Fasciola hepatica and Fasciola gigantica:: Cloning and characterisation of 70 kDa heat-shock proteins reveals variation in HSP70 gene expression between parasite species recovered from sheep

Fasciola hepatica and Fasciola gigantica are trematode parasites responsible for fasciolosis, a disease of ruminant animals which is also increasingly recognised as a disease in humans. By biochemical and in silico methods, we have cloned and characterised the 70 kDa heat-shock proteins (HSP70s) of F hepatica and F gigantica. The nucleotide and protein sequences for HSP70 were found to be 98% and 99% identical between liver fluke species, respectively, and to encode conserved amino acid motifs that are of putative functional importance. Western blot analysis demonstrated that HSP70 proteins were expressed at a higher level in F gigantica recovered from sheep relative to F hepatica, but HSP70 was not detected in the excretory-secretory products of these liver fluke samples. Real-time reverse-transcriptase PCR analysis of HSP70 expression in parasites from sheep, but not cattle, showed HSP70 expression to be higher in F gigantica than F hepatica. These results suggest that hosts refractory to F gigantica are associated with higher HSP70 expression by this parasite and that HSP70 expression may represent a biochemical marker of the stress response of F gigantica. (c) 2007 Elsevier Inc. All rights reserved.