scholarly journals Engineered Lactococcus lactis Secreting IL-23 Receptor-Targeted REX Protein Blockers for Modulation of IL-23/Th17-Mediated Inflammation

2019 ◽  
Vol 7 (5) ◽  
pp. 152 ◽  
Author(s):  
Tina Vida Plavec ◽  
Milan Kuchař ◽  
Anja Benko ◽  
Veronika Lišková ◽  
Jiří Černý ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Cell Surface ◽  
Lactococcus Lactis ◽  
Probiotic Bacterium ◽  
Host Cells ◽  
Bacterial Surface ◽  
Cdna Sequences ◽  
Secretion Signal ◽  
Antibody Conjugate

Lactococcus lactis, a probiotic bacterium of food origin, has recently been demonstrated as a suitable strain for the production and in vivo delivery of therapeutically important proteins into the gut. We aimed to engineer recombinant L. lactis cells producing/secreting REX binding proteins that have been described as IL-23 receptor (IL-23R) blockers and IL-23R antagonists suppressing the secretion of cytokine IL-17A, a pivotal step in the T-helper Th17-mediated pro-inflammatory cascade, as well as in the development of autoimmune diseases, including inflammatory bowel disease (IBD). To reach this goal, we introduced cDNA sequences coding for REX009, REX115, and REX125 proteins into plasmid vectors carrying a Usp45 secretion signal, a FLAG tag sequence consensus, and a LysM-containing cA surface anchor (AcmA), thus allowing cell–surface peptidoglycan anchoring. These plasmids, or their non-FLAG/non-AcmA versions, were introduced into L. lactis host cells, thus generating unique recombinant L. lactis–REX strains. We demonstrate that all three REX proteins are expressed in L. lactis cells and are efficiently displayed on the bacterial surface, as tested by flow cytometry using an anti-FLAG antibody conjugate. Upon 10-fold concentration of the conditioned media, a REX125 secretory variant can be detected by Western blotting. To confirm that the FLAG/non-FLAG REX proteins displayed by L. lactis retain their binding specificity, cell-surface interactions of REX proteins with an IL-23R-IgG chimera were demonstrated by flow cytometry. In addition, statistically significant binding of secreted REX009 and REX115 proteins to bacterially produced, soluble human IL-23R was confirmed by ELISA. We conclude that REX-secreting L. lactis strains were engineered that might serve as IL-23/IL-23R blockers in an experimentally induced mouse model of colitis.

scholarly journals Proteoglycans in host–pathogen interactions: molecular mechanisms and therapeutic implications

2010 ◽  
Vol 12 ◽  
Author(s):  
Allison H. Bartlett ◽  
Pyong Woo Park
Keyword(s):  
Cell Surface ◽  
Virulence Factors ◽  
Molecular Mechanisms ◽  
Biological Significance ◽  
Host Cells ◽  
Microbial Pathogens ◽  
Therapeutic Implications ◽  
Core Proteins

Many microbial pathogens subvert proteoglycans for their adhesion to host tissues, invasion of host cells, infection of neighbouring cells, dissemination into the systemic circulation, and evasion of host defence mechanisms. Where studied, specific virulence factors mediate these proteoglycan–pathogen interactions, which are thus thought to affect the onset, progression and outcome of infection. Proteoglycans are composites of glycosaminoglycan (GAG) chains attached covalently to specific core proteins. Proteoglycans are expressed ubiquitously on the cell surface, in intracellular compartments, and in the extracellular matrix. GAGs mediate the majority of ligand-binding activities of proteoglycans, and many microbial pathogens elaborate cell-surface and secreted factors that interact with GAGs. Some pathogens also modulate the expression and function of proteoglycans through known virulence factors. Several GAG-binding pathogens can no longer attach to and invade host cells whose GAG expression has been reduced by mutagenesis or enzymatic treatment. Furthermore, GAG antagonists have been shown to inhibit microbial attachment and host cell entry in vitro and reduce virulence in vivo. Together, these observations underscore the biological significance of proteoglycan–pathogen interactions in infectious diseases.

