The development of antibody-based drugs is continuing to expand at a rapid pace, especially for use at mucosal surfaces to prevent or treat infectious diseases and other conditions. A better understanding of how the Fc region of antibodies interacts with Fc-binding proteins at mucosal sites can inform an optimal design for antibody-based drugs. The Human Contraception Antibody (HCA) is a human IgG1 monoclonal antibody currently under development as a topical vaginal contraceptive. HCA binds to sperm via its Fab domains and causes rapid agglutination with other sperm in close proximity resulting in near complete immobilization of sperm over a wide area. In order to determine whether HCA participates in Fc-mediated functions in the female reproductive tract (FRT), we assessed the activity of HCA and engineered variants in three assays of Fc-mediated functions: complement-dependent cytotoxicity (CDC), antibody-dependent cellular phagocytosis (ADCP), and mucus trapping. The physiological relevance of CDC was confirmed by characterizing complement levels and activity in cervical mucus. Finally, we described the activity of a novel Fc receptor expressed by vaginal epithelium. With complement, HCA significantly reduced sperm motility and increased the number of lysed sperm via CDC. Additionally, human cervical mucus was found to have sufficient levels of complement to induce the classical complement cascade. HCA-opsonized sperm associated with macrophages and were phagocytosed via ADCP. HCA also trapped sperm in ovulatory human cervical mucus, significantly reducing their progression. Variants of HCA with mutated or obstructed Fc domains had decreased abilities to perform these Fc functions, while multivalent IgM-like and IgA variants of HCA were very effective in both sperm agglutination and Fc assays. We also investigated the novel expression of Fc alpha RI (CD89) by human vaginal epithelium and provide evidence that this Fc receptor may transport IgA through the mucosa. Basal application of IgA resulted in IgA in apical supernatants which was significantly reduced following treatment with a CD89 blocker. In summary, these studies provide an improved understanding of the possible Fc functions of HCA and other antibodies in the human FRT, including interactions with complement, cervical mucus, and Fc receptors. Determining which interactions can occur in vivo and which are desired for a specific indication can inform the design of mucosally applied antibody-based drugs like HCA, a much-needed novel contraceptive antibody.
| Identifer | oai:union.ndltd.org:bu.edu/oai:open.bu.edu:2144/46885 |
| Date | 14 September 2023 |
| Creators | Mausser, Emilie Brigid |
| Contributors | Anderson, Deborah J. |
| Source Sets | Boston University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
| Rights | Attribution 4.0 International, http://creativecommons.org/licenses/by/4.0/ |
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