TREC AND KREC AS PROMISING PROGNOSTIC MARKERS FOR THE TUBERCULOSIS INFECTION ACTIVITY

Scientists around the Globe are making deliberate attempts to develop the new methods for predicting and diagnosing tuberculosis, but these measures are not enough to end its epidemic. The purpose of the study was to evaluate the excisional rings of the T-cell receptor (TREC) and K-deletion element of B-cells (KREC) in infants and preschool children at high risk of tuberculosis as a promising prognostic marker for tuberculosis infection activity. A cross-sectional study was conducted in Jan. - Sept. 2022. The observation group consisted of 87 children aged 1 to 7 [6 (5‒7)] y/o, of which 13 (14.9%) aged 1 to 3 y/o and 74 aged 4 to 7 y/o; 53 (60.9%) boys/34 (39.1%) girls. The three groups were formed: G1 (n=27) with an established diagnosis of tuberculosis (TB), G2 (n=34) with TB infection diagnosis made based on the results of tuberculin diagnosis and without signs of a local specific process, and [control] G3 (n=26) without signs of TB infection according to the results of specific skin tests and without signs of TB, i.e., conditionally healthy. All children, in addition to methods to confirm or exclude TB and methods of specific immunodiagnostics, have undergone a molecular genetic study: DNA extraction from a dry blood spot and quantitative determination of TREC and KREC by real-time PCR in values of TREC and KREC copies per 105 cells. In order to build the reference values of TREC and KREC quantitative indicators in dry blood spots, the results obtained in G3 were analyzed as well. Results: the reference values of TREC and KREC were established for children of early and preschool ages when extracting DNA from a dry blood spot. When assessing tuberculosis infection in children of early and preschool ages, statistically significant criteria were determined, such as: anti-tuberculosis therapy (F=42.001; p<0.001), positive or negative reaction to the recombinant tuberculosis allergen during an intradermal test (F=39.394; p<0.001), high blood TREC level (F=12.707; p<0.001), tuberculin reaction (F=10.625; p<0.001), and KREC level (F=3.182; p=0.039). Conclusion: high level of TREC can be considered as a marker for the activity or a personalized predictor for the risk of progression of TB infection in children of early and preschool ages with high risk of TB.