scholarly journals Hinge Influences in Murine IgG Binding to Cryptococcus neoformans Capsule

2021 ◽  
Author(s):  
Diane Sthefany Lima de Oliveira ◽  
Verenice Paredes ◽  
Adrielle Veloso Caixeta ◽  
Nicole Moreira Henriques ◽  
Maggie P. Wear ◽  
...  
Keyword(s):  
Cryptococcus Neoformans ◽  
Capsular Polysaccharide ◽  
List Type ◽  
Constant Region ◽  
Fine Specificity ◽  
Igg Binding ◽  
Key Points ◽  
Antibody Structure ◽  
V Region ◽  
Punctate Pattern

AbstractDecades of studies on antibody structure led to the tenet that the V region binds antigens while the C region interacts with immune effectors. In some antibodies, however, the C region affects affinity and/or specificity for the antigen. One such case is that of the 3E5 antibodies, a family of monoclonal murine IgGs in which the mIgG3 isotype has different fine specificity to the Cryptococcus neoformans capsule polysaccharide than the other mIgG isotypes. Our group serendipitously found another pair of mIgG1/mIgG3 antibodies based on the 2H1 hybridoma to the C. neoformans capsule that recapitulated the differences observed with 3E5. In this work, we report the molecular basis of the constant domain effects on antigen binding using recombinant antibodies. As with 3E5, immunofluorescence experiments show a punctate pattern for 2H1-mIgG3 and an annular pattern for 2H1-mIgG1. Also as observed with 3E5, 2H1-mIgG3 bound on ELISA to both acetylated and non-acetylated capsular polysaccharide, whereas 2H1-mIgG1 only bound well to the acetylated form, consistent with differences in fine specificity. In engineering hybrid mIgG1/mIgG3 antibodies, we found that switching the 2H1-mIgG3 hinge for its mIgG1 counterpart changed the immunofluorescence pattern to annular, but a 2H1-mIgG1 antibody with a mIgG3 hinge still had an annular pattern. The hinge is thus necessary but not sufficient for these changes in binding to the antigen. This important role for the constant region in binding of antibodies to the antigen could affect the design of therapeutic antibodies and our understanding of their function in immunity.Key pointsKey point 1- 2H1 antibodies recapitulate differences between mIgG isotypes observed with 3E5.Key point 2 – The hinge region is necessary but not sufficient for these differences.Key point 3 - The antibody constant region can also play a role in mIgG binding to antigen.

scholarly journals The capsule ofCryptococcus neoformansmodulates phagosomal pH through its acid-base properties

2018 ◽  
Author(s):  
Carlos M. De Leon-Rodriguez ◽  
Man Shun Fu ◽  
M. Osman Corbali ◽  
Radames J.B. Cordero ◽  
Arturo Casadevall
Keyword(s):  
Cryptococcus Neoformans ◽  
Capsular Polysaccharide ◽  
Glucuronic Acid ◽  
Pathogenic Fungus ◽  
Weak Acid ◽  
Phagocytic Cells ◽  
Acid Base ◽  
Encapsulated Cells ◽  
Human Pathogenic Fungus ◽  
Base Properties

AbstractPhagosomal acidification is a critical cellular mechanism for the inhibition and killing of ingested microbes by phagocytic cells. The acidic environment activates microbicidal proteins and creates an unfavorable environment for the growth of many microbes. Consequently, numerous pathogenic microbes have developed strategies for countering phagosomal acidification through various mechanisms that include interference with phagosome maturation. The human pathogenic fungusCryptococcus neoformansresides in acidic phagosome after macrophage ingestion that actually provides a favorable environment for replication since the fungus replicates faster at acidic pH. We hypothesized that the glucuronic acid residues in the capsular polysaccharide had the capacity to affect phagosome acidity through their acid-base properties. A ratiometric fluorescence comparison of imaged phagosomes containingC. neoformansto those containing beads showed that the latter were significantly more acidic. Similarly, phagosomes containing non-encapsulatedC. neoformanscells were more acidic than those containing encapsulated cells. Acid-base titrations of isolatedC. neoformanspolysaccharide revealed that it behaves as a weak acid with maximal buffering capacity around pH 4-5. We interpret these results as indicating that the glucuronic acid residues in theC. neoformanscapsular polysaccharide can buffer phagosomal acidification. Interference with phagosomal acidification represents a new function for the cryptococcal capsule in virulence and suggests the importance of considering the acid-base properties of microbial capsules in the host-microbe interaction for other microbes with charged residues in their capsules.ImportanceCryptococcus neoformansis the causative agent of cryptococcosis, a devastating fungal disease that affects thousands of individuals worldwide. This fungus has the capacity to survive inside phagocytic cells, which contributes to persistence of infection and dissemination. One of the major mechanisms of host phagocytes is to acidify the phagosomal compartment after ingestion of microbes. This study shows that the capsule ofC. neoformanscan interfere with full phagosomal acidification by serving as a buffer.

