A comparison of eight techniques for the evaluation of the auto-immune response to spermatozoa after vasectomy

Construction of a catsper1 DNA vaccine and its antifertility effect on male mice

Cation channel of sperm 1 (CATSPER1) is a unique sperm cation channel protein, and essential for sperm function and male fertility. CATSPER1 exclusively expresses in meiotic and postmeiotic spermatogenic cells, thus belongs to the spermatogenesis-specific antigen that escape central tolerance. We have previously demonstrated the immunocontraceptive potential of its transmembrane domains and pore region, and reported the antifertility effects of its B-cell epitopes on male mice. Aiming to develop DNA vaccine targeting CATSPER1 for male contraception, here the whole open reading frame of mouse Catsper1 was cloned into the plasmid pEGFP-N1 to obtain a DNA vaccine pEGFP-N1-Catsper1. The vaccine was confirmed to be transcribed and translated in mouse N2a cell in vitro and mouse muscle tissue in vivo. Intramuscular injection with the vaccine on male mice induced specific immune reaction and caused significant inhibition on sperm hyperactivated motility and progressive motility (P<0.001 for both), and consequently reduced male fertility. The fertility rate of experimental group was 40.9%, which was significant lower (P=0.012) than control group (81.8%). No significant change in mating behavior, sperm production and histology of testis/epididymis was observed. Given that Catsper1 exhibits a high degree of homology among different species, Catsper1 DNA vaccine might be a good strategy for developing an immunocontraceptive vaccine for human and animal use.

Potential contraceptive use of epididymal proteins: immunization of male rats with epididymal protein DE inhibits sperm fusion ability

Rat epididymal protein DE associates with the sperm surface during maturation and participates in sperm-egg fusion. Immunization of male rats with DE raised specific antibodies and produced a significant reduction in the animals' fertility. The present study focused on determining the in vivo mechanism involved in fertility inhibition. Wistar males were injected with DE, and antibody levels and animal fertility were evaluated. Results revealed an association between the two parameters, since animals with absorbance values lower than 0.5 in ELISA presented high fertility rates (66%, 100%) while those with absorbance values higher than 0.5 exhibited the lowest fertility rates (0%, 33%). Histological studies showed no evidence of orchitis, epididymitis, or vasitis in DE-immunized animals. ELISA results revealed the presence of anti-DE antibodies in epididymal and vas deferential fluids. Indirect immunofluorescence and ELISA experiments indicated that these antibodies would not interfere with the synthesis or secretion of DE or with its association with the sperm surface. Finally, while epididymal sperm recovered from DE-immunized animals presented no changes in motility, viability, or ability to undergo capacitation and acrosome reaction, they exhibited a significant decrease in their ability to fuse with zona-free eggs, with no effect on their ability to bind to the oolemma. Together these results indicate that immunization of male rats with epididymal protein DE specifically interferes with the sperm fertilizing ability, supporting the use of epididymal proteins for contraceptive vaccine development.

The indirect mixed antiglobulin reaction test using a commercially available kit for the detection of antisperm antibodies in serum

A simple procedure is described for the detection of antisperm antibodies of the IgG class in human serum using the indirect mixed antiglobulin reaction (MAR) test. The test uses only one dilution of serum (1/16) and no washing procedures. The test was performed in 361 sera. Comparative studies were conducted with the tray agglutination test (TAT) in 164 sera and with the direct MAR test on semen in 110 cases. In 24 sera with borderline test results, and in 13 sera with discordant findings, evidence of antisperm antibody activity was investigated by means of additional testing, namely, the adenosine triphosphate release cytotoxicity test (ARCT) and the indirect immunobead tests (IB) for IgA and IgM. Using the value of 40% reaction between motile spermatozoa and coated latex particles as the lower limit of significant activity, the indirect SpermMAR test has a sensitivity of 96% and specificity of 87%. The two false-negative indirect MAR results occurred in cases with IgM, the clinical significance of which is doubtful. Hence, the indirect MAR test appears to be an ideal screening procedure for sperm antibodies in serum since it is easy to perform and sensitive. Considering the false-positive rate of 13%, additional tests should, however, be performed on sera with a reaction of 40% or more in order to assess the relevance of the antibodies as a cause of infertility.

Sperm and seminal plasma antibodies in acquired immune deficiency (AIDS) and other associated syndromes

Although HIV has been established as the etiologic agent in AIDS, other contributory cofactors may be responsible for selective clinical manifestations of the syndrome. While the pathogenesis remains unclear, the development of immunologic abnormalities observed in some homosexual males with AIDS and AIDS-related complex may be attributed to repeated exposure to allogeneic sperm and seminal plasma components. Accordingly, antibody levels to semen fractions were measured in sera from 338 individuals (295 AIDS, 36 ARC, 16 randomly selected homosexuals, 29 patients with infectious hepatitis, 12 hemophiliacs, 20 rheumatic disease patients, and 24 healthy heterosexual adults). The methods were (i) passive hemagglutination for antibodies to human seminal plasma (HuSePl), and (ii) indirect immunofluorescence (IF) assay on methanol-fixed human sperm noting staining of acrosomal, equatorial, postnuclear, and tail main-piece regions. HuSePl was positive in 31% AIDS sera, while 39% were positive by IF. ARC sera were 30% positive for HuSePl and 38% positive IF. No control sera were positive. Results reveal a significant incidence of antibody to sperm and seminal plasma components in ARC and AIDS patients. Because of the known immunomodulating properties of both, it is possible that these responses may indicate risk factors for disease progression and severity.

