Identification of a capsid-derived Zika virus epitope with high IgG discriminatory performance

The identification of specific serological targets for Orthoflavivirus zikaense (ZIKV) remains challenging due to the high degree of structural similarity and antibody cross-reactivity among co-circulating arboviruses, particularly dengue virus (DENV). In this context, immunoinformatics-based approaches may contribute to the rational selection of candidate epitopes with potentially improved analytical specificity. In the present study, five conserved ZIKV peptides previously identified through an immunoinformatic pipeline were experimentally evaluated as candidate serological targets. Peptide reactivity was assessed by indirect ELISA using human serum samples positive for anti-ZIKV IgM and IgG antibodies. Distinct reactivity patterns were observed between antibody classes. IgM assays showed limited analytical discriminatory capacity, particularly due to reduced specificity for some peptides. In contrast, IgG-based analyses revealed more favorable analytical profiles. Among the peptides evaluated, a peptide identified in the capsid (PEP03) exhibited the most favorable analytical performance, with an area under the ROC curve (AUC) of 0.9183 (95% CI: 0.8301-1.000). An absence of detectable reactivity was observed among sera from DENV-positive patients, and minimal reactivity with chikungunya virus (CHIKV) positive samples under the experimental conditions employed. Other peptides tested in this study demonstrated variable analytical profiles, reinforcing the importance of rational epitope selection for serological applications. Overall, these findings provide preliminary analytical evidence that structurally derived ZIKV epitopes may exhibit distinct IgM and IgG recognition patterns and support the continued evaluation of capsid-derived epitopes as candidate targets for serological applications (IgG detection) in regions where multiple arboviruses co-circulate.