of presentation of an antigen at the B-cell surface affects activation thresholds and the cellular and biochemical events that follow activation of the resting, mature B cells. Co-culturing human tonsilar B cells with anti-IgM-dextran conjugates (surrogates for type II T-cell-independent antigen) resulted in both membrane IgM (mIgM)-triggered S/G2/M entry and apoptosis. Although high ligand valency (number of IgMs per dextran molecule) could compensate for low single-site affinity in triggering apoptosis, the effect was most pronounced when both factors were high. A protracted period of recurrent mIgM signaling events may influence whether apoptosis or cell cycle progression is the functional outcome of B cell encounter with multivalent antigen. Using our co-conjugates of anti-IgM and anti-CD21 (surrogate for complement C3d, ligand for the CD21:CD19:CD81 B cell complex), Dr. Mongini demonstrated that T-dependent antibody responses can be significantly enhanced.