scholarly journals Cryptococcus neoformans Chitin Synthase 3 Plays a Critical Role in Dampening Host Inflammatory Responses

mBio ◽  
2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Camaron R. Hole ◽  
Woei C. Lam ◽  
Rajendra Upadhya ◽  
Jennifer K. Lodge
Keyword(s):  
Immune Response ◽  
Cell Wall ◽  
Cryptococcus Neoformans ◽  
Inflammatory Responses ◽  
Pathogenic Fungi ◽  
Fungal Cell Wall ◽  
Chitin Synthase ◽  
Aids Patients ◽  
Fungal Cell ◽  
Content Type

ABSTRACT Cryptococcus neoformans infections are significant causes of morbidity and mortality among AIDS patients and the third most common invasive fungal infection in organ transplant recipients. One of the main interfaces between the fungus and the host is the fungal cell wall. The cryptococcal cell wall is unusual among human-pathogenic fungi in that the chitin is predominantly deacetylated to chitosan. Chitosan-deficient strains of C. neoformans were found to be avirulent and rapidly cleared from the murine lung. Moreover, infection with a chitosan-deficient C. neoformans strain lacking three chitin deacetylases (cda1Δcda2Δcda3Δ) was found to confer protective immunity to a subsequent challenge with a virulent wild-type counterpart. In addition to the chitin deacetylases, it was previously shown that chitin synthase 3 (Chs3) is also essential for chitin deacetylase-mediated formation of chitosan. Mice inoculated with the chs3Δ strain at a dose previously shown to induce protection with the cda1Δcda2Δcda3Δ strain die within 36 h after installation of the organism. Mortality was not dependent on viable fungi, as mice inoculated with a heat-killed preparation of the chs3Δ strain died at the same rate as mice inoculated with a live chs3Δ strain, suggesting that the rapid onset of death was host mediated, likely caused by an overexuberant immune response. Histology, cytokine profiling, and flow cytometry indicate a massive neutrophil influx in the mice inoculated with the chs3Δ strain. Mice depleted of neutrophils survived chs3Δ inoculation, indicating that death was neutrophil mediated. Altogether, these studies lead us to conclude that Chs3, along with chitosan, plays critical roles in dampening cryptococcus-induced host inflammatory responses. IMPORTANCE Cryptococcus neoformans is the most common disseminated fungal pathogen in AIDS patients, resulting in ∼200,000 deaths each year. There is a pressing need for new treatments for this infection, as current antifungal therapy is hampered by toxicity and/or the inability of the host’s immune system to aid in resolution of the disease. An ideal target for new therapies is the fungal cell wall. The cryptococcal cell wall is different from the cell walls of many other pathogenic fungi in that it contains chitosan. Strains that have decreased chitosan are less pathogenic and strains that are deficient in chitosan are avirulent and can induce protective responses. In this study, we investigated the host responses to a chs3Δ strain, a chitosan-deficient strain, and found that mice inoculated with the chs3Δ strain all died within 36 h and that death was associated with an aberrant hyperinflammatory immune response driven by neutrophils, indicating that chitosan is critical in modulating the immune response to Cryptococcus.

scholarly journals Cryptococcus neoformans Chitin Synthase 3 (Chs3) Plays a Critical Role in Dampening Host Inflammatory Responses

2019 ◽  
Author(s):  
Camaron R. Hole ◽  
Woei C. Lam ◽  
Rajendra Upadhya ◽  
Jennifer K. Lodge
Keyword(s):  
Immune Response ◽  
Cell Wall ◽  
Cryptococcus Neoformans ◽  
Inflammatory Responses ◽  
Critical Role ◽  
Pathogenic Fungi ◽  
Fungal Cell Wall ◽  
Chitin Synthase ◽  
Aids Patients ◽  
Fungal Cell

