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Contributions of the MyD88-dependent receptors IL-18R, IL-1R, and TLR9 to host defenses following pulmonary challenge with Cryptococcus neoformans.

Wang JP, Lee CK, Akalin A, Finberg RW, Levitz SM - PLoS ONE (2011)

Bottom Line: Signaling via the adapter protein, MyD88, is important in the host defense against Cryptococcus neoformans infection.Cytokine analysis of lung homogenates revealed that deficiency of IL-IR, IL-18R, or MyD88 is associated with diminished lung levels of IL-1β.In summary, we found that multiple signaling components can contribute the MyD88-dependent host responses to cryptococcal infection in vivo and each drives distinct pulmonary responses.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America. Jennifer.wang@umassmed.edu

ABSTRACT
Signaling via the adapter protein, MyD88, is important in the host defense against Cryptococcus neoformans infection. While certain Toll-like receptors (TLRs) can enhance the clearance of Cryptococcus, the contributions of MyD88-dependent, TLR-independent pathways have not been fully investigated. We examined the roles of IL-1R and IL-18R in vivo by challenging C57BL/6 mice with a lethal strain of Cryptococcus. We found that the absence of IL-18R, but not IL-1R, causes a shift in the survival curve following pulmonary delivery of a virulent strain of C. neoformans (H99). Specifically, IL-18R-deficient mice have significantly shorter median survival times compared to wild-type mice following infection. Cytokine analysis of lung homogenates revealed that deficiency of IL-IR, IL-18R, or MyD88 is associated with diminished lung levels of IL-1β. In order to compare these findings with those related to TLR-deficiency, we studied the effects of TLR9-deficiency and found that deficiency of TLR9 also affects the survival curve of mice following challenge with C. neoformans. Yet the lungs from infected TLR9-deficient mice have robust levels of IL-1β. In summary, we found that multiple signaling components can contribute the MyD88-dependent host responses to cryptococcal infection in vivo and each drives distinct pulmonary responses.

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Mice were infected i.n. with 2104 C. neoformans organisms and euthanized 12 days post-infection.(A) Fungal burden of C57BL/6 wild-type (n = 12) and TLR9 knockout (n = 12) mice after infection with C. neoformans. The numbers of CFU in the lungs, brain, and spleen were determined. Data are expressed as log10 CFU per gram of tissue. The results are expressed as individual data points for each animal and the bars represent the mean values. The dotted line indicates the lower limit of detection. Data are combined from two independent experiments with similar results.
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pone-0026232-g005: Mice were infected i.n. with 2104 C. neoformans organisms and euthanized 12 days post-infection.(A) Fungal burden of C57BL/6 wild-type (n = 12) and TLR9 knockout (n = 12) mice after infection with C. neoformans. The numbers of CFU in the lungs, brain, and spleen were determined. Data are expressed as log10 CFU per gram of tissue. The results are expressed as individual data points for each animal and the bars represent the mean values. The dotted line indicates the lower limit of detection. Data are combined from two independent experiments with similar results.

Mentions: In addition to IL-1R and IL-18R, TLR9 uses the adaptor MyD88 for its signaling. Because TLR9 reportedly plays a protective role in cryptococcal infection [5], [6], we wanted to confirm its protective role in our infection model. We infected TLR9 knockout mice with 2×104 CFU of H99 by i.n. inoculation and monitored for survival. TLR9-deficient mice did indeed exhibit significant differences in survival curves compared to WT mice (Figure 4). In two independent combined experiments, median survival was 26 days for WT mice versus 22 days for TLR9 knockout mice. In two additional independent experiments, WT (n = 12) and TLR9 knockout mice (n = 12) were infected with the same dose of H99. Mice were sacrificed at day 12 post infection and organs processed for assessment of fungal burden, cytokines, and histopathology. Overall, no significant differences were observed for CFU values for lung, brains, or spleens in WT versus TLR9 knockout animals (Figure 5A). Of the 23 cytokines and chemokines detected on the Bio-Plex panel, eight specific cytokines and chemokines were elevated in lungs from infected animals, but no significant differences were observed for WT versus TLR9 knockout animals (see Table 2). Finally, no global differences in lung pathology were observed between lungs of WT and TLR9 knockout mice at day 12 following infection with H99 when the same scoring criteria were applied as for the previous experiment (Figure 6A and B).


