Epstein-Barr Virus May Be Turning On Pathogenic Genes in ME/CFS

If there was ever a "prodigal virus" in ME/CFS it would surely be the Epstein-barr virus (EBV). Since the first EBV ME/CFS study 1984 no less than 51 ME/CFS or post-infectious viral studies have featured either Epstein-Barr virus or infectious mononucleosis in their titles. (That leaves out a considerable number of viral and immunological studies which didn't put EBV in their titles.) While hypotheses of chronic viral reactivation in ME/CFS have lost favor the virus is too complex, too fascinating, and simply too problematic for it not to continue to be studied.A PubMed search brings up over 500 EBV citations associated with multiple sclerosis and over 30,000 citations associated with the virus.  To get an indication of how broad EBV research continues to be - one of the latest  EBV studies determined if the stress of space flights results in increased levels of EBV reactivation in astronauts. (It did and they advised astronauts to stay away from immunocompromised individuals upon return home…)The research community clearly continues to find EBV - one of the few viruses our bodies are unable to kick out - a fascinating and important topic. Check out the first in  a series of two blogs on EBV's possible contributions to ME/CFS.

The Review

In his EBV and ME/CFS review longtime ME/CFS researcher Jonathan Kerr digs down into some past ME/CFS EBV findings which recent understanding of EBV is shedding some new light.Kerr notes that psychological stress is associated with EBV reactivation and maintaining that state of psychological stress can result in prolonged states of EBV reactivation and diseases such as ME/CFS, nasopharyngeal cancer and post-transplant lymphoproliferative disorder (PTLD).Many studies have found that stress triggers the release of glucocorticoids which tell the pathogen that the coast is clear and it's time to start growing the family and producing more virions.Whether or not the original ME/CFS trigger is associated with increased levels of  psychological stress, the dysfunctions found in both stress response axes (HPA axis, autonomic nervous system) post-ME/CFS suggests that psychological stress could  possibly give a bug like EBV a leg up in diseases like ME/CFS. Plus, other studies have found evidence of an immune hole which could give EBV an extra foothold in ME/CFS.In the U.S., Ariza and Williams have shown that attempts at EBV replication in ME/CFS can trigger the production of an enzyme called EBV dUTPase which, among other things, results in the production of pro-inflammatory cytokines which may produce fatigue, pain, flu-like symptoms, etc.Kerr's group in the U.K., though, has taken a different tack.

The 2008 Study

Assessing the expression of 88 genes Kerr suspected were playing a role in ME/CFS, his group was able to separate healthy controls from ME/CFS patients, and then break those ME/CFS patients into 7 subsets in 2008. No less than 12 of the genes his group assessed were known to be associated with EBV.Finding such a huge split in gene expression between ME/CFS patients and healthy controls, and then being able to split up the ME/CFS group into gene expression subsets with unique symptom profiles, was striking.One of the genes which stuck out back then is called Epstein-Barr Virus (EBV) induced gene 2 (EBI2). While EBI2 sounds like it comes from EBV, it's a human gene. As EBV begins to reactivate it induces the expression of this gene, which regulates B-cell functioning, T-cell mediated antibody responses, and inflammation.Kerr's 2008 study suggested the gene was working overtime in 55% of ME/CFS patients. In another analysis, EBI2 was upregulated in 38% of 31 patients vs zero of 40 healthy controls.

The 2010 Study

A larger (n=117 ME/CFS patients) 2010 study analyzed antibodies associated with EBV in eight gene expression subsets. As before, twelve of these genes were known to be associated with Epstein-barr virus (EBV)One subset - subset D - stood out in its severity. This group of patients, all females, demonstrated a consistency of the worst kind, posting the lowest functional scores  in no less than five of SF-36 functional domains (physical role, vitality, general health, bodily pain, and total score) and experiencing high rates of muscle pain and sleep issues.They also led the pack in the expression of  EBV associated genes. Their EB12 genes were turned on and pumping away at higher levels of activity than in any of the other groups. So were all the other 11 associated EBV genes.In other words, this appeared to be a highly afflicted EBV ME/CFS subset.  EBV may be involved in other subsets, but it appeared to be wreaking special havoc in this one.Interestingly, the abnormal antibody (EBNA IgG) result found indicated the antibody was not elevated but was reduced. Since antibodies play a key role in immune clearance, the low levels suggested an immune deficit could be present.  For one, they suggested EBV was probably more often found in its latent state in this group.EBV is found in two forms: its lytic form occurs mostly in epithelial cells, and its latent form in B-cells.  The low levels of EBNA IgG appear to suggest, if I have it right, that EBV is able to survive in B-cells longer, giving it more time, one would think, to possibly tweak those B-cells more. That's an interesting finding given the role B-cells play in autoimmunity.

Nine Years Later - Science Marches On

Nine years ago, not much was known about EB12 but science has been moving on. EB12 is now recognized as a "critical regulator of the immune response". It ordinarily plays a valuable role in the interaction between B and T-cell and the antibody response.As one might suspect, though, EBV activation of this gene is not associated with good outcomes.  Increased EBI2 expression appears to dysregulate the delicate immune response - increasing B-cell activity (and therefore the risk of autoimmunity)  - while inhibiting T-cell activity - and potentially suppressing the immune system's ability to deter pathogens and knock out cancerous cells. Kerr pointed out that EBI2 could also be contributing to the reduced cerebral perfusion, gray matter reduction and white matter hyper intensities found in both multiple sclerosis and ME/CFS.Given the findings of the past 11 years, Kerr suggested that the EB12 gene deserves a deeper look in this disease.  The possibility that a severely ill EBV subset - characterized by a hyperactivation of the EBI2 gene - is present, is, of course enticing. Given that ME/CFS often has an infectious trigger, a special EBV subset makes perfect sense, and if it is present, it may offer some unforseen opportunities.One of the advantages of having an upregulated gene that's been implicated in a bunch of nasty diseases is possible increased interest from big pharma. If the EBI2 gene is wreaking havoc in some of the more severely ill ME/CFS patients, help may be at hand in the future.  Kerr pointed to two EBI2 modulators  (GSK682753A, NIBR189) currently under development.Kerr acknowledged several caveats to his hypothesis. His findings need to be validated by other laboratories using other sets of ME/CFS patients. He noted that finding EBV antibodies in ME/CFS does not in any way indicate that the bug is causing ME/CFS - that is still in doubt. His hypothesis - that EBI2 upregulation is playing an important role in a subset of ME/CFS patients -  is unproven at this point.It’s a hypothesis though, which is consistent with the data presented thus far and could account for "many of the immune and neurological abnormalities" found in a group of patients.