ABSTRACTCryptococcus neoformans infections are significant causes of morbidity and mortality among AIDS patients and the third most common invasive fungal infection in organ transplant recipients. One of the main interfaces between the fungus and the host is the fungal cell wall. The cryptococcal cell wall is unusual among human pathogenic fungi in that the chitin is predominantly deacetylated to chitosan. Chitosan deficient strains of C. neoformans were found to be avirulent and rapidly cleared from the murine lung. Moreover, infection with a chitosan deficient C. neoformans lacking three chitin deacetylases (cda1Δ2Δ3Δ) was found to confer protective immunity to a subsequent challenge with a virulent wild type counterpart. In addition to the chitin deacetylases, it was previously shown that chitin synthase 3 (Chs3) is also essential for chitin deacetylase mediated formation of chitosan. Mice inoculated with chs3Δ at a dose previously shown to induce protection with cda1Δ2Δ3Δ die within 36 hours after installation of the organism. Mortality was not dependent on viable fungi as mice inoculated with heat-killed preparation of chs3Δ died at the same rate as mice inoculated with live chs3Δ, suggesting the rapid onset of death was host mediated likely caused by an over exuberant immune response. Histology, cytokine profiling, and flow cytometry indicates a massive neutrophil influx in the mice inoculated with chs3Δ. Mice depleted of neutrophils survived chs3Δ inoculation indicating that death was neutrophil mediated. Altogether, these studies lead us to conclude that Chs3, along with chitosan, plays critical roles in dampening cryptococcal induced host inflammatory responses.IMPORTANCECryptococcus neoformans is the most common disseminated fungal pathogen in AIDS patients, resulting in ∼200,000 deaths each year. There is a pressing need for new treatments for this infection, as current antifungal therapy is hampered by toxicity and/or the inability of the host’s immune system to aid in resolution of the disease. An ideal target for new therapies is the fungal cell wall. The cryptococcal cell wall is different than many other pathogenic fungi in that it contains chitosan. Strains that have decreased chitosan are less pathogenic and strains that are deficient in chitosan are avirulent and can induce protective responses. In this study we investigated the host responses to chs3Δ, a chitosan-deficient strain, and found mice inoculated with chs3Δ all died within 36 hours and death was associated with an aberrant hyperinflammatory immune response driven by neutrophils, indicating that chitosan is critical in modulating the immune response to Cryptococcus.

scholarly journals Potential of Chemically Synthesized Oligosaccharides To Define the Carbohydrate Moieties of the Fungal Cell Wall Responsible for the Human Immune Response, Using Aspergillus fumigatus Galactomannan as a Model

mSphere ◽  
2020 ◽  
Vol 5 (1) ◽  
Author(s):  
Sarah Sze Wah Wong ◽  
Vadim B. Krylov ◽  
Dmitry A. Argunov ◽  
Alexander A. Karelin ◽  
Jean-Phillipe Bouchara ◽  
...  
Keyword(s):  
Immune Response ◽  
Cell Wall ◽  
Aspergillus Fumigatus ◽  
Fungal Cell Wall ◽  
Human Pathogens ◽  
Cell Wall Polysaccharides ◽  
Fungal Cell ◽  
Content Type ◽  
Human Immune Response ◽  
Synthetic Oligosaccharides

ABSTRACT Methodologies to identify epitopes or ligands of the fungal cell wall polysaccharides influencing the immune response of human pathogens have to date been imperfect. Using the galactomannan (GM) of Aspergillus fumigatus as a model, we have shown that synthetic oligosaccharides of distinct structures representing key fragments of cell wall polysaccharides are the most precise tools to study the serological and immunomodulatory properties of a fungal polysaccharide.

scholarly journals Chitosan Biosynthesis and Virulence in the Human Fungal Pathogen Cryptococcus gattii

mSphere ◽  
2019 ◽  
Vol 4 (5) ◽  
Author(s):  
Woei C. Lam ◽  
Rajendra Upadhya ◽  
Charles A. Specht ◽  
Abigail E. Ragsdale ◽  
Camaron R. Hole ◽  
...  
Keyword(s):  
Cell Wall ◽  
Fungal Pathogen ◽  
Cryptococcus Gattii ◽  
Fungal Cell Wall ◽  
Fungal Pathogenesis ◽  
Protective Response ◽  
Fungal Cell ◽  
Fungal Virulence ◽  
Content Type ◽  
Mammalian Infection

ABSTRACT Cryptococcus gattii R265 is a hypervirulent fungal strain responsible for the recent outbreak of cryptococcosis in Vancouver Island of British Columbia in Canada. It differs significantly from Cryptococcus neoformans in its natural environment, its preferred site in the mammalian host, and its pathogenesis. Our previous studies of C. neoformans have shown that the presence of chitosan, the deacetylated form of chitin, in the cell wall attenuates inflammatory responses in the host, while its absence induces robust immune responses, which in turn facilitate clearance of the fungus and induces a protective response. The results of the present investigation reveal that the cell wall of C. gattii R265 contains a two- to threefold larger amount of chitosan than that of C. neoformans. The genes responsible for the biosynthesis of chitosan are highly conserved in the R265 genome; the roles of the three chitin deacetylases (CDAs) have, however, been modified. To deduce their roles, single and double CDA deletion strains and a triple CDA deletion strain were constructed in a R265 background and were subjected to mammalian infection studies. Unlike C. neoformans where Cda1 has a discernible role in fungal pathogenesis, in strain R265, Cda3 is critical for virulence. Deletion of either CDA3 alone or in combination with another CDA (cda1Δ3Δ or cda2Δ3Δ) or both (cda1Δ2Δ3Δ) rendered the fungus avirulent and cleared from the infected host. Moreover, the cda1Δ2Δ3Δ strain of R265 induced a protective response to a subsequent infection with R265. These studies begin to illuminate the regulation of chitosan biosynthesis of C. gattii and its subsequent effect on fungal virulence. IMPORTANCE The fungal cell wall is an essential organelle whose components provide the first line of defense against host-induced antifungal activity. Chitosan is one of the carbohydrate polymers in the cell wall that significantly affects the outcome of host-pathogen interaction. Chitosan-deficient strains are avirulent, implicating chitosan as a critical virulence factor. C. gattii R265 is an important fungal pathogen of concern due to its ability to cause infections in individuals with no apparent immune dysfunction and an increasing geographical distribution. Characterization of the fungal cell wall and understanding the contribution of individual molecules of the cell wall matrix to fungal pathogenesis offer new therapeutic avenues for intervention. In this report, we show that the C. gattii R265 strain has evolved alternate regulation of chitosan biosynthesis under both laboratory growth conditions and during mammalian infection compared to that of C. neoformans.

