Zdenek Vrozina Profile picture
Feb 17 14 tweets 2 min read Read on X
One of the most important recent studies on post-COVID biology delivers a concerning message.
SARS-CoV-2 doesn’t just affect immune cells.
It can leave long-lasting changes directly in the immune proteins circulating in our blood.🧵
Think of the immune system in three layers.
immune cells (T, B, NK…)
signaling molecules
effector proteins - antibodies and complement
This study shows persistent changes in the deepest layer - the effector proteins themselves.
Researchers analyzed blood samples from more than 400 people after COVID-19.
They identified hundreds of chemical alterations in proteins - called ncAA modifications.
It’s about proteins becoming chemically different.
The most striking finding?
Some of these changes did not disappear after recovery.
They were still detectable up to 12 months after infection.
This suggests COVID can leave a long-lasting/persistent molecular imprint on the immune system.
The most affected systems were two core pillars of immunity.
Antibodies and the complement system.
These are the main drivers of inflammation and tissue damage during immune responses.
In antibodies, modifications appeared in the most critical regions.
The antigen-binding sites,
the Fc regions that activate immune cells and complement
In other words -
Even if antibodies recognize targets correctly, their effector strength may be altered.
The strongest signal was seen in the complement system.
Unlike coagulation changes - which mostly normalized -
many complement protein modifications persisted.
This raises concern about sustained inflammatory activation.
The study highlights one particularly important mechanism - deamidation of amino acids!
This modification is
irreversible (!)
alters protein charge
can change protein function
may create new autoantigenic epitopes
In essence, it can act as a molecular memory of inflammatory stress.
The authors describe this phenomenon as structural immune imprinting.

The immune system may not only remember pathogens.
It may also carry long-lasting chemical alterations of its own proteins.
So it is a strong biological signal that COVID-19 can leave a deep, long-lasting molecular reprogramming of immune effector systems.
These findings align with broader observations in post-COVID research
chronic low-grade inflammation
thrombo-inflammatory states
persistent immune dysregulation
Sum:
COVID-19 may leave a lasting chemical imprint on key immune proteins - particularly antibodies and complement - potentially keeping the immune system in a chronically altered state.
Further research is urgently needed to understand the clinical impact!
Liu at al., Widespread ncaas Imprints in the Serum Proteome of COVID-19 Convalescents Uncovering Immune System Sequelae. mcponline.org/article/S1535-…
Ignoring these persistent immune alterations is a major public-health failure. The long-term population burden of chronic inflammation, immune dysregulation, and post-COVID illness may ultimately rival - or exceed - the acute waves of 2020–2021. @szupraha @ZdravkoOnline @adamvojtech86 @adamkova_vera

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More from @ZdenekVrozina

Feb 18
Researchers looked at markers of cellular and mitochondrial damage in the blood of people with Long COVID and linked them to cognition, psychological distress, and inflammation. They identified several surprising associations🧵
Finding 1. Long COVID = lower relative ccf-mtDNA
At first glance, this is surprising.
People usually expect - mitochondrial damage - more mtDNA released into blood.
But here, researchers found lower relative levels.
But this does not necessarily mean less damage.
It likely reflects dysregulation of mitochondrial quality control (mitophagy).
Read 14 tweets
Feb 16
Reinfection during the Omicron era is associated with about twice the risk of a documented long COVID diagnosis in children. Online September 2025, print issue February 2026🧵
This is a large US cohort study using data from 40 pediatric hospitals and including 465,717 children and adolescents (<21 years).
It compares the risk of long COVID (PASC) after
a first SARS-CoV-2 infection
a reinfection during the Omicron era.
Reinfection significantly increases the risk of long COVID in children.
PASC diagnosis rates
~904 cases per million after first infection
~1,884 per million after reinfection
Relative risk
≈ 2× higher after reinfection (RR 2.08).
Read 12 tweets
Feb 16
Which brain circuits were most affected in this study - and what might that mean in everyday life?
The study shows something fundamental - reduced regulatory capacity of the brain. The problem is coordination, not character🧵
The most affected system was the salience network
(insula + anterior cingulate cortex).
Think of it as the brain’s regulatory switch.
It evaluates what is important, controls attention, and shifts the brain between rest and performance modes.
When this network becomes dysregulated, the result is reduced capacity to regulate mental load.
Faster overload, lower tolerance to distraction, increased irritability under fatigue, and difficulty sensing internal limits.
Read 18 tweets
Feb 16
With longer duration of Long COVID, some key brain connections become weaker - especially those linked to prefrontal regulatory areas.
At the same time, other connections become stronger.
A new fMRI study shows this reflects a progressive reorganization of how brain networks communicate🧵
The study didn’t just look at isolated brain regions.
It examined how entire brain networks coordinate during cognitive effort - because performance depends less on single areas and more on how well networks synchronize
That synchronization was disrupted in Long COVID.
The main problem wasn’t damage to one function, but impaired regulation - the brain’s ability to detect what matters and shift efficiently into task-focused mode.
Read 21 tweets
Feb 13
A new macaque study looked at how immune memory forms after infections with different SARS-CoV-2 variants.
The main pattern is familiar from other viruses -
immune imprinting tends to stay biased toward earlier variants, even after later infections.🧵
The model is useful because it allows sequential infections under controlled conditions (Wuhan - Delta - Omicron), something that’s hard to observe clearly in humans.
Omicron as a primary infection = relatively weak new immune imprint
After first Omicron infection in macaques -
variant-specific anti-Omicron RBD antibodies developed slowly
overall immunogenicity was lower
T-cell responses were also weaker.
Read 10 tweets
Feb 12
A new study in Neuron links nuclear pore breakdown to TDP-43 pathology in ALS and related dementias.
This pathway is especially relevant because SARS-CoV-2 can both cleave TDP-43 and disrupt nuclear transport - potentially hitting the same vulnerability from two directions.🧵
The nuclear pore is a critical cellular gate.
It regulates the movement of RNA and proteins between the nucleus and cytoplasm.
In ALS and some dementias, this gate is known to fail - and TDP-43 leaves the nucleus and accumulates in toxic aggregates.
But why the pore breaks down has been unclear.
The study identifies a key player - VCP.
Normally, it acts as a cellular cleanup system, removing damaged proteins.
The problem arises when it becomes overactive.
Read 16 tweets

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