Screening of an Antigen Target for Immunocontraceptives from Cross-Reactive Antigens between Human Sperm andUreaplasma urealyticum

Abstract

ABSTRACTEpidemiologic studies indicated that some infertile men who were infected withUreaplasma urealyticumdisplayed positive antisperm antibodies in their serum and/or semen. The purpose of this study was to investigate the possible mechanism of antisperm antibodies production after infection withU. urealyticumand to analyze the relationship betweenU. urealyticumand infertility. The existence of cross-reactive antigens (61, 50, and 25 kDa) betweenU. urealyticumand human sperm membrane proteins was confirmed. Among the cross-reactive antigens, the urease complex component UreG ofU. urealyticumwas determined. By searching the Swiss-Prot protein database, a pentapeptide identity (IERLT) between UreG and human nuclear autoantigenic sperm protein (NASP) was found. Furthermore, using Western blot analysis and enzyme-linked immunosorbent assay, the cross-reaction between the NASP and UreG was verified. Both anti-rUreG antibody and the antiserum against the synthetic peptide NASP393-408 containing the pentapeptide inhibited mouse sperm egg binding and fusion. After immunization by rUreG or the synthetic peptide, 81.2 and 75% female mice became sterile, respectively. The effect on fertility in mice immunized with the synthetic peptide was reversible. These findings proved for the first time that it was feasible to screen antigens for immunocontraceptives from cross-reactive antigens between sperm and microorganisms which induce infertility.