Fig. 1.

IFN-γ treatment leads to liver-stage P. vivax elimination in cultured human HC04 hepatocytes via an NO-independent process. (A and B) Human HC04 hepatocytes were infected with P. vivax sporozoites (MOI = 1) for 4 h, washed three times with complete medium to remove noninvading sporozoites, and treated with 400 U IFN-γ/mL for 4 h. They were then washed three times and maintained in complete medium until they were harvested on day 4, when they were processed for IFA to quantify the number of surviving parasites. Data are mean ± SEM from at least three independent experiments; the results are expressed relative to the full control, defined as 100%. (Scale bar: 5 µm.) (C) HC04 cells were treated or not with IFN-γ (400 U/mL) for 4 h, after which iNOS mRNA expression was analyzed by RT-PCR. GAPDH served as the internal control. mRNAs from HC04 cells treated with LPS served as the positive control. (D) HC04 cells were treated or not with IFN-γ (400 U/mL) for 4 h, after which NO production in the supernatant was measured using the Griess reaction assay. RAW264.7 cells treated with LPS in the presence or absence of the iNOS inhibitors aminoguanidine (AG) and L-NAME served as the positive control. Data are mean ± SEM from at least three independent experiments. (E) HC04 cells were infected with P. vivax sporozoites as in A and B, washed, treated with IFN-γ with or without the iNOS inhibitors for 4 h, washed again, and maintained in complete medium until day 4, when the surviving parasites were quantified by IFA. Data are mean ± SEM of at least three independent experiments; the results are expressed relative to the full control, defined as 100%. N.S., not significant.