Author contribution: Mishina ES — study design; collection and processing of specimens; data analysis; manuscript preparation; Zatolokina MA, Mnikhovich MV, Kharchenko VV — study concept; manuscript editing. The final version of the manuscript was approved by all the authors.

Compliance with ethical standards: the study was approved by the Regional Ethics Committee of Kursk State Medical University (Protocol № 4 dated June 10, 2019). The study complied with the ethical standards for medical research studies involving humans. Informed consent was obtained from all study participants.