Leukocyte telomere dynamic change in patients with mild to moderate covid-19 during three weeks of follow-up: Relation with therapy.

Background: A three-year COVID-19 pandemic revealed aspectrum of disease severity and clinical manifestations. Themost intriguing part of this phenomenon lays in inter-individual variability in COVID-19 course among patients,which is attributable to patient's age, comorbidities and general health status. Focus of this follow-up study was toassess leukocyte telomere length change in mild-to-moderate COVID-19 patients and concomitant influence ofinflammation, oxidative stress (OS), pulmonary involvementand implemented therapy on the course of the disease. Methods: Routine biochemical/haematological parameters, markers of OS (prooxidants and antioxidants), vitaminD, IgM and IgG antibodies level and relative length ofleukocyte telomeres (rLTL) were measured at three timepoints (at diagnosis, after 14 and 21 days from the diseaseonset) in blood samples of 31 consecutive COVID-19patients, with a mild (n = 16) and moderate (n = 15) form ofthe disease, treated on an outpatient basis. Results: Although the patients had reduced rLTL at baseline (median: 0.592; 25th - 75th percentiles: 0.518-0.724), it significantly increased during the follow-up(median: 0.773; 25th - 75th percentiles: 0.615-0.923; P<0.01). The rate of telomere attrition was associated withthe extent of OS and pulmonary involvement. During follow-up, the burden of OS was reduced, while antioxidantdefence mechanisms were recovered. The use of antibiotics and N-acetylcysteine-propolis supplementation wasassociated with telomere lengthening. Conclusions: Results of this study revealed significant interaction between OS, inflammation and leukocyte telomerelength attrition in COVID-19. Our data suggest that rRTLcan be a biomarker that enables more precise therapy decision and accurate patient status estimation.