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Infect. Immun. doi:10.1128/IAI.01171-06
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Screening an antigen target for immunocontraceptives from cross-reactive antigens between human sperm and Ureaplasma urealyticum

Department of Histology & Embryology, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Laboratory of Molecular Cell Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China

^* To whom correspondence should be addressed. Email: liux{at}sibs.ac.cn. chenx{at}shsmu.edu.cn.

	Abstract

Epidemiologic studies indicated that some infertile men who were infected with Ureaplasma urealyticum (U. urealyticum) displayed 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 by U. urealyticum and to analyze the relationship between U. urealyticum and infertility. The existence of cross-reactive antigens (61, 50, 25 kDa) between U. urealyticum and human sperm membrane proteins was confirmed. Among the cross-reactive antigens, the urease complex component UreG (UreG) of U. urealyticum was determined. By searching 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 ELISA, 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.