Hepatitis B Surface Antigen S Gene is an Effective Carrier Molecule for Developing GnRH DNA Immunocastration Vaccine in Mice

Relatively molecular mass of GnRH antigens is small and hence needs to couple to a large carrier molecule to enhance its immunogenicity. This study investigated whether hepatitis B surface antigen S (HBsAg‐S) gene can be used as an effective carrier molecule for developing GnRH DNA immunocastration vaccine. Two copies of human GnRH gene were fused with HBsAg‐S gene for constructing a recombinant plasmid pVAX‐HBsAg‐S‐2GnRH that coded for 27 kDa target fusion protein. Ten male mice were divided into two equal groups, treatment and control. The vaccine (50 μg/mice) prepared in saline solution was injected into male mice at weeks 0, 1, 2, 4 and 7 of the experiment. Vaccine's efficacy was evaluated in terms of GnRH‐specific IgG antibody response, plasma testosterone levels, testicular weight and extent of the testicular tissue damage. The specific anti‐GnRH antibody titre in vaccinated animals was significantly higher than in controls in only 4th week of immunization (p < 0.05). In addition, vaccinated animals showed lower testicular weight than those of the controls (p < 0.05). Spermatogenesis in seminiferous tubules in vaccinated animals was suppressed. In conclusion, in this study, the engineered plasmid to be used as a GnRH DNA vaccine induced antibody response and suppressed spermatogenesis in mice. This suggests that HBsAg‐S gene can be an effective carrier molecule for developing GnRH DNA immunocastration vaccine when relatively molecular mass of the aimed antigens is small.