Rim Pathway-Mediated Alterations in the Fungal Cell Wall Influence Immune Recognition and Inflammation

ABSTRACT Compared to other fungal pathogens, Cryptococcus neoformans is particularly adept at avoiding detection by innate immune cells. To explore fungal cellular features involved in immune avoidance, we characterized cell surface changes of the C. neoformans rim101Δ mutant, a strain that fails to...

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Autores principales:	Kyla S. Ost, Shannon K. Esher, Chrissy M. Leopold Wager, Louise Walker, Jeanette Wagener, Carol Munro, Floyd L. Wormley, J. Andrew Alspaugh
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2017
Materias:	Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/0ebb86e885204bba94fcdc384f483b88
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spelling	oai:doaj.org-article:0ebb86e885204bba94fcdc384f483b882021-11-15T15:51:06ZRim Pathway-Mediated Alterations in the Fungal Cell Wall Influence Immune Recognition and Inflammation10.1128/mBio.02290-162150-7511https://doaj.org/article/0ebb86e885204bba94fcdc384f483b882017-03-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.02290-16https://doaj.org/toc/2150-7511ABSTRACT Compared to other fungal pathogens, Cryptococcus neoformans is particularly adept at avoiding detection by innate immune cells. To explore fungal cellular features involved in immune avoidance, we characterized cell surface changes of the C. neoformans rim101Δ mutant, a strain that fails to organize and shield immunogenic epitopes from host detection. These cell surface changes are associated with an exaggerated, detrimental inflammatory response in mouse models of infection. We determined that the disorganized strain rim101Δ cell wall increases macrophage detection in a contact-dependent manner. Using biochemical and microscopy methods, we demonstrated that the rim101Δ strain shows a modest increase in the levels of both cell wall chitin and chitosan but that it shows a more dramatic increase in chito-oligomer exposure, as measured by wheat germ agglutinin staining. We also created a series of mutants with various levels of cell wall wheat germ agglutinin staining, and we demonstrated that the staining intensity correlates with the degree of macrophage activation in response to each strain. To explore the host receptors responsible for recognizing the rim101Δ mutant, we determined that both the MyD88 and CARD9 innate immune signaling proteins are involved. Finally, we characterized the immune response to the rim101Δ mutant in vivo, documenting a dramatic and sustained increase in Th1 and Th17 cytokine responses. These results suggest that the Rim101 transcription factor actively regulates the C. neoformans cell wall to prevent the exposure of immune stimulatory molecules within the host. These studies further explored the ways in which immune cells detect C. neoformans and other fungal pathogens by mechanisms that include sensing N-acetylglucosamine-containing structures, such as chitin and chitosan. IMPORTANCE Infectious microorganisms have developed many ways to avoid recognition by the host immune system. For example, pathogenic fungi alter their cell surfaces to mask immunogenic epitopes. We have created a fungal strain with a targeted mutation in a pH response pathway that is unable to properly organize its cell wall, resulting in a dramatic immune reaction during infection. This mutant cell wall is defective in hiding important cell wall components, such as the chito-oligomers chitin and chitosan. By creating a series of cell wall mutants, we demonstrated that the degree of chito-oligomer exposure correlates with the intensity of innate immune cell activation. This activation requires a combination of host receptors to recognize and respond to these infecting microorganisms. Therefore, these experiments explored host-pathogen interactions that determine the degree of the subsequent inflammatory response and the likely outcome of infection.Kyla S. OstShannon K. EsherChrissy M. Leopold WagerLouise WalkerJeanette WagenerCarol MunroFloyd L. WormleyJ. Andrew AlspaughAmerican Society for MicrobiologyarticleMicrobiologyQR1-502ENmBio, Vol 8, Iss 1 (2017)
institution	DOAJ
collection	DOAJ
language	EN
topic	Microbiology QR1-502
