DESCRIPTION: Studies reported this year have shed new light on the first steps of HIV-1 infection of CD4+ cells and have provided new targets for therapeutic intervention. This proposal focuses on the development and evaluation of antagonists of the HIV-1 permissive chemokine receptors. The antagonists prepared in these studies are intended for therapeutic and prophylactic application in HIV-1 infection. Their development and characterization will further our understanding of the molecular requirements for HIV-1 entry and pathogenesis. Large panels of antibodies reactive with the native ectodomains of the chemokine receptors will be prepared from combinatorial antibody libraries displayed on phage. The antibodies will be utilized to create functional topographical maps of the chemokine receptor domains involved in chemokine binding and HIV-1 interactions. Specific high-affinity antibodies are required not only for therapeutic application, but are also required to address questions regarding the site and level of expression of the chemokine receptors and will aid in the development of gene therapy strategies which target them. We will also evolve small high-affinity peptide antagonists of HIV-1 entry which may serve as lead compounds in the design of low molecular weight inhibitors and which have the potential to mimic the domains of env which interact with the chemokine receptors. These, together with the epitopes on the chemokine receptors critical for HIV-1 entry, may find application in future vaccine strategies. With selective and potent antibody antagonists of the chemokine receptors we will address the therapeutic and prophylactic potential of targeting this early step in the HIV-1 lifecycle in a small animal model, the hu PBL-SCID mouse. In collaborative studies we will use antibodies to aid in the crystallographic determination of the structures of the chemokine receptors and apply NMR to investigate structures of small peptide antagonists of these receptors to aid in drug design studies. Cumulatively, these studies will provide a more thorough understanding of the role of the chemokine receptors in the biology and pathology of HIV and will result in novel strategies for the treatment and prevention of HIV-1 infection.