Application of proteomic methods for identification of sperm immunogenic antigens

Although the immunogenic properties of sperm have been explored for a few decades, none of the antigens studied so far appears to be an effective target, to inhibit the fertilization process or shown the full spectrum of sperm antigenic potential. Antisperm antibodies (ASA) collected from infertile individuals and prepubertal boys with cryptorchidism together with two-dimensional (2D) electrophoresis have been employed. Immunoreactive antigens were cored from silver stained 2D gels and analyzed by mass spectrometry (MS). The obtained sequences were searched in the published protein databases. Altogether, 35 different sperm entities were identified in accessible protein databases, out of which 10 appeared to be sperm-specific. Additionally, 6 amino acid sequences indicated novel (hypothetical) proteins. Seventeen sperm entities were detected in sera samples from immune infertile males and 18 entities in ASA-positive seminal plasma (SP). Interestingly, we identified a few sperm structures, none of them sperm specific in sera samples from infertile females. Although, infertile males from whom the ASA-positive SP samples were obtained, did not have ASA in their circulation, the range of sperm antigens detected by systematic and local antibodies overlapped to a great extent (six identical entities). Sera samples from prepubertal boys allowed to show antigens, previously thought to be only present on mature sperm. Three out of four detected were sperm-specific. Using serum and SP of ASA-positive infertile adults and sera samples of prepubertal boys with testicular failure, we have extended the range of known, immunogenic sperm proteins as well as identified some novel antigens (n = 6) of human sperm for further characterization.