Comparison of immune responses elicited by recombinant protein and eukaryotic expression plasmid based on histidine rich protein 2 of Plasmodium falciparum

OBJECTIVE: To identify the immune characteristics of different vaccine prototypes based on HRP2 and to provide experimental evidence for developing P. f. blood stage vaccines. METHODS: BALB/c mice were immunized with recombinant protein TP-HRP2 or eukaryotic expression plasmid pcDNA3.1(-)/HRP2. The kinetics and specificities of antibody responses were analyzed. The proliferation tests of spleen cells were done, and P. f. growth inhibition assays were done with immune sera. RESULTS: The mice immunized with TP-HRP2 in Freund's adjuvant produced high-level and high-specificity antibody response. The antibodies appeared rapidly and lasted for a longer time. Cellular responses were induced simultaneously, and the immune sera could inhibit the development of parasite in IRBCs. The mice immunized with pcDNA3.1(-)/HRP2 produced middle-level antibody response which had some specificity, however, the induction of antibodies required repeated inoculation and a longer duration. Immune cells were well primed and the memorial immune response was obvious but the immune sera had no effect on the growth of P.f. in vitro. CONCLUSION: Both the recombinant protein and plasmid DNA based on HRP2 have different immune characteristics in mice. HRP2 recombinant protein has the potential in practical application.