Fig. 2. A weekly BNZ treatment regimen of 500 mg/kg cures mice chronically infected with T. cruzi.

(A) Schematic of infection, treatment and assessment of treatment efficacy. C57BL/6 wild-type mice (14-15 mice in each group) were infected intraperitoneally with 10⁴ trypomastigotes of the ARC-0704 strain of T. cruzi and left untreated or treated weekly, starting at 120 days post-infection, with BNZ at 100 or 500mg/kg concentration over 50 weeks. At 50 weeks of treatment mice treated with 500mg/kg/wk were switched to a regimen of 100mg/kg/wk of BNZ from week 50 to 55, followed by a cessation of treatment at 55 weeks and termination of the experiment at week 77 (500w/100w/STOP). The mice receiving 100mg/kg/wk of BNZ were divided in three groups on week 50 of treatment; one group was switched to a 500mg/kg/wk of BNZ until week 77 (100w/500w); a second group continued with the same regimen of 100mg/kg/wk of BNZ until week 77 (100w/100w), and in the third group the 100mg/kg/wk treatment was stopped at week 55 (100w/STOP). In all the groups the experiment was terminated at 77 weeks of treatment. (B) Expression of the T_cm marker CD127 in blood on CD8⁺ TSKB20-tetramer⁺ T cells from mice untreated and undergoing different weekly treatment regimens. Data are shown as mean ± standard error of the mean. Arrows indicate the initiation of the treatment (120dpi= week 0) and week 50 where changes in the treatment regimens occurred for the treated groups (see description in A). The area in gray denotes 5 weeks corresponding to weeks 50-55 where the mice previously treated with BNZ at 500mg/kg/wk were switched to 100mg/kg/wk (see description in A). (C) T. cruzi DNA isolated from skeletal muscle of untreated or treated mice at 77 weeks from experiment depicted in (A-B) and assayed by qPCR. A statistically significant difference was set at p=0.05. (D) Blood from these mice collected at 77 weeks was submitted to hemoculture assays and analyzed for parasite growth for >60 days.