Expression, purification and characterization of a recombinant Plasmodium vivax thrombospondin related adhesive protein (PvTRAP)

Abstract

Thrombospondin Related Adhesive Protein (TRAP) is a transmembrane parasite molecule responsible in sporozoite-host interactions. This molecule is one of the most promising vaccine candidates against the pre-erythrocytic forms of malaria. In the present study, a gene encoding the Plasmodium vivax TRAP (PvTRAP) was expressed in Escherichia coli (M15 strain) using the expression plasmid pQE30. The expressed recombinant protein PvTRAP of about 70kDa was achieved, purified and refolded according to the standardized refolding procedure. This refolded protein (PvTRAP) showed a single band monomeric form with SDS-PAGE and blot analysis. In reduced and alkylated form, PvTRAP showed less binding to hepatoma (HepG2) liver cells, when compared to the normal purified and refolded form. Purified and refolded recombinant PvTRAP bound Duffy-positive human erythrocytes, while no binding was observed with Duffy-negative erythrocytes. Our report on PvTRAP is currently documented for the first time and it has been able to provide an experimental evidence of the biochemical and binding properties of PvTRAP in the invasion of hepatocytes and interaction with Duffy-positive and Duffy-negative human erythrocytes. In conclusion, our findings have been able to demonstrate the potential of PvTRAP as a promising target for vivax malaria vaccine candidate.