Elevated antibody responses to Epstein-Barr virus linked to increased risk of multiple sclerosis

New findings reveal how a specific immune response to the Epstein-Barr virus could trigger multiple sclerosis, highlighting the intricate link between viral infection and autoimmune disease.

In a recent study published in the Journal of Clinical Investigation, a group of researchers investigated the role of a distinct antibody signature against the Epstein-Barr virus nuclear antigen-1 (EBNA1, specifically EBNA381-452) and its association with high cross-reactive autoimmune responses that may contribute to the development of multiple sclerosis (MS).

Background

MS is a chronic autoimmune disease characterized by inflammation and demyelination in the central nervous system (CNS). The risk of developing MS is thought to significantly increase following infection with Epstein-Barr virus (EBV), as antibodies against EBNA1 can cross-react with CNS proteins, potentially leading to undesirable autoreactive immune responses.

A specific sequence in EBNA1, known as EBNA381-452, has been implicated in this process. However, the exact mechanisms by which immune responses specific to EBNA381-452 might trigger MS onset remain incompletely understood, highlighting the need for further research to clarify their role in disease pathogenesis.

About the study

The study included a cohort of 270 EBV-seropositive MS patients, matched with 270 healthy controls based on age, sex, and the timing of EBV seroconversion. Plasma samples collected from each participant were analyzed at three key time points: during primary EBV infection, at the time of MS diagnosis for patients, and at a matched time point for the controls.

Researchers observed that MS patients had not only higher antibody levels but also elevated T and B cell counts responsive to both EBV and central nervous system proteins, suggesting a broader immune involvement in MS progression.

To evaluate specific immune responses, the researchers used an EBNA381-452-derived peptide library to analyze the detailed specificity of EBNA381-452-specific antibody responses in both MS patients and healthy controls. These antibody responses were measured against various epitopes, including those that cross-react with CNS-derived proteins such as glial cell adhesion molecule (GlialCAM), alpha-crystallin B chain (CRYAB), myelin basic protein (MBP), and anoctamin 2 (ANO2).

The individual antibody responses against four EBNA-derived peptides and their corresponding cross-reactive CNS-derived peptides (specific regions include EBNA386-405/GlialCAM370-389, EBNA393-412/CRYAB2-21, EBNA409-428/MBP205-224, and EBNA426-445/ANO2135-154) were quantified. The analysis focused on identifying any detectable EBNA381-452-specific antibody responses during the initial EBV infection phase and at the time of MS diagnosis.

The researchers also assessed the correlation between the levels of **specific immune cell types—**Cluster of Differentiation (CD)19+ B cells, CD4+ T cells, and CD8+ T cells, which are reactive to both EBNA and CNS peptides—by collecting peripheral blood mononuclear cells (PBMCs) from a subset of 20 MS patients and 80 healthy controls.

The data were analyzed to determine the presence of highly elevated immune responses among MS patients compared to controls, with a series of statistical analyses applied to determine the reliability and significance of these findings.

Study results

The study revealed that MS patients demonstrated significantly higher EBNA-specific antibody responses compared to healthy controls at the time of MS diagnosis. Specifically, the antibody responses against epitopes linked to cross-reactive immune responses with CNS-derived proteins, including GlialCAM, CRYAB, MBP, and ANO2, were markedly elevated in MS patients. This finding suggests the possible role of these cross-reactive antibodies in the pathogenesis of MS.

Quantifying individual antibody responses demonstrated that neither the MS patients nor the controls had detectable EBNA381-452-specific antibody responses during the primary EBV infection.

The study highlights that MS patients' immune responses were highly correlated between antibody levels and immune cell activation, suggesting a dual role of humoral and cellular immunity in the disease’s development.

However, at the time of MS diagnosis, MS patients were found to have overall higher titers of EBNA- and CNS-derived peptide-specific antibodies compared to their healthy counterparts.

Notably, up to 53% of the healthy controls showed antibody titers against individual EBNA- and CNS-derived peptides comparable to those observed in MS patients.

The results suggested that the cumulative presence of high titers of cross-reactive EBNA- and CNS-peptide-specific antibody responses may be associated with increased susceptibility to developing MS on an individual basis.

Further analysis of the data indicated that nearly all MS patients (99.6% and 98.5%) had high titers against three or more cross-reactive peptide regions, whereas only 11.5% and 21.5% of controls exhibited similarly elevated levels. Elevated EBNA-specific antibody responses targeting three or more cross-reactive peptide regions were associated with a substantial increase in MS risk, calculated as a 1,366-fold increase.

In addition to antibody responses, the study found that MS patients displayed a significant accumulation of CD19+ B cells, CD4+ T cells, and CD8+ T cells specific to EBNA and CNS peptides.

These immune cells showed a high correlation with corresponding antibody responses, suggesting that higher levels of both EBNA- and CNS-reactive immune cells may be a hallmark of MS patients compared to healthy individuals. This accumulation of immune cells suggested an increased immune reactivity related to the interplay between EBV and CNS proteins in MS.

Conclusions

The study concluded that MS patients appear to exhibit a significant accumulation of immune responses directed specifically against EBNA381-452 and its corresponding cross-reactive counterparts derived from CNS proteins. These elevated EBNA-specific antibody responses and corresponding T and B cell responses suggest a potential link between EBV infection and MS pathogenesis, underlining the need for further research to explore the exact mechanisms involved.