Abstract: 　HT5"H]Objective To clone and express the 3R, 6R and 9R repeat fragments of Plasmodium falciparum (Pf11 1) gene. Methods Three repeat fragments from the genomic DNA of Plasmodium falciparum 3D7 strain cultivated were amplified by using the designed primers.The PCR products were cloned into the pT7 vector for bi direction sequencing.The sequencing results were analysised by GENETYX MAC. And then the amplified fragments were subcloned into pET32a(+) or pET32b(+) in order to express the recombinant proteins under the induction of IPTG in E coli BL21. Results 3R,6R and 9R fragments with sizes of 552 bp, 630 bp and 444 bp respectively were successfully amplified by PCR. The sequence analysis showed that there were 4 more 3AA units and one more 6AA unit in Pf11.1 gene of 3D7 strain as compared with Palo Alto strain. The homologies of the nucleotide sequence between the 3R fragment and the 6R fragment of the two strains were 92.8% and 95 1%,respectively. The amplified 9R fragment contains 13 9AA repeat units. The three recombinant proteins were expressed in BL21 strain with molecular weights of 45,60 and 42 kDa. Conclusion We got the 3R, 6R and 9R fragments separately by PCR and expressed them in E.coli successfully. The Pf11.1 gene of 3D7 strain is highly homologous to that of the Palo Alto strain.

Key words: Plasmodium falciparum, PCR, transmission blocking vaccine, Pf11.1