I know how much you like EAE studies, but as I'm a MouseDoctor I have been asked by the Government to be more open about animal experiments, so we need to report this stuff. Some are interested, if not don't read
If you look at the EDSS after early treatment with alemtuzumab in MS, it improves.
Therefore does alemtuzumab cause remyelination and repair or save nerves?
This was suggested to be a mechanism via a process that involves the production of a cytokine called brain-derived neurotrophic factor. Is this how it works?
So in this study they made mice that lacked BDNF and so couldn't secrete it into the brain, when they got EAE...What happened?
LEVEL: ADVANCED AND THOSE INTERESTED IN SCIENCE AND DATA INTERPRETATION..and ETHICS of Animal Use and learning English Slang
Punchline: It says to me the best for of repair is to treat early and effectively and allow the natural repair mechanism to work
The murine anti-CD52 antibody, an equivalent of the humanized antibody alemtuzumab, which is successfully used in the treatment of multiple sclerosis, was used to explore a potential neuroprotective effect driven by immune cell derived brain-derived neurotrophic factor (BDNF). Therefore, lineage specific constitutive knock-out mice with a BDNF deficiency in T cells and macrophages were used and compared to treated wildtype mice. Neither therapeutic nor preventive application of the murine anti-CD52 antibody in an animal model of multiple sclerosis, the MOG35-55 EAE, revealed a beneficial contribution of immune cell derived BDNF to the disease outcome. Furthermore, preventive application of the murine anti-CD52 antibody worsened the clinical EAE disease course and could only be overcome by a prolonged recovery phase after treatment and before disease induction.
The authors of the paper say
- •Alemtuzumab depletes CD52-expressing lymphocytes and monocytes
- •Alemtuzumab mediates increased BDNF expression from mononuclear cells of MS patients
- •BDNF T cell and macrophages knock-out EAE mice showed no difference in the clinical course after alemtuzumab application
- •Preventive alemtuzumab treatment worsened EAE clinical score through the increased repopulation with macrophages
- •Neuroprotective alemtuzumab effects are not mediated through a direct effect on immune cells
What do we make of this
Some "crazy" people have suggested that the autoimmune response in MS is protective and have coined the term "protective autoimmunity". It created a "band wagon" and as such when it was found that lymphocytes that repopulate after alemtuzumab secrete BDNF and other molecules and people on alemtuzumab improved and so the "mousers" created a new sexy term on which to hang their observations
Jones, J.L., Anderson, J.M., Phuah, C.L., Fox, E.J., Selmaj, K., Margolin, D., Lake, S.L.,
Palmer, J., Thompson, S.J., Wilkins, A., Webber, D.J., Compston, D.A., Coles, A.J.,
2010 Aug. Improvement in disability after alemtuzumab treatment of multiple
sclerosis is associated with neuroprotective autoimmunity. Brain 133, 2232–2247
Now I say "crazy" (but could have said lazy because they forgot to think) because the people (not those above) who coined this term have no interest in human biology and only work on animals and do not really MS. They are interested in mechanisms not human health.
Neuroinflammation is about protection (kill the infection) and repair (deal with the damage caused by killing the infection and repair the damage from the infection) and so of course the immune system will promote repair. I have now problem with this. Likewise I have no problem with BDNF secreting lymphocytes promoting repair....but on balance having the immune system in your brain is not beneficial and you simply have to look to therapy. If, the major role of lymphocytes entering the brain was for repair, MS drugs would not work and they would make MS worse. Two minutes of thought and the sexy idea would have been in need of viagra:-).
The study looks a so called "therapeutic treatment" (After in graphs below) and treat when signs develop.
First thing that has to be said it this has no relevance to human use as you do not give alemtuzumab or any other DMT during attack....you give steroids. It also mean that they treat the whole group when on animal develops disease, surely they should stagger the treatment so they all start treatment at the same point because doing it this way 10-25% of the animals never got disease started, skewing the data terribly.
However looking at the data (After) it looks like the animal lacking BDNF (blue) in their lymphocytes did not recover (see the black line) as well (compared to black) supporting the views of Jones et al. above and different from the claims made. However as we do not know the individual scores we can not be sure.
CD52 depletion clipped the beginning or the tail.
Now they say that treatment of alemtuzumab worsened EAE.
However, Basically alemtuzuamb zaps human CD4 for about 2-3 years, but in mice it lasts 1-2 months so what can happen when the immune cells return....yep you guessed it..disease returns. I do not buy it that it really worsening disease. We showed that previously.
This is not uncommon you remove a drug and disease returns. Do again what do the human studies should. yep exactly alemtuzuamb has a very long term beneficial effect in humans
So they then ask what happens when you deplete before (in graph above) EAE induction which is again something irrelevant to MS as you do not treat before you give disease.
Why not try and prevent a relapse and do something relevant...I guess too much hard work:-(
Anyway you deplete nearly 2 months before they induce EAE and then they get....Yep a "dogs breakfast".
Some animals will have repopulated their cells and can be induced to get disease and some maybe be less. Those lacking BDNF behaved in the control ground as found in the earlier experiment (before and after) but sadly the control group of normal animals (in black in before graph) has a mean of about 1 (a bit of a limp tail) whereas before they were nearly paralysed (7), so rather than repeat an experiment such that there is consistent disease and thus having a "quality control" element, they explain one that doesn't. Do a similar experiment many months after treatment and is it worse it looks pretty similar the control group this time is about 4.
Is it because macrophages increase, but if you deplete T and B cells with alemtuzumab and you are working in percentages and not absolute numbers as one goes down the other must go up.
So I am not sure the data supports the title and it is still possible that alemtuzumab is causing the release of something that is beneficial to stimulate repair.
However, even if the conclusions of the study are correct and this will be all that gets remembered and not the data.
However, the point of examining this paper is to make these comment.
1. If alemtuzumab is effective it will stop T cell traffic and so the T cells won't go into the CNS to release BDNF etc. This will be the case in the EAE study too.
2. However, the most obvious and simplest answer to understand the behaviour is that we know that early MS lesions are surrounded with early oligodendrocytes that can come in and cause repair. This fails in MS (notably in the white matter in the grey matter remyelination (REPAIR) is seen in very old people who have had long standing MS) because of the repeated inflammatory insults, but get rid of that and the repair can occur naturally. In an animal the default to demyelination is always remyelination within a few weeks.
What happens with other highly active MS treatments, I suspect the same, however because the trial with alemtuzumab was so soon after diagnosis they have the most reserve to recover, so we will need new studies.
The problem with this mouse study is that mice do not show particularly good demyelination as the nerves tend to die once the myelin goes and therefore there would be nothing for the cells to repair. Therefore it is hard to test
I believe that EAE studies can have value to understand biology and perhaps should not publically be negative, but unless we are honest about the failings of animal studies we cannot hope to improve this type of work. As part of our day job we do Journal clubs where the contents of studies are reported, this is about constructive criticism and learning.
P.S. I teach on reading papers and will perhaps today's figures will feature.