“At last big genomics comes to EBV. Not all EBV viruses are the same; within the populations of the world different strains of EBV exist and within an individual different forms of EBV can evolve. The rapid evolution of viruses between populations and within individuals is well described for many viruses so why should EBV be any different? Why is this important? I hypothesised several years ago that maybe the strain of EBV that triggers, or drives, MS is a different strain to that that lives and thrives in the general population. In other words for EBV to cause MS it needs to be a mutant-EBV. There are analogies to this hypothesis. Almost all the common viruses that result in chronic slow viral infections of the brain have mutant strains that do the dirty work. This was first described for the measles virus; the strain of measles that causes subacute sclerosing panencephalitis (SSPE); the measle virus that causes SSPE has a mutation in its M protein. Similarly, the strain of herpes simplex virus that causes encephalitis has a specific mutation in its genome that allows it infect the brain. JCV that causes PML in MSers on natalizumab has several mutations in its coat protein, VP1, and a mutation in the part of its genome that regulates its function. These examples support the hypothesis of why we should be taking a deep look into the EBV genome of MSers. Where would we look? The obvious place to look is in the blood or saliva, where the virus is found normally. However, this may the wrong compartment to look. I would suggest we take a look in the brain and cervical, or neck, lymph nodes of people with MS. This is the place we are more likely to find the mutant strain lurking. What is needed to do these studies? (1) Tissue collected in a special way from people dying with MS, (2) a new breed of scientist and (3) deep pockets.”
“A new breed of scientist. To test the tissue-specific EBV strain hypothesis we need virologists with skills in deep sequencing and bioinformatics. These people exist but not in the field of MS. if anyone out there with the skills is keen to bring their know-how and expertise the field of MS please contact me I would love to support you. Unfortunately, I don’t have the skill set to take this project on; any grant review panel would reject an application from me without letting me pass GO.”
“Deep pockets. As always research costs money and this project will require a team of people with funding for 3-5 years to make any dent in this hypothesis. The project may have to involve technologies that push the bubble of technological innovation. For example, I envisage having to capture single cells from the brains of MSers and sequence the EBV genomes from individual cells. All this will requires time, patience, access to emerging technology, skills and money.”
|Is the strain of EBV that causes MS a mutant ninja turtle?|
Background: Most people in the world (~90%) are infected by the Epstein-Barr virus (EBV), which establishes itself permanently in B-cells. Infection by EBV is related to a number of diseases including infectious mononucleosis, multiple sclerosis and different types of cancer. So far, only seven complete EBV strains have been described, all of them coming from donors presenting EBV-related diseases.
Lassmann et al. Epstein-Barr virus in the multiple sclerosis brain: a controversial issue–report on a focused workshop held in the Centre for Brain Research of the Medical University of Vienna, Austria. Brain. 2011 Sep;134(Pt 9):2772-86.
Recent epidemiological and immunological studies provide evidence for an association between Epstein-Barr virus infection and multiple sclerosis, suggesting a role of Epstein-Barr virus infection in disease induction and pathogenesis. A key question in this context is whether Epstein-Barr virus-infected B lymphocytes are present within the central nervous system and the lesions of patients with multiple sclerosis. Previous studies on this topic provided highly controversial results, showing Epstein-Barr virus reactivity in B cells in the vast majority of multiple sclerosis cases and lesions, or only exceptional Epstein-Barr virus-positive B cells in rare cases. In an attempt to explain the reasons for these divergent results, a workshop was organized under the umbrella of the European Union FP6 NeuroproMiSe project, the outcome of which is presented here. This report summarizes the current knowledge of Epstein-Barr virus biology and shows that Epstein-Barr virus infection is highly complex. There are still major controversies, how to unequivocally identify Epstein-Barr virus infection in pathological tissues, particularly in situations other than Epstein-Barr virus-driven lymphomas or acute Epstein-Barr virus infections. It further highlights that unequivocal proof of Epstein-Barr virus infection in multiple sclerosis lesions is still lacking, due to issues related to the sensitivity and specificity of the detection methods.
OBJECTIVE: To determine whether the activation of innate immune responses, which can be elicited by pathogenic and endogenous triggers, is associated with the presence of Epstein-Barr virus (EBV) infection in themultiple sclerosis (MS) brain.
METHODS: White matter postmortem MS (n = 10) and control tissue (n = 11) was analyzed for the expression of the proinflammatory cytokine interferon α (IFNα) by immunohistochemistry and for EBV by using the highly sensitive method of EBV-encoded RNA (EBER) in situ hybridization.
RESULTS: We detected overexpression of IFNα in active areas of white matter MS lesions but not in inactive MS lesions, normal-appearing white matter, or normal brains. The presence of IFNα in macrophages and microglia (expressing human leukocyte antigen class II) is suggestive of local production as part of an acute inflammatory process. Interestingly, EBERs were also specifically detected in areas where IFNα was overexpressed in these preselected active MS lesions. EBER+ cells were also found in CNS lymphoma and stroke cases, but were absent in other control brains. We next addressed a potential mechanism, e.g., the role of EBERs in eliciting IFNα production, and transfected EBERs into human embryonic kidney (HEK) cells. We used HEK cells that stably expressed Toll-like receptor-3, which recognizes double-stranded RNAs, associated with many viral infections. EBERs elicited IFNα production in vitro.
CONCLUSION: These findings suggest that latent EBV infection may contribute to the inflammatory milieu in active MS lesions by activating innate immune responses, e.g., IFNα production. Unraveling the underlying mechanisms may help in uncovering causal pathways and developing better treatment strategies for MS and other neuroinflammatory diseases.