LPS-Activated Monocytes Are Unresponsive to T4 Phage and T4-Generated Escherichia coli Lysate.

Katarzyna Bocian,Michał Zarzycki,Grażyna Korczak-Kowalska,Beata Weber-Dąbrowska,Andrzej Górski,Jan Borysowski,Piotr Wierzbicki,Danuta Kłosowska

doi:10.3389/fmicb.2016.01356

Abstract

A growing body of data shows that bacteriophages can interact with different kinds of immune cells. The objective of this study was to investigate whether T4 bacteriophage and T4-generated Escherichia coli lysate affect functions of monocytes, the key population of immune cells involved in antibacterial immunity. To that end, we evaluated how T4 and E. coli lysate influence the expression of main costimulatory molecules including CD40, CD80 and CD86, TLR2, TLR4 on monocytes, as well as the production of IL-6 and IL-12 in cultures of peripheral blood mononuclear cells (PBMCs). Separate experiments were performed on unactivated and LPS-activated PBMCs cultures. Both studied preparations significantly increased the percentage of CD14+CD16-CD40+ and CD14+CD16-CD80+ monocytes in unactivated PBMCs cultures, as well as the concentration of IL-6 and IL-12 in culture supernates. However, neither purified T4 nor E. coli lysate had any significant effect on monocytes in LPS-activated PBMCs cultures. We conclude that LPS-activated monocytes are unresponsive to phages and products of phage-induced lysis of bacteria. This study is highly relevant to phage therapy because it suggests that in patients with infections caused by Gram-negative bacteria the administration of phage preparations to patients and lysis of bacteria by phages are not likely to overly stimulate monocytes.

Highlights

Bacteriophages are increasingly considered as a means of treatment of bacterial infections, including those caused by antibiotic-resistant bacteria (Miedzybrodzki et al, 2012; Kutter et al, 2015)
In order to investigate the effects of T4 bacteriophage and T4generated E. coli lysate on monocytes, we determined: (1) the expression of main costimulatory molecules including CD40, CD80, and CD86, (2) the expression of TLR2 and TLR4 molecules, and (3) the production of IL-6 and IL-12
In the first set of experiments, we evaluated whether T4 bacteriophage and T4-generated E. coli lysate affect the expression of CD40, CD80, and CD86 in CD14+CD16− monocytes

Summary

Introduction

Bacteriophages are increasingly considered as a means of treatment of bacterial infections, including those caused by antibiotic-resistant bacteria (Miedzybrodzki et al, 2012; Kutter et al, 2015). During treatment, phages can interact with bacteria, and with different populations of immune cells including those involved in the induction of antibacterial immune responses (Górski et al, 2012). An important kind of immune cells engaged in antibacterial immunity are monocytes (Lauvau et al, 2015). These are cells of myeloid origin that constitute 5–12% of leukocytes in the peripheral blood in humans. While unactivated monocytes undergo apoptosis, activation by different factors associated with ongoing infection or inflammation results in apoptosis inhibition, and monocytes migrate into inflamed tissues, phagocytose apoptotic cells, cellular debris, and different

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