Contributions of the MyD88-dependent receptors IL-18R, IL-1R, and TLR9 to host defenses following pulmonary challenge with Cryptococcus neoformans.

Wang JP, Lee CK, Akalin A, Finberg RW, Levitz SM - PLoS ONE (2011)

Mice were infected i.n. with 2104 C. neoformans organisms and euthanized 12 days post-infection.(A) Fungal burden of C57BL/6 wild-type (n = 12) and TLR9 knockout (n = 12) mice after infection with C. neoformans. The numbers of CFU in the lungs, brain, and spleen were determined. Data are expressed as log10 CFU per gram of tissue. The results are expressed as individual data points for each animal and the bars represent the mean values. The dotted line indicates the lower limit of detection. Data are combined from two independent experiments with similar results.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3198470&req=5

pone-0026232-g005: Mice were infected i.n. with 2104 C. neoformans organisms and euthanized 12 days post-infection.(A) Fungal burden of C57BL/6 wild-type (n = 12) and TLR9 knockout (n = 12) mice after infection with C. neoformans. The numbers of CFU in the lungs, brain, and spleen were determined. Data are expressed as log10 CFU per gram of tissue. The results are expressed as individual data points for each animal and the bars represent the mean values. The dotted line indicates the lower limit of detection. Data are combined from two independent experiments with similar results.
Mentions: In addition to IL-1R and IL-18R, TLR9 uses the adaptor MyD88 for its signaling. Because TLR9 reportedly plays a protective role in cryptococcal infection [5], [6], we wanted to confirm its protective role in our infection model. We infected TLR9 knockout mice with 2×104 CFU of H99 by i.n. inoculation and monitored for survival. TLR9-deficient mice did indeed exhibit significant differences in survival curves compared to WT mice (Figure 4). In two independent combined experiments, median survival was 26 days for WT mice versus 22 days for TLR9 knockout mice. In two additional independent experiments, WT (n = 12) and TLR9 knockout mice (n = 12) were infected with the same dose of H99. Mice were sacrificed at day 12 post infection and organs processed for assessment of fungal burden, cytokines, and histopathology. Overall, no significant differences were observed for CFU values for lung, brains, or spleens in WT versus TLR9 knockout animals (Figure 5A). Of the 23 cytokines and chemokines detected on the Bio-Plex panel, eight specific cytokines and chemokines were elevated in lungs from infected animals, but no significant differences were observed for WT versus TLR9 knockout animals (see Table 2). Finally, no global differences in lung pathology were observed between lungs of WT and TLR9 knockout mice at day 12 following infection with H99 when the same scoring criteria were applied as for the previous experiment (Figure 6A and B).

Bottom Line: Signaling via the adapter protein, MyD88, is important in the host defense against Cryptococcus neoformans infection.Cytokine analysis of lung homogenates revealed that deficiency of IL-IR, IL-18R, or MyD88 is associated with diminished lung levels of IL-1β.In summary, we found that multiple signaling components can contribute the MyD88-dependent host responses to cryptococcal infection in vivo and each drives distinct pulmonary responses.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America. Jennifer.wang@umassmed.edu

ABSTRACT
Signaling via the adapter protein, MyD88, is important in the host defense against Cryptococcus neoformans infection. While certain Toll-like receptors (TLRs) can enhance the clearance of Cryptococcus, the contributions of MyD88-dependent, TLR-independent pathways have not been fully investigated. We examined the roles of IL-1R and IL-18R in vivo by challenging C57BL/6 mice with a lethal strain of Cryptococcus. We found that the absence of IL-18R, but not IL-1R, causes a shift in the survival curve following pulmonary delivery of a virulent strain of C. neoformans (H99). Specifically, IL-18R-deficient mice have significantly shorter median survival times compared to wild-type mice following infection. Cytokine analysis of lung homogenates revealed that deficiency of IL-IR, IL-18R, or MyD88 is associated with diminished lung levels of IL-1β. In order to compare these findings with those related to TLR-deficiency, we studied the effects of TLR9-deficiency and found that deficiency of TLR9 also affects the survival curve of mice following challenge with C. neoformans. Yet the lungs from infected TLR9-deficient mice have robust levels of IL-1β. In summary, we found that multiple signaling components can contribute the MyD88-dependent host responses to cryptococcal infection in vivo and each drives distinct pulmonary responses.

Show MeSH
Related in: MedlinePlus