Direct Tissue Examination Findings in Long COVID and ME/CFS
Full Citation:: VanElzakker MB, Bues HF, Brusaferri L, et al. Neuroinflammation in post-acute sequelae of COVID-19 (PASC) as assessed by [11C]PBR28 PET imaging. Brain, Behavior, and Immunity. 2024;118:345–358. (VanElzakker et al. 2024) DOI:: 10.1016/j.bbi.2024.03.014 PMID:: 38642615 Published:: 2024 Study Design:: TSPO PET neuroimaging study Sample Size:: Approximately 20 PASC patients Key Findings:: Increased TSPO PET signal (marker of glial activation/neuroinflammation) in brainstem and other brain regions of PASC patients compared to controls. Provides direct brain-level evidence that neuroinflammation is present in long COVID. Conclusion:: Neuroinflammation is detectable in PASC brain tissue via PET imaging, supporting neuroimmune mechanisms. Limitations:: Moderate sample size; TSPO tracers bind to both microglia and astrocytes; single timepoint. Certainty Assessment::
- *Quality:* Medium-High (Brain, Behavior, and Immunity; PET imaging gold standard)
- *Sample:* Moderate (n~20)
- *Replication:* First published PASC TSPO PET study
- *Score:* 0.55Full Citation:: Miller SJ, Dhodapkar RM, Sutova HE, et al. SARS-CoV-2 induces Alzheimer’s disease-related amyloid-\(\beta\) pathology in ex vivo human retinal explants and retinal organoids. Science Advances. 2025;11(27):eads5006. (Miller et al. 2025) DOI:: 10.1126/sciadv.ads5006 PMID:: 40614201 PMCID:: PMC12227045 Published:: 2025 Study Design:: Ex vivo human tissue + iPSC retinal organoid infection model Key Findings:: SARS-CoV-2 infection of human retinal explants and retinal organoids induces amyloid-\(\beta\) pathology. Virus triggers neurodegenerative proteinopathy in accessible ocular tissue, suggesting a possible retinal biomarker for CNS pathology. First author SJ Miller (Yale). Conclusion:: SARS-CoV-2 directly induces Alzheimer’s-related amyloid pathology in retinal tissue, supporting the antimicrobial hypothesis of amyloid-\(\beta\) and providing a window into CNS effects. Limitations:: Ex vivo / organoid model, not in vivo human; long-term consequences unknown. Certainty Assessment::
- *Quality:* High (Science Advances; ex vivo human tissue)
- *Sample:* Not applicable (ex vivo)
- *Replication:* Single study
- *Score:* 0.60Full Citation:: Lederer K, Bettini E, Parvathaneni K, et al. Germinal center responses to SARS-CoV-2 mRNA vaccines in healthy and immunocompromised individuals. Cell. 2022;185(6):1008–1024. (Lederer et al. 2022) DOI:: 10.1016/j.cell.2022.01.027 PMID:: 35202565 Published:: 2022 Study Design:: Lymph node fine-needle aspiration with spectral flow cytometry Sample Size:: 54 subjects (healthy + immunocompromised) Key Findings:: Direct lymph node sampling to characterize germinal center B cell and Tfh cell responses after SARS-CoV-2 mRNA vaccination. Established LN FNA methodology for assessing GC dynamics in humans. Locci is co-author. Conclusion:: SARS-CoV-2 mRNA vaccines elicit robust GC reactions in draining lymph nodes; responses impaired in immunocompromised individuals. Limitations:: Vaccine response study, not disease study. No ME/CFS or LC patients included. Certainty Assessment::
- *Quality:* High (Cell; robust methodology)
- *Sample:* N=54
- *Replication:* Replicated by multiple groups
- *Score:* 0.70ME/CFS Relevance:: Establishes the methodological framework for examining lymph node tissue directly in post-infectious syndromes. The same FNA approach could test whether GC dysfunction characterizes ME/CFS.
