Tuesday, 15 November 2016

EBV and B cells

Trends Mol Med. 2016 Nov 8. pii: S1471-4914(16)30149-6. doi: 10.1016/j.molmed.2016.10.007. [Epub ahead of print]

EBV Infection and Multiple Sclerosis: Lessons from a Marmoset Model.

'tHart BA, Kap YS, Morandi E, Laman JD, Gran B.


Abstract


Multiple sclerosis (MS) is thought to be initiated by the interaction of genetic and environmental factors, eliciting an autoimmune attack on the central nervous system. Epstein-Barr virus (EBV) is the strongest infectious risk factor, but an explanation for the paradox between high infection prevalence and low MS incidence remains elusive. We discuss new data using marmosets with experimental autoimmune encephalomyelitis (EAE) - a valid primate model of MS. The findings may help to explain how a common infection can contribute to the pathogenesis of MS. We propose that EBV infection induces citrullination of peptides in conjunction with autophagy during antigen processing, endowing B cells with the capacity to cross-present autoantigen to CD8+CD56+ T cells, thereby leading to MS progression.


Our biggest pathogenic contender to date for causing MS is EBV (Epstein-Barr virus), closely followed by endogenous retroviruses and HHV-6 (Human herpes virus-6). But trying to prove this has been no mean feat, as MS-EBV association studies in people are hampered by the fact that difference between the prevalence of EBV in MS (100%) and the healthy (>90%) population is small. Therefore, scientists need to come up with more inventive ways of studying disease associations, which is where animal models come in.

Marmosets evolutionarily are ~ 50 million years in proximity to humans, sharing both genetic and immunological similarities. Like us they're exposed from birth to pathogens, creating a similar pathogen-educated immune system that may present us with the answer that we're seeking.

To date, the autoimmune hypothesis around MS is basically attributed to T cells; for instance, crossreactive CD4+ Tcells recognising EBV and myelin epitopes as one and the same (resulting in the proinflammtory targeting of myelin and demyelination). What about B cells? 'tHart et al. argue using evidence from the marmoset model, that B cells infected with the virus may endow them with the capacity to activate self aggressive CD8+ T cells already present in our immune repertoires (normal B cells are less capable of doing this). Moreover, they state that the frequency of human B cells that actually contain the virus is small (<0.01%) , which may explain the low frequency of MS in the population despite the high prevalence of EBV! And, that is how a new hypothesis is born.

7 comments:

  1. Interesting post. I feel I've been too grim, anything positive helps!

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  2. NDG, and those MSers who claim never to have had Infectious Mononucleosis or who hold that they have anti-EBV tests as negative, in the latter case they would be false negatives, or could MS be muticausal?

    I had Mono, just horrible, the worst headache I've had so far, outside the throat that was horrible, besides the strong fever ...

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  3. It's likely that there is more than one way for the autoimmunity to start, but a majority may be explained by a single starting point.

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    Replies
    1. I would like to learn a little more about these mechanisms.

      I take some nutraceuticals in the "hope" of not reactivating EBV, but they are nutraceuticals, they don't even come close to effect if there was really an antiviral against EBV...

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  4. To create a vaccine for the EBV would benefit the whole world (except for the pharmaceutical companies!) I have just read this from the UK Cancer research site -
    "Each year 200,000 cancers worldwide are caused by Epstein Barr Virus (EBV). We want to find a way to reduce that figure to zero."

    So our Grand Challenge is to:

    ERADICATE EBV-INDUCED CANCERS FROM THE WORLD


    Read more at https://www.cancerresearchuk.org/funding-for-researchers/how-we-deliver-research/grand-challenge-award/challenge2#wHxFls53CoyVHlq7.99

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  5. EBV infected B cells (Reed-Sternberg cells) modify the behaviour of the immune system in Mixed Cellularity Hodgkin's Lymphoma causing wide scale effects through out the body even when the cancer is very small and localised. The only reason we know one causes the other is that the cancer grows big enough to find (the lymphoma actually contains very few cancer cells). If they stopped growing when they were small we would still be considering the symptoms as an autoimmune disease. Maybe this is true of MS.

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