In sex crimes cases, mixed stain samples(a mixture of sperm and vaginal epithelial cells) are common and important biological evidence. Identification of sperm sources is the key of cases detected. The lack of effective technique of sperm separation from mixed stain samples is the bottleneck of sperm test. In the pre-sent study, the group chose sperm surface antigen, Fertilin β, as antigen to prepare specific antibodies, and further coupled the antibody to a solid phase of agarose beads, in order to establish a new sperm separation system. First, antigen Fertilin β recombinant plasmid was constructed. A cDNA for Fertilin β 341—373aa was amplified by polymerase chain reaction(PCR), and was cloned into a prokaryotic expression plasmid, pGEX-4T-1 vector. Second, GST-Fertilin β(341—373aa) fusion protein was induced and purified. Against this antigen, the Fertilin β antibodies were obtained from serum of rabbit immunized. ELISA and Western blot analysis demonstrated the specificity of the antibody against Fertilin β antigen. Then, the specific recognition of the antibody to sperm was identified by the immunofluorescence assay, in which Fertilin β protein in the sperm head can detected by the antibody, whereas in the vaginal epithelial cells showed negative detection. Finally, the sperm detection system using the solid phase of Fertilin β antibody was established, in which the Fertilin β antibody was coupled to ProteinA/G agarose beads and was able to separate sperm from the mixture. In conclusion, the Fertilin β antibody was successfully prepared, which was able to bind to the rear of the sperm head. Furthermore, the Fertilin β solid phase antibody system was generated, which could bind to the sperm surface, so as to isolate the sperms from the mixed stain samples. This sperm separation method from mixed stain samples provided a new detection for sexual offenses.