Full Citation:: Eberhardt N, Noval MG, Kaur R, et al. SARS-CoV-2 infection triggers pro-atherogenic inflammatory responses in human coronary vessels. Nature Cardiovascular Research. 2023;2(11):1034–1049. (Eberhardt et al. 2023) DOI:: 10.1038/s44161-023-00336-5 PMID:: 38076343 Published:: 2023 Study Design:: Ex vivo human coronary tissue analysis (autopsy/surgery specimens) Key Findings:: SARS-CoV-2 Spike protein detected in coronary plaque macrophages. COVID-19 infection triggers pro-atherogenic inflammatory gene expression in human coronary arteries. Direct tissue evidence that SARS-CoV-2 promotes vascular inflammation at the plaque level. Conclusion:: SARS-CoV-2 infection directly promotes pro-atherogenic inflammation in the coronary vasculature, providing mechanism for increased cardiovascular risk post-COVID. Limitations:: Ex vivo analysis; primarily descriptive without interventional component. Certainty Assessment::
- *Quality:* High (Nature Cardiovascular Research)
- *Sample:* Moderate
- *Replication:* Consistent with clinical epidemiology of increased MI risk post-COVID
- *Score:* 0.65Full Citation:: Schlick S, Lucio M, Wallukat G, et al. Post-COVID-19 syndrome: retinal microcirculation as a potential marker for chronic fatigue. International Journal of Molecular Sciences. 2022;23(22):13982. (Schlick et al. 2022) DOI:: 10.3390/ijms232213982 PMID:: 36430175 Published:: 2022 Study Design:: Retinal OCT-A imaging cross-sectional study Sample Size:: 40 PCS patients Key Findings:: Retinal microcirculation parameters measured by OCT-A significantly correlated with self-reported chronic fatigue severity in PCS. Direct retinal vascular imaging reveals microcirculatory pathology linked to fatigue symptoms. Conclusion:: Retinal microcirculation may serve as a biomarker for chronic fatigue severity in PCS, supporting microvascular involvement in symptom persistence. Limitations:: Cross-sectional; moderate sample size; correlation does not establish causation. Certainty Assessment::
- *Quality:* Medium (IJMS)
- *Sample:* n=40
- *Replication:* Single study
- *Score:* 0.45Full Citation:: Cañadas P, Gonzalez-Vides L, Alberquilla García-Velasco M, et al. Neuroinflammatory findings of corneal confocal microscopy in long COVID-19 patients, 2 years after acute SARS-CoV-2 infection. Diagnostics. 2023;13(22):3469. Cañadas et al. (2023) DOI:: 10.3390/diagnostics13223469 PMID:: 37892009 Published:: 2023 Study Design:: Corneal confocal microscopy cross-sectional study Sample Size:: 50 long COVID patients, 2 years post-infection Key Findings:: Reduced corneal nerve fiber density and increased immune cell infiltrate detected by corneal confocal microscopy. Direct corneal tissue-level evidence of persistent small nerve fiber pathology and neuroinflammation in long COVID years after acute infection. Conclusion:: Ocular neuroinflammation persists for at least 2 years after SARS-CoV-2 infection, suggesting ongoing tissue-level immune dysregulation. Limitations:: Cross-sectional; corneal findings may not directly reflect CNS pathology. Certainty Assessment::
- *Quality:* Medium (Diagnostics)
- *Sample:* n=50
- *Replication:* Single study
- *Score:* 0.50Full Citation:: Mátyás BB, Benedek I, Blîndu E, et al. Elevated FAI index of pericoronary inflammation on coronary CT identifies increased risk of coronary plaque vulnerability after COVID-19 infection. International Journal of Molecular Sciences. 2023;24(8):7394. Mátyás et al. (2023) DOI:: 10.3390/ijms24087394 PMID:: 37108558 Published:: 2023 Study Design:: Coronary CT angiography study Sample Size:: 128 patients Key Findings:: Increased pericoronary fat attenuation index (FAI) post-COVID-19, indicating enhanced local vascular inflammation and plaque vulnerability. Imaging surrogate for arterial tissue-level inflammatory response. Limitations:: Single-center; retrospective; FAI is an indirect marker of inflammation. Certainty Assessment::
- *Quality:* Medium (IJMS)
- *Sample:* n=128
- *Replication:* Consistent with known cardiovascular risk post-COVID
- *Score:* 0.55Full Citation:: Blagova O, Lutokhina Y, Kogan E, et al. Chronic biopsy proven post-COVID myoendocarditis with SARS-Cov-2 persistence and high level of antiheart antibodies. Clinical Cardiology. 2022;45(11):1159–1167. (Blagova et al. 2022) DOI:: 10.1002/clc.23927 PMID:: 35855554 Published:: 2022 Study Design:: Endomyocardial biopsy with virological and immunological analysis Sample Size:: 14 post-COVID patients Key Findings:: Endomyocardial biopsy-proven inflammation months after COVID-19. SARS-CoV-2 detected in myocardium by PCR. Elevated anti-heart antibodies. Direct tissue evidence of viral persistence and ongoing autoimmune response in cardiac tissue. Limitations:: Small n; selected population (symptomatic enough to undergo biopsy); single center. Certainty Assessment::
