Shuffling of pig interleukin-2 gene and its enhancing of immunity in mice to Pasteurella multocida vaccine

In order to explore the safe and effective adjuvant for promotion of immunity of animals against infection, the experiment was carried out to shuffle Tibet pig IL-2 cDNA with other IL-2 cDNA from human, yak and mouse, and the effect of shuffled IL-2 (IL-2S) gene in vivo was investigated on immunity of mice to Pasteurella multocida. The IL-2S protein was found to remarkably promote the proliferation of pig lymphoblasts than the native pig IL-2 protein. Then the IL-2S gene was cloned into VR1020 eukaryotic plasmid (VRIL2S) and enwrapped with chitosan nanoparticles (CNP-VRIL2S). Twenty-one day old female Kunming mice were muscularly inoculated respectively with the CNP-VRIL2, CNP-VRIL2S and CNP-VR1020 along with Pasteurella multocida vaccine, and orally challenged with virulent Pasteurella multocida on 28 days post-vaccination. The blood was weekly collected to detect the change of IgG, IgA, IgM, specific antibody, IL-2, IL-4 and IL-6 by ELISA. The immunoglobulins, specific antibody and interleukins significantly increased in CNP-VRIL2S group compared with the control mice after vaccination and challenge, and 9 of 10 immunized mice survived challenge, while the all control mice manifested severe symptoms and lesions, and finally died of infection. These indicated that VRIL2S entrapped with CNP is a novel safe and effective adjuvant to boost the specific immunity and resistance of animal against infectious pathogen, which could facilitate the development of highly promising powerful adjuvant.