scholarly journals BCR-Induced VLA-4 Activation in the TCL1 Transgenic Mouse Model for Chronic Lymphocytic Leukemia

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 1730-1730
Author(s):  
Eva Szenes ◽  
Andrea Härzschel ◽  
Erika Tissino ◽  
Pischeli Justine ◽  
Julia Gutjahr ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Chronic Lymphocytic Leukemia ◽  
Mouse Model ◽  
Cell Surface ◽  
Research Funding ◽  
Lymphocytic Leukemia ◽  
Tumor Infiltration ◽  
Wild Type ◽  
Inside Out

Introduction. Ibrutinib, a small molecule inhibitor of Bruton's tyrosine kinase (BTK), has proven to be an efficient treatment for chronic lymphocytic leukemia (CLL). A distinct characteristic of ibrutinib therapy is transient lymphocytosis. Recently, we have demonstrated that CLL patients with high levels of CD49d show reduced lymphocytosis and inferior nodal response under ibrutinib due to residual activity of BCR-induced inside-out activation of the CD49d/CD29 integrin VLA-4 (Tissino E et al. J Exp Med. 2018;215(2):681-697). Here, we used Tcl1 transgenic (tg) mice as a model to further validate the observation of VLA-4 activation under ibrutinib and to study involved signaling pathways and the effect of VLA-4 inhibition in vivo. Methods. Surface receptor expression analysis of various receptors was performed by flow cytometry. The phosphorylation of signaling molecules was measured by phosflow and western blotting. VLA-4 affinity state was determined by a real-time kinetic assay described in Chigaev A et al. J Biol Chem. 2001;276(52):48670-8. To analyze the distribution of individual VLA-4 molecules on the cell surface, immunofluorescence approaches and superresolution microscopy (STORM, Abbelight) were employed. Mouse treatment studies were performed upon transplantation of TCL1-tg splenocytes to wild-type C57BL/6J mice using the small molecule VLA-4 inhibitor firategrast in drinking water. Tumor infiltration of different organs was measured by flow cytometry. Results. Analyzing the surface expression of CD49d and other homing receptors, we found that TCL1-tg mice correspond with the CD49d-high CLL cohort. We found that both CLL cells from TCL1-tg mice and human CD49d-high CLL show similar CD49d expression levels as the corresponding healthy B cells (human: N = 116 CD49d-high CLL and 32 healthy donor, P = 0.8717; mouse: N = 12 per group, P = 0.6845). Next, we analyzed the impact of BCR pathway inhibitors on the phosphorylation of signaling molecules involved in the BCR pathway after activation by anti-IgM (aIgM) in TCL1-tg leukemic cells. Ibrutinib and idelalisib showed specific patterns of inhibition of BTK and PI3K, respectively. The combination of ibrutinib and idelalisib proved to be the most efficient in reducing the phosphorylation of BTK, SYK, ERK1/2 and Akt upon IgM activation, compared to the phosphorylation of stimulated cells without inhibition (N = 6, P = 0.0003, 0.0305, 0.0039, 0.0019, respectively). IgM stimulation induced VLA-4 high affinity as well as a reorganization of VLA-4 molecules on the cell surface, forming areas of high VLA-4 density. BCR-induced inside-out activation of VLA-4 remained functional upon treatment with ibrutinib (N = 5, cnt vs aIgM P = 0.0017, cnt vs ibrutinib+aIgM P = 0.0499), while idelalisib reduced VLA-4 activation more effectively (N = 5, cnt vs aIgM P = 0.0014, cnt vs idelalisib+aIgM P = 0.0803), suggesting a pivotal role of PI3K in the transmission of the exogenous antigen signal to the integrin. Finally, to analyze the potential of VLA-4 blockage in a tumor setting similar to VLA-4-high CLL patients, we treated wild-type C57BL/6J mice (N = 6 mice per group), which were transplanted with TCL1-tg splenocytes, with the CD49d inhibitor firategrast. This treatment reduced the tumor load in spleen and bone marrow. Conclusion. We found that the TCL1-tg mouse model is adequate to study the activity of the BCR-VLA-4 axis in CLL. Using this model, we show that a) BCR stimulation induces both, an increase in VLA-4 affinity as well as avidity (clustering), b) that PI3K is an essential transmitter between BCR and VLA-4, and c) that VLA-4 inhibition alters tumor infiltration patterns in vivo. Synergies of VLA-4 blockage with established therapy options as a possible way of reducing microenvironment-induced resistance development are currently been investigated. Disclosures Egle: Celgene: Honoraria, Other: Advisory board and Travel support. Greil:Eisai: Honoraria; Daiichi Sankyo: Consultancy, Honoraria; Sandoz: Honoraria; Genentech: Honoraria, Research Funding; Cephalon: Consultancy, Honoraria, Research Funding; Sanofi Aventis: Honoraria; Janssen-Cilag: Honoraria; AstraZeneca: Consultancy, Honoraria, Other: Travel/accomodation expenses, Research Funding; GSK: Research Funding; Boehringer Ingelheim: Honoraria; AbbVie: Consultancy, Honoraria, Research Funding; Roche: Consultancy, Honoraria, Other: Travel/accomodation expenses, Research Funding; Pfizer: Honoraria, Research Funding; Bristol-Myers-Squibb: Consultancy, Honoraria, Other: Travel/accomodation expenses, Research Funding; Merck: Consultancy, Honoraria, Research Funding; Mundipharma: Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Other: Travel/accomodation expenses, Research Funding; Celgene: Consultancy, Honoraria, Other: Travel/accomodation expenses, Research Funding; Novartis: Consultancy, Honoraria, Other: Travel/accomodation expenses, Research Funding; MSD: Consultancy, Honoraria, Other: Travel/accomodation expenses, Research Funding; Takeda: Consultancy, Honoraria, Research Funding; Ratiopharm: Research Funding; Gilead: Consultancy, Honoraria, Other: Travel/accomodation expenses, Research Funding.

