Abstract: AIM: To observe the level of immune responses of BALB/c mice induced by direct injection of the recombinant plasmid DNA and to provide evidence for the application of DNA vaccine of Plasmodium falciparum (P.f.) in animals and humans. METHODS: The recombinant plasmid pcDNA3 Pf8 encoding the hybrid antigens of PfCMR MSP1 19 was constructed . The presence of Pf8 plasmid was detected in the muscle, liver, kidney, heart, spleen and lung by PCR. ELISA, T lymphocyte transformation test, inhibitory assay of the growth and development of P. f . in vitro were used to determine the level of humoral and Th-cell responses. RESULTS: pcDNA 32Pf 8 was amplified by PCR technique in the different tissues from BALB/c mice which were injected with pcDNA 32Pf 8. The immune serum was specifically recognized by the soluble antigens of P. f alciparum ( iter: 1÷ 2 560 by ELISA ). The specific proliferative response of spleen T cells from immunized mice was remarkablely higher than that of control group , the transformation rate being up to 32.82±3.64%. The immune serum could also inhibit the growth and development of the erythrocytic stages of P.f alciparum in vitro. CONCLUSION: Direct in jection with the recombinant plasmid pcDNA 32 Pf 8 specifically elicites BALB/c mice to generate humoral and cell-mediated immune responses, the resulting immune serum being inhibitory to the growth and development of P.f . in vitro.

Key words: Plasmodium falciparum, polyvalent antigen, immune response, DNA vaccine, recombinant plasmid DNA