An improved immunoassay for Neurocysticercosis using Taenia solium diagnostic cyst glycoproteins calibrated to fucose equivalents.

BACKGROUND: Neurocysticercosis (NCC), a common brain infection caused by Taenia solium metacestode larvae, is a major cause of acquired epilepsy. It is diagnosed serologically using the enzyme-linked immunoelectrotransfer blot (EITB), which detects antibodies against seven Taenia solium cyst glycoproteins. However, like many serological tests for NCC, EITB sensitivity is low for pauci-cyst infections. THIS STUDY AIMED: to improve the diagnostic performance of EITB by calibrating antibody binding based on immunogen equivalents of glycoprotein fucose content of each cyst glycoprotein. METHODS: Six of the seven cyst glycoproteins were purified by preparative SDS-PAGE and enzymatically N-deglycosylated. Peptide and glycan fractions were isolated to assess their binding to cysticercus antibodies. Glycosylation, particularly core fucosylation, emerged as a key antigenic determinant. Binding was optimized by titrating glycoprotein concentrations according to N-glycan content, with the strongest binding observed at 0.25 pmoles of fucose per glycoprotein. A dot blot assay incorporating these calibrated glycoproteins was evaluated using serum from 52 NCC patients [10 cases of multi-lesion NCC (MNCC), 32 solitary cysticercus granulomas (SCG), 6 solitary calcified cysticerci (SCC), and 4 resolving solitary cysticercus granulomas (RNCC)] and 60 non-NCC controls. A sample was considered positive for cysticercus antibodies and NCC if the binding intensity to any glycoprotein exceeded the mean + three standard deviations of controls. RESULTS: Compared to EITB, the dot blot assay increased detection of serum cysticercus antibodies by 30% for MNCC, 40% for SCG, 83% for SCC and 50%for RNCC while retaining 100% specificity. CONCLUSION: Standardizing antigen concentration by fucose equivalents markedly improved cysticercus antibody detection, particularly in NCC cases of low infection loads. The study highlights a role for antigen calibration based on immunogen equivalents in enhancing the sensitivity of serological assays for NCC without compromising specificity.