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.