NIE Antigen Mapping for Serological Diagnostic of Strongyloidiasis.

Strongyloidiasis is a neglected tropical disease for which scalable serological diagnostics are essential to support control programmes. The Strongyloides stercoralis NIE antigen is widely used for antibody detection, but its antigenic determinants remain incompletely defined. Here, we performed epitope mapping of the NIE antigen using a panel of 23 overlapping 15-mer peptides and 4 bioinformatically predicted peptides. Immunoreactivity was evaluated by detecting IgG assay in sera from infected and noninfected individuals. Full-length NIE showed excellent diagnostic performance (AUC = 0.934), whereas four peptides (11, 12, 17, 18) demonstrated moderate discrimination (AUC = 0.59-0.64). Combining peptides improved performance (AUC > 0.70), with peptides 12 and 18 consistently contributing to the best models. Structural mapping revealed two solvent-exposed regions corresponding to peptide pairs 11-12 and 17-18. These findings identify key immunoreactive regions within NIE and provide a structural basis for antigen engineering, while confirming the superior performance of the full-length antigen for serodiagnosis.