HIV neutralization through use of antibodies and pharmacokinetics of topical applications
Chou, Chia-Wei Thomas
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The Human Immunodeficiency Virus Type 1 (HIV-1), a sexually transmitted retrovirus that causes the Acquired Immunodeficiency Syndrome (AIDS), infects over two million people a year. Several methods introduced to prevent HIV-1 transmission, such as condoms, circumcision and antiretroviral drugs, have proven to be partially effective, but more effective approaches are being sought. Topical microbicides are being developed to provide a women-controlled method to prevent the transmission of HIV-1. Unfortunately, most of the candidate microbicide compounds tested to date have either elicited undesirable mucosal inflammation and epithelial lesions leading to increased seroconversions, or have been ineffective. One novel approach currently being explored is the use of monoclonal antibodies as components of topical microbicides. Monoclonal antibodies can be produced inexpensively by transfection into Nicotiana plants. We hypothesize that anti-HIV monoclonal antibodies produced in Nicotiana (MAb-N) will be effective in neutralizing HIV- 1 when used as topical microbicides at mucosal sites, and set out to test whether they retain their efficacy under physiological conditions. We tested the pharmacodynamics of anti-HIV MAb-N efficacy in Cynomolgus macaques following application of the antibodies in the vaginal compartment. We further studied the ability of MAb-N to cross through the vaginal epithelium using an EpiVaginal tissue model. To determine the pharmacodynamics of HIV neutralizing activity after the application of anti-HIV MAb-Ns to the vaginal mucosa, we used a neutralization assay based on HIV-expression in the TZM-bl cell line to test the efficacy of various doses of MAbs in a time course after they had been administered intravaginally in gel form to Cynomolgus macaques. To determine the pharmacokinetics of Mab-N transport across the vaginal epithelium, monoclonal antibodies were added to the apical surface, and a human-IgG ELISA was used to detect Mab-N that had crossed the epithelium into the basal supernatant. Immunohistology was used to confirm and validate ELISA data for evidence of transfer of Mabs across the epithelial layer. Our results show that anti-HIV MAb-Ns were effective in neutralizing cell-free HIV in TZM-bl neutralization assays. We found that MAb-Ns retained their anti-viral efficacy in monkeys after 4-hours. However, neutralizing activity was decreased after 24- hours and 72-hours, with wide variability in effectiveness between individual macaques. Mab-ns tested in the EpiVaginal tissue model showed minimal transfer of antibodies across the epithelium, ranging from 0.005% to 0.09%. Immunohistological data showed that antibodies applied apically to tissue models concentrated only in the superficial layers of the stratum corneum and did not penetrate the epithelium. Our data indicate that anti-HIV MAb-Ns are effective in neutralizing HIV-1 following vaginal application for at least 4 hours, and that they do not pass through the vaginal epithelium in significant amounts. Our data support their further development as vaginal microbicides.
Thesis (M.A.)--Boston University