Contraceptive vaccine development based on the antigens (Ag) of the zona pellucida (AP) has been greatly facilitated by new insights into the autoimmune response to the ZP3 antigen. Murine ZP3 immunization results in autoimmune ovarian disease (AOD), and AOD may be responsible for ovarian dysfunctions. AOD and contraceptive effect have distinct immune mechanisms, and this provides the basis for the design of a novel murine ZP3 chimeric peptide (CP) vaccine. The CP vaccine induces ZP3 antibody (Ab) regardless of genetic background of the subjects, and without concomitant pathogenic T cell response to ZP3. The ZP3 CP-immunized mice develop significant infertility that corresponds positively to the serum ZP3 Ab titers, and the infertility reverses completely as the ZP3 Ab levels decline. We have since designed a similar ZP3 CP vaccine for the primates, and in the proposed research, we will extend this work toward the design of a safe and efficacious human contraceptive vaccine. Overall, the studies in the first two Specific Aims will derive the most efficient ZP vaccine formulation to be used in a pre-clinical trial in Aim 3.
In Aim 1, which focuses on the evaluation of ZP2 as a vaccine Ag, we will identify murine ZP2 T and B cell epitopes and extrapolate to the corresponding primate epitopes. Also, based on the ontogeny of ZP2 and ZP3, we will determine whether one or both of these ZP proteins would be the most suitable vaccine candidates.
In Aim 2, we will further define the mechanism of CP vaccine action, select the B cell epitopes of the ZP proteins that stimulate the most contraceptive antibody response in vivo, ad identify the foreign t cell epitopes that drive a primate ZP3/ZP2 antibody response without obvious genetic restriction.
In Aim 3, we will study primates, for: 1) autoimmune oophoritis and oocyte loss in response to primate ZP3/ZP2 T cell epitope, 2) any ovarian pathologic response to a primate ZP3/ZP2 CP vaccine, and 3) in vitro ZP3/ZP2 Ab effect on sperm binding to the ZP, and 4) a formal fertility trial in the monkey. We anticipate the results of this study to provide the foundation for a phase I clinical trial on the human ZP3/ZP2 contraceptive vaccine.
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