scholarly journals Magnitude, change over time, demographic characteristics and geographic distribution of excess deaths among nursing home residents during the first wave of COVID-19 in France: a nationwide cohort study

2021 ◽  
Author(s):  
Florence Canouï-Poitrine ◽  
Antoine Rachas ◽  
Martine Thomas ◽  
Laure Carcaillon-Bentata ◽  
Roméo Fontaine ◽  
...  
Keyword(s):  
Nursing Home ◽  
General Population ◽  
Excess Mortality ◽  
Nursing Home Residents ◽  
Primary Objective ◽  
List Type ◽  
Key Points ◽  
Standardized Mortality Ratios ◽  
Using Data ◽  
Excess Deaths

AbstractImportanceNursing home (NH) residents are particularly vulnerable to SARS-CoV-2 infections and coronavirus disease 2019 (COVID-19) lethality. However, excess deaths in this population have rarely been documented.ObjectivesThe primary objective was to assess the number of excess deaths among NH residents during the first wave of the COVID-19 pandemic in France. The secondary objectives were to determine the number of excess deaths as a proportion of the total excess deaths in the general population and determine whether a harvesting effect was present.DesignWe studied a cohort of 494,753 adults (as of March 1st, 2020) aged 60 and over in 6,515 NHs in mainland France. This cohort was exposed to the first wave of the COVID-19 pandemic (from March 1st to May 31st, 2020) and was compared with the corresponding, reference cohorts from 2014 to 2019 (using data from the French National Health Data System).Main outcome and measuresThe main outcome was all-cause death. Weekly excess deaths and standardized mortality ratios (SMRs) were estimated.ResultThere were 13,505 excess deaths among NH residents. Mortality increased by 43% (SMR: 1.43). The mortality excess was higher among males than among females (SMR: 1.51 and 1.38, respectively) and decreased with age (SMRs in females: 1.61 in the 60-74 age group, 1.58 for 75-84, 1.41 for 85-94, and 1.31 for 95 or over; Males: SMRs: 1.59 for 60-74, 1.69 for 75-84, 1.47 for 85-94, and 1.41 for 95 or over). We did not observe a harvesting effect (up until August 30th, 2020). By extrapolating to all NH residents nationally (N=570,003), the latter accounted for 51% of the total excess deaths in the general population (N=15,114 out of 29,563).ConclusionNH residents accounted for about half of the total excess deaths in France during the first wave of the COVID-19 pandemic. The excess death rate was higher among males than females and among younger residents than among older residents. We did not observe a harvesting effect. A real-time mortality surveillance system and the identification of individual and environmental risk factors might help to design the future model of care for older dependent adults.Key pointsDuring the first wave of the COVID-19 pandemic in France, the mortality among nursing home residents increased by 43%.Nursing home residents accounted for 51% of the total excess deaths in France.The excess mortality was higher among younger residents than among older residents.The excess mortality was higher among males than among females.We did not observe a harvesting effect during the study period (ending on August 30th, 2020, i.e., three months after the end of the first wave).

scholarly journals Mapping densely distributed membrane receptors in blood platelets with expansion microscopy

