We cloned and expressed Echinostoma caproni HSP70 in Escherichia coli. This molecule presents an open reading frame (ORF) of 655 amino acids, and a theoretical molecular weight of 71 kDa. E. caproni HSP70 protein showed a high homology to other helminth molecules, major differences being located in the C-terminal region of the molecule, with a hydrophobic portion. Studies of protein and messenger RNA (mRNA) expression revealed a distinct pattern, depending on the host (low- or high-compatible). Specific polyclonal antisera raised against the recombinant protein expressed in Escherichia coli demonstrated its selective presence in excretory/secretory products (ESP) of adult parasites obtained from high-compatible hosts. Immunological studies showed clearly the association of HSP70 with the parasite surface and other structures, including eggs.
SUMMARYWith the current paucity of vaccine targets for parasitic diseases, particularly those in
childhood, the aim of this study was to compare protein expression and immune
cross-reactivity between the trematodes Schistosoma haematobium, S. bovis
and Echinostoma caproni in the hope of identifying novel intervention
targets. Native adult parasite proteins were separated by 2-dimensional gel
electrophoresis and identified through electrospray ionisation tandem mass spectrometry to
produce a reference gel. Proteins from differential gel electrophoresis analyses of the
three parasite proteomes were compared and screened against sera from hamsters infected
with S. haematobium and E. caproni following
2-dimensional Western blotting. Differential protein expression between the three species
was observed with circa 5% of proteins from S.
haematobium showing expression up-regulation compared to the other two species.
There was 91% similarity between the proteomes of the two Schistosoma
species and 81% and 78·6% similarity between S. haematobium and
S. bovis versus E. caproni, respectively. Although
there were some common cross-species antigens, species-species targets were revealed
which, despite evolutionary homology, could be due to phenotypic plasticity arising from
different host-parasite relationships. Nevertheless, this approach helps to identify novel
intervention targets which could be used as broad-spectrum candidates for future use in
human and veterinary vaccines.
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