Investigation of the relationship of serum ttv dna levels and disease severity in COVİD-19 patients

AIM: In the pathogenesis of COVID-19, there is a fundamental relationship between the immune response to the agent and disease severity. TTV activity is related to immune response and immune system. In this thesis study, we aimed to compare TTV viral load and disease severity in patients who require outpatient follow-up, hospitalisation or intensive care, and to examine the potential for use as a biomarker for immunosuppressive therapy to be applied in a possible connection. MATERIAL AND METHOD: For the thesis study, 257 samples followed up in the ward or inpatient with a diagnosis of COVID-19 between 1 December 2020 and 30 April 2021 at Istanbul University-Cerrahpaşa, Cerrahpaşa Medical Faculty Hospital were included. The presence and quantification of TTV DNA in patients was performed by realtime PCR method. Biochemistry results of the patients were obtained from routine examinations. Intergroup comparisons were made with appropriate statistical evaluation. FINDINGS: Of the patients included in the study, 116 were female and 141 were male. The patient groups consisted of 257 patients, including 128 patients followed up in the outpatient clinic, 99 patients hospitalised in the COVID-19 ward and 30 patients hospitalised in the intensive care unit. There was no statistical difference between genders in terms of TTV DNA positivity. TTV DNA copy numbers were 177,963.12+972,146.16 copies/ml in outpatients, 10,760.12+54,604.89 copies/ml in ward patients and 3,203.25+6,427.63 copies/ml in ICU patients. According to these results, the mean TTV viral load was statistically higher in outpatients than in patients hospitalised in the ward and transferred to ICU (p<0.001), and the mean in ward patients was statistically higher than in ICU patients (p<0.001). When the survivors (103.81+66.97) and the deceased patients (4,974.36+7,667.54 copies/ml) were compared, although the TTV viral load was higher in the deceased patients, there was no statistically significant difference between them. When other biochemical markers (cell free DNA, lymphocyte count, thrombocyte count, creatinine, fibrinogen, CRP, AST, ALT, LDH, troponin, CK, procalcitonin, ferritin and d-dimer) were compared with TTV DNA levels, TTV DNA levels were statistically correlated with lymphocyte (p=0.01) and platelet (p=0.04) levels. RESULTS: As a result of the thesis study, TTV viral load differences were observed in outpatients, ward and intensive care unit patients. It was concluded that these differences may be due to natural immunity triggered by COVID-19, which may play a role in viral clearance. The cross-sectional planning of the thesis study and the inability to collect longitudinal samples during patient follow-up were considered as a limitation. However, basal TTV DNA load and subsequent viral load monitoring may be useful in determining the cytokine storm and directing the immunosuppressive treatment to be applied if necessary. Another use of this test may be the evaluation of vaccine responses, which should be considered as a potential biomarker for the prediction of both COVID-19 and other vaccine efficacies.