Do you believe that “viral persistence” is the cause of ongoing MECFS and LC?

Well that is the question. But then when you have widespread muscle pain with influenza or a typhoid vaccination there isn't any inflammation in the muscles as far as we know. So it is not an unfamiliar question. I have a simple suggestion (with a bit of elaboration) but I need to get it written out clearly. Like for RA I think the answer may be hiding in plain sight.

 

Not tactless! Yeah, she was talking about other patients who had a sports-related injury a while back and continued to have pain and tenderness/swelling long term, especially when they recently overused that joint. That's why she was surprised I wasn't a sports person and didn't have signs of RA--I was exhibiting athlete-level stiffness just from being on my feet sporadically during the day.

For what it's worth, I haven't experienced that particular symptom as much since I started taking a stimulant and now a malic acid supplement. I still get occasional stiffness in the morning since the malic acid has long worn off by then, but then it goes away once I roll out my ankles out a bit.

That's one of the reasons I see such a big link in between energy metabolism and PEM/other ME/CFS symptoms--the biggest differences for me came from things that primarily affect energy metabolism. It's also why I'm not too convinced about viral persistence or viral reactivation causing PEM--as far as I know, I didn't get sick with any cold or flu or anything for a whole year before developing ME/CFS (it was somewhat gradual for me, worsening over a period of a few months before I just had to drop out of school). Negative antibody tests for EBV, Hep C, and whatever else my doctor could check for. It's possible I had a completely asymptomatic infection, but I think my ME/CFS is much more closely aligned with a period of extreme prolonged stress and how that probably interacted with pre-existing Hasimoto's or some other perfect storm of genetic predisposition + triggers.

Obviously this might all just be me, or maybe there are other confounding factors, but I really think there's something to the energy metabolism piece of the puzzle. I think we have to look at some mechanism that can potentially occur as a result of viral infection, but can also occur without it.

 

I'd be interested to hear when you have a chance.

In the mean time, there's still evidence of similar cytokine responses in influenza and typhoid vaccination, correct? Thinking along parsimonious lines, wouldn't that indicate that a certain combination of cytokines in muscle tissue could trigger pain and stiffness on their own, and there's an additional step leading to histopathological inflammation that just doesn't get carried out in ME/CFS or influenza/typhoid vaccine responses? Then all you need to identify is one intermediate step after initial cytokine signaling that differentiates ME/CFS or influenza/typhoid vaccine responses from conditions which also present with inflammation.

 

But cytokines don't look parsimonious. There are at least twenty cytokines associated with inflammation in various ways and contexts. And we know they all do different things both at inflammatory sites and elsewhere. And we have reason to think that the system is 'designed' to generate quite different responses in different contexts. Inflammation is one but B lymphocyte deletion by CD56/57+ cells is not associated with inflammation.

And the effect of a cytokine or something like complement is totally dependent on where it is. If cytokines are produced by cells in tissue outside blood vessels they call white cells out of the blood by up regulating adhesion molecules and providing chemotactic gradients. If cytokines are present in circulation there is no reason for cells to go out of the circulation, so no reason for inflammation. In theory circulating cytokine might up regulate ICAM-1 everywhere but to get the necessary local concentration you would probably have died of septic shock half an hour earlier.

Complement even reverses its function. Complement activation in tissue generates chemotaxins - C3a in particular. Complement activation in blood mediates immediate silent clearance via red cell CR1 and spleen. Pro-inflammatory becomes anti-inflammatory.

So with typhoid vaccine you get release of pyrogenic factors, maybe Il-1 or TNF, very likely from Kuppfer cell activation. Kuppfer cells are mature macrophages capable of rapid cytokine secretion but weirdly they are inside the portal venues, so do not incite hepatitis. Cytokines from Kuppfer cells presumably activate further signals in muscle that sensitise nerve endings - quite likely the prostanoids that naproxen blocks. Inflammation does not come into it.

So yes, a combination of signals can trigger pain and stiffness in muscle on their own but let's not confuse that with inflammation. There isn't going to be a 'further step' unless there are some specific local events in muscle generating localising signals and we have no reason to think there are.

