[CTL response to pre-erythrocytic stage vaccine candidate of plasmodium falciparum in HLA-A*0201 transgenic mice detected by ELISPOT assay].

The importance of cytotoxic T-lymphocyte (CTL) against malaria parasite in pre-erythrocytic stage has been presented in relevant researches. In order to investigate whether one CTL epitope (YLNKIQNSL) involved in a chimeric pre-erythrocytic stage vaccine candidate of Plasmodium falciparum which was expressed and purified in the laboratory can stimulate in vivo CTL response, HLA-A*0201 transgenic mice were immunized with this vaccine candidate. Enzyme-linked immunosorbent spot (ELISPOT) assay was performed on the splenocytes from the immunized transgenic mice. Positive result indicated that this CTL epitope can be in vivo processed and correctly presented.

[Evaluation of immunogenicity and protection efficacy of the recombinant hypoxanthine-guanine-xanthine of plasmodium falciparum in mice].

OBJECTIVE: To investigate immunogenicity and protection efficacy of the recombinant hypoxanthine-guanine-xanthine (HGXPRT) of Plasmodium falciparum expressed in Pichia pastoris. METHODS: 35 BALB/c mice were divided randomly into five groups: HGXPRT+ISA720 experiment group, HGXPRT+Freund experiment group, ISA720 adjuvant control group, Freund adjuvant control group, and blank control group. BALB/c mice were subcutaneously immunized three times with the HGXPRT protein formulated by either Freund or ISA720 adjuvants at a three weeks interval. Mice were bled via tail vein at 2 weeks after each immunization. Specific antibodies were detected by ELISA as well as IFAT using cultured parasites. The immunized mice were challenged with 10(5) P. yoelii 10 days after the third immunization and parasitemia was monitored daily by examining Giemsa-stained thin film. RESULTS: Strong immune response was induced by the HGXPRT antigen formulated with the adjuvant. Antibody titers of more than 1:10(5) were detected after the third immunization while no specific antibody was detected in the mice immunized with adjuvants only. The antibodies against HGXPRT recognized the cultured parasite by IFAT. Four days after mice were challenged with P. yoelii, high parasitemia appeared in the two control groups, which were 24 h earlier than experiment groups. The mean parasitemia of HGXPRT+ISA720 experiment group (29.3%) was significantly lower than that of control groups (70.0%) (P<0.05). The mean parasitemia of HGXPRT+Freund experiment group (51.0%) was significantly lower than that of adjuvant control (60.7%) and blank control(70.0%) (P<0.05). CONCLUSION: HGXPRT of P. falciparum expressed in Pichia pastoris was highly immunogenic in mice. Antibody against the recombinant protein recognizes the cultured parasites, and immunization of mice with the recombinant protein provides partial protection against the challenge of P. yoelii.