Our goal is to investigate the safety and therefore the feasibility of contraceptive vaccines based on gamete antigens. Autoimmune ovarian disease (oophoritis) is considered to be the major potential complication of vaccines that utilize the ZP3 glycoprotein and sperm antigens. The proposal is in 4 parts. Studies in aims 1 to 3 will elucidate the pathogenetic mechanism of autoimmune oophoritis in order to understand how the complication can be avoided.
In aim 4, we will investigate the hypothesis that immunization with sperm antigens may lead to production of antibodies to zona pellucida through induction of anti-idiotype antibodies.
In Aim 1, we will study the well-characterized 15-mer peptide 328-342 from murine ZP3 which can induce antibody that inhibits fertility, and trigger T cell response that causes autoimmune oophoritis. The critical question is: can we elicit antibody response without concomitant T cell response? We will synthesize multiple truncated and single amino acid substituted ZP3 peptides, and produce ZP3 peptide-specific T cell clones and monoclonal antibodies in female (C57BL/6xA/J)F1 (B6AF1) mice. They will be used to dissect and dissociate the T cell epitopes, the B cell epitopes, and the oophoritis-inducing epitopes in the ZP3 peptide with respect to amino acid sequence and critical amino acid residues.
In Aim 2, we will obtain monoclonal antibodies to additional B cell epitopes of ZP3 in B6AF1 female mice immunized with the truncated ZP3 peptide, 330-339. Although 330-339 does not elicit antibody to peptide 328-342, it induces T cell response to 328-342 and autoimmune oophoritis. We now have evidence that endogenous ovarian antigens from injured ovaries of mice immunized with 330-339 can stimulate antibody response to ZP3 determinants located outside the peptide 328-342. With the monoclonal antibodies we will characterize the antigenic epitopes, and identify epitopes shared between human and mouse ZP3.
In Aim 3, we will investigate whether antibody alone is sufficient for 1) autoimmune oophoritis and/or 2) reversible infertility. Female B6AF1 mice will be immunized with ZP3 B call epitope as a linear peptide sequence, coupled to the foreign carrier protein, keyhole limpet hemocyanin. Others will receive monoclonal antibodies to ZP3. Mice with high antibody titers will be evaluated for reproductive performance and fertility reversal, ovarian function and ovarian immunopathology.
In Aim 4, we will address the hypothesis that antibody to sperm antigens, which interact with the zona pellucida during fertilization, may elicit anti-idiotypic autoantibodies that recognize the zona pellucida (and hence autoimmune oophoritis). We will produce rabbit anti-idiotype antibodies to monoclonal and polyclonal antibodies to several well-defined sperm antigens, and determine their binding to zona pellucida from the same species as that of the sperm antigens.
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