scholarly journals Aged platelets have an impaired response to thrombin as quantitated by P-selectin expression

Blood ◽  
1994 ◽  
Vol 83 (1) ◽  
pp. 161-166 ◽  
Author(s):  
J Peng ◽  
P Friese ◽  
E Heilmann ◽  
JN George ◽  
SA Burstein ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Cell Surface ◽  
Dose Response ◽  
Intravenous Infusion ◽  
Total Population ◽  
Response Curves ◽  
Dose Response Curves

Abstract After the intravenous infusion of N-hydroxysuccinimido biotin into dogs, 80.6% +/- 9.7% (n = 5) of platelets were covalently labeled with biotin. The in vivo survival of the biotinylated platelets was monitored by flow cytometry and was normal as compared with previous reports for dog platelets. The ability of the biotinylated platelets to be activated was analyzed by measuring the expression of cell-surface P- selectin after incubation with graded concentrations of thrombin. When P-selectin expression was examined 3 hours after labeling, biotinylated platelets were indistinguishable from the nonlabeled population of platelets, indicating that biotinylation did not adversely affect the cells. On consecutive days after biotinylation, the thrombin dose- response curves for biotinylated and nonbiotinylated platelets were repeated, and as the biotinylated-platelets aged, they became less responsive to thrombin. On days 3, 4, and 5, the thrombin EC50 for the aged, biotinylated platelets as compared with the total population of platelets was 136%, 150%, and 178%, respectively. Increasing age clearly impairs the reactivity of platelets towards thrombin as quantitated by the expression of cell-surface P-selectin.

