Application of recombinant SMR-domain containing protein of angiostrongylus cantonensis in immunoblot diagnosis of human angiostrongyliasis.

The aim of this study was to find novel proteins expressed from an Angiostrongylus cantonensis adult female worm cDNA library for serodiagnosis of angiostrongyliasis. An immuno-dominant clone, fAC22, was identified by immunoscreening with pooled positive sera from proven angiostrongyliasis patients. The clone contained an open reading frame of 2,136 bp encoding a 80.5 kDa protein with a predicted isoelectric point of 5.8. The deduced amino acid sequence (712 amino acids) contained the conserved domain of Small mutS related (Smr) superfamily protein, with similarity with the Smr domain protein of Brugia malayi. The fusion His-tagged 81 kDa recombinant protein expressed as inclusion body in Escherichia coli was solubilized and purified by Ni-affinity chromatography for use in immunoblot analysis. Its sensitivity, specificity, positive and negative predictive values in immunodiagnostic test was 93.5, 91.5, 79.0 and 97.5%, respectively. Although some cross-reactivity of the antigen was observed among gnathostomiasis, bancroftian filariasis, ascariasis, echinococcosis, paragonimiasis and opisthorchiasis, sera from 14 other infections were all negative. These data indicate its possible application in immunodiagnosis of clinically suspected angiostrongyliasis. Key words: Angiostrongylus cantonensis,eosinophilic meningitis, recombinant fusion protein, immunodiagnosis