Monday, 2 July 2018

EBV in the brain

Epstein Barr Virus (EBV) is a herpes virus which is spread by saliva and infects around 95% of us during our lifetimes. In the majority of people EBV infection does not cause prominent symptoms - it may cause a ‘flu-like’ illness which gets better on its own, or it may go completely unnoticed.


Some people who are infected with EBV experience a more severe illness - termed glandular fever or infectious mononucleosis -  characterised by fatigue, sore throat, lymph node enlargement, fevers, and a mild hepatitis (liver inflammation). EBV is also associated with the development of various cancers, including lymphoma and head and neck cancer.
There is lots of evidence to suggest a link between EBV infection and the risk of developing MS:
  1. The high levels of antibodies (suggesting a specific immune response) against EBV in pwMS;
  2. The slightly higher rates of EBV infection in pwMS (I.e probably 100% of pwMS are infected vs 95% of the general population);
  3. The increased risk of developing MS after glandular fever (around 2.5x more likely);
  4. The detection of EBV infection in the brains of pwMS (in some reports).
The hypothesis that EBV infection is an important step in developing MS makes sense a priori as well: we know that EBV evades the immune system by infecting B cells, driving them towards dormancy, and then promoting their long-term survival. EBV has involved an ingenious arsenal of tricks to promote its own survival by fashioning a long-term niche for itself inside B cells. This dormant period is termed ‘latent EBV infection’. A minority of EBV-infected cells will enter the ‘lytic phase’ of infection, in which the virus rapidly replicates, kills the host cells, and is shed to infect other cells. Given the relatively recent slew of data suggesting that B cells are key drivers of the disease, any factor which promotes survival of B cells and hijacks the normal pathways of B cell maturation could conceivably predispose people to developing the disease.
So a crucial question is whether EBV is present in the brains of people with MS. This has been slightly controversial - some people have said yes, and others have been unable to replicate those results.
This study used a combination of biopsy and post-mortem brain tissue to see whether EBV-infected B cells could be detected in the brain. Participants were 17 pwMS and 9 controls without neurological diseases.
Latent EBV infection was detected using a marker called Latent Membrane Protein 1 (LMP1), and lytic infection was detected using a marker called BZLF1. LMP1 was detected in chronic lesions both with and without active inflammation. Importantly, LMP1 was also present in the brains of healthy individuals. BZLF1 was present in both control brains and brains from pwMS. Interestingly, BZLF1 was not present in chronic active lesions - this is a surprising finding which implies that lytic infection is present in healthy brains, in chronic inactive lesions, but not in lesions with acute inflammation.


To validate these findings, the authors used a different technique – in situ hybridisation - to detect EBV infection in a subset of cases (7 pwMS and 4 controls). They used a marker called EBER-1, a small RNA molecule which is produced by EBV during latency. EBER-1 was detected in 6/7 pwMS and 2/4 controls.
However, when the authors tried to quantify their findings, they found that there were no statistically significant differences between MS and control brains in terms of the number of EBV-infected cells, using any of the three markers.
For me this paper does not answer the killer question it set out to answer. It highlights the difficulties of detecting EBV infection - to name a few: the discrepancy between different techniques and markers, the nonspecific nature of these markers, and the low absolute numbers of infected cells.
I am not sure how to interpret these results. EBV-infected B cells appear to be present in both control and ‘MS’ brains, and may be slightly more common in MS. However, the data do not support any stronger claims about the presence or quantity of EBV in the brains of pwMS. The main issue I have with the study is the incredible heterogeneity of the participants: of the 17 pwMS, no clinical details were available for 9, 3 had tumefactive MS - a rare, highly aggressive form - and the others had a mix of primary and secondary progressive disease. This crucially limits the conclusions that can be drawn and is probably a major reason that the results were so noisy. It is also not clear which results are from biopsies and which from post-mortem - although the authors say there was little difference between these two, it would be reassuring to see some results to support this statement.
In short - this study is an attempt to put to bed the question of whether EBV infection is present in the brains of people with MS. In my view it does not settle the debate. The best evidence to date does suggest that EBV is present in both MS and control brains, but is more common in pwMS (90% vs 24%).
Clearly, the presence of EBV-infected B cells in the brain is not sufficient to drive disease activity. Further work needs to be done to understand why some people are perfectly healthy despite having EBV in their brain, whereas others go on to develop MS. Deeper understanding of how EBV  is linked to MS is an essential first step towards developing safe treatments (and vaccines) which target EBV. EBV-targeted treatments are already in early stages of development.


***

Abstract

Objective We sought to confirm the presence and frequency of B cells and Epstein-Barr virus (EBV) (latent and lytic phase) antigens in archived MS and non-MS brain tissue by immunohistochemistry.
Methods We quantified the type and location of B-cell subsets within active and chronic MS brain lesions in relation to viral antigen expression. The presence of EBV-infected cells was further confirmed by in situ hybridization to detect the EBV RNA transcript, EBV-encoded RNA-1 (EBER-1).
Results 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.
Conclusions Together, our observations suggest an uncharacterized link between the EBV virus life cycle and MS pathogenesis.


20 comments:

  1. 'I am not sure how to interpret these results' 'suggest that EBV is present in both MS and control brains, but is more common in pwMS.

    No, this does not follow from this study, as the 'controls' here are non-inflammatory normals. Relevant pathological controls, which may well attract EBV latent and active cells into the CNS are required. Alternatively look at the pcr detection of EBV in CSF/serum relation to highly active MS. For example, look at Rinaldi F et al Neurology Jan 1, 2018;5(1), where pcr fails to detect EBV by pcr in a highly active case in relation to alrmtuzumab treatment. The case for a direct role for EBV in MS is becoming much weaker as the evidence accumulates. Think of something else, apart from 'autoimmunity' which also fails to show a specific target(s).

