Expression and cross-species reactivity of fatty acid-binding protein of Clonorchis sinensis

Clonorchis sinensis is a Chinese liver fluke that chronically resides in the biliary tract. The fatty acid-binding protein (FABP) is known to play an important role in the intracellular transport of long-chain fatty acids that are obtained by the fluke from the host. Although FABP has stimulated considerable interest as a vaccine target candidate, the nature of FABP from C. sinensis (CsFABP) remains unclear. In this paper, we describe the cloning and expression of recombinant FABP and immune cross-reaction by Western blot analysis. Sequence analysis revealed that the CsFABP cDNA contained a single open reading frame (ORF) coding for 134 amino acids with an estimated molecular mass of a 15.2 kDa. The DNA sequence of CsFABP cDNA showed significant homology to schistosome cytosolic FABPs, with a 49% amino acid sequence identity and 89% similarity to Schistosoma japonicum. This DNA also showed a high sequence similarity at the amino acid level to S. mansoni (Sm14; 83%) and Fasciola hepatica (80%). The CsFABP cDNA was cloned into expression vector pET28a, expressed in Escherichia coli and the recombinant protein purified by affinity chromatography. The recombinant CsFABP was cross-reacted with sera obtained from patients with fascioliasis and paragonimiasis. These results suggest that CsFABP may be useful as a vaccine for clonorchiasis.