Comparative characteristics of cytokine content in neutrophil supernatants after incubation with daily cultures of S. aureus with or without spA gene

Abstract

The study was aimed for assessment of cytokine profile in the whole blood neutrophil supernatants stimulated by Staphylococcus aureus, with and without the spА gene. 20 clinical isolates of S. aureus were tested in vitro. Ten of them carried spА gene and other 10 were without the spА gene. We selected the strains with very high ability to secrete cytokine-like substances (CLS), both in terms of the level and spectrum of the cytokines. The S. aureus strains were divided into two groups depending on the spА status according to the data from the spА genotyping databank (http://spa.ridom.de/). The neutrophils of donors were isolated in a double gradient of Ficoll-Verografin, according to the standard method, at a concentration of 5 106. The bacteria were taken at a ratio of 1:20 to neutrophils (at a concentration of 108 bacteria/mL). The effect of staphylococci on cytokine secretion by neutrophils was determined with a Magpix-100 device (USA), using immunofluorescence multiplex kits from BioRad (USA) for the detection of 17 cytokines (G-CSF, GM-CSF, IFN, IL-1, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12p70, IL-13, IL-17A, TNF, MCP-1, MIP-1) after 1 hour incubation with the neutrophils. Results: It has been shown that staphylococci with a high degree of CLS activity, regardless of presence or absence of the spА gene, affected the ability of neutrophils to secrete cytokines. At the same time, S. aureus carrying the spА gene caused increased secretion of IL-1, TNF, IL-6 (pro-inflammatory cytokines), but, at the same time, it reduced secretion of IL-8, MIP-1 (chemokines). S. aureus strains devoid of spА genes have a more diverse spectrum and more pronounced effect on cytokine secretion of proinflammatory cytokines by neutrophils, e.g., IL-10, IL-12p70, IL-17A, IL-1, IL-2, TNF and the G-CSF growth factor. Both variants of staphylococci caused reduction of IL-6 secretion.