All this sort of stuff became clear to us in the 1980 and 1990s as we identified the signals and the way they affect different tissue responses. That has all been forgotten it seems. Every tissue has different rules. In cytokine driver terms TNF for joints, IL-1 for skin, something else for muscle maybe. Each tissue is decorated with a different range of modulatory proteins like TGFbeta, CD55, CD59. The idea of 'cytokine balance', whether pro- and anti- inflammatory or so-called 'TH1 and Th2' is a travesty of the way the system works. Disease mechanisms lie in the fine detail of how each individual pathway can get subverted in a unique way.

 

IL-6 for muscles?

 

It might well be a mix. There's different phenotypes in both conditions and one root cause or pathology might be difficult to gauge.
Viruses have some involvement, but whether it's persistence or some immune process viruses trigger - more research is needed.
There is some research on biopsies on viral reservoirs but they haven't been extensively researched to know for sure

 

I agree--I've been eagerly following the systems biology work by Nicolas Chevrier showing that pairs of cytokines elicit specific transcriptomic signatures in different tissues. Thanks for your additional insight as well.

I remember a single-cell transcriptomic study that showed increased chemotaxis gene program expression in monocytes--perhaps it was from the Hanson lab?

I understand your points about lack of histopathological inflammation, though I still see a path forward with macrophage-mediated cytokine release in the muscle tissue in reaction to activity. The explanation doesn't rely on a "global pro-inflammatory state" that doesn't exist. It would be enough if macrophages in the muscle tissue end up releasing the specific cytokine program that elicits pain and stiffness in the muscle. Muscles are a massive organ, after all.

There's also probably some overlap in other tissues as well, even if it's not the exact same in all tissues. And once you get into immune signaling, that does occur on a time scale associated with PEM, especially if the same metabolic mechanism would impair a major negative feedback mechanism for that signaling.

A pathological "upper ceiling" on ATP generation from oxidative phosphorylation doesn't mean that ATP is inadequate in all cells in all contexts. So it won't look like conditions where ATP production is severely impaired across the body. It would primarily become an issue in cases where oxidative phosphorylation needs to be ramped up beyond that upper ceiling in specific contexts, such as in the brain and muscle. And if that issue has knock-on effects in immune signaling, you have a phenomenon that would occur on the timescale of PEM and explains why it is triggered by overexertion to begin with.

Furthermore, if a specific cell has a temporary energy demand that is higher than what OxPhos can produce in the moment, that's still going to trigger even more pathways that take longer to resolve, both on a cellular and systemic level. It's not just going to stop being an issue once the temporary demand goes away, as @SNT Gatchaman alluded to.

Obviously this would require much further investigation to confirm--my main point here is that an ATP-related mechanism is by no means too simplistic to explain the complexity of ME/CFS. You'd absolutely need to tie in immune signaling to get a full picture, but that doesn't mean it's implausible on its own especially if can neatly tie together so many disparate findings.

 

Of course, but that isn't necessarily inflammation. And in the twenty minutes after a typhoid vaccine when you suddenly feel aches all over there isn't time for any inflammation.

Sure, but since CRP does not rise presumably there isn't inflammation here either.

It is just a matter of using precise language so as not to end up with false assumptions.

Yes, but the clinical presentation for the generalised problems like heart failure mostly shows in brain and muscle too and it doesn't look like ME/CFS.

But why rely on ATP and redox for the story when the story works perfectly well with the immune signalling on its own?

But as a clinician it doesn't seem to me to fit and my impression is that everyone is talking about it simply because everyone has been talking about it for so long - the oldest story in the book that never got very far. The people who work on basic mitochondrial biology don't think much of the idea either. And I haven't seen any substantive evidence for it yet. Why can't we just build a story out of the immune signals?

 

The explanation doesn't require histopathological inflammation at all. As you said yourself, cytokines =/= inflammation. All you'd need are the specific cytokine combination needed to elicit muscle pain and stiffness sans inflammation.

I'd expect a difference in situations where ATP function is globally severely limited, vs. where it can generally keep up with demand except for specific contexts. Esp if the failure to keep up in those specific contexts has knock-on effects that might be reliant on some residual level of OxPhos capacity to be carried out.

Energy metabolism and immune signaling are intrinsically connected at many points. Many examples where signaling and phenotypic changes in immune cells are mediated by energy metabolism and cannot happen without it, or where energy metabolism can trigger immune signaling on its own without a pathogenic stimulus. We're probably working towards the same point. If there is a complete story of only immune signals that doesn't rely on metabolism, I'll happily accept it once I see it. But given emerging evidence on their interconnectedness, I think this is where the two come together.