Acquired immune deficiency syndrome (AIDS) and autoimmunity--mutually exclusive entities?

Loss of normal immune homeostasis occurs in acquired immune deficiency syndrome (AIDS). We evaluated patients at the University of Cincinnati and New York University Medical Centers for serologic evidence of autoimmune changes. Specifically, tests for antinuclear and organ-specific antibodies by immunofluorescence, antisperm and anti-seminal plasma antibodies, rheumatoid factor by latex and sensitized sheep cell agglutination techniques, anti-polyadenosine (poly A), and single-stranded DNA antibodies were performed in human immunodeficiency virus (HIV) antibody-positive sera. A parallel study of mitogen responsiveness was performed and showed inhibition of response by AIDS and AIDS-related complex (ARC) sera. In spite of evidence of polyclonal B-cell activation, hyperglobulinemia, and the presence of antibodies to many infectious agents, as well as the known cellular immune abnormalities, the patients tested had a striking absence of these autoantibodies. The only major difference noted from normal controls, was a low but significant level of antibody binding to poly A. The autoimmune connective tissue diseases were not observed in this group of patients.

Temporal appearance of antisperm autoantibodies in Lewis rats following vasectomy

An indirect enzyme-linked immunosorbent assay (ELISA) was employed to monitor antisperm autoantibodies in 16 Lewis rats for up to 36 weeks following vasectomy. This assay was capable of discriminating all prevasectomy from postvasectomy sera at a 1:16 dilution. Weekly serum samples were obtained for the first 13 weeks and bimonthly samples thereafter. Half of the animals developed a positive antisperm autoantibody response by the end of the first postoperative week. By the end of the second week, 81% of the animals had positive responses. The greatest proportion (88%) of animals having a positive response over the course of the study was found at the end of the seventh postoperative week and the highest mean absorbance value for all 16 animals was observed at this time. Only 25% of the animals had positive responses for antisperm autoantibody at the end of the 35th week of the study. These findings indicate that circulating antisperm autoantibodies arise in the Lewis rat earlier than has been generally appreciated. The time course is similar to that of antibody titers to infectious agents or arising from inoculation of rats with spermatozoa. These findings on autoantibody levels in the Lewis rat are compared with the dynamics of antisperm autoantibody formation in man.

An enzyme-linked immunosorbent assay for measuring antisperm autoantibodies following vasectomy in Lewis rats

An indirect enzyme-linked immunosorbent assay (ELISA) was devised to measure antisperm auto-antibodies in the Lewis rat following vasectomy. The assay system was validated by employing prevasectomy sera and postvasectomy antisera, previously demonstrated to contain antisperm antibodies by indirect immunofluorescence. A standardized ELISA protocol was developed employing 10(5) sperm per microtiter plate well and sucrose-polyvinylpyrrolidone as a postcoat stabilizer solution. The ELISA was shown to yield significant detectable antibody at dilutions of 1/512 or greater in the most reactive sera. A standard for scoring positive titers was adopted: 1.96 standard deviations above the mean of the preimmune value. Using the criterion, 88% of 7-week postvasectomy samples could be discriminated from preimmune samples at a 1:16 dilution, which was adopted for subsequent assays. The ELISA demonstrated 73% and 91% reproducibility for an intraassay analysis of single prevasectomy and postvasectomy serum samples (7 weeks postvasectomy) tested in 160 determinations on a standard sperm pool. When this single antigen pool was employed in 35 determinations at 0, 1, and 4 weeks in an interassay study, 56% and 70% reproducibility was found for pre- and postvasectomy sera respectively. A correlation (r = 0.75) was made between a single absorbance value and the endpoint titer of the same sera, which indicated that single absorbance values could be used to predict serum titer and single dilutions could be used for general screening of a large number of samples. The ELISA described provides a rapid, sensitive, and reliable method that discriminated between samples taken before and after vasectomy.

Common specificities of auto- and iso-antibodies to human spermatozoa

The specificities of antispermatozoal antibodies in humans were compared using the ability of F(ab')2 fragments prepared from sera containing spermatozoal antibodies to block access to antigenic sites on spermatozoa. Reciprocal blocking experiments were carried out on a panel of 13 sera which came from both men and women, had different modes of agglutination, and came from widely separated population centers. The blocking experiments confirmed that specificities of antispermatozoal antibodies bear little relation to those suggested by observed modes of agglutination. F(ab')2 fragments from head-agglutinating sera could inhibit the immobilizing activity of a tail-agglutinating sera and vice versa. Similarly, the sera from men and women could inhibit each other, as could sera collected from patients living in widely separated localities. It is concluded that there are more than one, but a limited number, of antigens on the spermatozoal surface capable of generating antibodies with antifertility effects. It is also concluded that these antigens occur all over the sperm surface but may be concentrated in certain areas and that the observed modes of agglutination depend at least as much on the characteristics of the antibodies as on their specificities.