Application of recombinant angiostrongylus cantonensis galectin-2 protein for serodiagnosis of human angiostrongyliasis by immunoblotting

Angiostrongyliasis is a foodborne disease caused by a zoonotic nematode, Angiostrongylus cantonensis, which produces eosinophilic meningitis or meningoencephalitis (EOM) in humans. Definitive diagnosis is rarely possible because worms are almost never recovered from patients. Human disease can be diagnosed by clinical symptoms and serological tests. Presently, diagnosis is performed by serological detection of antibodies against specific somatic antigens (molecular mass 29-31 kDa) extracted from female worms. The life cycle of A. cantonensis must be maintained in the laboratory to provide a source of this diagnostic antigen. Here, we cloned and expressed recombinant A. cantonensis galectin-2 (rAcGal2) corresponding to a 31-kDa antigenic peptide. Recombinant protein was purified and used in immunoblot tests, which showed reactions with human serum panels consisting of six confirmed angiostrongyliasis and 24 clinically diagnosed cases of EOM-associated with angiostrongyliasis, 160 samples from patients with other parasitic infections, and 30 samples from normal healthy subjects. Accuracy, sensitivity, specificity, and positive and negative predictive values were 95.0%, 93.3%, 95.3%, 75.7%, and 98.9%, respectively. The test was nonreactive with sera of human gnathostomiasis and cysticercosis, two diseases that could present similar neurological symptoms. Recombinant AcGal2 has potential as a diagnostic antigen and could replace native parasite antigens in further development of an angiostrongyliasis serodiagnostic test kit.