Improvement of the immunity of pig to Hog cholera vaccine by recombinant plasmid with porcine interleukin-6 gene and CpG motifs

In order to observe the dosage-effect of recombinant pig interleukin-6 gene and CpG motifs on the immune responses of swine to vaccine, a novel recombinant eukaryotic VPIL6C plasmid was packed with chitosan nanoparticles (CNP) prepared by ionic cross linkage, which contains pig interleukin-6 gene and immunostimulatory sequence consisted of 11 CpG motifs. CNP-VRIL6C was then utilized to inoculate 30-day-old piglets intramuscularly at the dosage of 0.5, 1.0 and 1.5 mg/per capita, respectively. Meanwhile, the piglets were injected with attenuated classical Hog cholera vaccine and designated as A1, A2 and A3 group. The blood was weekly collected from the piglets after vaccination to detect the changes of immunoglobulins, specific antibody, interleukins, IFN-γ and immune cells. The results were found that compared to those of the control piglets injected with VR1020-CNP, the content of IgG, IgA and IgM, specific antibodies, IL-2, IL-6 and IFN-γ significantly increased in the sera from the treated three groups from 14 to 70 days after vaccination (P < 0.05); the number of TH, TC and CD3+ positive T cells raised obviously in the blood of VPIL6C treated piglets (P < 0.05). Also the above immune indexes of A1 group were significantly lower to different extent in comparison with those of A2 and A3 group from 14 to 56 days post inoculation (P > 0.05). Moreover, the lymphocytes also remarkably elevated in the treated groups (P < 0.05). These indicate that VPIL6C entrapped with CNP is a novel effective adjuvant to boost the humoral and cellular immunity of pig to Hog cholera, implying it's potentiality to enhance the resistance of pig against infectious diseases.