Synergistic neutralizing antibody response to a dengue virus type 2 DNA vaccine by incorporation of lysosome-associated membrane protein sequences and use of plasmid expressing GM-CSF

We have previously shown that a dengue virus type 1 DNA vaccine expressing premembrane (prM) and envelope (E) genes was immunogenic in mice and monkey s and that rhesus monkeys vaccinated with this construct were completely to partially protected from virus challenge. In order to improve the immunoge nicity of dengue DNA vaccines, we have evaluated the effect of lysosome tar geting of antigens and communization with a plasmid expressing GM-CSF on an tibody responses. A dengue virus type 2 candidate vaccine containing prM an d E genes was constructed in which the transmembrane and cytoplasmic region s of E were replaced by those of the lysosome-associated membrane protein ( LAMP). The modified vaccine construct expressed antigen that was colocalize d with endogenous LAMP in lysosomal vesicles of transfected cells, whereas the antigen expressed from the unmodified construct was not. It was hypothe sized that targeting of antigen to the lysosomal compartment will increase antigen presentation by MHC class II, leading to stronger CD4-mediated immu ne responses. Mice immunized with the modified construct responded with sig nificantly higher levels of virus neutralizing antibodies compared to those immunized with the unmodified construct. Communization of mice with a plas mid expressing murine GM-CSF enhanced the antibody response obtained with e ither the unmodified or the modified construct alone. The highest antibody responses were noted when the modified construct was coinjected with plasmi d expressing the GM-CSF gene. These results could form the basis for an eff ective tetravalent dengue virus DNA vaccine. (C) 2001 Academic Press.