<div>Figure legends</div><div><b>Figure 1:</b> Evaluation of serological markers indicating
intestinal barrier leakage and damage. PCS patients exhibited
significantly higher serum levels of Lipopolysaccharide-binding protein
(LBP) compared to convalescent SARS-CoV-2 participants and healthy
controls (A). In contrast, serum levels of sCD14 were significantly
lower in PCS patients than in all other groups (B). When examining the
LBP/sCD14 ratio, PCS patients again showed a significantly higher ratio
compared to convalescent SARS-CoV-2 participants and healthy controls
(C). Serum levels of I-FABP showed no differences between the groups
(D). Kruskal-Wallis test and Dunn’s multiple comparison test were used
to identify significant differences between all test groups. *
p&lt;0.05. **p&lt;0.01. ***p&lt;0.001</div><div><b>Figure 2</b> : Evaluation of pro-inflammatory immune mediators and
cytokines related to intestinal barrier integrity. Serum samples were
analyzed for IFN-γ, TNF-α, IL-6, IL-1-β, IL-8, and IL-33. Significant
increases in IL-6 levels and decreases in serum and IL-1-β levels were
observed in PCS patients (A-C). However, many pro-inflammatory cytokine
ELISA results were below the manufacturer’s Limit of Detection (LOD) and
had to be excluded before statistical analysis. Serum IL-33 levels were
significantly lower in PCS patients compared to SARS-CoV-2 negative
control participants (D). Data on IL-8 and IFN-γ levels are not shown as
they did not exhibit statistical significance or a disease-specific
pattern. Kruskal-Wallis test and Dunn’s multiple comparison test were
used to identify significant differences between all test groups. *
p&lt;0.05. **p&lt;0.01. ***p&lt;0.001</div><div>Author contributions</div><div>RJ and UE involved in conceptualization. RJ, and KL and involved in
methodology. RJ, WV, SJ and ZS involved in formal analysis. SM and UE
involved in resources. RJ, WV and SJ involved in data curation. RJ and
UE involved in writing original draft preparation. RJ, WV, SJ, KL, SM,
ZS and UE involved in writing—review and editing. RJ and UE involved
in visualization. UE involved in supervision and project administration.
UE involved in funding acquisition.</div><div>All authors have read and agreed to the published version of the
manuscript.</div><div>Acknowledgments</div><div>We like to thank all PCS and ME/CFS patients and other participants who
made this scientific study possible. Your contributions have enriched
our research, providing valuable insights that will help improve
diagnosis and treatment.</div><div>Funding information</div><div>The project was partially supported by WE&amp;ME Foundation and the
“Medizinisch-Wissenschaftlicher Fonds des Buergermeisters der
Bundeshauptstadt Wien” (Medical-Scientific Fund of the Major of Vienna;
project number: 22094). The sponsors had no role in the design,
execution, interpretation, or writing of the study.</div><div>Conflict of interests</div><div>The authors declare no conflict of interest.</div><div>Institutional Review Board Statement</div><div>The study was conducted according to the guidelines of the Declaration
of Helsinki and approved by the Ethics Committee of the Medical
University of Vienna (vote number: 2281/2020; approved: January
19<sup>th</sup> 2021).</div><div>Informed Consent Statement</div><div>Informed consent was obtained from all subjects involved in the study.</div><div>Data Availability Statement</div><div>The raw data supporting the conclusions of this article will be made
available by the authors on request.</div>