Immunomodulation of Japanese encephalitis vaccine through CpG oligodeoxynucleotides in mice

Synthetic oligodeoxynucleotides (ODN) containing unmethylated cytosine guanine (CpG) dinucleotides motifs act as immune adjuvant and provide means of modulation to immune responses when co-delivered with antigens. They stimulate both innate and adaptive immune responses and induce T helper 1 (Th1) immune responses. We investigated the immunomodulation of Japanese encephalitis (JE) vaccine using CpG ODN as an adjuvant. Mice were immunized with one dose of JE vaccine 0.1 ml with different concentrations (10, 25 and 100 microg) of CpG ODN. The serum antibody level and cytokines were evaluated and compared with mice immunized with two doses of JE vaccine alone. Our studies revealed that anti-JE antibody level in mice immunized with single dose of 0.1 ml JE vaccine and 100 microg CpG ODN were almost equal to mice immunized with two doses of JE vaccine alone. Furthermore, CpG ODN enhanced the production of TNF-alpha and Th1-mediated cytokines, including IFN-gamma and IL-2 compared with JE vaccine alone. In addition, absence of any significant changes in biochemical, haematological and histological studies suggest that CpG ODN are safe adjuvants for JE vaccine. Therefore, it is inferred that CpG ODN are effective and improve the efficacy of JE vaccine.