| In recent years, the researches indicate that the development of a vaccine based on sperm antigens represent a promising approach for contraception. However, the results were disappointed for its low contraceptive effects or severe side effects. The fundamental reasons are: (1) the sperm/testis specific proteins are autoantigens with low antigenicity, (2) there are lots of molecules involved the process of fertilization. So, the key steps for developing a contraceptive vaccine are selecting the more important molecule(s) as target antigen(s) and enhancing its antigenicity.As we know, the key steps inducing fertilization are the interactions of sperm-ZP and sperm-egg plasma membrane, which is the main focus in researching contraceptive vaccine. There are so many molecules involved the fertility, such as: Spl7, a mammalian testis- and sperm-specific protein, can specifically bind with zona pellucida, dextran, dextran sulfated, and fucoidin. Another germ cell cyritestin is a testis-and sperm-specific protein belonging to the ADAM family. It has a disintegrin domain at the N-terminal, known as a integrin ligand, that suggests cyritestin could be involved in sperm adhesion and fusion with the egg membrane previous study demonstration. The chimeric peptide, which involved the conservative amino acid sequence of cyritestin or immunodominant B cell epipote of SP17 and the promiscuous T-cell epitope of bovine ribonuclease immunized mice and induced part infertility. Meanwhile, the male mice deficient for germ-cell cyritestin are infertile. Therefore, both Spl7 and cyritestin are important molecules in the process of fertilization. Nevertheless, people can not get fully satisfied the results in some contraceptive researches for their limited effectsrespectively.Herein, we have modified the chimeric peptide format to construct a designed contraceptive vaccine. This modification includes: (1) selecting two important molecules as candidates, (2) choosing a promiscuous T-cell epitope, and two B-cell epitopes or conserved amino acid sequences from the two important molecules, (3) connecting them adequately through analysis by the molecule designing software. Therefore, the synthetic new antigen may interfere with the process of fertilization by multiple ways and its contraceptive effects may be enhancing.Based on the molecule designing methods, the B-lymphocyte cell epitope of sperm/testis specific protein SP17 and cyritestin which interfere with fertilization in mouse, as well as the promiscuous TH cell epitope of the ribonuclease (RNase) in bovine were selected. We obtained the new amino acid sequence with thirty-five residues was gotten. Balb/C and C57 Bl/6 female mice were immunized by the new antigen emulsified with the Freund's Adjuvant or the ISCOMs (immunostimualting complexes)matrix. Female mice serum and vaginal secretion antibodies, their fertility and the pathological changes were determined. On the other hand, the effects of the anti-serum against synthetic peptide on the sperm-egg interaction during IVF and the location of P3 peptide in sperm were watched. The main results and conclusions were as follows:1) The new antigen P3 peptide which harvested from the 430A peptide synthesizer were verified by the mass spectrograph and HPLC, that the ratio of mass /charge of the synthetic peptide was equal to the molecular weight in theory and its purity was above 95%. The Western blot analysis show that the antiserum induced by the new antigen plus hemocyanin could bind with the22KD and 55KD proteins, which were existed in the testis tissue protein of mouse, rat and human.2) The purified peptide emulsified in an equal volume of Freund's Adjuvant and immunized the female Balb/C mice with 8-10 weeks old. The antiserums and the washings of vaginal membrane were detected by ELISA, and shown the highest level of the specific antibody IgG was 1:6000 , while the IgA was 1:300. Both the rate of lymphocyte proliferation and the level of cytokine secreted by lymphocyte was higher in the experiment...
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