Modulation of immune response to Plasmodium falciparum apical membrane antigen 1 DNA vaccine by cytokine plasmids

OBJECTIVE: To explore the effect of cytokine encoding plasmids on DNA immunization in mice. METHODS: Prototype DNA vaccine VR1020/E which contain Plasmodium falciparum apical membrane antigen 1 (AMA1) ectodomain was constructed, and eukaryotic expression vectors pcDNA3/GM-CSF, pcDNA3.1(-)/IL-4, pIL-12 and pGM-CSF/pTPA-E were also built. BALB/c mice were immunized with VR1020/E alone or with VR1020/E plus different cytokine plasmids. Serum IgG and its subtype were determined by ELISA and in vitro splenocyte proliferation assay was done. RESULTS: GM-CSF, IL-4 and IL-12 encoding plasmids all promoted mice immune response to VR1020/E, the antibody level increased 7 to 10 times and splenocyte proliferation was enhanced too. Plasmid pcDNA3/GM-CSF induced much more IgG1 whereas plasmid pIL-12 induced much more IgG2a. CONCLUSION: Cytokine encoding plasmids might be used as adjuvant in AMA1 DNA immunization.