Dr. Jeroen den Dunnen

Taken together, both “ends” of the antibody response appear affected in Long COVID:
– the antigen binding part (Fab)
– the tail (Fc)
This may not only impede SARS-CoV-2 clearance, but also hint at broader immune dysfunction.

🔹 Aberration 2: Impaired class switching.
Normally, B cells switch from IgM to potent, long-lasting IgG.
In Long COVID, this switch is blunted — reducing the production of high-affinity IgG needed for viral clearance.

🔹 Aberration 1: Immunological imprinting (“original antigenic sin”).
Instead of mounting fresh responses to SARS-CoV-2, B cells fall back on memory from seasonal coronaviruses. The result: antibodies less effective against the new virus.

The results:
– Reduced SARS-CoV-2 spike-specific IgG and IgA
– Elevated IgG against spike of seasonal coronaviruses
This points to two distinct immunological abnormalities 👇

Aberrant immune responses have long been suspected to play a role in #LongCOVID.
Here, we examined antibody profiles against both SARS-CoV-2 and the “everyday” seasonal coronaviruses. 2/6

Seasonal Coronavirus‐Induced Immunological Imprinting and Previous Herpesvirus Infections in Patients With Long COVID Long COVID (LC) is a post-acute infection syndrome affecting 5%–10% of individuals infected by SARS-CoV-2. Here, we aimed to study SARS-CoV-2 humoral immunity, immunological imprinting by endemic cor...

Long COVID patients show immunological imprinting and impaired antibody class switching: fewer IgG/IgA antibodies against SARS-CoV-2 spike, but more against seasonal coronaviruses.
Interesting finding by my PhD student Ashwin Mak in J Med Virol: onlinelibrary.wiley.com/doi/10.1002/... 1/6

Also pretty proud of my team Oliver Chen, Amélie Bos, and Ashwin Mak (2 oral presentations, 3 posters) that resp. showed that Long COVID autoantibodies remain pathogenic for years, can directly affect skeletal muscle cells, and that patients show impaired antibody isotype switching. 7/

@virusesimmunity.bsky.social showed that IgG of Long COVID patients that is transferred to mice partially ends up in the brain, indicating that these IgGs may disrupt the blood-brain barrier. Could be an important step in the development of neurological symptoms. 6/

Circulating cell-free RNA signatures for the characterization and diagnosis of myalgic encephalomyelitis/chronic fatigue syndrome | PNAS People living with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) experience heterogeneous and debilitating symptoms that lack suffici...

Maureen Hansen presented her recently published work on identification of circulating cell-free RNA signatures for the characterization and diagnosis of ME/CFS: www.pnas.org/doi/10.1073/... 5/

Analysis of 977 Long COVID Patients Reveals Prevalent Neuropathy and Association with Anti-Ganglioside Antibodies Background Long COVID (LC) is a novel condition that is characterized by persistent symptoms that last from months to years following a SARS-CoV-2 infection. While LC symptoms vary widely, neuropathy ...

Esther Melamed showed that 25% of the patients in their (large) cohort display anti-ganglioside antibodies (not included in most autoantibody arrays): www.medrxiv.org/content/10.1... Let’s all check this in our cohorts! 4/

In vivo models: more and more mouse models are being developed to study pathophysiology and therapies. Nadia Roan showed that machine learning is a promising strategy to boost the quality of Long COVID models, and (successfully) test therapies. 3/

First, a call to action from @virusesimmunity.bsky.social to combine all our data internationally. Maureen Hansen mentioned that such a repository website already exists for #MECFS MAPMECFS.org. Could we make this for Long COVID as well? 2/

Big thanks to @keystonesymposia.bsky.social @virusesimmunity.bsky.social @ahandvanish.bsky.social @daltmann.bsky.social and others for organization of the second #LongCOVID Keystone #KSLongCOVID26. I’ll mention a few personal highlights. 1/

Huge congratulations to my talented postdoc @oliverch77.bsky.social on obtaining the prestigious Veni grant! On your way to start your own research group 🙂. www.zonmw.nl/en/news/200-...

