A COMBINATORIAL PHAGE DISPLAY LIBRARY FOR THE GENERATION OF SPECIFIC FAB FRAGMENTS RECOGNIZING HUMAN SPERMATOZOA AND INHIBITING FERTILIZING-CAPACITY IN-VITRO

To select a source of lymphocytes for the generation of an anti-sperm- biased combinatorial phage display library, venous blood was obtained from 34 vasovasostomy (vasectomy reversal) patients approximately 3 mo after surgery. Using a variety of immunoassays, serum was analyzed fo r antibodies against human spermatozoa, and a patient was selected on the basis of high titer of antibodies that recognized the equatorial r egion of the sperm head and inhibited sperm fertilizing capacity in vi tro. Total RNA isolated from the stored lymphocytes of this individual was reversed transcribed, and gamma 1 (Fd) region and kappa chains we re amplified by polymerase chain reaction for the successful construct ion of an antibody phage display library. The library was panned again st human spermatozoa to isolate sperm-specific phage that recognized t he equatorial region of the sperm head. Three preparations of Fab were tested via the hamster egg penetration test. Each preparation signifi cantly (p < 0.005) inhibited sperm-egg binding and fusion, with one pr eparation (designated Fab-G) causing complete inhibition. Sequence ana lysis of the kappa light gene encoding Fab-C revealed a 93% homology w ith the light chain of human anti-human immunodeficiency virus gp120 p 35 variable region. This technology may have a practical application i n characterization of the immune response to spermatozoa and for the d esign of sperm-based contraceptive vaccines.