A testis specific auto-antigen TSA70 belongs to Odf2/Cenexin family

The occlusion of testicular outflow following vasectomy leads to autoimmunity which is characterised by the production of antisperm antibodies. Although post-vasectomy autoimmune response has been reported in several species, very little is known about the sperm auto-antigens that are targeted. Using a vasectomised mouse, a number of monoclonal antibodies were generated with the aim of characterising the targeted sperm specific antigens. All the monoclonal antibodies were found to react with testicular proteins. One of the antibodies, D5E5 was then used for immunochemical characterisation of its cognate antigen that was found to be a testis specific autoantigen of - 70 kDa, termed TSA70. TSA70 is expressed postmeiotically in a stage specific pattern during spermiogenesis. TSA70 was observed to be conserved across the species as seen by its presence on rat, bull, marmoset and human spermatozoa. On mouse spermatozoa it was localised at the tip of acrosome and sperm tail as seen by indirect immunofluorescence. Following capacitation it was seen to spread all over the acrosome. However, the localisation on the acrosomal tip persisted even after acrosome reaction, which suggests that the antigen is likely to play a physiological role post acrosome reaction. Solubilisation with Triton X100, revealed the acrosomal component of TSA70 to be a matrix protein, whereas its counterpart on the tail had both a soluble as well as a particulate form. In vitro studies showed that the monoclonal antibody significantly reduced progressive motility of mouse spermatozoa. Preliminary sequence analysis showed that TSA70 belongs to the Odf2/ Cenexin family. These characterisation studies suggest that TSA70 is a conserved, testis specific sperm autoantigen with a definitive physiological role in reproduction.