Enhancement Of The Recombinant Plasmid With CpG Motifs On Immunity And Resistance Of Mice

In order to develop a safe and effective immunoadjuvant to enhance the immunity and resistance of animals against infection, a novel CpG Oligodeoxynucleotides containing 11 CpG motifs was synthesized and inserted into the VR1012 plasmid, designated as VR1C. Then the recombinant VR1C was entrapped with Chitosan nanoparticles (CNP) prepared by the method of ionic cross linkage, and employed to inject muscularly 3-weeks old Kunming mice; the blank VR1012 packed with CNP and saline were used to inoculate mice as the control groups. 28 days after inoculation, all mice were orally fed with 0.4ml 2x108CFU/ per mouse virulent hemorrhagic enteritis E. coli to challenge the resistance against infection. Sandwich ELISA was used to detect the content of immunoglobulins and interleukins in the sera of mice. The results found that compared with control mice, the content of IgG, IgA and IgM remarkably increased in the sera of VR1C-CNP treated mice(P＜0.05), so were the IL-2, IL-4 and IL-6. The number of lymphocytes and monocytes were also raised considerably in the blood of VR1C-CNP group (P＜0.05). After the challenge, these immune values and specific antibody to E. coli were elevated to different degrees in VR1C-CNP mice which were significantly higher than those of the control groups except the neutrophils; and the VR1C treated mice all survived without symptoms and lesions; while the control mice manifested evident symptoms and lesions with diffuse hemorrhage in stomach, small intestine and peritoneum. These demonstrated that VR1C-CNP could significantly enhance the nonspecific humoral and cellular immunity of mice against virulent bacteria challenge, and VR1C-CNP is a promising effective immune potentiator to promote innate immunity and resistance of animal against infection of virulent pathogens.