Distinguishing features of long COVID identified through immune profiling

The study titled “Distinguishing features of long COVID identified through immune profiling” focuses on the biological characteristics of long COVID (LC) using immune profiling.

Here’s a detailed summary:

Study Overview

  • Objective: To identify biological markers associated with long COVID by examining immune responses in recovered COVID-19 patients.
  • Participants: 275 individuals, including healthcare workers with prior SARS-CoV-2 infection, vaccinated controls, convalescent controls, and individuals with long COVID symptoms.
  • Methods: The study utilized multidimensional immune phenotyping, machine learning, and various analytical techniques to assess immune cell populations, antibody responses, and serum mediators.

Key Findings

  1. Altered Immune Cell Populations:
    • Significant differences in circulating myeloid and lymphocyte populations were observed in individuals with long COVID compared to controls.
    • Elevated levels of non-conventional monocytes and altered expression of major histocompatibility complex (MHC) class II in long COVID patients were noted.
  2. SARS-CoV-2-Specific Antibody Responses:
    • Participants with long COVID showed exaggerated humoral responses to SARS-CoV-2, especially against specific regions of the spike protein.
  3. Cortisol and Immune Mediators:
    • Cortisol levels were lower in long COVID participants.
    • Other immune mediators such as complement C4b, CCL19, and galectin-1 showed variations, indicating immune dysregulation.
  4. Autoantibodies to Exoproteome:
    • The study did not find significant differences in autoantibody reactivities between long COVID patients and controls.
  5. Antibody Responses to Herpesviruses:
    • Elevated antibody responses to certain herpesviruses, particularly Epstein–Barr virus (EBV), were observed in long COVID patients, suggesting potential viral reactivation.
  6. Unique Biological Markers:
    • Machine learning models identified key features strongly associated with long COVID, such as serum galectin-1 concentration and IgG against various EBV epitopes.


  • Implications: The study provides insights into the immunological changes associated with long COVID. It emphasizes the potential role of altered immune responses and herpesvirus reactivation in the condition.
  • Clinical Relevance: The findings may help guide future research into the pathobiology of long COVID and the development of relevant biomarkers for diagnosis and treatment.


This study underscores the complexity of long COVID and its impact on the immune system. The identification of unique immune markers and altered responses in long COVID patients contributes to a better understanding of the condition and paves the way for targeted therapeutic strategies.

Read More: https://www.nature.com/articles/s41586-023-06651-y

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