Effect of plasmid size on the immune response to Japanese Encephalitis virus DNA vaccine in mice

Abstract

Background: The envelope (E) protein, along with the pre-membrane (prM) protein of the Japanese encephalitis virus (JEV), are importantmediators of humoral immunity against the virus. Objective: To establish whether the plasmid size could influence the immunogenicityof this DNA vaccine candidate in terms of antibody inductive capacity. Methods: The prM and E genes of JEV were cloned in pCEP4 andpCDNA to produce the constructs pMEa and pcMEa, respectively. The former construct was approximately double the size of the latter.The plasmid constructs were used to immunize mice, both in terms of equal weight, as well as equal number of molecules. Results:The antibody-inductive capacity (both anti-JEV and neutralizing antibodies) of pCDNA was superior to that of the pCEP4. Importantly,the mice challenge studies indicated that the higher titer of neutralizing antibodies of the pCDNA group lead to higher survival in thisgroup. Conclusion: A smaller plasmid would be better for preparing a DNA vaccine construct.