The effect of streptococcal arginine deiminase on Th17 lymphocyte differentiation in vitro

BACKGROUND: The mTOR/S6K metabolic intracellular signaling cascade plays a key role in regulating the activation and differentiation of Th17/Treg lymphocyte populations. Pathogens can disrupt T-lymphocyte differentiation programs and weaken immune responses through arginine depletion mechanisms. AIM: To evaluate the effect of bacterial arginine-hydrolyzing enzyme arginine deiminase on the balance of Th17/Treg helper T-cell polarization in vitro. MATERIALS AND METHODS: Experiments were conducted using mononuclear leukocytes from healthy donors. Lymphocyte activation and differentiation were induced with activating antibodies and a cytokine cocktail. Recombinant Streptococcus pyogenes arginine deiminase was used. The enzyme’s arginine-hydrolyzing activity was confirmed by a modified Sakaguchi method. Mitochondrial oxidative phosphorylation activity was analyzed via MTT assay. The proportion of Th17, Treg, and IL-17A+/Foxp3+ transitional lymphocyte populations was assessed using monoclonal antibodies and flow cytometry. RESULTS: The enzyme caused a significant sevenfold decrease in arginine concentration in mononuclear leukocyte cultures. The arginine deficiency induced by arginine deiminase activity could not be compensated even by supplementing supraphysiological concentrations of the amino acid. Differentiation was accompanied by a significant reduction in oxidative phosphorylation (p 0.001). Arginine deiminase inhibited mitochondrial respiration in both intact (p 0.001) and differentiated cells (p 0.05). The enzyme’s activity suppressed Th17 cell differentiation (p 0.05) but did not affect IL-17A+/Foxp3+ transitional cells, Treg lymphocytes, or the Th17/Treg ratio. CONCLUSIONS: Arginine deiminase may disrupt adaptive immune development and diminish the effectiveness of protective immune responses.