Primary study on the functions of prokaryotic expression products of Leptospira interrogans vwA1 and vwA2 genes

Abstract

Objective To generate the prokaryotic expression systems of vwA1 and vwA2 genes of Leptospira interrogans serogroup Icterohaemorrhagiae serovar Lai strain Lai,and to determine the correlation among the target recombinant expressed products rVwA1 and rVwA2 and platelet-associated hemorrhage.Methods The vwA1 and vwA2 genes of L.interrogans strain Lai were amplified using high fertility PCRs and then the amplification products were sequenced.The prokaryotic expression systems of vwA1 and vwA2 genes were generated by using routine genetic techniques.The expression and dissolubility of rVwA1 and rVwA2 proteins were examined by SDS-PAGE plus Bio-Rad Gel Image Analyzer.Ni-NTA affinity chromatography was used to extract the expressed rVwA1 and rVwA2.Real-time fluorescence quantitative RT-PCRs were performed to determine the changes of vwA1-mRNA and vwA2-mRNA levels in the leptospires of L.interrogans strain Lai before and after infection of human umbilical vein endothelial cell line (HUVEC).The ability of leptospiral rVwA1 binding to human platelets was detected by flow cytometry.A hydrolytic test plus SDS-PAGE were applied to examine the cleavage of leptospiral rVwA2 by a human von Willebrand factor lysase (ADAMTS13).Results The nucleotide and putative amino acid sequences of the cloned leptospiral vwA1 and vwA2 genes were 100％ identities compared to the reported corresponding genes.The generated prokaryotic expression systems of vwA1 and vwA2 genes could express soluble rVwA1 and rVwA2,respectively.When L.interrogans strain Lai infected HUVEC for 8 h,both the vwA1-mRNA and vwA2-mRNA levels were significantly up-regulated (P＜0.05).The result of flow cytometry showed that the leptospiral rVwA1 was able to combine with human platelets with a 60.8％ binding rate. Human recombinant vWF-A2 ( rhvWF - A 2 ),but not the leptospiral rVwA 2,could be hydrolyzed by human ADAMTS 13.Conclusion The vwA1 and vwA2 genes may play roles during infection of L.interrogans species,and the function of vwA1 gene product is referring to the hemorrhage in leptospirosis. Key words: Leptospira interrogans; vwA1 gene/vwA2 gene; Prokaryotic expression; Platelet/hemorrhage