The long-term goal of this research is to develop drug delivery systems that target human immunodeficiencies virus (HIV)/host cell entry mechanisms. HIV gains entry into host cells through a molecular recognition event, involving a viral envelope glycoprotein, gp120. The major cellular receptor for HIV is the envelope protein CD4 which is highly expressed on T lymphocytes. However, HIV can infect CD4 negative cells such as neural cells and colonic epithelial cells, which are both CD4-. In contrast to the HIV/CD4+ protein/protein recognition event, these CD4- cells bind gp120 through a glycolipid known as galactosyl ceramide (GalCer 1). Currently, most antiviral therapies target inhibition of either protease and/or reverse transcriptase activity. The proposed research adopts an alternative approach to inhibiting viral replication by interfering with initial recognition events between gp120 and host cell receptors. The hypothesis of the proposed research is that analogs of GalCer can be used as homing devices to specifically bind to gp120 in the region that neural cells and intestinal cells bind. The immediate objective of the proposed research is to characterize single and dual ligand binding of GalCer analogs and polyanions to gp120 in a manner that maximizes their interaction and provides the basis for the design of therapies based on specific interactions with gp120. In order to accomplish these goals, GalCer analogs and polyanions will be synthetically prepared and screened using ELISA. This will also be done for the GalCer analogs so that direct comparisons can be made. Epifluorescence and total internal reflectance fluorescence microscopy (TIRF) will be used to rigorously determine the stoichiometry and equilibrium binding constants of the most promising candidates. In addition, dual presentation of ligands at a functional lipid surface will be examined to determine if binding affinities increase when GalCer analogs and polyanions are presented to gp120 in combination. These combined studies are expected to provide a knowledge base for the rational design of drug delivery systems targeting HIV entry mechanisms into both CD4+ and CD4- hosts.
