EBNA1_381-452 and Cross-Reactive Antibody Responses Reveal Immune Signatures in Multiple Sclerosis

Infection with the Epstein-Barr virus is a prerequisite for the development of multiple sclerosis (MS). Recent evidence has identified an antibody response against a peptide region of the Epstein-Barr virus nuclear antigen-1 (EBNA1_AE; alternative epitope, amino acid residues 381-452) that harbors cross-reactive potential against multiple autoantigens. It is currently unclear whether this antibody response is a driver of MS pathology. The presence of EBNA1-cross-reactive IgG responses in the CSF and their correlation with disease activity may provide insight into this matter. The aim of this study was to characterize the EBNA1_AE response in peripheral blood and CSF of a clinically well-defined cohort of patients with MS and identify whether cross-reactive antibody responses are linked to disease characteristics.

In this cross-sectional study, we quantified IgG reactivity against 4 20-mer peptides in the EBNA1_AE region and their corresponding autoantigens using indirect ELISA in plasma of patients with untreated relapse-onset MS (n = 211) and healthy spouse controls (n = 63). We extended this analysis to paired serum-CSF samples from 61 patients with MS to determine intrathecal IgG responses.

We observed an increased antibody response to EBNA1_AE and corresponding autoantigens, supporting Epstein-Barr virus molecular mimicry in MS peripheral blood. Dimensionality reduction and clustering of 9 epitope-specific IgG responses identified 3 distinct peripheral immune signatures: EBNA1_AE-high cross-reactive, EBNA1_AE-high selective, and EBNA1_AE-low, indicating that high EBNA1_AE responses are not necessarily associated with high IgG responses against autoantigens. The cross-reactive signature, characterized by elevated reactivity to all EBNA1_AE epitopes and their corresponding autoantigens, was enriched in MS. Increased IgG responses to a number of EBNA1_AE epitopes were observed in patients who recently experienced a clinical relapse. The immune signatures were confirmed in the serum of the paired serum-CSF cohort. The Reiber antibody index for IgGs related to the EBNA1_AE-high cross-reactive immune signature suggested intrathecal synthesis.

Our findings contribute to the accumulating evidence of a role for EBNA1_AE molecular mimicry in MS pathology and demonstrate heterogeneity in EBNA1_AE-directed immune responses among patients with MS, differing in cross-reactivity and intrathecal enrichment.