[Protective immunoresponse to CVB3 induced by gene immunization with pcDNA3-VP1]

To induce Coxsackie virus B type 3 (CVB3)-specific immune response by using a DNA vaccine containing CVB3-VP1 and to observe its protection against CVB3 challenge.

The gene coding for VP1 was obtained by RT-PCR and then was cloned into plasmid pcDNA3 to construct pcDNA3-VP1. In-vitro expression of VP1 was performed by transfection of pcDNA3-VP1 into Hela cells. Expressed product was detected by ELISA. BALB/c mice were immunized intramuscularly with 50 microg DNA three times, and challenged by 5xLD(50) CVB3 four weeks after the last immunization.

pcDNA3-VP1 had been constructed and the expression product was detected in the culture supernatant of Hela cells 24 hours after transfection. CVB3-specific IgM and IgG elicited in the mice immunized with pcDNA3-VP1 were significantly higher than those in the control mice immunized with pcDNA3. Specific proliferation of the splenic lymphocytes and activity of CVB3-specific CTLs from the pcDNA3-VP1 immunized mice were much stronger than those in the controls. pcDNA3-VP1 could protect 33.3% mice from lethal CVB3 challenge, while control mice only survived 6.7 days. Infiltration of inflammatory cells or unusual proliferation of connective tissue, indicating ongoing myocarditis or fibrosis, were not found in pcDNA3-VP1 immunized mice, but did exist in control mice.

Intramuscular immunization with pcDNA3-VP1 may be a promising approach against CVB3 infection.