scholarly journals Interaction of Cryptococcus neoformans Extracellular Vesicles with the Cell Wall

2014 ◽  
Vol 13 (12) ◽  
pp. 1484-1493 ◽  
Author(s):  
Julie M. Wolf ◽  
Javier Espadas-Moreno ◽  
Jose L. Luque-Garcia ◽  
Arturo Casadevall
Keyword(s):  
Cell Wall ◽  
Plasma Membrane ◽  
Cryptococcus Neoformans ◽  
Extracellular Vesicles ◽  
Protein Composition ◽  
Multivesicular Body ◽  
Dense Matrix ◽  
Fungal Cell ◽  
Content Type ◽  
Pass Through

ABSTRACTCryptococcus neoformansproduces extracellular vesicles containing a variety of cargo, including virulence factors. To become extracellular, these vesicles not only must be released from the plasma membrane but also must pass through the dense matrix of the cell wall. The greatest unknown in the area of fungal vesicles is the mechanism by which these vesicles are released to the extracellular space given the presence of the fungal cell wall. Here we used electron microscopy techniques to image the interactions of vesicles with the cell wall. Our goal was to define the ultrastructural morphology of the process to gain insights into the mechanisms involved. We describe single and multiple vesicle-leaving events, which we hypothesized were due to plasma membrane and multivesicular body vesicle origins, respectively. We further utilized melanized cells to “trap” vesicles and visualize those passing through the cell wall. Vesicle size differed depending on whether vesicles left the cytoplasm in single versus multiple release events. Furthermore, we analyzed different vesicle populations for vesicle dimensions and protein composition. Proteomic analysis tripled the number of proteins known to be associated with vesicles. Despite separation of vesicles into batches differing in size, we did not identify major differences in protein composition. In summary, our results indicate that vesicles are generated by more than one mechanism, that vesicles exit the cell by traversing the cell wall, and that vesicle populations exist as a continuum with regard to size and protein composition.

scholarly journals Protein Kinase A and High-Osmolarity Glycerol Response Pathways Cooperatively Control Cell Wall Carbohydrate Mobilization inAspergillus fumigatus

mBio ◽  
2018 ◽  
Vol 9 (6) ◽  
Author(s):  
Leandro José de Assis ◽  
Adriana Manfiolli ◽  
Eliciane Mattos ◽  
João H. T. Marilhano Fabri ◽  
Iran Malavazi ◽  
...  
Keyword(s):  
Cell Wall ◽  
Protein Kinase ◽  
Glycogen Synthesis ◽  
Fungal Cell Wall ◽  
Cell Wall Biosynthesis ◽  
Fungal Cell ◽  
Content Type ◽  
High Osmolarity ◽  
High Osmolarity Glycerol ◽  
Kinase A

