DNA/MVA combined immunization: antibody response to Plasmodium falciparum merozoite surface protein 1 in mice

OBJECTIVE: To explore the effect of DNA/MVA combined immunization in enhancing antibody response to MSP1. METHODS: DNA vaccine and recombined MVA were constructed based on synthesized MSP1 gene (3D7). BALB/c mice were primed with DNA solely or together with GM-CSF expressing plasmid and then boosted with rMVA/ 190. Serum IgG and subtype IgG1 and IgG2a were assayed by ELISA. All mice were challenged with allelic replaced Plasmodium berghei. RESULTS: Antibodies to MSP1-190 were detected after DNA immunization with an end-point dilution titer of 1:2500. When GM-CSF plasmid was added, the antibody end-point dilution titer reached 1:11150, with an increase of 53 and 10 times respectively after MVA boosting. Among them anti-19000 antibodies were prominent, 1/4-1/3 of total IgG in serum. However, when the mice were challenged with Pb-PfM19 no prolonged survival was observed (P>0.05). CONCLUSION: High titer antibodies can be elicited in mice by using codon optimized MSPI gene and DNA/MVA combined immunization. The specificity and protection of these antibodies is being further investigated.