scholarly journals Rab3D Regulates a Novel Vesicular Trafficking Pathway That Is Required for Osteoclastic Bone Resorption

2005 ◽  
Vol 25 (12) ◽  
pp. 5253-5269 ◽  
Author(s):  
Nathan J. Pavlos ◽  
Jiake Xu ◽  
Dietmar Riedel ◽  
Joyce S. G. Yeoh ◽  
Steven L. Teitelbaum ◽  
...  
Keyword(s):  
Bone Resorption ◽  
Vesicular Trafficking ◽  
Osteoclastic Bone Resorption ◽  
Wild Type ◽  
Trafficking Pathway ◽  
Golgi Network ◽  
Deficient Mice ◽  
Constitutively Active

ABSTRACT Rab3 proteins are a subfamily of GTPases, known to mediate membrane transport in eukaryotic cells and play a role in exocytosis. Our data indicate that Rab3D is the major Rab3 species expressed in osteoclasts. To investigate the role of Rab3D in osteoclast physiology we examined the skeletal architecture of Rab3D-deficient mice and found an osteosclerotic phenotype. Although basal osteoclast number in null animals is normal the total eroded surface is significantly reduced, suggesting that the resorptive defect is due to attenuated osteoclast activity. Consistent with this hypothesis, ultrastructural analysis reveals that Rab3D−/− osteoclasts exhibit irregular ruffled borders. Furthermore, while overexpression of wild-type, constitutively active, or prenylation-deficient Rab3D has no significant effects, overexpression of GTP-binding-deficient Rab3D impairs bone resorption in vitro. Finally, subcellular localization studies reveal that, unlike wild-type or constitutively active Rab3D, which associate with a nonendosomal/lysosomal subset of post-trans-Golgi network (TGN) vesicles, inactive Rab3D localizes to the TGN and inhibits biogenesis of Rab3D-bearing vesicles. Collectively, our data suggest that Rab3D modulates a post-TGN trafficking step that is required for osteoclastic bone resorption.

scholarly journals Osteopontin Deficiency Produces Osteoclast Dysfunction Due to Reduced CD44 Surface Expression

2003 ◽  
Vol 14 (1) ◽  
pp. 173-189 ◽  
Author(s):  
M. A. Chellaiah ◽  
N. Kizer ◽  
R. Biswas ◽  
U. Alvarez ◽  
J. Strauss-Schoenberger ◽  
...  
Keyword(s):  
Bone Resorption ◽  
Surface Expression ◽  
Wild Type ◽  
Exogenous Addition ◽  
Load To Failure ◽  
Ruffled Border ◽  
Osteoclast Function ◽  
Deficient Mice

Osteopontin (OPN) was expressed in murine wild-type osteoclasts, localized to the basolateral, clear zone, and ruffled border membranes, and deposited in the resorption pits during bone resorption. The lack of OPN secretion into the resorption bay of avian osteoclasts may be a component of their functional resorption deficiency in vitro. Osteoclasts deficient in OPN were hypomotile and exhibited decreased capacity for bone resorption in vitro. OPN stimulated CD44 expression on the osteoclast surface, and CD44 was shown to be required for osteoclast motility and bone resorption. Exogenous addition of OPN to OPN−/− osteoclasts increased the surface expression of CD44, and it rescued osteoclast motility due to activation of the αvβ3 integrin. Exogenous OPN only partially restored bone resorption because addition of OPN failed to produce OPN secretion into resorption bays as seen in wild-type osteoclasts. As expected with these in vitro findings of osteoclast dysfunction, a bone phenotype, heretofore unappreciated, was characterized in OPN-deficient mice. Delayed bone resorption in metaphyseal trabeculae and diminished eroded perimeters despite an increase in osteoclast number were observed in histomorphometric measurements of tibiae isolated from OPN-deficient mice. The histomorphometric findings correlated with an increase in bone rigidity and moment of inertia revealed by load-to-failure testing of femurs. These findings demonstrate the role of OPN in osteoclast function and the requirement for OPN as an osteoclast autocrine factor during bone remodeling.

