Long COVID involves activation of proinflammatory and immune exhaustion pathways, 2025, Aid et al.

[Jonathan Edwards]

From this perspective, chronically elevated cytokines like IL‑6 or TNF alpha are not the main drivers of ME/CFS, but rather a result of mitochondrial dysfunction.

Except that we do not have any evidence of 'mitochondrial dysfunction' as far as I know. And what is making the mitochondria dysfunct? And if the effect was on cytokines like IL-6 we still don't have an answer as to why CRP is normal.

I personally do not know what 'systemic inflammation' means, beyond a raised CRP or other evidence for cytokine elevation, and we don't have these. We actually have negative data on them.

And if there is a vicious cycle then sommething other than normal pathways are being used because for most other situations where there is energy failure or cytokine production there is no such cycle. So we are back to having no answer?

There is no evidence for hypoxia in ME/CFS or LC as far as I know.

 

[Dude]

@Jonathan Edwards

In the hypothesis paper, mitochondrial problems are discussed and reference is made to the following review:

Key Pathophysiological Role of Skeletal Muscle Disturbance in Post COVID and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS): Accumulated Evidence - PubMed

Based on this pathomechanism, future treatment approaches should focus on normalizing the cause of ionic disbalance. Current treatment strategies targeting hypoperfusion have the potential to improve the dysfunction of ion transporters.

pubmed.ncbi.nlm.nih.gov

In my view, the evidence for mitochondrial dysfunction is already quite compelling. Examples include the handgrip test and gastroparesis, both of which are frequently observed in severely affected patients and are also common in primary mitochondrial disorders. In addition, an electron microscopy study was able to directly demonstrate structural mitochondrial damage.


I agree that, so far, there are no validated and standardized clinical mitochondrial biomarkers that are established for the diagnosis of ME.


The article also briefly discusses hypoperfusion, and thus reduced tissue blood flow, as a possible cause of mitochondrial dysfunction and muscle abnormalities. This could explain the early rise in lactate levels. This would represent a state of relative oxygen deficiency rather than classical hypoxia.


Here is the explanation of the Wirth model copied from another thread:


According to the hypothesis, mitochondrial dysfunction is not primarily caused by an intrinsic defect of the mitochondria themselves, but rather by a disturbance of cellular ion homeostasis, particularly dysfunction of the sodium–calcium exchanger (NCX).


Hypoxia or hypoperfusion leads to an energy deficit (ATP depletion). As a result, energy-dependent ion pumps—especially the Na⁺/K⁺-ATPase—function less efficiently, intracellular sodium levels rise, and the NCX operates in reverse mode.


In this state, calcium increasingly flows into the cell instead of being extruded. The elevated cytosolic calcium also enters the mitochondria, leading to:


• mitochondrial calcium overload

• inhibition of oxidative phosphorylation

• increased production of reactive oxygen species (ROS)

• further ATP depletion

• secondary activation of pro-inflammatory pathways, resulting in elevated cytokines


Mitochondrial dysfunction is therefore secondary and maintained by a self-perpetuating loop of energy failure, calcium dysregulation, and chronic low-grade inflammation.

 

[Jonathan Edwards]

In my view, the evidence for mitochondrial dysfunction is already quite compelling. Examples include the handgrip test and gastroparesis, both of which are frequently observed in severely affected patients and are also common in primary mitochondrial disorders. In addition, an electron microscopy study was able to directly demonstrate structural mitochondrial damage.

OK, but I have had the study of chronic disabling musculoskeletal disease as my job for a lifetime and if this is the level of evidence I am not very impressed. Grip strength goes down with almost anything - from painful conditions to just generally feeling ill. A recent study of 'gastroparesis' suggested that the tests that are supposed to show it don't predict anything useful clinically - they are also inconsistent. Again, poor stomach emptying is probably very non-specific - it occurs when you have flu. One or two EM studies claim mitochondrial shape changes but I am not aware of anything confirmed and there are many EM studies claiming such things that never pan out. Often tissue preparation is a problem.

People like the idea of mitochondrial dysfunction because it feels as if energy is lacking but it doesn't make a lot of sense clinically. Unfortunately, in a field like ME/CFS where we know so little there tends to be a preponderance of amateur theorising from people who don't actually have a grasp of the bigger picture. I don't know of anyone much other than Wirth (and local friends) in the research field who thins his theory makes much sense.

