A dot-blot-immunoassay for semen identification using a polyclonal antibody against semenogelin, a powerful seminal marker

Abstract

Among various seminal plasma proteins, semenogelin (Sg), produced in the seminal vesicle, has been considered a candidate for demonstrating the presence of semen. Sg consists of two proteins, one 52kDa (Sg-I) in size, and the other a mixture of 71 and 76kDa proteins (Sg-II). Recombinant Sg-I and Sg-II proteins were obtained using a baculovirus system and then injected into a rabbit to produce the respective antibodies [Characterization of recombinant precursor proteins of the human seminal plasma sperm motility inhibitor synthesized in insect cells, Int. J. Mol. Med. 2 (1998) 693]. When liquefied seminal plasma was immunoblotted with the anti-Sg-I and Sg-II antibodies, the anti-Sg-II antibody identified a wider range of the polypeptides originating from Sg than did the anti-Sg-I antibody. A dot-blot-immunoassay using anti-Sg-II antibody revealed a clear immunoreactive spot even when the semen was diluted 6400-fold. However, this assay showed that the Sg antigen was undetectable in saliva, urine, vaginal secretions, sweat, nasal secretions and serum. To determine the stability of Sg antigenic activity, filter paper with dried semen stains were kept at 37, 4 and 22°C for 1, 6 and 18 months, respectively, and the Sg antigenic activity was examined. The activity was detectable in an area not less than 0.5cm×0.5cm under all of the above environmental conditions during each period. Finally, semen was mixed with saliva or blood at various volumetric ratios, and used as a source of dried stains. The Sg antigenic activity was detectable in the stains until the ratio of semen to saliva or blood reached 1:8. These results suggest that Sg may be useful as a marker for semen identification.