spellingShingle	Microbiology QR1-502 Kyla S. Ost Shannon K. Esher Chrissy M. Leopold Wager Louise Walker Jeanette Wagener Carol Munro Floyd L. Wormley J. Andrew Alspaugh Rim Pathway-Mediated Alterations in the Fungal Cell Wall Influence Immune Recognition and Inflammation
description	ABSTRACT Compared to other fungal pathogens, Cryptococcus neoformans is particularly adept at avoiding detection by innate immune cells. To explore fungal cellular features involved in immune avoidance, we characterized cell surface changes of the C. neoformans rim101Δ mutant, a strain that fails to organize and shield immunogenic epitopes from host detection. These cell surface changes are associated with an exaggerated, detrimental inflammatory response in mouse models of infection. We determined that the disorganized strain rim101Δ cell wall increases macrophage detection in a contact-dependent manner. Using biochemical and microscopy methods, we demonstrated that the rim101Δ strain shows a modest increase in the levels of both cell wall chitin and chitosan but that it shows a more dramatic increase in chito-oligomer exposure, as measured by wheat germ agglutinin staining. We also created a series of mutants with various levels of cell wall wheat germ agglutinin staining, and we demonstrated that the staining intensity correlates with the degree of macrophage activation in response to each strain. To explore the host receptors responsible for recognizing the rim101Δ mutant, we determined that both the MyD88 and CARD9 innate immune signaling proteins are involved. Finally, we characterized the immune response to the rim101Δ mutant in vivo, documenting a dramatic and sustained increase in Th1 and Th17 cytokine responses. These results suggest that the Rim101 transcription factor actively regulates the C. neoformans cell wall to prevent the exposure of immune stimulatory molecules within the host. These studies further explored the ways in which immune cells detect C. neoformans and other fungal pathogens by mechanisms that include sensing N-acetylglucosamine-containing structures, such as chitin and chitosan. IMPORTANCE Infectious microorganisms have developed many ways to avoid recognition by the host immune system. For example, pathogenic fungi alter their cell surfaces to mask immunogenic epitopes. We have created a fungal strain with a targeted mutation in a pH response pathway that is unable to properly organize its cell wall, resulting in a dramatic immune reaction during infection. This mutant cell wall is defective in hiding important cell wall components, such as the chito-oligomers chitin and chitosan. By creating a series of cell wall mutants, we demonstrated that the degree of chito-oligomer exposure correlates with the intensity of innate immune cell activation. This activation requires a combination of host receptors to recognize and respond to these infecting microorganisms. Therefore, these experiments explored host-pathogen interactions that determine the degree of the subsequent inflammatory response and the likely outcome of infection.
format	article
author	Kyla S. Ost Shannon K. Esher Chrissy M. Leopold Wager Louise Walker Jeanette Wagener Carol Munro Floyd L. Wormley J. Andrew Alspaugh
author_facet	Kyla S. Ost Shannon K. Esher Chrissy M. Leopold Wager Louise Walker Jeanette Wagener Carol Munro Floyd L. Wormley J. Andrew Alspaugh
author_sort	Kyla S. Ost
title	Rim Pathway-Mediated Alterations in the Fungal Cell Wall Influence Immune Recognition and Inflammation
title_short	Rim Pathway-Mediated Alterations in the Fungal Cell Wall Influence Immune Recognition and Inflammation
title_full	Rim Pathway-Mediated Alterations in the Fungal Cell Wall Influence Immune Recognition and Inflammation
title_fullStr	Rim Pathway-Mediated Alterations in the Fungal Cell Wall Influence Immune Recognition and Inflammation
title_full_unstemmed	Rim Pathway-Mediated Alterations in the Fungal Cell Wall Influence Immune Recognition and Inflammation
title_sort	rim pathway-mediated alterations in the fungal cell wall influence immune recognition and inflammation
publisher	American Society for Microbiology
publishDate	2017
url	https://doaj.org/article/0ebb86e885204bba94fcdc384f483b88
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Rim Pathway-Mediated Alterations in the Fungal Cell Wall Influence Immune Recognition and Inflammation

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