scholarly journals ASXL2 Is Recurrently Mutated in t(8;21) AML and Regulates Hematopoietic Development

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 1051-1051
Author(s):  
Vikas Madan ◽  
Lin Han ◽  
Norimichi Hattori ◽  
Anand Mayakonda ◽  
Qiao-Yang Sun ◽  
...  
Keyword(s):  
Gene Expression ◽  
Bone Marrow ◽  
Research Funding ◽  
Hematopoietic Differentiation ◽  
Wild Type ◽  
Flow Cytometric ◽  
Deficient Mice

Abstract Chromosomal translocation t(8;21) (q22;q22) leading to generation of oncogenic RUNX1-RUNX1T1 fusion is a cytogenetic abnormality observed in about 10% of acute myelogenous leukemia (AML). Studies in animal models and recent next generation sequencing approaches have suggested cooperativity of secondary genetic lesions with t(8;21) in inducing leukemogenesis. In this study, we used targeted and whole exome sequencing of 93 cases (including 30 with matched relapse samples) to profile the mutational landscape of t(8;21) AML at initial diagnosis and post-therapy relapse. We identified recurrent mutations of KIT, TET2, MGA, FLT3, NRAS, DHX15, ASXL1 and KMT2Dgenes in this subtype of AML. In addition, high frequency of truncating alterations in ASXL2 gene (19%) also occurred in our cohort. ASXL2 is a member of mammalian ASXL family involved in epigenetic regulation through recruitment of polycomb or trithorax complexes. Unlike its closely related homolog ASXL1, which is mutated in several hematological malignancies including AML, MDS, MPN and others; mutations of ASXL2 occur specifically in t(8;21) AML. We observed that lentiviral shRNA-mediated silencing of ASXL2 impaired in vitro differentiation of t(8;21) AML cell line, Kasumi-1, and enhanced its colony forming ability. Gene expression analysis uncovered dysregulated expression of several key hematopoiesis genes such as IKZF2, JAG1, TAL1 and ARID5B in ASXL2 knockdown Kasumi-1 cells. Further, to investigate implications of loss of ASXL2 in vivo, we examined hematopoiesis in Asxl2 deficient mice. We observed an age-dependent increase in white blood cell count in the peripheral blood of Asxl2 KO mice. Myeloid progenitors from Asxl2 deficient mice possessed higher re-plating ability and displayed altered differentiation potential in vitro. Flow cytometric analysis of >1 year old mice revealed increased proportion of Lin-Sca1+Kit+ (LSK) cells in the bone marrow of Asxl2 deficient mice, while the overall bone marrow cellularity was significantly reduced. In vivo 5-bromo-2'-deoxyuridine incorporation assay showed increased cycling of LSK cells in mice lacking Asxl2. Asxl2 deficiency also led to perturbed maturation of myeloid and erythroid precursors in the bone marrow, which resulted in altered proportions of mature myeloid populations in spleen and peripheral blood. Further, splenomegaly was observed in old ASXL2 KO mice and histological and flow cytometric examination of ASXL2 deficient spleens demonstrated increased extramedullary hematopoiesis and myeloproliferation compared with the wild-type controls. Surprisingly, loss of ASXL2 also led to impaired T cell development as indicated by severe block in maturation of CD4-CD8- double negative (DN) population in mice >1 year old. These findings established a critical role of Asxl2 in maintaining steady state hematopoiesis. To gain mechanistic insights into its role during hematopoietic differentiation, we investigated changes in histone marks and gene expression affected by loss of Asxl2. Whole transcriptome sequencing of LSK population revealed dysregulated expression of key myeloid-specific genes including Mpo, Ltf, Ngp Ctsg, Camp and Csf1rin cells lacking Asxl2 compared to wild-type control. Asxl2 deficiency also caused changes in histone modifications, specifically H3K27 trimethylation levels were decreased and H2AK119 ubiquitination levels were increased in Asxl2 KO bone marrow cells. Global changes in histone marks in control and Asxl2 deficient mice are being investigated using ChIP-Sequencing. Finally, to examine cooperativity between the loss of Asxl2 and RUNX1-RUNX1T1 in leukemogenesis, KO and wild-type fetal liver cells were transduced with retrovirus expressing AML1-ETO 9a oncogene and transplanted into irradiated recipient mice, the results of this ongoing study will be discussed. Overall, our sequencing studies have identified ASXL2 as a gene frequently altered in t(8;21) AML. Functional studies in mouse model reveal that loss of ASXL2 causes defects in hematopoietic differentiation and leads to myeloproliferation, suggesting an essential role of ASXL2 in normal and malignant hematopoiesis. *LH and NH contributed equally Disclosures Ogawa: Takeda Pharmaceuticals: Consultancy, Research Funding; Sumitomo Dainippon Pharma: Research Funding; Kan research institute: Consultancy, Research Funding.