2021 ◽  
Author(s):  
Hannah S. Heil ◽  
Max Aigner ◽  
Sophia Maier ◽  
Vanessa Göb ◽  
Charly Kusch ◽  
...  
Keyword(s):  
Blood Platelets ◽  
Super Resolution ◽  
Membrane Receptors ◽  
List Type ◽  
Platelet Receptor ◽  
Key Points ◽  
Major Vessel ◽  
Integrin Clustering ◽  
Receptor Interactions ◽  
3D Scenarios

AbstractInterrogating small platelets and their densely packed, highly abundant receptor landscape is key to understand platelet clotting. Blot clots can save lives when stopping blood loss after an injury, but also kill when blocking a major vessel. The highly abundant and densely distributed GPIIb/IIIa receptors are one reason why the underlying key distributions and interactions, in particular the relevance of integrin clustering, are not fully understood. Such dense receptor scenarios are difficult to assess even by super-resolution fluorescence microscopy. Here, we quantify various receptor interactions, and demonstrate that expansion microscopy can pinpoint such challenging interactions where conventional methods fail in such dense 3D scenarios with highly abundant receptors. We successfully combine dual-color expansion and confocal microscopy with colocalization analysis and assess platelet receptor organization without the need of a super-resolution microscope. We reveal that GPIIb/IIIa receptors are organized in pre-formed clusters in resting platelets – a pattern that orchestrates platelet clotting. We show that 4x expansion is most straight-forward for platelet imaging, while 10x expansion provides highest precision which turned out to be absolutely necessary for the most difficult of the scenarios described here.Graphical AbstractNonstandard Abbreviations and AcronymsGPIX: glycoprotein IXExM: expansion microscopyKey PointsMapping of the very dense, highly abundant platelet receptor landscape requires 10x Expansion MicroscopyExM reveals that GPIIb/IIIa receptors are organized in pre-formed clusters in resting platelets.

UDP Glucuronate Decarboxylase and Synthesis of Capsular Polysaccharide in Cryptococcus neoformans

1982 ◽  
Vol 152 (2) ◽  
pp. 932-934
Author(s):  
Eric S. Jacobson ◽  
William R. Payne
Keyword(s):  
Cryptococcus Neoformans ◽  
Capsular Polysaccharide ◽  
Decarboxylase Activity

UDP glucuronate decarboxylase activity was comparable in encapsulated and non-encapsulated strains of Cryptococcus neoformans , required NAD ( K a = 0.2 mM), and was inhibited by NADH ( K i = 0.1 mM) and UDP xylose.

scholarly journals Monoclonal Antibodies Reactive with Immunorecessive Epitopes of Glucuronoxylomannan, the Major Capsular Polysaccharide of Cryptococcus neoformans

2003 ◽  
Vol 10 (5) ◽  
pp. 903-909 ◽  
Author(s):  
Suzanne Brandt ◽  
Peter Thorkildson ◽  
Thomas R. Kozel
Keyword(s):  
Monoclonal Antibody ◽  
Immune Response ◽  
Monoclonal Antibodies ◽  
Cryptococcus Neoformans ◽  
Capsular Polysaccharide ◽  
Passive Immunization ◽  
The Other ◽  
Serotype A ◽  
Humoral Immune ◽  
New Information

ABSTRACT Cryptococcus neoformans is surrounded by an antiphagocytic capsule whose primary constituent is glucuronoxylomannan (GXM). An epitope shared by GXM serotypes A, B, C, and D is immunodominant when mice are immunized with serotype A GXM. In contrast, an epitope shared only by serotypes A and D is immunodominant when mice are immunized with serotype D. Hybridomas secreting antibodies reactive with subdominant epitopes were identified through a positive-negative screening procedure in which antibody-secreting colonies were characterized by reactivity with both the immunizing polysaccharide and GXMs from each of the four major serotypes. In this manner, a monoclonal antibody (MAb) that was reactive with an epitope shared only by serotypes A and B was identified and designated F10F5. Such an epitope has not been described previously. Immunization of mice with de-O-acetylated serotype A GXM generated a hybridoma that secreted an antibody, designated F12D2, that was reactive with all four serotypes. Unlike previously described monoclonal and polyclonal panspecific antibodies, the reactivity of MAb F12D2 was not altered by de-O-acetylation of GXM. These results indicate that there are at least two panspecific GXM epitopes; one epitope is dependent on O acetylation for antibody reactivity, and the other is independent of O acetylation. This study identifies strategies for production of MAbs that are reactive with subdominant or cryptic GXM epitopes and provides new information regarding the antigenic makeup and the humoral immune response to GXM, an essential virulence factor that is a target for active and passive immunization.

