Immunization against lysozyme-like proteins affect sperm function and fertility in the rat

Proteins of the epididymal and testicular mileu contribute to sperm maturation and a vast majority of them remain uncharacterised. In this study, the role of three Lysozyme-like (LYZL) proteins, namely LYZL1, LYZL4 and LYZL6 in sperm function was assessed using in vitro neutralization and auto antibodies generation model. Rats immunized with LYZL1, LYZL4 and LYZL6 proteins had a litter size of 5.93, 8.47 and 2.10 respectively compared to 9.96 in the control rats. The litter size was further reduced to 4.53, 7.67 and 1.23 for the corresponding proteins in the second mating conducted 14 weeks after immunization. Epididymal and testicular fluids obtained from the immunized rats displayed a very high antibody titre against all the three proteins. Sperm count was significantly reduced in rats immunized with LYZL1 or LYZL6 and to a lower extent in LYZL4 group. Acrosome reaction associated calcium release was inhibited in spermatozoa obtained from LYZL1 or LYZL4 or LYZL6 immunized rats as well as in spermatozoa incubated with antiserum against the three proteins. Impairment in path velocity, progressive velocity and track speed were observed in spermatozoa obtained from LYZL6 immunized rats. Treatment of spermatozoa with LYZL6 recombinant protein did not potentiate calcium release and acrosome reaction. Results of this study indicate a role for LYZL proteins in sperm function and further studies are warranted to explore them as potential contraceptive agents.