scholarly journals Apolipoprotein E receptor 2 is involved in the thrombotic complications in a murine model of the antiphospholipid syndrome

Blood ◽  
2011 ◽  
Vol 117 (4) ◽  
pp. 1408-1414 ◽  
Author(s):  
Zurina Romay-Penabad ◽  
Renan Aguilar-Valenzuela ◽  
Rolf T. Urbanus ◽  
Ronald H. W. M. Derksen ◽  
Maarten T. T. Pennings ◽  
...  
Keyword(s):  
Apolipoprotein E ◽  
Thrombus Formation ◽  
Convincing Evidence ◽  
Wild Type ◽  
Glycoprotein I ◽  
Thrombotic Complications ◽  
Deficient Mice ◽  
Pathogenic Effects

Abstract Antiphospholipid (aPL)/anti-β2 glycoprotein I (anti-β2GPI) antibodies stimulates tissue factor (TF) expression within vasculature and in blood cells, thereby leading to increased thrombosis. Several cellular receptors have been proposed to mediate these effects, but no convincing evidence for the involvement of a specific one has been provided. We investigated the role of Apolipoprotein E receptor 2 (ApoER2′) on the pathogenic effects of a patient-derived polyclonal aPL IgG preparation (IgG-APS), a murine anti-β2GPI monoclonal antibody (E7) and of a constructed dimeric β2GPI I (dimer), which in vitro mimics β2GPI-antibody immune complexes, using an animal model of thrombosis, and ApoER2-deficient (−/−) mice. In wild type mice, IgG-APS, E7 and the dimer increased thrombus formation, carotid artery TF activity as well as peritoneal macrophage TF activity/expression. Those pathogenic effects were significantly reduced in ApoER2 (−/−) mice. In addition, those effects induced by the IgG-APS, by E7 and by the dimer were inhibited by treatment of wild-type mice with soluble binding domain 1 of ApoER2 (sBD1). Altogether these data show that ApoER2 is involved in pathogenesis of antiphospholipids antibodies.

scholarly journals P-Selectin Glycoprotein Ligand 1 (Psgl-1) Is a Physiological Ligand for E-Selectin in Mediating T Helper 1 Lymphocyte Migration

2000 ◽  
Vol 192 (11) ◽  
pp. 1669-1676 ◽  
Author(s):  
Takako Hirata ◽  
Glenn Merrill-Skoloff ◽  
Melissa Aab ◽  
Jing Yang ◽  
Barbara C. Furie ◽  
...  
Keyword(s):  
Contact Hypersensitivity ◽  
Th1 Cells ◽  
Wild Type ◽  
T Helper ◽  
Lymphocyte Migration ◽  
T Helper 1 ◽  
Deficient Mice

