Serum arginase, a biomarker of treatment efficacy in human African trypanosomiasis

Abstract

Arginase serum levels were increased in human African trypanosomiasis patients and returned to control values after treatment. Arginase hydrolyzes l-arginine to l-ornithine, which is essential for parasite growth. Moreover, l-arginine depletion impairs immune functions. Arginase may be considered as a biomarker for treatment efficacy.

Fig 1

Determination of arginase I expression (left panel) and arginase activity (right panel) in sera from controls (n = 23) and patients with human African trypanosomiasis (n = 32) from the Couloir focus (Republic of Congo). ●, Controls; ◆, stage 1 patients; ■, stage 2 patients. Black lines represent the medians and quartiles for each group. The arginase activity was higher in HAT patients than in controls (median, 4.82 U/liter versus 2.65 U/liter, P < 0.001). Serum arginase I expression was higher in HAT patients than in controls (median, 37 ng/ml versus 17 ng/ml, P < 0.001).

Fig 2

Determination of arginase I expression (left panel) and arginase activity (right panel) in sera from patients with human African trypanosomiasis before treatment and 6 months later (n = 12). Open circles (○) represent the median for each group. Values for each patient are joined by a black line, and medians are joined by a dashed line. Arginase I expression values (median, 43 ng/ml before treatment) decreased after treatment (median, 18.5 ng/ml, P < 0.005) to return to healthy control values (17 ng/ml). Arginase activity (median, 5.54 U/liter before treatment) decreased after treatment (median, 2.72 U/liter, P < 0.001) to return to healthy control values (2.65 U/liter).