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  • The American Association of Immunologists  (5)
  • English  (5)
  • 1
    Online Resource
    Online Resource
    Identification of a phagosomal F-actin structure that evades dendritic cell immunity to Cryptococcus gattii
    The American Association of Immunologists ; 2020
    In:  The Journal of Immunology Vol. 204, No. 1_Supplement ( 2020-05-01), p. 156.9-156.9
    Details
    In: The Journal of Immunology, The American Association of Immunologists, Vol. 204, No. 1_Supplement ( 2020-05-01), p. 156.9-156.9
    Abstract: Hypervirulent Cryptococcus gattii is a major cause of life-threatening cryptococcosis in immunocompetent individuals and responsible for the ongoing outbreak in the Pacific Northwest. This deadly fungus is known to subvert dendritic cell (DC) maturation and concomitant T cell immunity via immune evasion mechanisms that are poorly understood. Here, we show that primary human DC can phagocytose endemic yeasts but trafficking to the late phagolysosome is blocked by retention of a filamentous actin (F-actin) cage surrounding the phagosomes. Structural studies by super resolution microscopy revealed a novel highly branched F-actin cage that physically interfered with lysosomal fusion. Mechanistically, we demonstrate that C. gattii F-actin cage promotes immune evasion by silencing the canonical RelA signaling of the NF-κB pathway required for DC costimulation and T cell activation. Disruption of the F-actin cage through targeted inhibition or by TNF-α signaling reprogrammed quiescent DC to immunocompetent antigen-presenting cells (APCs) and revealed the existence of a negative feedback loop between periphagosomal F-actin aggregation and pro-inflammatory NF-κB signaling. Collectively, our results have uncovered a unique mechanism of DC immune subversion by organisms such as hypervirulent C. gattii and revealed the potential clinical significance of the immunomodulatory function of phagosomal F-actin in host-pathogen interaction.
    Type of Medium: Online Resource
    ISSN: 0022-1767 , 1550-6606
    URL: Article
    DOI: 10.4049/jimmunol.204.Supp.156.9
    RVK:
    XA 54100
    RVK:
    XA 10000
    Language: English
    Publisher: The American Association of Immunologists
    Publication Date: 2020
    detail.hit.zdb_id: 1475085-5
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  • 2
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    β1 Integrins Are Required To Mediate NK Cell Killing of Cryptococcus neoformans
    The American Association of Immunologists ; 2018
    In:  The Journal of Immunology Vol. 201, No. 8 ( 2018-10-15), p. 2369-2376
    Details
    In: The Journal of Immunology, The American Association of Immunologists, Vol. 201, No. 8 ( 2018-10-15), p. 2369-2376
    Abstract: Cryptococcus neoformans is a fungal pathogen that causes fatal meningitis and pneumonia. During host defense to Cryptococcus, NK cells directly recognize and kill C. neoformans using cytolytic degranulation analogous to killing of tumor cells. This fungal killing requires independent activation of Src family kinase (SFK) and Rac1-mediated pathways. Recognition of C. neoformans requires the natural cytotoxicity receptor, NKp30; however, it is not known whether NKp30 activates both signal transduction pathways or whether a second receptor is involved in activation of one of the pathways. We used primary human NK cells and a human NK cell line and found that NKp30 activates SFK → PI3K but not Rac1 cytotoxic signaling, which led to a search for the receptor leading to Rac1 activation. We found that NK cells require integrin-linked kinase (ILK) to activate Rac1 for effective fungal killing. This observation led to our identification of β1 integrin as an essential anticryptococcal receptor. These findings demonstrate that multiple receptors, including β1 integrins and NKp30 and their proximal signaling pathways, are required for recognition of Cryptococcus, which activates a central cytolytic antimicrobial pathway leading to fungal killing.
    Type of Medium: Online Resource
    ISSN: 0022-1767 , 1550-6606
    URL: Article
    DOI: 10.4049/jimmunol.1701805
    RVK:
    XA 54100
    RVK:
    XA 10000
    Language: English
    Publisher: The American Association of Immunologists
    Publication Date: 2018
    detail.hit.zdb_id: 1475085-5
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  • 3
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    Online Resource
    Cryptococcus gattii Capsule Blocks Surface Recognition Required for Dendritic Cell Maturation Independent of Internalization and Antigen Processing
    The American Association of Immunologists ; 2016
    In:  The Journal of Immunology Vol. 196, No. 3 ( 2016-02-01), p. 1259-1271
    Details
    In: The Journal of Immunology, The American Association of Immunologists, Vol. 196, No. 3 ( 2016-02-01), p. 1259-1271
    Abstract: Cryptococcus gattii is an emerging fungal pathogen on the west coast of Canada and the United States that causes a potentially fatal infection in otherwise healthy individuals. In previous investigations of the mechanisms by which C. gattii might subvert cell-mediated immunity, we found that C. gattii failed to induce dendritic cell (DC) maturation, leading to defective T cell responses. However, the virulence factor and the mechanisms of evasion of DC maturation remain unknown. The cryptococcal polysaccharide capsule is a leading candidate because of its antiphagocytic properties. Consequently, we asked if the capsule of C. gattii was involved in evasion of DC maturation. We constructed an acapsular strain of C. gattii through CAP59 gene deletion by homologous integration. Encapsulated C. gattii failed to induce human monocyte-derived DC maturation and T cell proliferation, whereas the acapsular mutant induced both processes. Surprisingly, encapsulation impaired DC maturation independent of its effect on phagocytosis. Indeed, DC maturation required extracellular receptor signaling that was dependent on TNF-α and p38 MAPK, but not ERK activation, and the cryptococcal capsule blocked this extracellular recognition. Although the capsule impaired phagocytosis that led to pH-dependent serine-, threonine-, and cysteine-sensitive protease-dependent Ag processing, it was insufficient to impair T cell responses. In summary, C. gattii affects two independent processes, leading to DC maturation and Ag processing. The polysaccharide capsule masked extracellular detection and reduced phagocytosis that was required for DC maturation and Ag processing, respectively. However, the T cell response was fully restored by inducing DC maturation.
