I. Semchuk¹, A. Kharina¹, N. Korniienko², M. Rudyk¹, R. Dovhyi¹,
K. Ostrovska^1, K. Liashenko¹, Yu. Kortous¹, L. Skivka¹

¹NSC “Institute of Biology and Medicine”,
Taras Shevchenko National University of Kyiv, Ukraine;
²NPBC-UKRAINE LLC;
*e-mail: 03semiramida02@knu.ua

Received: 19 November 2025; Revised: 22 January 2026;
Accepted: 30 January 2026; Available on-line: February 2026

The growing use of bacteriophages in the treatment of antibiotic-resistant infections highlights the need to clarify their direct effects on innate immune cells. This study investigated the effect of polyvalent phage preparation Pyofag on oxidative metabolism and phagocytic function of nonsensitized peripheral blood monocytes and granulocytes under physiological whole-blood conditions. Blood samples from healthy donors were collected using lithium heparin, incubated with Pyofag at phage-to-cell ratios of 1:2, 1:5, and 1:10, centrifuged and the cell pellet was used. ROS production was assessed with the use of DCFDA, phagocytic activity was estimated by fluorescent polystyrene latex beads-uptake intensity. The percentage of phagocytic cells and their mean fluorescence index (MFI) were measured by flow cytometry. It was shown that Pyofag induced statistically significant moderate ROS generation in both phagocyte populations only at the highest dose, remaining markedly lower than that induced by phorbol 12-myristate 13-acetate. Upon Pyofag treatment, only minor reduction in the proportion of phagocytosing monocytes and minor increased in the percentage of phagocytosing granulocytes was observed with no effect on MFI. The mild oxidative activation and stable phagocytic performance observed in Pyofag-treated blood phagocytes point to a noninflammatory, balanced immunomodulatory profile, supporting the safety of this phage preparation for potential systemic administration.

Keywords: bacteriophages, granulocytes, immune modulation, monocytes, phagocytosis, Pyofag, reactive oxygen species