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NCT Number: NCT04813718

Post COVID-19 Syndrome and the Gut-lung Axis

The outbreak of the novel coronavirus (SARS-CoV-2)-infected disease (COVID-19) began in December 2019, spread throughout China in early 2020 and developed as a pandemic thereafter.

Based on current knowledge, Covid-19 infection causes mild to moderate respiratory and gastrointestinal symptoms in the majority of patients. In a smaller percentage severe disease courses are observed, often with the need of hospitalization and intensive care treatment. Apparently, symptoms can persist for relatively long time after viral clearance, suggesting the existence of a "Post-Covid" syndrome. A study from the UK identified fatigue, breathlessness and psychosocial stress as common symptoms after discharge from the hospital. Covid-19 infection is frequently characterized by a hyperinflammatory phenotype and a cytokine storm. The Covid-19 cytokine storm is characterised by rapid proliferation and hyperactivation of T cells, macrophages, mast cells, neutrophil granulocytes and natural killer cells, and the overproduction of inflammatory cytokines and chemical mediators released by immune or nonimmune cells. Early data also suggest that even if symptoms are just 'mild to moderate' during the acute infection, fibrotic lung damage develops in some patients. This may lead to long-term pulmonary complications for a subset of patients. The mechanisms for post-Covid pulmonary fibrosis are still unclear: inflammation triggering fibrosis, epithelial and endothelial injury with inadequate fibroproliferation and vascular damage are considered to be possible mechanisms.

A potential therapeutic target in ameliorating post-Covid symptoms could be the gut microbiome. Gut microbiome alterations have been described in Covid-19. The gut-lung axis as a link between dysbiosis, barrier dysfunction, translocation of bacterial products and hyperinflammation has been proposed as a potential therapeutic target. Probiotics have been proposed to be a possible modulator of the deranged gut-lung axis in Covid-disease and post-Covid syndrome. Currently 11 studies are registered in clinicaltrials.gov for treatment of acute Covid disease and prevention of the disease (including one study from Graz), but no study related to post-Covid syndrome could be found.

Therefore, it is currently unclear, which clinical, immune system or microbiome related biomarker would be the best to study the effect of a microbiome-based intervention in post-Covid syndrome.

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This study is active but is not currently recruiting participants.

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Key information

Conditions

Covid19 COVID-19 Coronaviridae Infections Coronavirus Infections Infections Lung Diseases Nidovirales Infections Pneumonia Pneumonia, Viral RNA Virus Infections Respiratory Tract Diseases Respiratory Tract Infections Virus Diseases

Age range

18 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Medical University Graz

Graz, Austria

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • 18 years or older
  • Covid-19 infection with severe disease defined within the last 12 months (defined as one or more of the following: hospitalization, need for oxygen supply, need for intensive care treatment, need for specific treatment of Covid disease, antibiotic treatment)
  • Subjective presence of residual symptoms of Covid disease OR no residual symptoms of Covid disease (Controls)
  • Informed consent

Exclusion criteria

  • Continuous probiotic treatment in the last 4 weeks before inclusion
  • Pre-existing lung diseases

Treatment and study plan

Omni-Biotic Pro Vi 5

Dietary Supplement

Pre- and probiotic

Placebo

Dietary Supplement

Placebo

Primary outcomes

  1. Microbiome composition

    Time frame: 6 months

    16 sRNA sequencing

  2. Intestinal barrier

    Time frame: 6 months

    Change in zonulin levels over time and with/without the intervention

  3. sCD14

    Time frame: 6 months

    Change in sCD14 levels over time and with/without the intervention

  4. endotoxin

    Time frame: 6 months

    Change in endotoxin levels serum over time and with/without the intervention

  5. TNFalpha

    Time frame: 6 months

    Change in TNFalpha levels serum over time and with/without the intervention

  6. Interleukin 1b

    Time frame: 6 months

    Change in Interleukin 1b serum levels over time and with/without the intervention

  7. Interleukin 6

    Time frame: 6 months

    Change in interleukin 6 serum levels over time and with/without the intervention

  8. Interleukin 6 receptor

    Time frame: 6 months

    Change in Interleukin 6 receptor serum levels over time and with/without the intervention

  9. interleukin 8

    Time frame: 6 months

    Change in interleukin 8 serum levels over time and with/without the intervention

  10. interleukin 10

    Time frame: 6 months

    Change in interleukin 10 serum levels over time and with/without the intervention

  11. interleukin 17

    Time frame: 6 months

    Change in interleukin 17 serum levels over time and with/without the intervention

  12. interleukin 23

    Time frame: 6 months

    Change in interleukin 23 serum levels over time and with/without the intervention

  13. neutrophil function burst function

    Time frame: 6 months

    Change in neutrophil burst function over time and with/without the intervention

  14. neutrophil function phagocytosis

    Time frame: 6 months

    Change in neutrophil phagocytosis function over time and with/without the intervention

  15. neutrophil NET formation

    Time frame: 6 months

    Change in neutrophil NET formation over time and with/without the intervention

  16. neutrophil surface receptor expression

    Time frame: 6 months

    Change in neutrophil surface receptor expression over time and with/without the intervention

  17. monocyte burst

    Time frame: 6 months

    Change in monocyte burst over time and with/without the intervention

  18. monocyte phagocytosis

    Time frame: 6 months

    Change in monocyte phagocytosis over time and with/without the intervention

  19. monocyte function surface receptor expression

    Time frame: 6 months

    Change in monocyte surface receptor expression over time and with/without the intervention

  20. T cell immunophenotyping

    Time frame: 6 months

    Change in T cell subtypes over time and with/without the intervention

  21. B cells immunophenotyping

    Time frame: 6 months

    Change in B cell subtypes over time and with/without the intervention

  22. Spirometry

    Time frame: 6 months

    Change in spirometry measurements over time and with/without the intervention

  23. Lung volume

    Time frame: 6 months

    Change in lung volume over time and with/without the intervention

  24. Gas diffusion

    Time frame: 6 months

    Change in pulmonary gas diffusion over time and with/without the intervention

Sponsors and collaborators

Lead sponsor

Medical University of Graz

Other

Collaborators

  • CBmed Ges.m.b.H.

Registry information

Official study title

Post COVID-19 Syndrome: A Pilot Study to Explore the Gut-lung Axis

Important dates

Study start
2021
Primary completion
2022
Study completion
2025
First posted
Mar 24, 2021
Registry last updated
Nov 25, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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