P-selectin glycoprotein ligand 1 (PSGL-1) is a sialomucin expressed on leukocytes that mediates neutrophil rolling on the vascular endothelium. Here, the role of PSGL-1 in mediating lymphocyte migration was studied using mice lacking PSGL-1. In a contact hypersensitivity model, the infiltration of CD4+ T lymphocytes into the inflamed skin was reduced in PSGL-1–deficient mice. In vitro–generated T helper (Th)1 cells from PSGL-1–deficient mice did not bind to P-selectin and migrated less efficiently into the inflamed skin than wild-type Th1 cells. To assess the role of PSGL-1 in P- or E-selectin–mediated migration of Th1 cells, the cells were injected into E- or P-selectin–deficient mice. PSGL-1–deficient Th1 cells did not migrate into the inflamed skin of E-selectin–deficient mice, indicating that PSGL-1 on Th1 cells is the sole ligand for P-selectin in vivo. In contrast, PSGL-1–deficient Th1 cells migrated into the inflamed skin of P-selectin–deficient mice, although less efficiently than wild-type Th1 cells. This E-selectin–mediated migration of PSGL-1–deficient or wild-type Th1 cells was not altered by injecting a blocking antibody to L-selectin. These data provide evidence that PSGL-1 on Th1 cells functions as one of the E-selectin ligands in vivo.

scholarly journals The Functional Paradox of CD43 in Leukocyte Recruitment: A Study Using CD43-deficient Mice

1998 ◽  
Vol 188 (11) ◽  
pp. 2181-2186 ◽  
Author(s):  
Richard C. Woodman ◽  
Brent Johnston ◽  
Michael J. Hickey ◽  
Diane Teoh ◽  
Paul Reinhardt ◽  
...  
Keyword(s):  
Platelet Activating Factor ◽  
Flow Chamber ◽  
Cell Interactions ◽  
Dual Function ◽  
Wild Type ◽  
Flow Conditions ◽  
Deficient Mice

Although there is considerable evidence implicating a role for CD43 (leukosialin) in leukocyte cell–cell interactions, its precise function remains uncertain. Using CD43-deficient mice (CD43−/−) and intravital microscopy to directly visualize leukocyte interactions in vivo, we investigated the role of CD43 in leukocyte–endothelial cell interactions within the cremasteric microcirculation under flow conditions. Our studies demonstrated significantly enhanced leukocyte rolling and adhesion after chemotactic stimuli in CD43−/− mice compared with wild type mice. Using an in vitro flow chamber, we established that the enhanced rolling interactions of CD43−/− leukocytes, primarily neutrophils, were also observed using immobilized E-selectin as a substrate, suggesting that passive processes related to steric hindrance or charge repulsion were likely mechanisms. Despite increased adhesion and rolling interactions by CD43−/− leukocytes, we uncovered a previously unrecognized impairment of CD43−/− leukocytes to infiltrate tissues. Oyster glycogen–induced neutrophil and monocyte infiltration into the peritoneum was significantly reduced in CD43−/− mice. In response to platelet activating factor, CD43−/− leukocytes were impaired in their ability to emigrate out of the vasculature. These results suggest that leukocyte CD43 has a dual function in leukocyte–endothelial interactions. In addition to its role as a passive nonspecific functional barrier, CD43 also facilitates emigration of leukocytes into tissues.

scholarly journals Effects of Erythromycin on Osteoclasts and Bone Resorption via DEL-1 Induction in Mice

Antibiotics ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 312
Author(s):  
Hikaru Tamura ◽  
Tomoki Maekawa ◽  
Hisanori Domon ◽  
Takumi Hiyoshi ◽  
Satoru Hirayama ◽  
...  
Keyword(s):  
Gene Expression ◽  
Bone Resorption ◽  
Bone Loss ◽  
Alveolar Bone ◽  
Dependent Manner ◽  
Wild Type ◽  
Immunomodulatory Effects ◽  
Related Factors ◽  
Deficient Mice

