Effect of a DNA vaccine harboring two copies of inhibin α (1-32) fragments on immune response, hormone concentrations and reproductive performance in rats

The objective was to investigate the effects of a novel DNA vaccine (pcISI) harboring two copies of inhibin α (1-32) fragments on immune response, hormone concentrations and reproductive performance in rats. Female Wistar rats (n = 18 per group) were immunized (twice, 4 wk apart) with 10, 50, or 100 μg (T1, T2 and T3, respectively), of the pcISI plasmid. At 4 wk after the second immunization, plasma antibody titers were higher (P < 0.05) in T3 than in either T1 or T2 (0.341 ± 0.123, 0.236 ± 0.068, and 0.251 ± 0.077, respectively, mean ± SD). Concurrrently, plasma concentrations of FSH and estradiol were highest (P < 0.05) in T3, and were higher (P < 0.05) in T1 and T2 than in control groups. For antibody-positive rats, there was a correlation (P < 0.01) between antibody titer and FSH concentrations after two pcISI immunizations. The number of mature follicles in the T3 group (46.00 ± 4.65) was higher (P < 0.05) than in two control groups (29.25 ± 3.72 and 27.92 ± 3.48), and also higher (P < 0.05) than in T1 and T2 (37.17 ± 4.99 and 38.75 ± 7.09). Antibody-positive rats had more mature ovarian follicles than negative rats (46.75 ± 4.23 vs. 35.60 ± 3.38, P < 0.05). Moreover, litter size and number of placentas were increased (P < 0.05) in the pcISI immunization groups, except for the T1 group, compared to the control groups. In conclusion, the pcISI DNA vaccine successfully induced a humoral immune response, improved reproductive hormone concentrations, stimulated follicular development, and increased number of placentas and litter size. Furthermore, 100 μg yielded the best immune response.