May 1, 2024 | Significant evidence now exists implicating the Epstein-Barr virus (EBV) as a causal factor in the development of multiple sclerosis (MS), making treatment of the virus a priority. To that end, research scientists at Trinity College Dublin have developed a blood test to measure the immune response to EBV that could be used as an outcome measure in future clinical trials in people with established MS, reports Hugh Kearney, Ph.D., a neurologist in Trinity’s school of medicine.
Over the past two years, thinking about how to treat MS has shifted from treating the immune system to addressing underlying EBV infection, he says. The turning point was a longitudinal, large-scale study in U.S. military recruits (Science, DOI: 10.1126/science.abj8222) providing a strong epidemiological link between EBV infection and risk of developing MS.
One follow-on study found molecular mimicry between transcription factor EBV nuclear antigen 1 (EBNA-1) whose protein makeup looks very similar to a central nervous system protein called glial cell adhesion molecule (GlialCAM) expressed by oligodendrocytes cells producing myelin in the brain, says Kearney. In MS, myelin and the cells that make it are attacked by immune cells.
This prompted the idea that the linkage between EBNA1 and GlialCAM was mechanistic for MS, with further research suggesting several factors module the likelihood that individuals with EBNA-1 antibodies go on to develop full-blown MS, Kearney continues. Natural killer cells and co-existing cytomegalovirus infection appear to be among the ways these antibodies are controlled.
A “call to arms” to prioritize the investigation of EBV as a cause of MS published last year in Lancet Neurology (DOI: 10.1016/S1474-4422(22)00471-9). “The current paradigm is to treat the immune system with either immunosuppressants or immunomodulation and it’s kind of agnostic to the etiology of the disease,” says Kearney.
Debate was ongoing for two decades, vacillating between the theory that there was, or wasn’t, a link between EBV and MS. The chief difficulty has been the mismatch between the number of people in the general population with EBV and the tiny fraction of those who go on to develop the disease, he points out.
If the EBV was going to be targeted in clinical trials, outcome measures would be needed, the Trinity team reasoned. So, they developed a diagnostic for measuring immune response to anti-viral treatments. An article describing the use of their functional assay to analyze the cellular response to EBNA-1 in people with MS is newly published in Neurology Neuroimmunology and Neuroinflammation (DOI: 10.1212/NXI.0000000000200217).
Public perceptions about MS relate largely to physical disabilities, which differ considerably from the experiences of people with the disease, says Kearney. In multiple quality-of-life studies, and in the MS clinic he runs at St. James’s Hospital in Dublin, patients routinely cite fatigue as the most debilitating symptom. Fatigue, together with the other commonly reported symptoms—headache and changes in mood or levels of anxiety—are all typical after a viral infection.
Further strengthening the case that MS is strongly linked to persistent EBV infection, triggering an immune response, is that the EBV can be linked with B cells and latent infection in MS is marshaled by aberrant T cells, Kearney says. “We also know that aberrant T cells can migrate to the central nervous system and are commonly detected in spinal fluid, so there is both a clinical importance in terms of identifying what bothers people who have the disease... [and] scientific interest in terms of giving further weight to the concept that MS is primarily driven by the virus.”
What’s needed are more targeted treatments than the general immunosuppressive agents currently used in the clinic that come with a long list of potential associated side effects, he adds. Results of the cross-sectional study in his MS clinic showed that immune response to the EBV was higher in untreated MS relative to either healthy controls or people with epilepsy, another chronic brain disease.
Further, patients treated with B cell depleting therapies had a similar response to the EBV as healthy controls. This supports a theory that depletion of B cells also depletes EBV-infected cells and altered response to the virus, says Kearney.
Importantly, study results were produced using whole blood samples and currently used diagnostic equipment in accredited hospital laboratories, Kearney says. The test therefore has the potential to scale across multiple international sites.
Previous research efforts to document the immune response to EBV infection have all involved significant pre-processing or analytical techniques that never translated to clinical care, notes Kearney. The test developed by the Trinity team is based on an interferon gamma release assay routinely performed in the pathology lab for the detection of tuberculosis.
To adapt the assay as an outcome measure for EBV in people with MS, Kearney’s group added EBNA-1 peptides into blood samples rather than a component of tuberculosis, he explains. This means no additional research equipment and no temperature or freezing requirements.
Kearney says the novel test can be run in a straightforward fashion with results available within 24 hours. Another advantage with using the interferon gamma release assay is that a range of different inflammatory cytokines can be used as outcome measures.
For the paper, investigators used interferon gamma and interleukin-2. But those could be swapped out for other cytokines depending on the disease context and treatment, says Kearney.
The initial next step for the research team is to look longitudinally at the immune response of newly diagnosed patients before and after MS treatment to show that B cell depletion directly impacts their cellular response to EBNA-1, he continues. They will then engage other research centers in validation studies.
Longer term, they hope to partner with industry to add the test as an outcome measure in clinical trials, says Kearney. These could include trials attempting to treat EBV infection in MS using antivirals or vaccines.