Anti-human sperm monoclonal antibody HS-11: a potential marker to detect bovine sperm capacitation and acrosome reaction in vitro.

The crossreactivity between bull spermatozoa and monoclonal antibodies initially raised against mouse spermatozoa and human spermatozoa was tested by indirect immunofluorescent assay. The three anti-human spermatozoa monoclonal antibodies examined (HSK-9, HS-11, HS-63) crossreacted with methanol-fixed bull spermatozoa, whereas the anti-mouse spermatozoa monoclonal antibodies (MS-4 and MS-7) did not. A separate experiment was conducted to determine the binding ability of HSK-9, HS-11 and HS-63 with live (fresh) bull spermatozoa incubated (39 degrees C in CO2 incubator) in a capacitation medium (modified Tyrode's supplemented with 10 micrograms heparin ml-1). The binding of the monoclonal antibodies to the intra-acrosomal antigens of live bull spermatozoa was determined at 0, 2, 4, 6 and 8 h of incubation. At the beginning of incubation, binding was minimal (3.2 +/- 1.7%), but a much higher percentage of spermatozoa exhibited fluorescent staining after 2 h. The maximal binding was observed after incubation for 8 h (72.0 +/- 8.2%). The third experiment was performed to determine binding of HS-11 to frozen-thawed spermatozoa and to test whether there was any variation among bulls in HS-11 binding to spermatozoa, and to assess whether such binding is an indication of sperm capacitation. Frozen-thawed semen samples from five bulls were assessed for antibody binding after 0, 2, 4 and 6 h of incubation. Maximal binding was observed at 4 h. Lysophosphatidylcholine (100 micrograms ml-1) induced acrosome reaction assay was performed to assess sperm capacitation at various intervals.(ABSTRACT TRUNCATED AT 250 WORDS)