Reconstructing pathogen-specific antibody binding epitopes and age-dependent immune signatures from proteomic-scale peptide libraries.

High-density peptide arrays are useful for mapping linear antibody epitopes and resolution of antibody specificity in a single-assay platform. Here, we used peptide library screening to evaluate magnitude and breadth of humoral responses to enteric pathogens in the context of public health interventions. We characterized the epitope landscape to known immunogenic proteins to several viruses, bacteria, and parasites and used that to infer immunological profiles at age 3, 14, and 28 months. The peptide libraries detected immune signatures better for viruses compared with bacteria and parasites and captured distinct dynamics of protein-level variation in immune signatures over time. We found limited sensitivity for bacterial and protozoan pathogens whose humoral responses may depend more on conformational or natively modified epitopes than linear-peptide binding. Unbiased peptide libraries have potential utility for broad analysis of antibody responses in integrated serosurveillance, but our results reveal pathogen-specific limitations where peptide-based serology would be less predictive of true infection status and where it would provide greater surveillance value. Beyond assay performance, peptide arrays are useful for studying epitope architecture, and a practical implication would require augmentation with alternative antigen formats (whole-protein or folded antigens) in a complementary hybrid approach.