Loss of vesicular monoamine transporter 2 in striatum of long COVID and relationship to neuropsychiatric symptoms, 2026, Liu et al

[Jonathan Edwards]

My thinking is that if it's true that PET markers show activated glia in long covid, as the authors say, and if it's true that activated glia can cause synaptic remodeling, as they also say (I haven't read any of these studies yet), then that seems a decent enough idea for how an infection could cause (maybe temporary) synaptic changes that lead to ME/CFS or other symptoms.

Is there any evidence of activated microglia in Long Covid? I was not aware of that.
I don't think one can start joining dots like this until one can specify precisely where any glia might be activated and why there rather than all over. Encephalitis will activate microglia but general encephalitis produces coma and death. Local encephalitis produces specific localising signs, at least at some sites. In the context of a virus microglia are likely to get activated because of viral infection of cells - which cells and where and what evidence do we have?

These things are possible but theories that repeat fashionable memes without any very specific evidence and without detail on local context are usually dead ends.

And of course synaptic pruning goes on every day in the absence of glial activation - as part of learning from daily experience.

 

[forestglip]

Is there any evidence of activated microglia in Long Covid? I was not aware of that.

Me either. But that's what the thread paper says.

I haven't been able to read these studies yet. Of course, I know they could be less clear than the authors make them out to be, but I'm just thinking about the possibility.

The paper says this about previous microglial and astrocyte activation findings:


Reference 3 looks like the TSPO finding described in the protocol (S4ME thread):

• Neuroinflammation After COVID-19 With Persistent Depressive and Cognitive Symptoms, 2023, Braga et al

References 7 and 8 are also about TSPO in long COVID:

• Neuroinflammation in post-acute sequelae of COVID-19 (PASC) as assessed by [11C]PBR28 PET correlates with vascular disease measures, 2023, VanElzakker
• Glial activation among individuals with Neurological [PASC]: A Brain Fog Positron Emission Tomography Study of [18F]-FEPPA, 2025, Clouston+

Reference 6 tested a marker of monoamine oxidase B (MAO-B):

• Astrogliosis Marker [11C]SL25.1188 After COVID-19 With Ongoing Depressive and Cognitive Symptoms, 2025, Braga et al