A DNA vaccine expressing dengue type 2 virus premembrane and envelope genes induces neutralizing antibody and memory B cells in mice

A dengue DNA vaccine candidate was developed and evaluated for immunogenicity in mice. The vaccine, designated pcD2ME. is a pcDNA3-based plasmid encoding the signal sequence of premembrane (prM), prM and envelope (E) genes of the New Guinea C strain of dengue type 2 virus. CHO-K1 cells transfected with pcD2ME expressed prM and E as determined by immunochemical staining with monoclonal antibodies. BALB/c mice inoculated intramuscularly with 100 mu g of pcD2ME two or three times at an interval of 2 weeks developed a low level of neutralizing antibody (1:10 at a 90% plaque reduction). Immunization twice with 10 mu g or 1 mu g of pcD2ME or three times with 100 mu g of pcDNA3 did not induce detectable levels of neutralizing antibody. Mice immunized two or three times with 100 mu g of pcD2ME raised neutralizing antibody titers to 1:40 or greater on days 4 and 8 after challenge with 3 x 10(5) plaque forming units (PFU) of the New Guinea C strain of dengue type 2 virus, showing strong anamnestic responses to the challenge. In contrast, mice immunized two or three times with 100 mu g of pcDNA3 developed no detectable neutralizing antibody on days 4 and 8 after challenge. These results indicate that immunization with pcD2ME induces neutralizing antibody and dengue type 2 virus-responsive memory B cells in mice. (C) 2000 Elsevier Science Ltd, All rights reserved.