A Refined Human Linear B Cell Epitope Map of Outer Surface Protein C (OspC) From the Lyme Disease Spirochete, Borrelia burgdorferi

Background: A detailed understanding of the human antibody response to outer surface protein C (OspC) of Borrelia burgdorferi has important implications for Lyme disease diagnostics and vaccines. Methods: In this report, 13 peptides encompassing 8 reported OspC linear B-cell epitopes from OspC types A, B, and K, including the largely conserved C-terminus (residues 193-210), were evaluated by multiplex immunoassay (MIA) for IgG reactivity with ~700 human serum samples confirmed positive in a 2-tiered Lyme disease diagnostic assay (Bb+) and ~160 post-treatment Lyme disease (PTLD) serum samples. The vmp-like sequence E (VlsE) C6-17 peptide was included as a positive control. Results: Serum IgG from Bb+ samples were reactive with 10 of the 13 OspC-derived peptides tested, with the C-terminal peptide (residues 193-210) being the most reactive. Spearman’s rank correlation matrices and hierarchical clustering revealed a strong correlation between 193-210 and VlsE C6-17 peptide reactivity but little demonstrable association between 193-210 and the other OspC peptides or recombinant OspC. OspC peptide reactivities (excluding 193-210) were strongly correlated with each other and were disproportionately influenced by a subset of pan-reactive samples. In the PTLD sample set, none of the OspC-derived peptides were significantly reactive over baseline, even though VlsE C6-17 peptide reactivity remained. Conclusions: The asynchronous and potentially short-lived serologic response to OspC-derived peptides reveal the complexity of B-cell responses to B. burgdorferi lipoproteins and confounds interpretation of antibody profiles for Lyme disease diagnostics.