• Bioneutralization;
  • contraceptive vaccine;
  • cross-reactivity;
  • immunogenicity;
  • recombinant CGβ

PROBLEM: Prototype human chorionic gonadotropin (hCG) vaccines based on natural sources are unsuitable for widespread applications due to their complex manufacturing procedures, cost, and carrier-mediated immune suppression.

METHOD OF STUDY: Wistar rats were immunized with alum-adsorbed CGβ (recombinant), CGβ-TT, and nCGβ (native CGβ)-TT, whereas Bonnet monkeys were immunized with only CGβ. The anti-hCG antibody titre in the sera obtained at different time points were quantified by radioimmunoassay. The sera of Wistar rats were characterized in terms of their affinity to hCG, bioneutralization capacity (by inhibition of hCG-induced testosterone production in Leydig cells), and cross-reactivity with human luteinizing hormone, human follicle-stimulating hormone, and human thyroid-stimulating hormone (by direct binding assays).

RESULTS: Antigen-binding capacities of sera obtained upon immunization with CGβ were 3,080 ± 943 ng/ml (n = 6) and 3,993 ± 1,292 ng/ml (n = 4), respectively, in rats and monkeys. The analysis of data revealed that immunization of rats with CGβ produced antibodies comparable to that of CGβ-TT and nCGβ-TT.

CONCLUSION: The study opens up the possibility of producing pure and highly immunogenic CGβ by a recombinant DNA route, as a consistent source of antigen for birth control vaccine.