Finally, big thanks to the involved doctors Thadé Goderie, Niek Versfeld, and Alain Bauwens. And to Noaharu Kitajima, who previously described post-acute infection dizziness like this after influenza: pubmed.ncbi.nlm.nih.gov/27089972/ 10/10

So if dizziness is your ONLY post-COVID symptom, you could ask your GP to check your eardrum during nasal respiration. If it moves, placing a ventilation tube may work. If afterwards your eye muscles become painful, vestibulo-visual rehabilitation may work. 9/10

The good news is that vestibular asthenopia (tired and painful eyes, difficulty “scrolling” on screens) can also be fixed, by specialized vestibulo-visual rehabilitation. Which involves a rotating chair and weird 3D patterns…: 8/10

Vestibular asthenopia - PubMed Vestibular asthenopia, analogous to visual asthenopia, is a sensory (or sensory-motor) discomfort consisting of a set of subjective symptoms, the expression of which is essentially visual and whose or...

Yet, during these 6 months, the brain started “ignoring” the vestibular system, and learned to only rely on the eyes for balance. As soon as the vestibular system worked again, this caused something known as “vestibular asthenopia”: pubmed.ncbi.nlm.nih.gov/34556339/ 7/10

The treatment was remarkably simple: placing a ventilation tube, to counteract the movement of the eardrum. After 6 months, the dizziness instantly disappeared. 6/10

In this particular patient (me), dizziness only occurred during breathing. It turned out that the “open” eustachian tube made the eardrum move, triggering the inner ear (vestibular system), causing dizziness. 5/10

The eustachian tube is a connection between your nose and ear. It is typically closed, and only opens briefly to equalize pressure (e.g. when you’re flying). But sometimes it stays open: a patulous eustachian tube. 4/10

Quick summary: COVID-19 can cause dizziness by triggering a “patulous eustachian tube”, which can be fixed by placing a ventilation tube in your eardrum. Wait, a patulous what…? 3/10

Disclaimer: we think that cases like this are rare. Yet, if you do suffer from this, the good news is that the cause of dizziness could be easily fixed by an ear nose and throat doctor (and some specialized vestibular physiotherapy). 2/10

For people that suffer from post-COVID-19 dizziness (as their ONLY symptom), this case report may be of interest to you: casereports.bmj.com/content/18/6.... A tale from personal experience… 1/10

Absolutely, see my previous thread on this: bsky.app/profile/drde...

YouTube video by MECFS Research Foundation Jeroen den Dunnen | International ME/CFS Conference 2025: Autoimmunity as a cause of ME/CFS

All presentations of the #mecfsconference are now online! Thanks again to @scheibenbogen.bsky.social for organizing this, and bringing so many experts together. Check out the videos at: events.mecfs-research.org/en/events/co.... #MECFS #LongCovid
www.youtube.com/watch?v=k4m4...

My team is very much looking forward to join the @keystonesymposia.bsky.social on #LongCovid and other PAIS (2 talks, 3 posters). Organized by @virusesimmunity.bsky.social @ahandvanish.bsky.social on Aug 10-13 2025 in Santa Fe: www.keystonesymposia.org/conferences/...

YouTube video by Jeroen den Dunnen Amsterdam UMC Long-COVID clinical trial immunoadsorption

As presented at the International ME/CFS Conference 2025 #mecfsconference, in the @amsterdamumc.bsky.social we will start a clinical trial testing immunoadsorption in Long-COVID. More information about that in this movie: www.youtube.com/watch?v=fE7A... #LongCOVID #MECFS #ZonMw

And finally, all the great people I’ve met at this great conference, including @scheibenbogen.bsky.social @putrinolab.bsky.social, Rob Wust, @tronstadlab.bsky.social, Chris Puta, David Systrom, Yehuda Shoenfeld, Oystein Fluge, Alan Cash, and so many more. Let's crack this puzzle 😊. 7/7

Fifth, poster prize winner and young talent Anouck Slaghekke (team Rob Wust), showing microvascular dysfunction and basal membrane thickening in skeletal muscle, in both ME/CFS and Long-COVID. 6/7