Asparaginyl endopeptidase from the carcinogenic liver fluke, Opisthorchis viverrini, and its potential for serodiagnosis

Laha, Thewarach, Sripa, Jittiyawadee, Sripa, Banchob, Pearson, Mark, Tribolet, Leon, Kaewkes, Sasithorn, Sithithaworn, Paiboon, Brindley, Paul J., and Loukas, Alex (2008) Asparaginyl endopeptidase from the carcinogenic liver fluke, Opisthorchis viverrini, and its potential for serodiagnosis. International journal of infectious diseases, 12 (6). e49-e59.

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To isolate and characterize an asparaginyl endopeptidase from the carcinogenic liver fluke, Opisthorchis viverrini, and evaluate its expression profile, biochemical activity, and potential as an immunodiagnostic antigen.


The full length mRNA encoding an asparaginyl endopeptidase (family C13), Ov-aep-1, was isolated by immunoscreening of a cDNA bacteriophage library of adult O. viverrini using sera from patients infected with O. viverrini. Investigation of Ov-aep-1 transcripts in developmental stages of the parasite, and phylogenetic analysis, immunohistochemical localization, and recombinant protein expression and enzymology were employed to characterize the Ov-AEP-1 protein. Immunoblotting was used to assess the potential of this enzyme for immunodiagnosis of human opisthorchiasis.


Ov-AEP-1 is characteristic of the C13 cysteine protease family. Ov-aep-1 transcripts were detected in adult and juvenile worms, eggs, and metacercariae. Phylogenetic analysis indicated that Ov-AEP-1 is closely related to homologous proteins in other trematodes. Recombinant Ov-AEP-1 was expressed in bacteria in inclusion bodies and refolded to a soluble form. Excretory–secretory (ES) products derived from adult O. viverrini and refolded recombinant Ov-AEP-1 both displayed catalytic activity against the diagnostic tripeptide substrate, Ala–Ala–Asn-aminomethylcoumarin. Rabbit antiserum raised to recombinant Ov-AEP-1 identified the native AEP-1 protease in both somatic extract and ES products of adult worms. Anti-Ov-AEP-1 IgG immunolocalized the anatomical site of expression to the gut of the fluke, implying a physiological role in digestion of food or activation of other digestive enzymes. Recombinant Ov-AEP-1 was recognized by serum antibodies from patients with opisthorchiasis but not other helminth infections, with a sensitivity and specificity of 85% and 100%, respectively. The positive and negative predictive values are 100% and 67%, respectively.


The liver fluke, O. viverrini, has a gut-localized asparaginyl endopeptidase. Refolded recombinant Ov-AEP-1 is catalytically active and has potential for immunodiagnosis of human opisthorchiasis.

Item ID: 34147
Item Type: Article (Research - C1)
ISSN: 1878-3511
Keywords: Asparaginyl endopeptidase; legumain; Opisthorchis viverrini; liver fluke; cholangiocarcinoma; immunodiagnosis; protease
Funders: Thailand Research Fund, TRF, NIH-NIAID International Collaboration in Infectious Diseases, Sandler Family Foundation, Khon Kaen University
Projects and Grants: TRF grant No. MRG488004, NIH-NIAD Research award No. AI065871, KKU grant No. i50206
Date Deposited: 24 Jul 2014 00:58
FoR Codes: 06 BIOLOGICAL SCIENCES > 0605 Microbiology > 060599 Microbiology not elsewhere classified @ 100%
SEO Codes: 92 HEALTH > 9201 Clinical Health (Organs, Diseases and Abnormal Conditions) > 920109 Infectious Diseases @ 100%
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