CHARACTERIZATION OF CYSTEAMINE AS A POTENTIAL CONTRACEPTIVE ANTI-HIV AGENT

Cysteamine (beta-mercaptoethylamine, or MEA) is a thiol-reducing agent and has anti-HIV activity. Because of these properties, cysteamine wa s evaluated as a vaginal contraceptive and tested for its effects on s perm function and on other sexually transmitted microbes. Cysteamine w as contraceptive in the rabbit. Conception was inhibited completely wh en sperm were pretreated with 500 mu g/ml cysteamine and was inhibited by more than 60% when 7.5 mg cysteamine was applied vaginally as a su spension in 50% K-Y Jelly. Cysteamine had multiple effects on spermato zoa. Both acrosin (EC 3.4.21.10) and hyaluronidase (EC 3.2.1.35) were reversibly inhibited by cysteamine. Calculated IC50 values were 370 mu g/ml and 150 mu g/ml for acrosin and hyaluronidase, respectively. Cys teamine behaved as a poor spermicide when activity was measured by the 30-second Sander-Cramer test. However, sperm motility was inhibited c ompletely when cysteamine was preincubated for 10 minutes prior to mot ility evaluation, at concentrations as low as 50 mu g/ml. The calcium ionophore A23187-induced human acrosome reaction was inhibited by cyst eamine (IC50 = 0.5 mu g/ml). Neither herpes simplex virus nor Neisseri a gonorrhoeae was affected by cysteamine at concentrations as high as 500 mu g/ml and 100 mu g/ml, respectively. Cysteamine appears to have no effect on normal vaginal flora (i.e., lactobacillus). These results , together with published data, strongly support the further developme nt of cysteamine as a topical contraceptive anti-HIV agent.