Conformation-sensitive immunoassays improve the serodiagnosis of solitary cysticercus granuloma in Indian patients

Neurocysticercosis (NCC), infection of the central nervous system with larva of Taenia solium, presents in over 60% of patients in India as a solitary cysticercus granuloma (SCG). The low cyst number in these patients frequently results in an insignificant humoral response. Consequently, serological tests for patients with SCG must consider the detection of low antibody levels. Lentil lectin-specific T. solium glycoproteins of molecular weights 50, 38, 24, 18, 14 and 13 kDa are specific antigens for cysticercus antibodies in serological tests for NCC, however they do not detect antibodies in 40% of patients with SCG. To improve this rate of detection, the conformations of these protein antigens were altered to unmask additional epitopes available for antibody binding. Secondary structures of the proteins induced by reduction of disulfide bonds led to the loss of conformational epitopes necessary for cysticercus antibody recognition. Urea-induced tertiary conformations of the antigenic proteins led to the detection of antibodies in 46% of 60 patients with SCG who were serologically negative on immunoblots when the antigens were used in quaternary conformation. Conformation-sensitive immunoassays show potential for serodiagnosis of patients with SCG.