Defect of CARD9 leads to impaired accumulation of gamma interferon-producing memory phenotype T cells in lungs and increased susceptibility to pulmonary infection with Cryptococcus neoformans.
Caspase recruitment domain-containing protein 9 (CARD9) is an adaptor molecule signal that is critical for NF-κB activation and is triggered through C-type lectin receptors (CLRs), which are pattern recognition receptors that recognize carbohydrate structures. Previous studies have reported that Cryptococcus neoformans, a fungal pathogen that causes meningoencephalitis in AIDS patients, is recognized through some CLRs, such as mannose receptors or DC-SIGN. However, the role of CARD9 in the host defense against cryptococcal infection remains to be elucidated. In the present study, we analyzed the role of CARD9 in the host defense against pulmonary infection with C. neoformans. CARD9 gene-disrupted (knockout [KO]) mice were highly susceptible to this infection, as shown by the reduced fungal clearance in the infected lungs of CARD9 KO mice, compared to that in wild-type (WT) mice. Gamma interferon (IFN-γ) production was strongly reduced in CARD9 KO mice during the innate-immunity phase of infection. Reduced IFN-γ synthesis was due to impaired accumulation of NK and memory phenotype T cells, which are major sources of IFN-γ innate-immunity-phase production; a reduction in the accumulation of these cells was correlated with reduced CCL4, CCL5, CXCL9, and CXCL10 synthesis. However, differentiation of Th17 cells, but not of Th1 cells, was impaired at the adaptive-immunity phase in CARD9 KO mice compared to WT mice, although there was no significant difference in the infection susceptibility between interleukin 17A (IL-17A) KO and WT mice. These results suggest that CARD9 KO mice are susceptible to C. neoformans infection probably due to the reduced accumulation of IFN-γ-expressing NK and memory phenotype T cells at the early stage of infection.
Department of Medical Microbiology, Mycology and Immunology, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan.
Hideki
H
Yamamoto
Yuri
Y
Nakamura
Ko
K
Sato
Yurie
Y
Takahashi
Toshiki
T
Nomura
Tomomitsu
T
Miyasaka
Keiko
K
Ishii
Hiromitsu
H
Hara
Natsuo
N
Yamamoto
Emi
E
Kanno
Yoichiro
Y
Iwakura
Kazuyoshi
K
Kawakami
D000818:Animals; D053468:CARD Signaling Adaptor Proteins / Q000502:physiology*; D018925:Chemokines / Q000096:biosynthesis; D003455:Cryptococcus neoformans / Q000235:genetics; D004195:Disease Models, Animal; D007113:Immunity, Innate / Q000502:physiology; D007371:Interferon-gamma / Q000096:biosynthesis*; D008172:Lung Diseases, Fungal / Q000276:immunology / Q000382:microbiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D013601:T-Lymphocytes / Q000276:immunology*; D018417:Th1 Cells / Q000166:cytology; D058504:Th17 Cells / Q000166:cytology
D053468:CARD Signaling Adaptor Proteins; C505855:CARD9 protein, human; D018925:Chemokines; D007371:Interferon-gamma