<i>S. pyogenes</i> M49-16 arginine deiminase inhibits proliferative activity of human peripheral blood lymphocytes

Abstract

Arginine deiminase is one of three enzymes constituting the arginine deiminase system in bacteria. It was demonstrated that arginine deiminase exerts anti-proliferative effects on some primary and immortalized mouse and human cells. It is assumed that the inhibitory effect of arginine deiminase on cell proliferation might be related to its ability to result in the arginine exhaustion. T-lymphocytes depend on arginine for proliferation, T-cell receptor complex expression, and the differentiation of memory cells. The aim of the current study was to investigate an impact streptococcal arginine deiminase on functions of human peripheral blood lymphocytes. For this, we comparatively analyzed effects of Supernatant of Destroyed Streptococcal Cells (SDSCs) derived from parental strain S. pyogenes M49-16 and its isogenic mutant S. pyogenes M49-16delArcA bearing inactivated arginine deiminase gene (ArcA) on immune cell functions. An impact of supernatants on cell viability was estimated by staining with DAPI dye. Cell proliferation was assessed by MTT-test and flow cytometry by using the method based on intracellular protein staining with vital fluorescent CFSE (carboxyfluorescein succinimidyl ester) dye. In addition, the level of lymphocyte tyrosine phosphatase CD45 expression in various culturing conditions was evaluated. It was demonstrated that S. pyogenes M49-16 SDSCs had no impact on cells viability. Parental strain-derived SDSC exerted virtually no effect on intact cells proliferation, but considerably suppressed ConA-induced cell proliferation. At the same time, mutant strain-derived SDSC significantly stimulated spontaneous cell proliferation, but not that one after mitogen exposure. It was observed that increased proliferation was accompanied by upregulated CD45 expression, although it was not significant in all cases. These data allow to conclude that bacterial arginine deiminase could be one of pathogenicity factors able to limit lymphocyte proliferation and immune response and could be a part of pathogen strategy to suppress immune response in order to improve bacterial growth and dissemination.

Keywords

• arginine deiminase
• streptococcus pyogenes
• lymphocytes
• cfse
• proliferation
• cd45