scholarly journals 2590. Streptolysin O Enhances Binding of the Group A Streptococcal NAD+-Glycohydrolase Toxin to Oropharyngeal Keratinocytes

2019 ◽  
Vol 6 (Supplement_2) ◽  
pp. S900-S900
Author(s):  
Jorge J Velarde ◽  
Nicola Lynskey ◽  
Alessandro Piai ◽  
James Chou ◽  
Michael Wessels
Keyword(s):  
Flow Cytometry ◽  
Cell Surface ◽  
Solution Structure ◽  
Host Cells ◽  
Carbohydrate Binding ◽  
Carbohydrate Binding Module ◽  
Nad Glycohydrolase ◽  
Streptolysin O ◽  
Group A ◽  
Translocation Domain

Abstract Background Streptolysin O (SLO) and the NAD+-glycohydrolase (NADase) are co-toxins secreted by group A Streptococcus (GAS) that play a significant role in virulence. NADase requires SLO for translocation into the host cell cytoplasm, a process termed cytolysin-mediated translocation (CMT). Recently, we noted that interaction of the two toxins mutually increased their stability. Although NADase is predicted to bind to the host cell surface, this interaction is incompletely understood. Here, we investigate potential mechanisms by which NADase binds to oropharyngeal keratinocytes. Methods The amino terminal region of NADase has been implicated in CMT, but the structure of the putative translocation domain has not been characterized. We determined the solution structure of this domain by NMR spectroscopy. We used flow-cytometry and confocal microscopy to investigate whether NADase could interact directly with oropharyngeal keratinocytes. Finally, since we expect that NADase and SLO are co-expressed from the same operon, are secreted in a coordinated fashion, and interact in solution, we tested whether SLO affects NADase binding to host cells. Results The solution structure of the NADase translocation domain revealed a β-sandwich fold with an elongated N-terminal intrinsically disordered region. Structural homology searches (DALI) identified a potential carbohydrate binding module, suggesting the translocation domain could play a role in glycan binding. We also demonstrated by flow-cytometry that purified recombinant NADase toxin is able to independently interact with the cell surface of oropharyngeal keratinocytes. Importantly, interaction with SLO significantly enhanced the association of NADase with the cell surface, resulting in a 5-fold increase of the geometric mean fluorescence intensity. Conclusion The structure of the NADase translocation domain reveals a potential carbohydrate binding module, which may mediate binding of the toxin to a cell-surface glycan. Binding of NADase to host cells is markedly enhanced by its interaction with SLO. We conclude that interaction of the two toxins contributes to the CMT process by functionally increasing the local concentration of NADase at the cell surface. Disclosures All authors: No reported disclosures.

scholarly journals Role of G2-S16 Polyanionic Carbosilane Dendrimer in the Prevention of Respiratory Syncytial Virus Infection In Vitro and In Vivo in Mice

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2141
Author(s):  
Ignacio Rodriguez-Izquierdo ◽  
Rafael Ceña-Diez ◽  
Maria Jesús Serramia ◽  
Rosa Rodriguez-Fernández ◽  
Isidoro Martínez ◽  
...  
Keyword(s):  
Respiratory Syncytial Virus ◽  
Cell Surface ◽  
Host Cells ◽  
Carbosilane Dendrimer ◽  
Rsv Infection ◽  
Host Cell Surface ◽  
Syncytial Virus

The respiratory syncytial virus (RSV) causes respiratory infection and bronchiolitis, requiring hospitalization mainly in infants. The interaction between RSV, envelope glycoproteins G and F, and cell surface heparan sulfate proteoglycans (HSPG) is required for binding and entry into the host cells. A G2-S16 polyanionic carbosilane dendrimer was identified as a possible RSV inhibitor. We speculated that the G2-S16 dendrimer adheres to the host cell-surface HSPG, acts through binding to HS receptors, and prevents further RSV infection. The G2-S16 dendrimer was non-toxic when applied intranasally to Balb/c mice, and interestingly enough, this G2-S16 dendrimer inhibits 85% RSV. Therefore, our G2-S16 dendrimer could be a candidate for developing a new possible therapy against RSV infection.

