ANALYSIS OF INCREASING IN THE PROPORTION OF PATHOLOGICAL TREC/KREC LEVELS IN THE POST-PANDEMIC PERIOD

Abstract

Background. The COVID-19 pandemic has posed an unprecedented challenge to global public health. Poor clinical outcomes in COVID-19 are associated with a pathogenic triad of interrelated mechanisms: immune dysregulation, coagulopathy, and secondary immunodeficiency, which collectively establish a self-perpetuating cycle of progressive multiorgan dysfunction. The weakening of immune defenses stems in part from T- and B-cell depletion due to immune resource exhaustion during acute infection. The extent of immune system impairment can be assessed by quantifying biomarkers of lymphocyte function: T-cell receptor excision circles (TREC) and κ-deleting recombination excision circles (KREC) for T- and B-cells, respectively.

Aim. This study aimed to evaluate the prevalence of abnormal TREC/KREC levels in peripheral blood among apparently healthy individuals during the post-pandemic period.

Materials and Methods. We analyzed whole peripheral blood samples from 4,433 apparently healthy adults (≥18 years) residing in St. Petersburg and Leningrad Oblast, collected during two population studies: June 15-21, 2020 (n=717) and September 4-29, 2023 (n=3,716). TREC/KREC quantification was performed using real-time PCR with the «TREC/KREC-AmpPS» commercial kit (St. Petersburg Pasteur Institute, St. Petersburg, Russia) following manufacturer's protocol.

Results. The prevalence of reduced TREC/KREC levels increased significantly from pre-pandemic (14.2% and 5.7%, respectively) to post-pandemic periods (50.1% and 21.2%, respectively), representing a 3.6-fold increase. Significant differences in pathological biomarker levels were observed across all age groups. Characteristic immunological disturbances manifested as either isolated T-cell deficiencies or combined T/B-cell dysfunction, with no isolated B-cell defects detected - highlighting the pivotal role of T-cell impairment in observed immunopathological changes. Post-pandemic findings included decreased minimal population TREC values in older age groups and a paradoxical 50.5% increase in lower threshold KREC levels.

Conclusion. Our findings demonstrate a substantial rise in pathological TREC/KREC values, likely reflecting long-term immune alterations following COVID-19. These changes underscore the critical need for ongoing immunological surveillance in the post-pandemic era. Future research should focus on temporal dynamics of these disturbances and develop preventive strategies to mitigate long-term COVID-19 sequelae.

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