Macrolides are used to treat various infectious diseases, including periodontitis. Furthermore, macrolides are known to have immunomodulatory effects; however, the underlying mechanism of their action remains unclear. DEL-1 has emerged as an important factor in homeostatic immunity and osteoclastogenesis. Specifically, DEL-1 is downregulated in periodontitis tissues. Therefore, in the present study, we investigated whether the osteoclastogenesis inhibitory effects of erythromycin (ERM) are mediated through upregulation of DEL-1 expression. We used a ligature-induced periodontitis model in C57BL/6Ncrl wild-type or DEL-1-deficient mice and in vitro cell-based mechanistic studies to investigate how ERM inhibits alveolar bone resorption. As a result of measuring alveolar bone resorption and gene expression in the tooth ligation model, ERM treatment reduced bone loss by increasing DEL-1 expression and decreasing the expression of osteoclast-related factors in wild-type mice. In DEL-1-deficient mice, ERM failed to suppress bone loss and gene expression of osteoclast-related factors. In addition, ERM treatment downregulated osteoclast differentiation and calcium resorption in in vitro experiments with mouse bone marrow-derived macrophages. In conclusion, ERM promotes the induction of DEL-1 in periodontal tissue, which may regulate osteoclastogenesis and decrease inflammatory bone resorption. These findings suggest that ERM may exert immunomodulatory effects in a DEL-1-dependent manner.

scholarly journals Analysis of mice carrying targeted mutations of the glucocorticoid receptor gene argues against an essential role of glucocorticoid signalling for generating adrenal chromaffin cells

Development ◽  
1999 ◽  
Vol 126 (13) ◽  
pp. 2935-2944 ◽  
Author(s):  
S. Finotto ◽  
K. Krieglstein ◽  
A. Schober ◽  
F. Deimling ◽  
K. Lindner ◽  
...  
Keyword(s):  
Glucocorticoid Receptor ◽  
Chromaffin Cells ◽  
Essential Role ◽  
Adrenal Chromaffin Cells ◽  
Wild Type ◽  
Sympathetic Neurones ◽  
Adrenal Chromaffin ◽  
Deficient Mice

Molecular mechanisms underlying the generation of distinct cell phenotypes is a key issue in developmental biology. A major paradigm of determination of neural cell fate concerns the development of sympathetic neurones and neuroendocrine chromaffin cells from a common sympathoadrenal (SA) progenitor cell. Two decades of in vitro experiments have suggested an essential role of glucocorticoid receptor (GR)-mediated signalling in generating chromaffin cells. Targeted mutation of the GR should consequently abolish chromaffin cells. The present analysis of mice lacking GR gene product demonstrates that animals have normal numbers of adrenal chromaffin cells. Moreover, there are no differences in terms of apoptosis and proliferation or in expression of several markers (e.g. GAP43, acetylcholinesterase, adhesion molecule L1) of chromaffin cells in GR-deficient and wild-type mice. However, GR mutant mice lack the adrenaline-synthesizing enzyme PNMT and secretogranin II. Chromaffin cells of GR-deficient mice exhibit the typical ultrastructural features of this cell phenotype, including the large chromaffin granules that distinguish them from sympathetic neurones. Peripherin, an intermediate filament of sympathetic neurones, is undetectable in chromaffin cells of GR mutants. Finally, when stimulated with nerve growth factor in vitro, identical proportions of chromaffin cells from GR-deficient and wild-type mice extend neuritic processes. We conclude that important phenotypic features of chromaffin cells that distinguish them from sympathetic neurones develop normally in the absence of GR-mediated signalling. Most importantly, chromaffin cells in GR-deficient mice do not convert to a neuronal phenotype. These data strongly suggest that the dogma of an essential role of glucocorticoid signalling for the development of chromaffin cells must be abandoned.