scholarly journals Aged platelets have an impaired response to thrombin as quantitated by P-selectin expression

Blood ◽  
1994 ◽  
Vol 83 (1) ◽  
pp. 161-166
Author(s):  
J Peng ◽  
P Friese ◽  
E Heilmann ◽  
JN George ◽  
SA Burstein ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Cell Surface ◽  
Dose Response ◽  
Intravenous Infusion ◽  
Total Population ◽  
Response Curves ◽  
Dose Response Curves

After the intravenous infusion of N-hydroxysuccinimido biotin into dogs, 80.6% +/- 9.7% (n = 5) of platelets were covalently labeled with biotin. The in vivo survival of the biotinylated platelets was monitored by flow cytometry and was normal as compared with previous reports for dog platelets. The ability of the biotinylated platelets to be activated was analyzed by measuring the expression of cell-surface P- selectin after incubation with graded concentrations of thrombin. When P-selectin expression was examined 3 hours after labeling, biotinylated platelets were indistinguishable from the nonlabeled population of platelets, indicating that biotinylation did not adversely affect the cells. On consecutive days after biotinylation, the thrombin dose- response curves for biotinylated and nonbiotinylated platelets were repeated, and as the biotinylated-platelets aged, they became less responsive to thrombin. On days 3, 4, and 5, the thrombin EC50 for the aged, biotinylated platelets as compared with the total population of platelets was 136%, 150%, and 178%, respectively. Increasing age clearly impairs the reactivity of platelets towards thrombin as quantitated by the expression of cell-surface P-selectin.

scholarly journals The membrane microenvironment regulates the sequential attachment of bacteria to host cells

2020 ◽  
Author(s):  
Xavier Pierrat ◽  
Jeremy P.H. Wong ◽  
Zainebe Al-Mayyah ◽  
Alexandre Persat
Keyword(s):  
Cell Surface ◽  
Host Cell ◽  
Bacterial Adhesion ◽  
Bacterial Attachment ◽  
Host Cells ◽  
Receptor System ◽  
Surface Receptors ◽  
Inert Surfaces ◽  
Mechanical Microenvironment

AbstractPathogen attachment to host tissue is critical in the progress of many infections. Bacteria use adhesion in vivo to promote colonization and regulate the deployment of contact-dependent virulence traits. To specifically target host cells, they decorate themselves with adhesins, proteins that bind to mammalian cell surface receptors. One common assumption is that adhesin-receptor interactions entirely govern bacterial attachment. However, how adhesins engage with their receptors in an in vivo-like context remains unclear, in particular under the influence of a heterogeneous mechanical microenvironment. We here investigate the biophysical processes governing bacterial adhesion to host cells using a tunable adhesin-receptor system. By dynamically visualizing attachment, we found that bacterial adhesion to host cell surface, unlike adhesion to inert surfaces, involves two consecutive steps. Bacteria initially attach to their host without engaging adhesins. This step lasts about one minute during which bacteria can easily detach. We found that at this stage, the glycocalyx, a layer of glycosylated proteins and lipids, shields the host cell by keeping adhesin away from their receptor ligand. In a second step, adhesins engage with their target receptors to strengthen attachment for minutes to hours. The active properties of the membrane, endowed by the actin cytoskeleton, strengthen specific adhesion. Altogether, our results demonstrate that adhesin-ligand binding is not the sole regulator of bacterial adhesion. In fact, the host cell’s mechanical microenvironment relatively strongly mediated host-bacteria physical interactions, thereby playing an essential role in the onset of infection.

scholarly journals Therapeutic Targeting of Mesothelin in Acute Myeloid Leukemia with Chimeric Antigen Receptor T Cell Therapy