And why would the mitochondria be dysfuncting? Since people can get better spontaneously and many have better periods after bad periods it is pretty clear that ME/CFS is not a progressive primary mitochondrial disease. Maybe Wirth thinks it is all due to lack of oxygen supply but again the clinical picture just doesn't look like that. The day 1 CPET studies suggest that people with ME/CFS have reasonably normal energy availability.

 

[jnmaciuch]

Do you know of any similar studies that have looked at JAK STAT pathways and Il-6 in non LC ME and come up negative?

Off the top of my head, Montoya paper for cytokines and the scRNA-seq study with Hanson lab (Vu et al?). The latter was also on PBMCs, JAK-STAT pathways are mentioned but in the opposite direction as here iirc. I think there was also a cerebrospinal fluid cytokine assay done that showed only weak associations in other cytokines besides these—I’m blanking on the name, apologies. I will try to link the studies later when I have my laptop if they can’t be found by searching

 

[V.R.T.]

Off the top of my head, Montoya paper for cytokines and the scRNA-seq study with Hanson lab (Vu et al?). The latter was also on PBMCs, JAK-STAT pathways are mentioned but in the opposite direction as here iirc. I think there was also a cerebrospinal fluid cytokine assay done that showed only weak associations in other cytokines besides these—I’m blanking on the name, apologies. I will try to link the studies later when I have my laptop if they can’t be found by searching

That's interesting and a little dismaying as I had been entertaining a bit of hope that these findings might be relevant for ME/CFS too. Especially in light of the JAK-STAT trials.

On a related note, I remember you saying that if something you were speculating about had merit then hopefully some of those trials will pan out, but I can't remember the details. Perhaps it was the mtDNA stuff?

 

[Jonathan Edwards]

Do you know of any similar studies that have looked at JAK STAT pathways and Il-6 in non LC ME and come up negative?

There have been a number of studies of cytokines in ordinary ME/CFS, at one time reviewed by Peter Denton White. IL-6 did not come up. If anything there was some replication for TGF beta and maybe IL-8.

 

[jnmaciuch]

That's interesting and a little dismaying as I had been entertaining a bit of hope that these findings might be relevant for ME/CFS too. Especially in light of the JAK-STAT trials.

For what it’s worth, those negative findings don’t mean those pathways aren’t relevant in the disease, just that we don’t see signs of it in the blood in non-COVID ME/CFS (or outside of PEM, when these blood samples are usually taken). Plenty of illnesses involve these pathways but you may only find whispers in the blood if anything at all.

Though you can pretty much say that about any theory, no matter how baseless—if you don’t see positive evidence it’s just because you weren’t looking at the right place/time. For that reason I try not to put too much stock in any theory, even my own, until there’s hard evidence.

On a related note, I remember you saying that if something you were speculating about had merit then hopefully some of those trials will pan out, but I can't remember the details. Perhaps it was the mtDNA stuff?

Yes it’s the same mtDNA/interferon hypothesis. I was generously given data from another cell type on the hunch that it might also show signs of what I’m theorizing. That evidence is consistent with my theory but it’s indirect so I wouldn’t consider it proof—I’ve been trying to use it as preliminary support to gain interest from a collaborator with muscle samples so I can test the hypothesis more directly. Unfortunately I can’t share more details at the moment.

Even if I can get someone to provide muscle samples, I will probably have to do more small-scale “indirect” investigations first before I can do my dream experiment to actually prove/disprove my theory. The protocol is resource intensive and beyond my expertise/ability at the moment so I’d need another lab to agree to run a whole complicated study on an external idea, plus I’d have a lot of trouble securing enough funding for a robust study without more preliminary evidence that I’m on the right track.

At this point, having gained much more knowledge about interferon signaling from my other PhD projects, I’m not certain if a JAK inhibitor would target the right parts of the pathway if my theory ends up being correct. But there’s a chance it could have an effect.

 

[jnmaciuch]

Again, for metabolic dysregulation, that needs to be driven by something - what?

I agree that I don’t find the overall diagram compelling, but several interferon stimulated genes target key proteins in metabolic pathways. Changes in AMPK signaling, calcium metabolism, NAD metabolism, etc. are pretty well documented with interferon signaling.

