The emergency and rapid spread of drug resistant parasites and mosquitoes resistant to insecticides urgently demand new tools to control the disease. It is feasible to develop malaria vaccine based on animal and volunteers test. Scientists around the world are working on 3 types of malaria vaccine——pre erythrocytic, blood stage and transmission blocking. Some of the vaccine candidates are being tested in clinical trials and have been shown to be promising. It is very difficult to find a successful malaria vaccine due to its complex life cycle, antigen variations and multiple invasion pathways, but the vaccine will finally be developed.

95%. Conclusi on : The synthetic PfCP TCL gene is expressed in Pichia pastoris and a method of easy purification is developed. The recombinant PfCP TCL protein provides a base for investigating its immune function and potential as a component of combined malaria vaccine.

Objective:To synthesize the eba 175Ⅱf2 gene of Plasmodium falciparum and express it in Pichia pastoris in the secreting form. The recombinant protein and PfCP 2.9 protein were used for combined immunization to see if there is antigen competition. Methods: Asymmetric PCR based metho d was utilized to synthesize the 959bp eba 175Ⅱf2 gene. Plasmid containing the synthetic gene was introduced into Pichi a pa storis by electroporation for inducible expression. The recombinant EBA 175Ⅱ F2 p rotein was purified by ion exchange and gel filtration ch romatography. Results: The eba 175Ⅱf2 gene was successfully ex p ressed in Pichia pastoris in the secreting form. The antibody titers in mice immunized with the combined EBA 175ⅡF2 and PfCP 2.9 proteins w ere much higher tha n those with individual protein by ELISA. Conclusion: No antigen competition is found when using the combined EBA 175ⅡF2 and PfCP 2.9 immunization in mice, indicating the potential of combining the 2 antigens for vaccination.

Objective To determine the free thiols in the chimeric protein PfCP-2. 9 of Plasmodium falciparum expressed by Pichia pastoris. Methods Two experiments of reverse phase HPLC and Ellman' s reaction were applied to the PfCP-2.9 for the determination of its free thiols. For RP-HPLC analysis, three kinds of samples were tested: PfCP-2. 9, dithiothreitol-reduced PfCP-2.9 and indoacetic acid-alkylated PfCP-2.9. Results Both experiments showed that there were no any free thiols present in the PfCP-2. 9. Conclution The disulfide bonds between cysteine residues of PfCP-2. 9 were formed completely.

0.05). Conclusion The LDH method applied in the in vitro inhibition assay for P. falciparum seems simple, reliable and has generated a satisfactory result.

This is a review on the new progress in the study of regulation mechanism of Plasmodium falciparum Var gene family. The mutually exclusive expression system caused expression only one in 60 var genes while others were silenced. It was regulated on the transcriptional level mainly through three pathways:non-coding DNA elements,chromatin structure and perinuclear localization.

It remains an urgent need to develop effective malaria vaccine for global control of malaria.Application of high technologies such as biotechnology has facilitated the process of vaccine development for malaria.In the past 30 years,a large number of vaccine candidate antigens for malaria have been identified and some of them are currently in clinical trials.Major progress in malaria vaccine development has also been made in China.The PfCP-2.9 blood stage vaccine for malaria has entered clinical studies and some other vaccine candidates including combination malaria vaccine are currently in pre-clinical studies.The availability of various national research programs and international funding has stimulated laboratory and pre-clinical studies of malaria vaccine candidates.It remains a long-term goal to develop a safe and effective malaria vaccine to control and even eliminate the disease in the world,and many issues including malaria immunology and various types of technologies need to be addressed.However,efforts need to be continued toward the goal.

Objective:To express MSP1-31 gene of Plasmodium falciparum in Salmonella typhi CVD908 vaccine strain using a tetracycline-controlled P LtetO promoter. Methods:The MSP1-31 gene was cloned into the plasmid of pZE11 and transformed into the CVD908/tetR strain by electroporation. Expression of MSP1-31 in CVD908/tetR strain was detected using the method of Western blot. Results: The recombinant plasmid of pZE11/MSP1-31 was constructed, there was effective expression of MSP1-31 protein in CVD908/tetR strain in presence of tetracycline, and no expression of gene in absence of tetracycline. Conclusion: The recombinant Salmonella typhi strain in which the expression of Plasmodium falciparum MSP1-31 fragment induced by tetracycline is established successfully.

0.05) were found between 2 method s. A modified in vitro inhibi tion assay without refreshing medium during a period of 72 h is established by r eduction of initial parasitemia from 1% to 0.2% 0.5%.

Objective To produce an erythrocytic stage chimeric protein of Plasmodium berghei in Pichia pastoris and evaluate its immunogenicity. Methods The DNA sequences of AMA1 (Ⅲ) and MSP1-19 from P. berghei homologous to the corresponding sequences of P. falciparum chimeric antigen 2.9 (PfCP-2.9) were fused to generate a chimeric gene, designated as PbCP-2.9. The resulting gene was redesigned using Pichia preferential coden usage and expressed in P. pastoris in the secreted form. The recombinant protein was purified by Ni-NTA affinity chromatography. Three groups each with 10 BALB/c mice were im- munized subcutaneously with 20 ?g of purified PbCP-2.9 antigen formulated in Freund’s adjuvant, Montanide ISA720 and Montanide IMS 1 312, respectively. Three control groups each with 10 mice received only adjuvants emulsified with PBS. All the mice received three immunizations at 2-week intervals with the same dose of antigen. Serum samples were collected at preimmunization and one week after each immunization, and were analyzed for specific antibodies by ELISA and reaction with natural P. berghei proteins by IFAT. Results The PbCP-2.9 antigen with Mr 26 400 was successfully expressed in P. pastoris in secret- ed form. The recombinant protein can be recognized by the serum against blood stage parasites of P. berghei. High antibody responses were detected in all three PbCP-2.9-immune groups of mice by ELISA. However, mice immunized with PbCP-2.9 antigen in Freund’s adjuvant produced higher antibody titers than those with PbCP-2.9 antigen in Montanide ISA 206 and Montanide IMS 1312 adjuvants. The mean antibody titer in Freund’s adjuvant was 6.9-fold higher than in Montanide ISA 206 adjuvant and 5.6-fold higher than in Montanide IMS 1312 adjuvant after the second immunization (F=81.06, P