Antisperm antibodies (ASAs) in infertile males: subclass distribution of IgA antibodies and the effect of an IgA1 protease on sperm-bound antibodies.

PROBLEM

(1) To determine the IgA subclass distribution of antibodies in the serum and on the sperm of infertile male patients. (2) To determine the effect of an IgA1 protease on the binding of IgA antisperm antibodies (ASA).

METHOD

Fifteen infertile males with ASA in serum (10) or on sperm (5) were recruited for this study. Duration of infertility was at least one year. Monoclonal antibodies to human IgA1 and IgA2 were conjugated to immunobeads. The distribution of IgA1 and IgA2 subclass ASA was determined for positive serum and sperm samples. The effects of an IgA1 protease (isolated from Neisseria meningitidis strain HF13) on sperm-bound antibodies was evaluated by immunobead binding.

RESULTS

In serum, the IgA1 subclass ASA was predominate (91%) when compared with IgA2 (9%) subclass. Direct sperm-bound antibodies displayed a distribution more characteristic of the secretory immune system with IgA1 accounting for 63% and IgA2 accounting for 37% of the total IgA ASA. Enzyme treatment dramatically reduced the amount of serum IgA antibodies bound to sperm (P < 0.05). Similarly, a significant reduction in direct sperm-bound antibodies was observed after enzymatic treatment with no loss in sperm motility.

CONCLUSIONS

(1) Although IgA1 direct sperm-bound antibodies were dominant, when compared with serum there was a higher proportion of IgA2 subclass, which suggests a local production of IgA. (2) Specific IgA1 protease treatment is capable of reducing the amount of immunobead-detectable IgA on sperm. Hamster oocyte sperm-penetration assays are ongoing to determine if this treatment might improve sperm penetration rates.