Abstract: Objective To study effects of secreted CTLA-4 fusion Plasmodium falciparum DNA vaccine combined with GM-CSF on the humoral and cellular immune responses in mice. Methods The malaria antigen coding sequence fused with CTLA-4 extracellular region of mouse to be constructed as eukaryotic secretory expression vector VR1012-sES312-CTLA, recombinant protein in culture of transfected HEK293 cells was detected by Western blot. Balb/c mice were co-administrated with VR1012-sES312-CTLA and GM-CSF expression vector. After immunization specific antibody IgG titers and cytokines IFN-γ and IL-4 expression levels were evaluated by ELISA and ELISPOT respectively. Results The introduction of CTLA-4 into malaria DNA vaccine system and application of GM-CSF adjuvant significantly enhanced the specific immune response of the vaccine. Antibody titers in VR1012-sES312-CTLA and GM-CSF co-immunized mice have a 190-fold increase compared with the simple designed VR1012-ES312 immunization (P <0.001). Conclusion humoral and cellular immunity of malaria DNA vaccine were both significantly enhanced by dendritic cell-targeting modification and the introduction of GM-CSF molecular adjuvant into the immune system. This result provides a new idea for effectively raising the immune response level of malaria DNA vaccine.

Key words: malaria, DNA vaccine, CTLA-4, GMCSF