Oral and intranasal administration of somatostatin DNA vaccine mediated by attenuated Salmonella Enterica Serovar Typhimurium to promote growth of piglets
An attenuated strain ofSalmonella typhimuriumhas been used as a carrier for oral and intranasal genetic immunization. Here, we evaluate the efficacy of a vaccine strain ofS. typhimurium.CSO22 (pGM-CSF/SS, plasmid granulocyte-macrophage colony-stimulating factor/somatostatin) expressing two copies ofSSgenes. A total of 115 piglets, aged 2 months old, were either orally or intranasally immunized against the vaccine strain CSO22 (pGM-CSF/SS) with three dosages (5 × 1010colony forming units (CFU),
... rming units (CFU), 5 × 109CFU and 5 × 108CFU). For oral immunization, the specific anti-SS antibodies were detected in the immunized piglets. The levels of SS antibodies in the high-dose immunized group (5 × 1010CFU) were significantly higher than that in the phosphate buffered saline immunized group (P< 0.01) and 40% of animals were positive in SS antibodies in the high-dose immunized group. Moreover, the weight gain of the high-dose group was increased by 20.86%, 10.26% and 15.30% during 4, 8 and 12 weeks, respectively, after immunization in comparison to the control. For intranasal immunization, the growth of the low-dose group was increased by 10.23% in the whole test period (12 weeks). In conclusion, our results suggest that the recombinant strain could elicit anti-SS antibodies and improve the growth performance of immunized piglets, and that the oral immunization program is better than the intranasal program.