Construction and evaluation of the novel DNA vaccine harboring the inhibin α (1-32) and the RF-amide related peptide-3 genes for improving fertility in mice

To further improve fertility of animals, a novel gene RFRP-3 (RF-amide related peptide-3, RFRP-3) was used to construct DNA vaccines with INH alpha (1-32) (inhibin, INH) fragment for the first time. The aim of this study was to evaluate the effects of novel DNA vaccines on fertility in mice. Synthesized SINH and SRFRP (INH and RFRP genes were separately ligated to the C-terminus of the small envelope protein of the hepatitis B virus (HBV-S) gene) fragments were inserted into multiple cloning site of pIRES vector to develop p-SINH/SRFRP. The synthesized tissue plasminogen activator (TPA) signal sequence was then inserted into the p-SINH/SRFRP to construct p-TPA-SINH/TPA-SFRFP. Meanwhile, p-SINH was prepared and considered as positive control. Forty Kunming mice were equally divided into four groups and respectively immunized by electroporation with p-SINH, p-SINH/SRFRP and p-TPA-SINH/TPA-SRFRP vaccine (three times at 2 weeks interval) and saline as control. Results showed that the average antibodies (P/N value) of anti-INH and anti-RFRP in mice inoculated with p-TPA-SINH/TPA-SFRFP were significantly higher (P<0.05) than those inoculated with p-SINH/SRFRP and the positive rates were 100% (anti-INH) and 90% (anti-RFRP) respectively, at 2 weeks after the third immunization. Litter size of mice immunized with the three recombinant plasmids was higher (P<0.05) than- that of the control, and litter size of mice immunized with p-TPASINH/TPA-SRFRP significantly increased (P<0.05) compared with p-SINH. These results suggested that the p-TPA-SINH/TPA-SRFRP harboring INH and RFRP genes was successfully constructed and had good immunogenicity, and might effectively increase litter size.