ELISA assay for GP3 (A) or GP5 (B) specific antibodies in sera from mice immunized with recombinant DNA vaccines. The antibody levels in mice immunized with DNA vaccines were compared with control mice immunized with pVAX1 empty vector or PBS. Serum samples (n = 6) were collected at various time-points. Arrows indicate the time of administration of boost immunizations. Data are shown as the mean ± S.D.