Expression, purification and in vitro refolding of the recombinant truncated Saposin-like protein 2 antigen for development of diagnosis of human fascioliasis

•rtSAP2 expressed in Shuffle® T7 and Rosetta strains in soluble and insoluble forms.•rtSAP-2 was purified under native and denatured conditions.•Accurate folding of rtSAP2 was evaluated in western blots and ELISA.•Refolded rtSAP2 by dialysis method detected all of fasciola-infected samples.•Refolded protein is more appropriate than unfolded and FhE/S forms for diagnosis.