Interleukin-17-mediated control of parasitemia in experimental Trypanosoma congolense infection in mice - PubMed (original) (raw)
Interleukin-17-mediated control of parasitemia in experimental Trypanosoma congolense infection in mice
Zhirong Mou et al. Infect Immun. 2010 Dec.
Abstract
BALB/c mice are highly susceptible to experimental Trypanosoma congolense infections, whereas C57BL/6 mice are relatively resistant. Infected highly susceptible BALB/c mice die of systemic inflammatory response syndrome. Because interleukin-17 (IL-17) and Th17 cells regulate inflammatory responses, we investigated their role in the pathogenesis of experimental African trypanosomiasis in mice. We show that the production of IL-17 by spleen and liver cells and the serum IL-17 level increased after T. congolense infection in mice. Interestingly, infected highly susceptible BALB/c mice produced more IL-17 and had more Th17 cells than infected relatively resistant C57BL/6 mice. Paradoxically, neutralization of IL-17 with anti-IL-17 monoclonal antibody in vivo induced higher parasitemia in both the susceptible and the relatively resistant mice. Interestingly, anti-IL-17 antibody-treated mice had higher serum levels of alanine aminotransferase and aspartate aminotransferase, and the production of IL-10 and nitric oxide by liver cells was markedly decreased. Moreover, recombinant IL-17-treated mice exhibited significantly faster parasite control and lower peak parasitemia compared to control mice. Collectively, these results suggest that the IL-17/Th17 axis plays a protective role in murine experimental African trypanosomiasis.
Figures
FIG. 1.
Increased numbers of IL-17-producing cells and IL-17 production in BALB/c mice infected with T. congolense. Infected BALB/c mice were sacrificed at different days postinfection (as indicated), and the levels of IL-17 in the culture supernatant fluids of spleen and liver cells (A and B) and in serum (C) were determined by ELISA. At the time of sacrifice, spleen and liver cells were directly stained ex vivo for intracellular IL-17, and the percentage of CD4+IL-17+ (D and F) and CD4− IL-17+ (E and G) cells was determined within CD3+ cells by flow cytometry. The percentage of γδ TCR+ cells in spleens and livers from infected mice (day 8 postinfection) was also determined within CD3+ CD4− IL-17+ cells (H). The results are presented as means ± the standard errors (SE) and are representative of four (A to C), three (D to G), and two (H) independent experiments (n = 3 mice) with similar results. *, P < 0.05; ***, P < 0.001.
FIG. 2.
Increased inflammatory cytokine production in BALB/c mice infected with T. congolense. Infected BALB/c mice were sacrificed at different days postinfection, and the levels of cytokines in serum (A to C) and culture supernatant fluids of liver cells (D to F) were determined by ELISA. The results are presented as means ± the SE and are representative of three to four independent experiments (n = 3 mice) with similar results. *, P < 0.05; **, P < 0.01; ***, P < 0.001.
FIG. 3.
T. _congolense_-infected susceptible BALB/c mice produce more IL-17 and have more Th17 cells than infected relatively resistant C57BL/6 mice. Parasitemia (A) and IL-17 levels in serum (B) and culture supernatant fluids of spleen (C) and liver (D) cells from BALB/c mice (▪) and C57BL/6 mice (□) infected with T. congolense were determined. Spleen (E and F) and liver (G and H) cells were also stained with fluorochrome-conjugated anti-CD3, anti-CD4, and anti-IL-17 MAbs, and the percentages of CD4+L-17+ cells were evaluated after gating on CD3+ cells. The results are presented as means ± the SE and are representative of three independent experiments (n = 3 mice) with similar results. *, P < 0.05; **, P < 0.01; ***, P < 0.001.
FIG. 4.
Levels of proinflammatory cytokines in sera and culture supernatant fluid of liver cells from _T. congolense_-infected BALB/c and C57BL/6 mice. Sera (A to D) and supernatant fluids of liver cells (E to H) from infected BALB/c mice (▪) and C57BL/6 mice (□) were assayed for IL-6 (A and E), TNF (B and F), IFN-γ (C and G), and IL-10 (D and H) by ELISA. The results are presented as means ± the SE and are representative of three independent experiments (n = 3 mice) with similar results. *, P < 0.05; **, P < 0.01; ***, P < 0.001.
FIG. 5.
IL-17 mediates control of parasitemia in _T. congolense_-infected C57BL/6 mice. Infected C57BL/6 mice were treated with anti-IL-17 MAb (•) or control antibody (○) (A) or rIL-17 (▪) or PBS (□) (B), and daily parasitemia was determined as detailed in Materials and Methods. The results are presented as means ± the SE and are representative of two independent experiments (n = 3 to 5 mice) with similar results. *, P < 0.05; **, P < 0.01; ***, P < 0.001.
FIG. 6.
Anti-IL-17 MAb treatment is associated with alteration in IL-17, IL-10, and NO production in infected C57BL/6 mice. Antibody-treated mice were sacrificed at day 8 postinfection, and the production of IL-17 (A), IL-10 (B), IFN-γ (C), and TNF (D) in the culture supernatant fluids of liver cells was determined by ELISA. Liver cells were also stained directly ex vivo with fluorochrome-conjugated anti-CD3, anti-CD4, anti-IL-17, and anti-IL-10 antibodies, and the percentage of CD4+IL-17+ (E) and CD4+IL-10+ (F) cells was evaluated within CD3+ cells by flow cytometry. The ALT (G) and AST (H) levels in the serum from anti-IL-17 MAb-treated mice were also measured. (I) NO production by splenocytes and liver cell cultures was determined by Griess assay. (J) Also, trypanosome-specific antibodies (IgM, total IgG, IgG1, and IgG2a) in the sera of infected mice were measured by ELISA. The results are presented as means ± the SE and are representative of two independent experiments (n = 3 to 5 mice) with similar results. *, P < 0.05; **, P < 0.01.
FIG. 7.
IL-17RA expression by liver cells from _T. congolense_-infected BALB/c and C57BL/6 mice. The percentage (A) and MFI (B) of IL-17RA+ cells in liver from infected mice were evaluated by flow cytometry after staining with anti-IL-17RA antibody (black) or isotype control antibody (gray). **, P < 0.01.
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