You wouldn’t expect changes in those pathways to lead to a fundamental lack of ATP like in mitochondrial disorders. The paracrine anti-viral response didn’t evolve to induce cell death in uninfected bystander cells, just change their metabolic pathways enough so that their machinery is less permissive to being co-opted by a replicating virus. Transient interferon stimulation would be entirely consistent with someone performing normally on day 1 CPET but struggling on day 2, or struggling to maintain the same hand grip strength only for longer periods of time.

 

[Jonathan Edwards]

I agree that I don’t find the overall diagram compelling, but several interferon stimulated genes target key proteins in metabolic pathways. Changes in AMPK signaling, calcium metabolism, NAD metabolism, etc. are pretty well documented with interferon signaling.

I agree that it makes sense that way around.

 

[jnmaciuch]

I agree that it makes sense that way around.

And it would be a better explanation for the set of genes they’re claiming as an “exhaustion” signature—they’re just genes that get upregulated in T cells with chronic exposure to a particular cocktail of signals, after all.

 

[jnmaciuch]

And if the CRP is normal, as I think it is in these cases, how is IL-6 a central pathway?

A potential answer?

https://onlinelibrary.wiley.com/doi/10.1002/art.25042

So the balance of IFN-a and IL-6 determines whether CRP gets induced in the liver. Slightly elevated IL-6 may only be a feature of certain post-COVID cases, but if IFN is the common link between ME/CFS and debilitating LC, it would suppress CRP.

 

[PageofME]

@Jonathan Edwards

In the hypothesis paper, mitochondrial problems are discussed and reference is made to the following review:

Key Pathophysiological Role of Skeletal Muscle Disturbance in Post COVID and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS): Accumulated Evidence - PubMed

Based on this pathomechanism, future treatment approaches should focus on normalizing the cause of ionic disbalance. Current treatment strategies targeting hypoperfusion have the potential to improve the dysfunction of ion transporters.

pubmed.ncbi.nlm.nih.gov

In my view, the evidence for mitochondrial dysfunction is already quite compelling. Examples include the handgrip test and gastroparesis, both of which are frequently observed in severely affected patients and are also common in primary mitochondrial disorders. In addition, an electron microscopy study was able to directly demonstrate structural mitochondrial damage.


I agree that, so far, there are no validated and standardized clinical mitochondrial biomarkers that are established for the diagnosis of ME.


The article also briefly discusses hypoperfusion, and thus reduced tissue blood flow, as a possible cause of mitochondrial dysfunction and muscle abnormalities. This could explain the early rise in lactate levels. This would represent a state of relative oxygen deficiency rather than classical hypoxia.


Here is the explanation of the Wirth model copied from another thread:


According to the hypothesis, mitochondrial dysfunction is not primarily caused by an intrinsic defect of the mitochondria themselves, but rather by a disturbance of cellular ion homeostasis, particularly dysfunction of the sodium–calcium exchanger (NCX).


Hypoxia or hypoperfusion leads to an energy deficit (ATP depletion). As a result, energy-dependent ion pumps—especially the Na⁺/K⁺-ATPase—function less efficiently, intracellular sodium levels rise, and the NCX operates in reverse mode.


In this state, calcium increasingly flows into the cell instead of being extruded. The elevated cytosolic calcium also enters the mitochondria, leading to:


• mitochondrial calcium overload

• inhibition of oxidative phosphorylation

• increased production of reactive oxygen species (ROS)

• further ATP depletion

• secondary activation of pro-inflammatory pathways, resulting in elevated cytokines


Mitochondrial dysfunction is therefore secondary and maintained by a self-perpetuating loop of energy failure, calcium dysregulation, and chronic low-grade inflammation.

If your interested in ME/CFS and the mitochondria I can recommend you to go back to a research review from 2019 by the ME Association on the one hand and to another review on herpes reactivation and especially the HHV-6B hypothesis in ME/CFS on the other.

MEA Summary Review: The Role of Mitochondria in ME/CFS | 13 July 2019 - The ME Association

This latest review looks at energy production, and the ongoing search for clues as to what might be causing problems in ME/CFS.

meassociation.org.uk

Research Review: Reactivation of human herpesviruses and their role in ME/CFS and Long Covid - The ME Association

By Dr Katrina Pears 20 January 2023 To read the […]

meassociation.org.uk

HHV-6 reactivation theory as the cause of ME/CFS has been around since the 1990ies. Unfortunately, until recently nobody ever went directly after it. But now Jaqueline Cliff at Brunel Uni is doing that work.

