A bit of speculation for discussion. I'm not sure if the broad concepts here are all old news and previously hashed out, but recent publications had me wondering.
Assuming for the moment both the following papers turn out to be validated findings: I wondered how the results presented for the ME cohort (WASF3 disrupts mitochondrial respiration and may mediate exercise intolerance in ME/CFS) might relate to the recent findings in Covid and potentially LC (Core mitochondrial genes are down-regulated during SARS-CoV-2).
ME Findings
In the ME cohort, the findings suggest there is an ER stress response failure in muscle cells, that leads to upregulation of WASF3, which impairs the ETC's CIII(2)-CIV supercomplex formation, resulting in downregulation of respiration, with various metabolic compensatory mechanisms. In particular OXPHOS was downregulated and glycolysis upregulated.
Covid Findings
In a Covid cohort, they found that SARS-CoV-2 specifically inhibited mitochondrial ETC-related proteins and mRNAs associated with related mitochondrial protein importing. In particular this seemed to involve the microRNA miR-2392.
LC = ME or predisposes to developing ME?
Perhaps these two findings just represent completely different viral mechanisms, that can lead to a similar spectrum of exertional intolerance/PEM. Maybe there are many different forms of viral-induced OXPHOS suppression that are virus-specific, leading to heterogeneity and confusion when we try and evaluate them.
Some people get a short-run fatiguing illness for some months, often termed postviral fatigue syndrome, which may have symptoms of ME/CFS. Others develop ME/CFS (proper) that continues or worsens for a few years before recovery, while others go on to have years/decades of ME/CFS of varying severity. Sometimes multiple family members are affected, including over generations.
In Covid there is some evidence for persistent SARS-CoV-2 proteins in only some patients.
So perhaps a 2-stage process?
Stage 1
1. An acute viral infection (eg SARS-CoV-2) is associated with down-regulation of mitochondrial function as part of host response to deny resources to the virus [1] +/- viral immune evasion strategy [2].
2. This can lead to a short term illness with ME/CFS-like features such as exertion intolerance and PEM (characterised as a "post-viral fatigue syndrome").
3. Some/many/most people recover over months (eg here) after the virus has been controlled and the mitochondria are repaired or replaced (possibly mis-attributing various factors such as supplements, "brain rewiring" or manly thoughts)
Stage 2
4. However in some (possibly with a genetic component), this downregulated mitochondrial and innate immune (metabolically re-wired) dysfunction favours loss of immune control and consequently partial/early reactivation of latent herpesviruses
5. This secondary early-type reactivation adds further immune-evasion pathways (eg via different microRNAs [3], and perhaps causing the ER stress response failure [4]) which adds even more mitochondrial impairments, potentially across more cell types (esp immune cells, eg NKs [5])
6. Mitophagy may be specifically subverted as part of the immune evasion, preventing mitochondrial replacement and keeping the mitochondria energetically impaired and favouring ongoing "active" viral latency.
7. The sum of these mitochondrial impairments might now be too much for the natural recovery seen in #2, with continued immune evasion allowing ongoing latent herpesvirus activity, feeding back.
8. Because the latent herpesvirus reactivation is merely early (non-replicating), antiviral agents that target viral replication are likely ineffective [6]
---
[1] Innate metabolic responses against viral infections (2022, Nature Metabolism)
[2] Cellular metabolism hijacked by viruses for immunoevasion: potential antiviral targets (2023, Frontiers in Immunology)
[3] Selective inhibition of miRNA processing by a herpesvirus-encoded miRNA (Nature, 2022)
[4] Endoplasmic reticulum stress signaling: the microRNA connection (2013, American Journal of Physiology-Cell Physiology)
[5] Human NK Cells and Herpesviruses: Mechanisms of Recognition, Response and Adaptation (2019, Frontiers in Microbiology)
[6] Antiviral agents for infectious mononucleosis (glandular fever) (2016, Cochrane)
Assuming for the moment both the following papers turn out to be validated findings: I wondered how the results presented for the ME cohort (WASF3 disrupts mitochondrial respiration and may mediate exercise intolerance in ME/CFS) might relate to the recent findings in Covid and potentially LC (Core mitochondrial genes are down-regulated during SARS-CoV-2).
ME Findings
In the ME cohort, the findings suggest there is an ER stress response failure in muscle cells, that leads to upregulation of WASF3, which impairs the ETC's CIII(2)-CIV supercomplex formation, resulting in downregulation of respiration, with various metabolic compensatory mechanisms. In particular OXPHOS was downregulated and glycolysis upregulated.
Covid Findings
In a Covid cohort, they found that SARS-CoV-2 specifically inhibited mitochondrial ETC-related proteins and mRNAs associated with related mitochondrial protein importing. In particular this seemed to involve the microRNA miR-2392.
LC = ME or predisposes to developing ME?
Perhaps these two findings just represent completely different viral mechanisms, that can lead to a similar spectrum of exertional intolerance/PEM. Maybe there are many different forms of viral-induced OXPHOS suppression that are virus-specific, leading to heterogeneity and confusion when we try and evaluate them.
Some people get a short-run fatiguing illness for some months, often termed postviral fatigue syndrome, which may have symptoms of ME/CFS. Others develop ME/CFS (proper) that continues or worsens for a few years before recovery, while others go on to have years/decades of ME/CFS of varying severity. Sometimes multiple family members are affected, including over generations.
In Covid there is some evidence for persistent SARS-CoV-2 proteins in only some patients.
So perhaps a 2-stage process?
Stage 1
1. An acute viral infection (eg SARS-CoV-2) is associated with down-regulation of mitochondrial function as part of host response to deny resources to the virus [1] +/- viral immune evasion strategy [2].
2. This can lead to a short term illness with ME/CFS-like features such as exertion intolerance and PEM (characterised as a "post-viral fatigue syndrome").
3. Some/many/most people recover over months (eg here) after the virus has been controlled and the mitochondria are repaired or replaced (possibly mis-attributing various factors such as supplements, "brain rewiring" or manly thoughts)
Stage 2
4. However in some (possibly with a genetic component), this downregulated mitochondrial and innate immune (metabolically re-wired) dysfunction favours loss of immune control and consequently partial/early reactivation of latent herpesviruses
5. This secondary early-type reactivation adds further immune-evasion pathways (eg via different microRNAs [3], and perhaps causing the ER stress response failure [4]) which adds even more mitochondrial impairments, potentially across more cell types (esp immune cells, eg NKs [5])
6. Mitophagy may be specifically subverted as part of the immune evasion, preventing mitochondrial replacement and keeping the mitochondria energetically impaired and favouring ongoing "active" viral latency.
7. The sum of these mitochondrial impairments might now be too much for the natural recovery seen in #2, with continued immune evasion allowing ongoing latent herpesvirus activity, feeding back.
8. Because the latent herpesvirus reactivation is merely early (non-replicating), antiviral agents that target viral replication are likely ineffective [6]
---
[1] Innate metabolic responses against viral infections (2022, Nature Metabolism)
[2] Cellular metabolism hijacked by viruses for immunoevasion: potential antiviral targets (2023, Frontiers in Immunology)
[3] Selective inhibition of miRNA processing by a herpesvirus-encoded miRNA (Nature, 2022)
[4] Endoplasmic reticulum stress signaling: the microRNA connection (2013, American Journal of Physiology-Cell Physiology)
[5] Human NK Cells and Herpesviruses: Mechanisms of Recognition, Response and Adaptation (2019, Frontiers in Microbiology)
[6] Antiviral agents for infectious mononucleosis (glandular fever) (2016, Cochrane)
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