Bone Marrow Failure in RPS19-Deficient Mice Is Partly Caused by p53 Activation and Responds to L-Leucine Treatment

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 727-727
Author(s):  
Pekka Jaako ◽  
Shubhranshu Debnath ◽  
Karin Olsson ◽  
Johan Flygare ◽  
Stefan Karlsson
Keyword(s):  
Bone Marrow ◽  
Preliminary Data ◽  
Bone Marrow Failure ◽  
Mtor Pathway ◽  
Wild Type ◽  
Hematopoietic Progenitors ◽  
P53 Activation ◽  
Deficient Mice

Abstract Abstract 727 Diamond-Blackfan anemia (DBA) is a congenital erythroid hypoplasia associated with physical malformations and predisposition to cancer. Of the many different DBA disease genes known, all encode for ribosomal proteins, suggesting that DBA is a disorder relating to ribosomal biogenesis or function. Among these genes, ribosomal protein S19 (RPS19) is the most frequently mutated (25 % of the patients). The generation of animal models for DBA is pivotal in order to understand the disease mechanisms and to evaluate novel therapies. We have generated two mouse models for RPS19-deficient DBA by taking advantage of RNA interference (Jaako et al. Blood. 2010;116:193. ASH meeting abstract). These models contain RPS19-targeting shRNAs expressed by a doxycycline-responsive promoter downstream of the collagen A1 locus allowing an inducible and dose-dependent regulation of shRNA. As we have previously reported, the induction of RPS19 deficiency results in a reduction in the number of erythrocytes, platelets and white blood cells that with time leads to the exhaustion of hematopoietic stem cells and bone marrow failure. In the current study we have analyzed the role of p53 in RPS19-deficient hematopoiesis by crossing the transgenic mice into Trp53 null background. To isolate the hematopoietic phenotype we transplanted bone marrow cells from these mice into lethally irradiated wild-type recipients. We have previously shown that the severity of the hematopoietic phenotype in transplanted recipients is highly dependent on the level of RPS19 downregulation, and the recipients with low RPS19 expression die 2–3 weeks after induction because of bone marrow failure. Remarkably, the inactivation of Trp53 rescued the early mortality in these recipients. However, although the inactivation of Trp53 completely reversed the erythrocyte and leukocyte numbers in the recipients with intermediate RPS19 downregulation, the recipients with low RPS19 expression still developed a mild anemia and macrocytosis. p53 activation is known to inhibit the AKT/mTOR pathway, a central regulator of cell growth and survival. Although the role of this pathway in DBA pathogenesis remains poorly defined, some patients positively respond to treatment with amino acid L-leucine, a nutrient signal that stimulates mTOR activity. Currently we are studying the role of L-leucine in RPS19-deficient hematopoiesis both in vitro and in vivo. Our preliminary data confirm that L-leucine modestly enhances the proliferation of RPS19-deficient c-Kit -enriched hematopoietic progenitors in vitro (1.2 fold in 8 days), while there is no effect on wild-type cultures. Interestingly, the proliferative response in RPS19-deficient cultures appears more pronounced when cells are cultured in low cytokine concentration (1.6 fold in 8 days). Since primary cells from DBA patients are highly responsive to stem cell factor (SCF), which also mediates its effect partly via PI3K/AKT/mTOR pathway, we are studying whether L-leucine has a synergistic role with SCF enhancing the proliferation of hematopoietic progenitors. Finally, a 15% L-leucine supplement in drinking water partly rescues the erythrocyte and leukocyte number in RPS19-deficient mice. In summary, our results demonstrate a key role of p53 activation in RPS19-deficient DBA, although they also suggest that p53-independent pathways may contribute towards phenotype upon severe RPS19 deficiency. Furthermore, our preliminary data supports the role of L-leucine as a therapeutic agent in the treatment of DBA. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Immunoglobulin Class Switch Recombination Is Impaired in Atm-deficient Mice

