I'm just putting this out very quickly as it is quite late. There is a very interesting and potentially very exciting connection between Paul Fisher's work[1] showing an impairment in ATP synthase in ME/CFS immortalized lymphocytes and Bhupesh Prusty's work[2] showing increased fission (and decreased fusion) in mitochondria treated with ME/CFS serum, possibly due to HHV-6A (and potentially other herpes viruses like EBV and CMV).
This connection is telling us that the 'something in the blood' may be targeting ATP synthase. In particular, that it may be targeting and down-regulating a subunit of ATP synthase known as ATP5B.
It turns out that
ATP5B regulates mitochondrial fission and fusion in mammalian cells.[3]
If it is the ATP5B subunit being specifically targeted then that makes the 'something in the blood' more likely to be a microRNA (perhaps being carried by an exosome) versus a peptide, for example, which might be more likely if other parts of ATP synthase were being targeted.
Prusty did find a microRNA that HHV-6A promotes the expression of and that causes mitochondria to fission.[2] This microRNA may be targeting ATP5B.
(There is at least one compound, a small molecule known as M1 that may be capable of reversing such a down-regulation of ATP5B.[4])
[1]
https://forums.phoenixrising.me/thr...lized-lymphocytes-from-me-cfs-patients.77577/
[2]
https://www.healthrising.org/blog/2019/04/15/nih-chronic-fatigue-lipkin-davis-prusty-oh/
[3]
https://www.tandfonline.com/doi/full/10.1080/19768354.2016.1188855
[4]
https://www.ncbi.nlm.nih.gov/pubmed/22907892
Edit: I emailed Dr Fisher to take a look at this possibility.
Edit 2: Hmm, I just took another look at Dr Fisher's paper and he had found ATP5B to be upregulated. Not sure if that can be reconciled or not.