Abstract: Objective   To clone and express three VAR2CSA duffy antigen-binding ligand （DBL） domains （DBL4/5/6） encoded by var2csa gene of a Hainan isolate of Plasmdium falciparum, and study the difference of chondroitin sulfate A （CSA）-binding activity among them.  Methods   Three DBL domains was amplified by PCR and cloned into the vector pMD18-T. The recombinant plasmids were identified by enzyme digestion and sequencing, and then subcloned into the prokaryotic expression vector pET-22b. The recombinant plasmid was transformed into E. coli BL21 （DE3） and followed by expression of the protein induced by IPTG. The recombinant protein was purified with His GraciTrap kit and identified by SDS-PAGE and Western blotting. CSA-binding activity of the three recombinant DBL domains was assayed by ELISA.   Results   The target genes were amplified with the length of 996 bp, 859 bp and 894 bp. The constructed recombinant plasmids were identified by enzyme digestion and DNA sequencing. The recombinant proteins（DBL4/5/6） were purified, the relative molecular mass of DBL4, DBL5 and DBL6 was M_r  439 800, M_r  34 500 and M_r  36 000, respectively. The purified protein has been confirmed with immunogenicity by Western blotting. The results of adhesion experiment indicated that A₄₀₅ values of DBL5 domain with different concentration were significantly higher than that of DBL4 and DBL6.   Conclusion   The three recombinant proteins （DBL4/5/6） of VAR2CSA DBL domains were expressed, and DBL5 domain has high binding affinity with CSA.

Key words: Pregnancy-associated malaria, Plasmodium falciparum, var2csa, DBL, Chondroitin sulfate A