Study on the antifertility effects of the plasmid DNA vaccine expressing partial brLDH-C4'

Partial cDNA sequence coding for Microtus brandti radde (Brandt's vole) testes-specific lactate dehydrogenase (brLDH-C4) was amplified by reverse transcription-polymerase chain reaction (RT-PCR). By inserting the product into the eukaryotic expression vector pCR3.1, pCR3.1-brLDH-C4' was obtained as the prototype of contraceptive DNA vaccine. Immunization with pCR3.1-brLDH-C4' in BALB/c mice generated antibodies specific to purified brLDH-C4' and native mouse LDH-C4 protein. The birth rate of the pCR3.1-brLDH-C4' immunized mice was found to be decreased significantly (80% lower than that of those immunized with pCR3.1). Functions of the elicited antibodies in sera from pCR3.1-brLDH-C4' inoculated mice were further explored. The results indicated that the antibodies from the mice injected with pCR3.1-brLDH-C4' could cause the agglutination of normal sperm suspension, while the ovarian structure and the development of ovarian follicles of these mice were not impaired, which gives a possible explanation for the immunocontraceptive effects of the pCR3.1-brLDH-C4' DNA vaccine.