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 11-11 ◽  
Author(s):  
Quy Le ◽  
Sommer Castro ◽  
Thao T. Tang ◽  
Anisha Loeb ◽  
Amanda R. Leonti ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Flow Cytometry ◽  
T Cells ◽  
Cell Surface ◽  
Myeloid Leukemia ◽  
Car T Cells ◽  
Car T ◽  
Acute Myeloid

Background: Acute myeloid leukemia (AML) is one of the most highly refractory hematologic malignancies despite intensive combination chemotherapy and bone marrow stem cell transplantation. Lack of curative treatments is in large part due to our poor understanding of the disease biology and paucity of therapeutic targets. In an effort to identify actionable targets, we recently completed the largest genome, epigenome and transcriptome profiling of AML in nearly 3000 children and young adults. This discovery effort has led to the identification of a library of novel AML-restricted targets (high expression in AML, minimal-to-no expression in normal hematopoiesis) for therapeutic development. One such target was MSLN which encodes for mesothelin, a cell surface adhesion molecule that is highly expressed in 30-50% of AML cases in pediatric (Children Oncology Group) and adult (MD Anderson) cohorts and is entirely absent in normal bone marrow and peripheral blood CD34+ cells. MSLN expression in normal tissues is confined to mesothelial cells lining the pleura, pericardium, and peritoneum. Previous studies targeting MSLN in solid tumors have demonstrated clinical efficacy with minimal toxicities. Given that T cells genetically modified to express chimeric antigen receptors (CARs) are extremely effective at eradicating relapsed and refractory malignancy, we developed MSLN-directed CAR T cells for pre-clinical evaluation in AML. Methods: From primary patient samples, we verified MSLN expression by RT-PCR and confirmed mesothelin surface protein expression on leukemic blasts by flow-cytometry as well as detected soluble mesothelin in the plasma by ELISA. The VH and VL sequences from Amatuximab were used to create the scFv domain of the standard CAR (41-BB and CD3Zeta). For in vivo CAR T study, Nomo-1 cells, which express endogenous level of MSLN, and Kasumi-1 cells engineered to express MSLN with a lentivirus construct (Kasumi-1 MSLN+) were transplanted into NSG mice. Mock transduced MSLN-directed CAR T cells were infused 1 week (Nomo-1) and 2 weeks (Kasumi-1 MSLN+) following leukemic cell injection. Leukemic burden was measured by bioluminescence IVIS imaging weekly. For in vitro study, Nomo-1 cells were treated with GM6001 (50uM), a metalloprotease inhibitor, or DMSO control for 48 hr prior to evaluation of surface mesothelin by flow cytometry and soluble mesothelin in the culture supernatant by ELISA. Results: In vivo cytotoxicity of CAR T cells against Nomo-1 and Kasumi-1MSLN+ AML models demonstrated potent, target-dependent tumor killing. After 1- and 2-weeks post CAR T infusion, leukemic cells were eradicated in both Nomo-1 (p<0.0005, week 2, Figure 1A) and Kasumi-1 MSLN+ xenografts (p<0.005 at week 2, Figure 1B). Mesothelin undergoes shedding at the cell membrane as a result of ADAM17-mediated cleavage. Blocking ADAM17 activity with GM6001 in Nomo-1 cells led to increased cell surface mesothelin (Figure 1C) with a corresponding reduction in the shed form (Figure 1D), suggesting that GM6001 treatment stabilizes mesothelin on the cell surface. Furthermore, GM6001 treatment during co-culture of Nomo-1 and CAR T cells enhanced cytolytic activity of CAR T cells (Figure 1E). GM6001 treatment did not significantly impact cell viability of Nomo-1 cells in the absence of CAR T cells (data not shown). Conclusion: In this study, we demonstrate that mesothelin is a viable therapeutic target and a potential diagnostic biomarker in AML. We show that MSLN CAR T cells were highly effective in eliminating MSLN-positive AML cells in vitro and in vivo. Shedding contributes to the loss of mesothelin antigen and provides a source of soluble mesothelin that may interfere with antibody-based therapies, including CAR T cells. Modulating MSLN shedding by inhibiting ADAM17-mediated cleavage resulted in stabilized mesothelin and improved CAR T cell functionality. This work warrants further evaluation of MSLN CAR T cells to be tested in clinical trials for AML and demonstrates that inhibiting MSLN shedding is a promising approach to improve CAR T efficacy. Disclosures No relevant conflicts of interest to declare.