- *Quality:* Medium (Clinical Cardiology)
- *Sample:* n=14
- *Replication:* Consistent with broader viral persistence literature
- *Score:* 0.40Full Citation:: Yonker LM, Swank Z, Gilboa T, et al. Zonulin antagonist, larazotide (AT1001), as an adjuvant treatment for multisystem inflammatory syndrome in children: a case series. Critical Care Explorations. 2022;4(2):e0637. (Yonker et al. 2022) DOI:: 10.1097/CCE.0000000000000637 PMID:: 35211683 Published:: 2022 Study Design:: Case series (n=3) Key Findings:: Larazotide (zonulin antagonist, tight junction regulator) used as adjuvant therapy in MIS-C. Clinical improvement observed. Hypothesis: SARS-CoV-2 in gut lumen causes zonulin release, loosening tight junctions and enabling viral particle translocation into circulation. Larazotide blocks zonulin receptor, restoring gut barrier integrity. Limitations:: n=3, case series, no control. Not studied in ME/CFS or adult LC. Certainty Assessment::
- *Quality:* Low (case series)
- *Sample:* n=3
- *Replication:* Single case series
- *Score:* 0.20Full Citation:: Visser D, Pieperhoff L, Lorenzini L, et al. Decreased functional connectivity in post-COVID syndrome patients with high neuroinflammatory activity. NeuroImage. 2026;292:120624. (Visser et al. 2026) DOI:: 10.1016/j.neuroimage.2026.120624 PMID:: 42034234 Published:: 2026 Study Design:: Combined TSPO PET and resting-state fMRI Sample Size:: Approximately 50 post-COVID syndrome patients Key Findings:: Combined TSPO PET neuroinflammation imaging with resting-state fMRI connectivity. Patients with high neuroinflammatory activity showed decreased functional connectivity, linking glial activation to network-level brain dysfunction. Complements VanElzakker 2024 finding by adding functional consequence dimension. Limitations:: Cross-sectional; correlation between neuroinflammation and connectivity cannot establish directionality. Certainty Assessment::
- *Quality:* Medium-High (NeuroImage)
- *Sample:* n~50
- *Replication:* Complements VanElzakker 2024
- *Score:* 0.55Full Citation:: Kim DY, Youn J, Kang N, et al. Potential application of brain-gut axis-based treatments in Long COVID and ME/CFS: a case-based systematic review. Journal of Translational Medicine. 2026;24:298. (Kim et al. 2026) DOI:: 10.1186/s12967-026-06297-2 PMID:: 41668172 Published:: 2026 Study Design:: Case-based systematic review Key Findings:: Systematic review covering brain-gut axis dysregulation in ME/CFS and Long COVID. Addresses intestinal permeability (leaky gut), dysbiosis, microbial translocation, and neuroinflammation as linked across gut and brain compartments. Limitations:: Systematic review of existing literature, no new data. Certainty Assessment::
- *Quality:* Medium (J Transl Med, systematic review)
- *Replication:* Synthesizes multiple studies
- *Score:* 0.55Full Citation:: Saleem S, Hussain A, Haroon M, et al. Dynamic microclot profiling: thromboelastography advances precision management in long COVID and myalgic encephalomyelitis/chronic fatigue syndrome. Blood Coagulation & Fibrinolysis. 2026. (Saleem et al. 2026) DOI:: 10.1097/MBC.0000000000001278 PMID:: 42274123 Published:: 2026 Study Design:: Literature review Key Findings:: Reviews evidence for persistent fibrinoid microclots in LC and ME/CFS. Proposes thromboelastography as a diagnostic tool for detecting hypercoagulable state. Summarizes emerging field linking microclot formation, amyloid deposition, and impaired microcirculation. Limitations:: Review of emerging field; limited interventional data. Certainty Assessment::
- *Quality:* Medium (review)
- *Replication:* Synthesizes multiple labs' findings (Pretorius group, Kell group)
- *Score:* 0.50Full Citation:: Nemat-Gorgani M, Jensen MA, Davis RW. Glymphatic system dysregulation as a key contributor to myalgic encephalomyelitis/chronic fatigue syndrome. International Journal of Molecular Sciences. 2025;26(12):5798. (Nemat-Gorgani, Jensen, and Davis 2025) DOI:: 10.3390/ijms26125798 PMID:: 41373677 Published:: 2025 Study Design:: Narrative review Key Findings:: Reviews evidence for glymphatic system dysfunction in ME/CFS. DTI-ALPS studies find 66% of ME/CFS patients have reduced glymphatic scores. Proposes glymphatic failure as a unifying mechanism linking sleep disruption, neuroinflammation, cognitive impairment, and waste accumulation (amyloid, tau). Limitations:: Narrative review, not systematic; limited primary data on glymphatic function in ME/CFS. Certainty Assessment::
- *Quality:* Medium (IJMS, review)
- *Score:* 0.40