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.