scholarly journals Heterogeneous distribution of Candida albicans cell-surface antigens demonstrated with an Als1-specific monoclonal antibody

Microbiology ◽  
2010 ◽  
Vol 156 (12) ◽  
pp. 3645-3659 ◽  
Author(s):  
David A. Coleman ◽  
Soon-Hwan Oh ◽  
Xiaomin Zhao ◽  
Lois L. Hoyer
Keyword(s):  
Candida Albicans ◽  
Cell Surface ◽  
Spatial Localization ◽  
Host Cells ◽  
Yeast Cells ◽  
Cell Surface Antigens ◽  
Heterogeneous Distribution ◽  
Germ Tubes

Despite an abundance of data describing expression of genes in the Candida albicans ALS (agglutinin-like sequence) gene family, little is known about the production of Als proteins on individual cells, their spatial localization or stability. Als proteins are most commonly discussed with respect to function in adhesion of C. albicans to host and abiotic surfaces. Development of a mAb specific for Als1, one of the eight large glycoproteins encoded by the ALS family, provided the opportunity to detect Als1 during growth of yeast and hyphae, both in vitro and in vivo, and to demonstrate the utility of the mAb in blocking C. albicans adhesion to host cells. Although most C. albicans yeast cells in a saturated culture are Als1-negative by indirect immunofluorescence, Als1 is detected on the surface of nearly all cells shortly after transfer into fresh growth medium. Als1 covers the yeast cell surface, with the exception of bud scars. Daughters of the inoculum cells, and sometimes granddaughters, also have detectable Als1, but Als1 is not detectable on cells from subsequent generations. On germ tubes and hyphae, most Als1 is localized proximal to the mother yeast. Once deposited on yeasts or hyphae, Als1 persists long after the culture has reached saturation. Growth stage-dependent production of Als1, coupled with its persistence on the cell surface, results in a heterogeneous population of cells within a C. albicans culture. Anti-Als1 immunolabelling patterns vary depending on the source of the C. albicans cells, with obvious differences between cells recovered from culture and those from a murine model of disseminated candidiasis. Results from this work highlight the temporal parallels for ALS1 expression and Als1 production in yeasts and germ tubes, the specialized spatial localization and persistence of Als1 on the C. albicans cell surface, and the differences in Als1 localization that occur in vitro and in vivo.

Impaired Platelet Attack by fibronectin Binding Partner Msb2 of Candida Albicans

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 3299-3299
Author(s):  
Volker R. Stoldt ◽  
Khon C. Huynh ◽  
Rudiger E. Scharf
Keyword(s):  
Flow Cytometry ◽  
Cell Surface ◽  
Binding Sites ◽  
Yeast Cells ◽  
Affinity Column ◽  
Complete Medium ◽  
Relevant Factor ◽  
Alexa Fluor ◽  
Fibronectin Binding