2004 ◽  
Vol 200 (9) ◽  
pp. 1111-1121 ◽  
Author(s):  
Joanne M. Lumsden ◽  
Thomas McCarty ◽  
Lisa K. Petiniot ◽  
Rhuna Shen ◽  
Carrolee Barlow ◽  
...  
Keyword(s):  
B Cells ◽  
Dna Recombination ◽  
Class Switch Recombination ◽  
Intrinsic Defect ◽  
Wild Type ◽  
Immunoglobulin Class ◽  
Class Switch ◽  
Deficient Mice

Immunoglobulin class switch recombination (Ig CSR) involves DNA double strand breaks (DSBs) at recombining switch regions and repair of these breaks by nonhomologous end-joining. Because the protein kinase ataxia telengiectasia (AT) mutated (ATM) plays a critical role in DSB repair and AT patients show abnormalities of Ig isotype expression, we assessed the role of ATM in CSR by examining ATM-deficient mice. In response to T cell–dependent antigen (Ag), Atm−/− mice secreted substantially less Ag-specific IgA, IgG1, IgG2b, and IgG3, and less total IgE than Atm+/+ controls. To determine whether Atm−/− B cells have an intrinsic defect in their ability to undergo CSR, we analyzed in vitro responses of purified B cells. Atm−/− cells secreted substantially less IgA, IgG1, IgG2a, IgG3, and IgE than wild-type (WT) controls in response to stimulation with lipopolysaccharide, CD40 ligand, or anti-IgD plus appropriate cytokines. Molecular analysis of in vitro responses indicated that WT and Atm−/− B cells produced equivalent amounts of germline IgG1 and IgE transcripts, whereas Atm−/− B cells produced markedly reduced productive IgG1 and IgE transcripts. The reduction in isotype switching by Atm−/− B cells occurs at the level of genomic DNA recombination as measured by digestion–circularization PCR. Analysis of sequences at CSR sites indicated that there is greater microhomology at the μ–γ1 switch junctions in ATM B cells than in wild-type B cells, suggesting that ATM function affects the need or preference for sequence homology in the CSR process. These findings suggest a role of ATM in DNA DSB recognition and/or repair during CSR.

scholarly journals Role of Complement in Protection against Cryptococcus gattii Infection

2008 ◽  
Vol 77 (3) ◽  
pp. 1061-1070 ◽  
Author(s):  
Kileen L. Mershon ◽  
Alex Vasuthasawat ◽  
Gregory W. Lawson ◽  
Sherie L. Morrison ◽  
David O. Beenhouwer
Keyword(s):  
Complement Activation ◽  
Alternative Pathway ◽  
Complement Pathway ◽  
Wild Type ◽  
Complement Components ◽  
Factor B ◽  
Alternative Pathway Of Complement ◽  
Deficient Mice

ABSTRACT Previous studies have shown that the alternative pathway of complement activation plays an important role in protection against infection with Cryptococcus neoformans. Cryptococcus gattii does not activate the alternative pathway as well as C. neoformans in vitro. The role of complement in C. gattii infection in vivo has not been reported. In this study, we used mice deficient in complement components to investigate the role of complement in protection against a C. gattii isolate from an ongoing outbreak in northwestern North America. While factor B-deficient mice showed an enhanced rate of death, complement component C3-deficient mice died even more rapidly, indicating that the alternative pathway was not the only complement pathway contributing to protection against disease. Both C3- and factor B-deficient mice had increased fungal burdens in comparison to wild-type mice. Histopathology revealed an overwhelming fungal burden in the lungs of these complement-deficient mice, which undoubtedly prevented efficient gas exchange, causing death. Following the fate of radiolabeled organisms showed that both factor B- and C3-deficient mice were less effective than wild-type mice in clearing organisms. However, opsonization of C. gattii with complement components was not sufficient to prolong life in mice deficient in complement. Killing of C. gattii by macrophages in vitro was decreased in the presence of serum from factor B- and C3-deficient versus wild-type mice. In conclusion, we have demonstrated that complement activation is crucial for survival in C. gattii infection. Additionally, we have shown that the alternative pathway of complement activation is not the only complement pathway contributing to protection.

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