ABSTRACTAspergillus fumigatusmitogen-activated protein kinases (MAPKs) are involved in maintaining the normal morphology of the cell wall and providing resistance against cell wall-damaging agents. Upon cell wall stress, cell wall-related sugars need to be synthesized from carbohydrate storage compounds. Here we show that this process is dependent on cAMP-dependent protein kinase A (PKA) activity and regulated by the high-osmolarity glycerol response (HOG) MAPKs SakA and MpkC. These protein kinases are necessary for normal accumulation/degradation of trehalose and glycogen, and the lack of these genes reduces glucose uptake and glycogen synthesis. Alterations in glycogen synthesis were observed for thesakAandmpkCdeletion mutants, which also displayed alterations in carbohydrate exposure on the cell wall. Carbohydrate mobilization is controlled by SakA interaction with PkaC1 and PkaR, suggesting a putative mechanism where the PkaR regulatory subunit leaves the complex and releases the SakA-PkaC1 complex for activation of enzymes involved in carbohydrate mobilization. This work reveals the communication between the HOG and PKA pathways for carbohydrate mobilization for cell wall construction.IMPORTANCEAspergillus fumigatusis an opportunistic human pathogen causing allergic reactions or systemic infections such as invasive pulmonary aspergillosis, especially in immunocompromised patients. The fungal cell wall is the main component responsible for recognition by the immune system, due to the specific composition of polysaccharide carbohydrates exposed on the surface of the fungal cell wall called pathogen-associated molecular patterns (PAMPs). Key enzymes in the fungal cell wall biosynthesis are a good target for fungal drug development. This report elucidates the cooperation between the HOG and PKA pathways in the mobilization of carbohydrates for fungal cell wall biosynthesis. We suggest that the reduced mobilization of simple sugars causes defects in the structure of the fungal cell wall. In summary, we propose that SakA is important for PKA activity, therefore regulating the availability and mobilization of monosaccharides for fungal cell wall biosynthesis during cell wall damage and the osmotic stress response.

scholarly journals Pulmonary Iron Limitation Induced by Exogenous Type I IFN Protects Mice fromCryptococcus gattiiIndependently of T Cells

mBio ◽  
2019 ◽  
Vol 10 (3) ◽  
Author(s):  
Michael J. Davis ◽  
Shannon Moyer ◽  
Elizabeth S. Hoke ◽  
Edward Sionov ◽  
Katrin D. Mayer-Barber ◽  
...  
Keyword(s):  
Immune Response ◽  
T Cell ◽  
Cryptococcus Neoformans ◽  
Cryptococcus Gattii ◽  
Iron Limitation ◽  
Type I ◽  
Type I Ifn ◽  
Aids Patients ◽  
Content Type ◽  
Immune Pathways

ABSTRACTCryptococcus neoformanscauses deadly mycosis primarily in AIDS patients, whereasCryptococcus gattiiinfects mostly non-HIV patients, even in regions with high burdens of HIV/AIDS and an established environmental presence ofC. gattii. As HIV induces type I IFN (t1IFN), we hypothesized that t1IFN would differentially affect the outcome ofC. neoformansandC. gattiiinfections. Exogenous t1IFN induction using stabilized poly(I·C) (pICLC) improved murine outcomes in either cryptococcal infection. InC. neoformans-infected mice, pICLC activity was associated withC. neoformanscontainment and classical Th1 immunity. In contrast, pICLC activity againstC. gattiidid not require any immune factors previously associated withC. neoformansimmunity: T, B, and NK cells, IFN-γ, and macrophages were all dispensable. Interestingly,C. gattiipICLC activity depended on β-2-microglobulin, which impacts iron levels among other functions. Iron supplementation reversed pICLC activity, suggestingC. gattiipICLC activity requires iron limitation. Also, pICLC induced a set of iron control proteins, some of which were directly inhibitory to cryptococcusin vitro, suggesting t1IFN regulates iron availability in the pulmonary air space fluids. Thus, exogenous induction of t1IFN significantly improves the outcome of murine infection byC. gattiiandC. neoformansbut by distinct mechanisms; theC. gattiieffect was mediated by iron limitation, while the effect onC. neoformansinfection was through induction of classical T-cell-dependent immunity. Together this difference in types of T-cell-dependent t1IFN immunity for differentCryptococcusspecies suggests a possible mechanism by which HIV infection may select againstC. gattiibut notC. neoformans.IMPORTANCECryptococcus neoformansandCryptococcus gattiicause fatal infection in immunodeficient and immunocompetent individuals. While these fungi are sibling species,C. gattiiinfects very few AIDS patients, whileC. neoformansinfection is an AIDS-defining illness, suggesting that the host response to HIV selectsC. neoformansoverC. gattii. We used a viral mimic molecule (pICLC) to stimulate the immune response, and pICLC treatment improved mouse outcomes from both species. pICLC-induced action againstC. neoformanswas due to activation of well-defined immune pathways known to deterC. neoformans, whereas these immune pathways were dispensable for pICLC treatment ofC. gattii. Since these immune pathways are eventually destroyed by HIV/AIDS, our data help explain why the antiviral immune response in AIDS patients is unable to controlC. neoformansinfection but is protective againstC. gattii. Furthermore, pICLC induced tighter control of iron in the lungs of mice, which inhibitedC. gattii, thus suggesting an entirely new mode of nutritional immunity activated by viral signals.

Sign in / Sign up

Export Citation Format

Share Document