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    1. Aberrant immunity might be a better term than autoimmunity in the case of MS. EBV has never been suggested to be directly responsible but indirectly in combination with other factors is still likely, particularly now that the B cell is reinstated as a central player in MS.

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    2. I looked up that paper by Rinaldi. First, I see no results regarding the rtPCR. There's no figure associated with the statement in the text that EBV was not detected. What were the primers? What were the controls? Also, the people that did that experiment (L. Rossi) are not listed as co-authors. Why? Second, a negative result is a negative result. You can't point to an experiment that was negative and say this shows that it's not there.

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  2. This is an interesting article how viruses might activate genes to causes autoimmunity. Whilst not specific to MS there maybe something in it:
    https://www.google.com.au/amp/s/amp.smh.com.au/national/how-vet-ben-cunneen-s-tragic-death-inspired-a-scientific-breakthrough-20180701-p4zov7.html

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  3. Given that EBV infection is so common, does it present any advantage to the infected host? To ask my question another way: if we could stop EBV infection tomorrow, would there be any negative impact? I understand the upside, but would there be a downside ?

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    1. EBV does seem to be a co-factor in B cell development so some co-evolution seems to have taken place though doesn't seem to be essential in the development of a competent immune system

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  4. Thanks for this post - very interesting to see the latest research on EBV in relation to potentially being a contributing factor or cause of MS. I have PPMS and recall having swollen glands in my neck for months at a time as a teenager - looking back I suspect I actually had glandular fever. How is glandular fever detected and treated? Is this something where as a preventative measure for MS antivirals might be something to consider in the future? Can anyone elaborate "EBV-targeted treatments are already in early stages of development"?

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    1. There are no treatments for glandular fever (also called infectious mononucleosis, IM) other than supportive care--basically plenty of rest and lots of fluids until the symptoms subside. Signs of IM include enlarged lymph nodes, liver or spleen. There is also an antibody test.

      Scientists are working on vaccines for EBV, but I personally think it will be hard to achieve what they call "sterilizing immunity"--basically an immune state that prevents an EBV infection. EBV is a very efficient virus infecting 90-95% of the population.

      Scientists are also working on T cell therapy, basically training T cells to attack EBV infected cells. They are making pretty good progress. There is anecdotal evidence that it might be working as a treatment for MS, but I haven't seen convincing evidence yet.

      Aciclover and the prodrug cousins ganciclovir or valaciclovir can reduce lytic replication, but do nothing for latent infection. It's unclear whether the lytic or latent form of EBV might be involved in MS. This paper is trying to establish that it is involved in the first place. We have a small molecule program that targets latent EBV infection, but it is still in the very early stages of clinical development.

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  5. "BZLF1 was not present in chronic active lesions - this is a surprising finding which implies that lytic infection is present in healthy brains, in chronic inactive lesions, but not in lesions with acute inflammation."

    "There goes my hero
    Watch him as he goes"

    Sorry

    I mean "Black swan"

    :)

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  6. Important to mention a COI in this paper. The author recieved funding from Atara Biotherapeutics:
    Atara Biotherapeutics is developing off-the-shelf, allogeneic ATA188 and autologous ATA190 T-cell immunotherapies using a complementary targeted antigen recognition technology for specific EBV antigens believed to be important for the potential treatment of multiple sclerosis (MS).

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  7. But how come ATA 188 apears to work?
    This phase 1 drug is specific design to fight b-cells infected by EBV. We will wait and see further results

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    1. i may be asking questions there is no answer to. Is it just infected B-cells? And, unlike Rituxan and Ocrevus, does it also get into the CNS? Does it impact neurofilament light chain levels? Rituxan does not.

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  8. Mice doctor.

    I had severe glandular fever as a teenager, so bad I was hospitalised.

    Is there any link between the severity of your experience with EBV, and the course of MS?
    I am now mid 30s and had an aggressive onset of MS, which also left me hospitalised. I am RRMS, and taking a dmt.

    The lesion count at diagnosis was high, with black holes indicating this had been around without causing relapses, and through deep review, I recalled signs that may have been overlooked.

    Anyway, just curious if there is any prognosis Factor?

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  9. DrBenJ would be possible, it's according to the results of this study, that the non-presence of EBV in chronic, acute active lesions would be due to the immune system itself trying to get rid of the virus in the injured region, reactivating it while trying get rid of the virus, which would cause even more damage?

    It's known that EBV can infect astrocytes, for example.

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    1. To add to that, a new theory for Alzheimers wants plaques to be an innate immune response to viruses.

      Is there a difference between an RRMS patient and an SPMS patient who doesn't have relapses anymore? Could this be a reason why relapses and lesions eventually stop?

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    2. Amyloid beta protein protects brain from herpes infection by entrapping viral particles
      https://medicalxpress.com/news/2018-07-amyloid-beta-protein-brain-herpes.html

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  10. http://www.jimmunol.org/content/175/3/2010

    EBV load is not altered after long term antiretroviral therapy, so this doesnt seem to be the reason why a.t. works on MS.

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    1. But as far as I've read there are no good anti-retroviral drugs against EBV.
      This even is one of the problems in the treatments against cancers caused by EBV, so much so that the treatment is the immune exhaustion of B cells to try to eliminate the virus.

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    2. That was their hypothesis with AZT...

      https://www.sciencedirect.com/science/article/pii/S2211034818300828

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