SPECIFIC DEGRADATION OF CRYPTOCOCCUS NEOFORMANS 3723 CAPSULAR POLYSACCHARIDE BY A MICROBIAL ENZYME: I. ISOLATION, PARTIAL PURIFICATION, AND PROPERTIES OF THE ENZYME

1961 ◽  
Vol 7 (1) ◽  
pp. 53-60 ◽  
Author(s):  
Hans H. Gadebusch ◽  
John D. Johnson
Keyword(s):  
Cryptococcus Neoformans ◽  
Capsular Polysaccharide ◽  
Enzyme Reaction ◽  
Partial Purification ◽  
Intracellular Enzyme ◽  
Purification And Properties ◽  
Microbial Enzyme ◽  
Specific Degradation ◽  
Kinetics Of ◽  
Enzyme I

A partially purified intracellular enzyme from a species of Alcaligenes is described which specifically initiates the degradation of the he heteropolysaccharide of Cryptococcus neoformans, isolate 3723, The enzyme is active in the presence of serum and can be inactivated by heating at 45 °C for 10 minutes, The kinetics of the enzyme reaction are similar to those of other enzymes. Recovery and identification of the four known monosaccharides from enzymatic hydrolyzates suggest the presence of a number of other enzymes in these preparations.

scholarly journals Dysfunctional breathing and reaching one’s physiological limit as causes of exercise-induced dyspnoea

Breathe ◽  
2016 ◽  
Vol 12 (2) ◽  
pp. 120-129 ◽  
Author(s):  
Julie Depiazzi ◽  
Mark L. Everard
Keyword(s):  
Drug Therapy ◽  
Cardiopulmonary Exercise Testing ◽  
Cost Effective ◽  
List Type ◽  
Accurate Assessment ◽  
Key Points ◽  
Physiological Limit ◽  
Young Subjects ◽  
Dysfunctional Breathing ◽  
Exercise Induced

Key pointsExcessive exercise-induced shortness of breath is a common complaint. For some, exercise-induced bronchoconstriction is the primary cause and for a small minority there may be an alternative organic pathology. However for many, the cause will be simply reaching their physiological limit or be due to a functional form of dysfunctional breathing, neither of which require drug therapy.The physiological limit category includes deconditioned individuals, such as those who have been through intensive care and require rehabilitation, as well as the unfit and the fit competitive athlete who has reached their limit with both of these latter groups requiring explanation and advice.Dysfunctional breathing is an umbrella term for an alteration in the normal biomechanical patterns of breathing that result in intermittent or chronic symptoms, which may be respiratory and/or nonrespiratory. This alteration may be due to structural causes or, much more commonly, be functional as exemplified by thoracic pattern disordered breathing (PDB) and extrathoracic paradoxical vocal fold motion disorder (pVFMD).Careful history and examination together with spirometry may identify those likely to have PDB and/or pVFMD. Where there is doubt about aetiology, cardiopulmonary exercise testing may be required to identify the deconditioned, unfit or fit individual reaching their physiological limit and PDB, while continuous laryngoscopy during exercise is increasingly becoming the benchmark for assessing extrathoracic causes.Accurate assessment and diagnosis can prevent excessive use of drug therapy and result in effective management of the cause of the individual’s complaint through cost-effective approaches such as reassurance, advice, breathing retraining and vocal exercises.This review provides an overview of the spectrum of conditions that can present as exercise-­induced breathlessness experienced by young subjects participating in sport and aims to promote understanding of the need for accurate assessment of an individual’s symptoms. We will highlight the high incidence of nonasthmatic causes, which simply require reassurance or simple interventions from respiratory physiotherapists or speech pathologists.

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