    Type of Medium: Online Resource
    ISSN: 0022-1767 , 1550-6606
    URL: Article
    DOI: 10.4049/jimmunol.1501089
    RVK:
    XA 54100
    RVK:
    XA 10000
    Language: English
    Publisher: The American Association of Immunologists
    Publication Date: 2016
    detail.hit.zdb_id: 1475085-5
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  • 4
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    C3 complement mediates neutrophil control of cryptococcal lung infection and dissemination
    The American Association of Immunologists ; 2020
    In:  The Journal of Immunology Vol. 204, No. 1_Supplement ( 2020-05-01), p. 67.5-67.5
    Details
    In: The Journal of Immunology, The American Association of Immunologists, Vol. 204, No. 1_Supplement ( 2020-05-01), p. 67.5-67.5
    Abstract: The encapsulated budding yeast Cryptococcus neoformans causes meningitis and pneumonia particularly in immunocompromised individuals including HIV-infected patients. The organism is acquired by the pulmonary route where it disseminates via the bloodstream from the lung to the brain and causes meningitis. Since the lung vasculature is replete with several innate immune cells, it is conceivable that the host would mount an immune response in the pulmonary vasculature to prevent or at least limit the dissemination of C. neoformans to other sites of the body. Hence, we used intravital microscopy to study the host cell immune interactions that occur within the lung vasculature in a living mouse. We found that neutrophils, but not monocytes, interacted with and phagocytosed C. neoformans. Interestingly, additional neutrophils underwent accretion around the phagocytosed C. neoformans, forming a cast of the vasculature. Phagocytosis of C. neoformans was impaired by the presence of cryptococcal capsule, since acapsular strain of C. neoformans were rapidly phagocytosed by neutrophils compared with encapsulated strain. Neutrophil phagocytosis of C. neoformans and subsequent accretion was mediated by complement C3 in both acapsular and encapsulated strains. Mice deficient in C3 complement showed reduced clearance of C. neoformans from the lungs and brain, compared to C3 sufficient mice. These findings highlight the importance of neutrophils in the control of C. neoformans in the pulmonary vasculature and subsequent dissemination to the distal organs including the brain.
    Type of Medium: Online Resource
    ISSN: 0022-1767 , 1550-6606
    URL: Article
    DOI: 10.4049/jimmunol.204.Supp.67.5
    RVK:
    XA 54100
    RVK:
    XA 10000
    Language: English
    Publisher: The American Association of Immunologists
    Publication Date: 2020
    detail.hit.zdb_id: 1475085-5
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  • 5
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    Online Resource
    Distinctive signalling in NK cells during cytotoxicity to the yeast Cryptococcus neoformans
    The American Association of Immunologists ; 2016
    In:  The Journal of Immunology Vol. 196, No. 1_Supplement ( 2016-05-01), p. 135.12-135.12
    Details
    In: The Journal of Immunology, The American Association of Immunologists, Vol. 196, No. 1_Supplement ( 2016-05-01), p. 135.12-135.12
    Abstract: Cryptococcus is a fungal pathogen that subverts the adaptive immune response. Fortunately, NK cells are capable of directly recognizing, triggering cytotoxicity and killing Cryptococcus. Although, NK cytotoxicity against tumor and virally infected targets are well studied, less is known about anti-fungal signaling. In this study, we investigated a novel NK cytotoxicity pathway involving Rac, Src family kinases (SFK), and integrins. Methods The involvement of Rac, SFK, integrin-linked kinase (ILK), and integrins were explored using small molecule inhibitors, siRNA knockdown, activated Rac pull down assays, and immunoblots. Results Our studies found that Cryptococcus activated both SFK and Rac signaling pathways. Small molecule inhibitors of SFK and Rac blocked Erk and PI3K activity. siRNA knockdown of Rac also inhibited PI3K activity, suggesting that Rac was an upstream non-canonical activator of PI3K. Moreover, individually Rac and SFK were not sufficient for activation of PI3K. Inhibition of Rac also resulted in a 90% loss of anti-cryptococcal cytotoxicity. Additionally, inhibitors of ILK prevented Rac activation and caused an 80% reduction in cryptococcal killing. Lastly, siRNA knockdown of beta-1 integrins caused an inhibition of ILK activation and 50% reduction in cryptococcal killing. Conclusion We found beta-1 integrins to be a fungal receptor and Rac an activator of PI3K. These findings build a signaling model of anti-fungal killing that is different from the canonical tumor killing model that involves beta-2 integrins and Rac downstream of PI3K. Our model provides various potential therapeutic targets that could enhance fungal clearance mediated by the innate immune system.
    Type of Medium: Online Resource
    ISSN: 0022-1767 , 1550-6606
    URL: Article
    DOI: 10.4049/jimmunol.196.Supp.135.12
    RVK:
    XA 54100
    RVK:
    XA 10000
    Language: English
    Publisher: The American Association of Immunologists
    Publication Date: 2016
    detail.hit.zdb_id: 1475085-5
    Library Location Call Number Volume/Issue/Year Availability
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