Immunogenicity of a DNA vaccine for coxsackievirus B3 in mice: protective effects of capsid proteins against viral challenge.

Coxsackievirus (CVB) 3 induces viral myocarditis and ultimately dilated cardiomyopathy (DCM). However, there is no vaccine in clinical use. We constructed recombinant CVB3 plasmids using a highly effective mammalian expression vector and evaluated their immunogenicity in vivo on the basis of survival rate. Four recombinant plasmids were constructed, which encode CVB3 capsid proteins (VP1 or VP3) or VP1 partial proteins (VP1-1 or VP1-2), and used to immunize BALB/c mice by electroporation. Although VP1, VP3, VP1-1, and VP1-2 induced specific antibodies against the corresponding proteins in mice, neutralizing antibodies were not present in the sera. These recombinant plasmids, except VP1-1 (12.5%), dramatically increased the survival rate in mice at 46 days after challenge (42.9-75.0%, p<0.05). VP3 (75.0%) protected mice against viral infection and the middle regions of VP1 (VP1-2, 50.5%) conferred a protective effect like that conferred by VP1 (42.9%), suggesting that the epitopes in VP3 as well as in the middle of VP1 protect against CVB3 infection in vivo. In conclusion, some recombinant CVB3 plasmids used in this study reduced the destruction of myocytes and improved the survival rates in mice immunized and challenged compared with the control. Thus, pCA-VP3 as well as pCA-VP1 are good candidates for a CVB3 DNA vaccine.