Differences between antigenic determinants of pig and cat zona pellucida proteins

Despite many efforts, the control of reproduction in feral cat populations is still a problem in urban regions around the world. Immunocontraception i s a promising approach; thus the present study examined the suitability of the widely used pig zona pellucida proteins (pZP) for contraception in fera l domestic cats. Purified zona pellucida proteins obtained from pig and cat ovaries were used to produce highly specific antisera in rabbits. Antibodi es against pZP raised in rabbits or lions were not effective inhibitors of either in vitro sperm binding (cat spermatozoa to cat oocytes) or in vitro fertilization in cats, whereas antibodies against feline zona pellucida pro teins (fZP) raised in rabbits showed a dose-dependent inhibition of in vitr o fertilization. Immunoelectrophoresis, ELISA and immunohistology of ovarie s confirmed these results, showing crossreactivity of anti-fZP sera to fZP and to a lesser extent to pZP, but no interaction of anti-pZP sera with fZP . It is concluded that cat and pig zonae pellucidae express a very small nu mber of shared antigenic determinants, making the use of pZP vaccine in cat s questionable. A contraceptive vaccine based on feline zona pellucida dete rminants will be a better choice for the control of reproduction in feral c ats if immunogenity can be achieved.