Monoclonal antibody from vasectomized mouse identifies a conserved testis-specific antigen TSA70

Vasectomy results in the occlusion of testicular outflow, leading to autoimmunity characterized by the production of antisperm antibodies (ASA). Reports on the rise in ASA following vasectomy in several species are available; however, not much is known about the specific sperm autoantigens to which postvasectomy antibodies are directed. In the present study, monoclonal antibodies were generated using a vasectomized mouse. One of the monoclonal antibodies, D5E5, identified an approximately 70-kd antigen localized on the principal piece of the tail and also on the tip of the acrosome of mouse sperm. The cognate antigen was expressed postmeiotically in a stage-specific manner during spermiogenesis, starting from step 8 of elongating spermatids during spermiogenesis up to mature spermatozoa. The protein was conserved across the species, as observed by its presence in rat, bull, marmoset, and human sperm. Following capacitation, the antigen on the head was seen to shift to the acrosomal region and was lost after the acrosome reaction. However, the localization on tip of the acrosome still persisted, which indicates that the antigen may play a role post-acrosome reaction in sperm egg interaction. Resistance to Triton X-100 solubilization indicates that TSA70 could be an acrosomal matrix protein. In addition, we observed a significant reduction in forward progressive motility of mouse sperm treated in vitro with D5E5. In view of its testis specificity, acrosome and tail localization, and conserved nature, TSA70 is likely to play an important role in sperm function.