I suspect it's a broader debate in the field--the same argument came up with my old PI who thought that mitochondrial findings were irrelevant in my RA data until I pointed out some important connections. I may be able to prove those connections here, I may not.

Excited to see where the data takes me at this point.

 

I think this one:

Single-cell transcriptomics of the immune system in ME/CFS at baseline and following symptom provocation (2024, Cell. Rep. Med.)

 

Yes I believe that's the one! Thank you

 

Yes, that is what I have been saying all along.

I think not keeping up in specific contexts always pretty much applies. People on ITU just lie there gasping for breath but people in marginal heart failure 'generally keep up with demand' until they have to use muscles a bit more. It looks very different and the time scales are very different.

Yes, but I am sceptical that that matters much to disease mechanisms. Jo Cambridge and I had a field day working out chronic immune disease mechanisms in the 1990s without ever needing to talk about metabolism. Diseases involve very specific signalling errors. Ischaemia and metabolic failure often occur at the end of effector pathways but they seem to me much too non-specific to be useful for picking out one disease rather than another.

What appears to you as 'emerging connectedness' appears to my like re-inventing a rusty wheel I am afraid. We had these arguments in 1980. The fashionable dogma in immunology is almost all bullshit. Progress comes from ignoring it and focussing on specifics.

I cannot see any need to invoke metabolism in RA. The signalling pathways are all there with antibodies, receptors, cytokines and adhesion molecules.

Which presumably shows that cells sometimes respond to signals in places where the response has no function.

These debates are very useful. They sharpen our arguments. But I ain't heard nothing so far that I haven't heard for several decades. People think a fatigue syndrome must be short of energy so look for metabolic shifts. Richard Edwards, Joan Round and David Jones in our department looked for energy metabolism changes in the 1980s. They found nothing. If energy was really a problem that remains surprising.

 

So if a shift in macrophage cellular metabolism triggers the release of cytokines that cause muscle pain but don't, on their own, cause inflammation, that fits with PEM.

I hear you, I don't think it's useful to get caught up in hype for its own sake. I'm hardly a die-hard mitochondrial person, I just feel that it explains my own experience with ME/CFS vastly better than other explanations.

I'm primarily interested in mitochondrial function to try to explain the borderline remission I'm currently experiencing after starting a malic acid supplement. I'm able to walk 2-3 miles a day now when that was unthinkable a few months ago. One of the first things I noticed was that it felt like I was actually using the air I breathe and my heart didn't need to work as hard. And I have a mostly bedbound friend who was able to get up and bake and watch a movie for the first time in months. Others have expressed similar boosts from it, though not everyone, so it seems to be a subset-specific response.

The clearest explanation for me is via malic acid/malate's role in electron shuttling for OxPhos, since it would also directly explain a plethora of metabolomic findings as well as other observations in the illness. But if an immune-signal explanation is able to explain all that without incorporating metabolism, I'll be personally satisfied. So far, I don't see it. I just need to do the due diligence of chasing down one lead at a time thoroughly.

 

But without the implication of metabolism. Just immune signalling. And it might not be macrophages producing cytokines. They might be altering gene expression in response to cytokines from other cells.

I think the signals may well be ones we have known about for yonks. But nobody has actually thought about how viral myalgia works without inflammation. A very simple connection was missed and a wrong connection made instead.

When we were working on RA the crucial shift was realising that Henry Kunkel and his disciples had done this for immune complexes. They decided that the immune complexes they found in RA could not be causing inflammation because they did not fix complement. We realised that they DID cause inflammation BECAUSE they didn't fix complement. The pathways were all known but despite working in a department with an international reputation for immune complex work nobody around us had twigged.

 

I remember you saying that the cause of ME/CFS might turn out to be something quite new, because if it wasn't, we'd probably have solved it by now. Does your theory involve the possibility of something quite new, or do you think it's a wrinkle on things that biomedicine already knows?

 

Oh, both, of course. It will be quite new in that we have not thought of that sort of possibility - a bit like prion disease - but I suspect it will involve joining up mechanisms that we have known about for a long time.