Abstract Abstract 3299 Introduction: Platelets can bridge innate and adaptive immunity. To attack microorganisms, platelets store microbicidal and immune stimulatory proteins in their α-granules. Platelet integrins and their plasma ligands can govern both binding of the pathogens and activation of platelets with subsequent secretion of their granular constituents. Fibronectin, a large dimeric glycoprotein, with specific binding sites for platelet integrins (α5β1, αvβ3, and αIIbβ3) and collagens, circulates in plasma and is a component of the extracellular matrix. C. albicans can also bind fibronectin. The ability to germinate and grow in hyphae is a relevant factor of virulence in vivo. The integrity of the C. albicans cell surface during filamentation is sensed by Msb2, a transmembrane protein. Recently, it has been shown that Msb2 can be shedded, thus providing a putative mechanism of C. albicans to escape from the host attack. We now hypothesized that Msb2 has a binding site for plasma fibronectin and that shedded (soluble) Msb2 can protect C. albicans from opsonization by fibronectin. Material and methods: Fibronectin purified from human fresh frozen plasma by gelatin-sepharose affinity column was labeled with alexa fluor 488 according the manufacturer's instructions. To induce germination, C. albicans was cultured in complete medium (yeast extract, peptone, and dextrose) at 30°C, washed and starved for 1 h at room temperature before dilution in PBS supplemented with fetal calf serum (10 %) to a final optical density of 0.4 at 37°C. Msb2 heme agglutinin (HA)-tagged purified by affinity chromatography using anti-HA antibody-coupled agarose beads was kindly provided by J. Ernst (Szafranski-Schneider E, PLoS Pathog. 2012;8(2):e1002501). C. albicans yeast and hyphae forms or plates (24 wells) coated with 10 μg/ml purified HA-tagged Msb2 or 10μg/ml unlabeled fibronectin, and blocked with 1% BSA were incubated with various concentrations fibronectin-alexa fluor 488 for 60 min or 120 min. Flow cytometry (FACS, Beckman Coulter), confocal laser scanning microscope (LSM, Zeiss) and fluorometer (Fluoroskan Ascent, Thermo Scientific) were used to measure the fluorescent fibronectin. Results: Binding of 5, 10, 50, and 100 μg/ml fibronectin to 10 μg/ml immobilized Msb2 revealed saturation at 10 μg/ml fibronectin. Immobilized Msb2 bound 2.6 fold more fluorescent fibronectin than BSA (p=0.016). Immobilized fibronectin bound 30 % more fluorescent fibronectin than Msb2 and significantly more than BSA (p<0.01). C. albicans germination over time at 30 min, 60 min, and 120 min generated 5–10 %, 40 %, and 90 % hyphae, as determined by microscopy and confirmed by flow cytometry. Induction of C. albicans hyphae enhanced binding of fibronectin (40 μg/ml) from 1.7 % positive yeast cells (baseline), 6 % at 30 min, 11.7 % at 60 min, and 12.6 % at 120 min (p<0.05). As shown by LSM, C. albicans germ tubes are a main target for fluorescent fibronectin. Germination of C. albicans yeast form increased binding of platelets up to fivefold after 30 min and twentyfold after 60 min (p<0.05). Moreover, pre-treatment of C. albicans hyphae with fibronectin (40 μg/ml) enhanced the binding of platelets caused by integrin αIIbβ3 fibronectin interaction. Abciximab (2 μg/ml), a specific αIIbβ3 antagonist, blocked binding of platelets to C. albicans opsonized by fibronectin. Binding of fluorescent fibronectin was not homogeneously distributed on the cell surface of C. albicans and upon addition of soluble Msb2 binding of fluorescent fibronectin diminished as documented by LSM. Conclusion: Hyphae of C. albicans, a relevant factor of virulence, are attacked by platelets. Fibronectin, a ligand of the platelet integrins, opsonizes the hyphae of C. albicans and fosters platelet binding to C. albicans. Hence, platelets and fibronectin, with its intrinsic multivalent binding sites to collagen and platelet integrins (α5β1, αvβ3, and αIIbβ3) can support the platelet-mediated host defense against C. albicans. Msb2 is a novel fibronectin binding protein. Binding of fibronectin to C. albicans is impaired in the presence of soluble Msb2. Hence, shedding of Msb2 in vivo can protect C. albicans against the platelet-mediated host attack. Disclosures: No relevant conflicts of interest to declare.

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