Reactivation of herpesviruses in Myalgic Encephalomyelitis

Human Herpesvirus 6B in Myalgic Encephalomyelitis pathogenesis: temporal analysis of viral reactivation and immunity toelucidate cause vs effect

www.brunel.ac.uk

Virologists have known for a long time that replicating viruses have the capacity to produce molecules that hamper mitochondrial functioning, possibly as a way to slow down immune reactions. Hence, severe fatigue/exhaustion like we know it from ME/CFS is a typical feature of chronic viral infections like AIDS, and hepatitis B & C too.

 

[Jonathan Edwards]

HHV-6 reactivation theory as the cause of ME/CFS has been around since the 1990ies. Unfortunately, until recently nobody ever went directly after it. But now Jaqueline Cliff at Brunel Uni is doing that work.

Jo Cambridge and I have shared various projects with Jackie C and I think her studies are very interesting. But if we all have HHV6 to reactivate then the 'cause' we are looking for would need to be something that makes HHV6 reactivate in people with ME/CFS rather than the rest of us. And the problem is that HHV6 reactivation might just be an epiphenomenal sign of some more general regulatory issue. The task is then to find what the upstream problem is.

 

[Dude]

This might also be of interest, as it fits the topic.

Recently, a new post-infectious clinic opened in my area (Vienna). It is run by immunologists who stay closely up to date with the latest scientific findings.

Their treatment approach is based on these newer insights. Much of it is still experimental, but it goes beyond the usual off-label medications that most of us are familiar with. According to the clinic, the results so far have been quite positive.

I have not had the opportunity to attend myself due to very long waiting times, but someone from my local support group did. This is what they reported:

They run a bunch of tests and were given a list of possible treatment options. One of them was the following:

Due to strong inflammatory markers (particularly elevated IL-18 and increased CD8 activity), biologics targeting IL-18 may be considered in coordination with an internist or autoimmune specialist.
JAK inhibitors such as tofacitinib, baricitinib, or ruxolitinib are also potential options.

I am not an immunologist, so I cannot judge how sound or appropriate this approach is. However, I do find it striking that such treatments are being offered at all, given that there is still very little clinical data available. He got ill with ME after a Covid infection.

 

[Jonathan Edwards]

Due to strong inflammatory markers (particularly elevated IL-18 and increased CD8 activity), biologics targeting IL-18 may be considered in coordination with an internist or autoimmune specialist.
JAK inhibitors such as tofacitinib, baricitinib, or ruxolitinib are also potential options.

I am not an immunologist, so I cannot judge how sound or appropriate this approach is.

Hi @Dude,
This is standard charlatanry from pseudoimmunologists - which have been around for ever, so no surprises there. Treatments like that should not be offered outside trials. If all there is is IL-18 then there isn't much of a mark of inflammation. It is babble. Compare these people with genuine immunologists like Fluge and Mella, who introduce well thought out therapies in carefully documented trials.

 

[Chandelier]

1000-word article in The Washington Post:

https://www.washingtonpost.com/health/2025/12/15/long-covid-chronic-inflammation-treatment/

 

[PageofME]

Jo Cambridge and I have shared various projects with Jackie C and I think her studies are very interesting. But if we all have HHV6 to reactivate then the 'cause' we are looking for would need to be something that makes HHV6 reactivate in people with ME/CFS rather than the rest of us. And the problem is that HHV6 reactivation might just be an epiphenomenal sign of some more general regulatory issue. The task is then to find what the upstream problem is.

HHV-6B reactivation is already quite well understood from the research into the problem in immuno-suppressed patients. So there is no need to reinvent the wheel.

Immune response to HHV-6 and implications for immunotherapy - PMC

Most adults remain chronically infected with HHV-6 after resolution of a primary infection in childhood, with the latent virus held in check by the immune system. Iatrogenic immunosuppression following solid organ transplantation (SOT) or ...

pmc.ncbi.nlm.nih.gov

 

[Jonathan Edwards]

HHV-6B reactivation is already quite well understood from the research into the problem in immuno-suppressed patients. So there is no need to reinvent the wheel.

I don't follow. Since we have no evidence for 'immuno-suppression' in ME/CFS presumably we do have to find another explanation. (Large numbers of studies of ME/CFS have found immune cell populations and behaviour to be normal, with maybe some cells showing a bit more activation. There were some papers claiming defects in NK cells but even the original authors had trouble replicating those. Jackie could not replicate any NK defect.)