Improvement Of The Immunity Of Piglets To PRRS Vaccine By A Porcine IL-4 And IL-6 Fusion Gene Encapsulated In Chitosan Nanoparticles

In order to develop an effective immune molecule to boost pig resistance against porcine reproductive and respiratory syndrome (PRRS), this study was conducted to explore the effect of a fusion gene encoding porcine interleukin-4(IL-4) and IL-6 (PIL4/IL6) on the immunity of piglets to PRRS vaccine. The recombinant eukaryotic expression plasmid containing the fusion PIL4/IL6 gene was encapsulated in chitosan nanoparticles (CNP) prepared by the ionotropic gelation method, designated as VPIL4/IL6-CNP. Then 21-day old piglets were divided into four groups and intramuscularly injected respectively with 0.5mg VPIL4/IL6-CNP, VPIL4+VPIL6-CNP, VR1020-CNP and VR1020 along with the inactivated vaccine. The blood was weekly collected from piglets after vaccination to detect the changes of immunoglobulin, specific antibody, IL-2, IL-4, IL-6 and immune cells. Compared with those of control piglets, the amount of immunoglobulin and specific antibody to PRRSV increased significantly in the sera of piglets treated with VPIL4/IL6-CNP (P<0.05). Furthermore, the levels of interleukins increased in the sera of the treated piglets (P<0.05) and the number of lymphocytes and monocytes were also significantly elevated in the treated groups (P<0.05). Meanwhile, the humoral and cellular immune responses in the VPIL4/IL6-CNP piglets were significantly stronger than those of the VPIL4+VPIL6-CNP group (P<0.05). These results suggest that VPIL4/IL6-CNP is a novel promising imunoenhancer for PRRS vaccine to promote the humoral and cellular immunity of piglets, facilitating the development of safe and effective immune adjuvant to enhance the immunity of pig against infection.