ECTRIMS-Questioning the EBV

Epstein Barr Virus is it, isn't it. 
You do the experiment and try and disprove the hypothesis.

P1069 - CSF B-cells in relapsing multiple sclerosis are driven towards a similar, antigen-experienced, inflammatory fate

A. Ramesh1,2, R.D. Schubert1,2, R. Dandekar1,2, A. Greenfield1,2, R. Loudermilk1,2, E. Tran1,2, R. Gomez1,2, A.J. Green1,3, R. Bove1,2, X. Jia1,2, J.L. DeRisi4,5, J.M. Gelfand1,2, B.A.C. Cree1,2, S.L. Hauser1,2, M.R. Wilson1,2

Three prominent hypotheses for the role that B-cells play in MS are 

(1) clonally expanded B-cells in the central nervous system (CNS) target unidentified autoantigens resulting in pathogenic antibody secretion and/or antigen presentation to pathogenic T cells, 

(2) CNS B-cells display a pro-inflammatory phenotype or cause tissue injury through secreted factors other than pathogenic autoantibodies, and 

(3) virally-infected B-cells trigger CNS demyelination.

We isolated cerebrospinal fluid (CSF) and peripheral blood B-cells from treatment naïve, relapsing MS patients (n=7 [5 female], age=23-40 years, disease duration=37-252 days) and sorted them into the following B-cell categories: 

double negative, 
unswitched memory, 
switched memory, 

We performed RNA extraction, reverse transcription, and amplification using random hexamer primers to generate a cDNA library for Illumina sequencing. 

We then used custom bioinformatics tools to assess for 
(1) shared clonal connections and/or similar immunoglobulin class restriction between B-cells , 
(2) differential gene expression between peripheral and CNS B-cell subsets, 
(3) presence of intracellular viral transcripts.

We describe a multi-pronged bioinformatics protocol that mines a unified transcriptomic B-cell dataset to answer questions regarding clonal connections, B-cell phenotypes and infectious triggers of MS. Our findings support the hypothesis that B-cells originating in the periphery undergo clonal expansion and sustain a pro-inflammatory shift in the CSF in MS, without detectable viral infection.

Therefore memory B cells enter from the periphery and may expand in the CNS, but there is no virus detected. This perhaps is where contention lies as there have been some that have suggested that Epstein Barr Virus is a problem, But it is not in the CNS, according to this.

But according to others

Serafini B, Scorsi E, Rosicarelli B, Rigau V, Thouvenot E, Aloisi F. Massive intracerebral Epstein-Barr virus reactivation in lethal multiple sclerosis relapse after natalizumab withdrawal. J Neuroimmunol. 2017; 307:14-17.

Rebound of disease activity in multiple sclerosis patients after natalizumab withdrawal is a potentially life-threatening event. To verify whether highly destructive inflammation after natalizumab withdrawal is associated with Epstein-Barr virus (EBV) reactivation in central nervous system infiltrating B-lineage cells and cytotoxic immunity, we analyzed post-mortem brain tissue from a patient who died during a fulminating MS relapse following natalizumab withdrawal. Numerous EBV infected B cells/plasma cells and CD8+ T cells infiltrated all white matter lesions; the highest frequency of EBV lytically infected cells and granzyme B+ CD8+ T cells was observed in actively demyelinating lesions. These results may encourage switching to B-cell depleting therapy after natalizumab discontinuation.

Moreno MA, Or-Geva N, Aftab BT, Khanna R, Croze E, Steinman L, Han MH. Molecular signature of Epstein-Barr virus infection in MS brain lesions.Neurol Neuroimmunol Neuroinflamm. 2018 Jun 7;5(4):e466.  We report the presence of EBV latent membrane protein 1 (LMP-1) in 93% of MS and 78% of control brains, with a greater percentage of MS brains containing CD138+ plasma cells and LMP-1-rich populations. Notably, 78% of chronic MS lesions and 33.3% of non-MS brains contained parenchymal CD138+ plasma cells. EBV early lytic protein, EBV immediate-early lytic gene (BZLF1), was also observed in 46% of MS, primarily in association with chronic lesions and 44% of non-MS brain tissue. Furthermore, 85% of MS brains revealed frequent EBER-positive cells, whereas non-MS brains seldom contained EBER-positive cells. EBV infection was detectable, by immunohistochemistry and by in situ hybridization, in both MS and non-MS brains, although latent virus was more prevalent in MS brains, while lytic virus was restricted to chronic MS lesions..

However it does not make sense if EBV infected B cells were the targets. As  other diseases are associated with EBV infection too. So one week you would have MS and the next week Lupus and then arthritis, so there must be some specificity in the system. However, does it say EBV is not involved. Probably not. 

Either technology is not sensityive enough to detect the virus or there is a problem of wishful thinking. However, I am not going to get trapped in this argument as it still fails to exclude EBV having an important role in MS, as EBV-free memory cells may be descended from memory cells that contained episomal EBVLaurence M, Benito-León J. Epstein-Barr virus and multiple sclerosis: updating Pender's hypothesis. 2017:8-14.