SMALL ANIMAL MODELS FOR MICROBICIDE TESTING

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The overall goal of this project is to develop a vaginal dosage formulation that is an effective contraceptive which simultaneously protects against the sexual transmission of human immunodeficiency virus (HIV) and Chlamydia. Ideally, this would be achieved in a single active agent, but its attainment with a compatible combination of agents may prove more realistic. Candidate materials to be tested include compounds known to interfere with sperm function and compounds considered likely to interfere with the mechanisms of transmission of HIV. Four types of in vitro tests will be carried out: (1) Cytotoxicity which will include different assays under various conditions. (2) Spermatozoa: The P.I.'s research during the last 25 years has concentrated primarily on studies of sperm structure and function. The assays of sperm will concentrate on identifying agents which interfere with function including sperm metabolism, motility, and penetration of cervical mucus as well as agents which agglutinate spermatozoa. (3) HIV: This laboratory has been instrumental in elucidating the mechanisms of sexual transmission of HIV and developing in vitro methods to assay agents which inhibit sexual transmission of HIV. Assays will include a fluorescence-based cytotoxicity and cell-cell adherence assays, and an ELISA which detects the ability of agents to interfere with transmission of HIV from HIV-infected lymphocytes to epithelial cells derived from the human cervix. (4) Chlamydia: Screening for anti-Chlamydial activity will involve blocking infection of cells derived from the human cervix. We are developing a novel technique for Chlamydial testing. This method, which will employ a highly sensitive fluorescence cytotoxicity assay and uses a cell line derived from the human cervix, should be much more rapid, quantitative, and appropriate than the existing assays. Based on information in the literature and on our preliminary findings, the following five lead compounds have been selected for testing: (1) chlorhexidine, (2) propranolol, (3) 4'-acetamidophenyl-4-guanidinobenzoate, (4) diethyldithiocarbamate, and (5) dextran sulfate. Animal studies will include inhibition of Chlamydia trachomatis infection in mice, a system which the P.I. has worked with previously. In addition, fertility and vaginal irritability studies will be carried out in rabbits. For studies of simian immunodeficiency virus (SIV) transmission we will contract Dr. Christopher J. Miller, at the California Primate Research Center, who will test inhibition of cell-free and cell-associated SIV transmission in rhesus monkeys. Within the five-year funding period we expect to have prepared one or more agents for clinical tests of effectiveness in humans. In formulating materials for such tests, particular cognizance will be taken of the necessity of protecting the entire vaginal surface in order to prevent transmission of HIV. Attention will also be directed to the desirability of effectiveness for at least 24 h. Preparation for testing effectiveness in humans will include assessment of vaginal irritation, preliminary assessment of carcinogenic potential by means of mutagenicity assays, and tests for teratogenic potential and toxicity in animal models.