The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Bernard La Scola - One of the best experts on this subject based on the ideXlab platform.
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Acanthamoeba Polyphaga mimivirus prevents amoebal encystment mediating serine proteinase expression and circumvents cell encystment
Journal of Virology, 2015Co-Authors: Paulo V M Boratto, Bernard La Scola, Jonas D Albarnaz, Gabriel Magno De Freitas Almeida, Lucas Moreira Botelho, Alide Caroline Lima Fontes, Adriana Oliveira Costa, Daniel Assis Santos, Claudio A Bonjardim, Erna Geessien KroonAbstract:Acanthamoeba is a genus of free-living amoebas distributed worldwide. Few studies have explored the interactions between these protozoa and their infecting giant virus, Acanthamoeba Polyphaga mimivirus (APMV). Here we show that, once the amoebal encystment is triggered, trophozoites become significantly resistant to APMV. Otherwise, upon infection, APMV is able to interfere with the expression of a serine proteinase related to amoebal encystment and the encystment can no longer be triggered.
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Acanthamoeba Polyphaga mimivirus and other giant viruses: an open field to outstanding discoveries
Virology Journal, 2014Co-Authors: Jônatas S Abrahão, Bernard La Scola, Paulo V M Boratto, Fábio P Dornas, Lorena Cf Silva, Gabriel M Almeida, Phillipe Colson, Erna G KroonAbstract:In 2003, Acanthamoeba Polyphaga mimivirus (APMV) was first described and began to impact researchers around the world, due to its structural and genetic complexity. This virus founded the family Mimiviridae . In recent years, several new giant viruses have been isolated from different environments and specimens. Giant virus research is in its initial phase and information that may arise in the coming years may change current conceptions of life, diversity and evolution. Thus, this review aims to condense the studies conducted so far about the features and peculiarities of APMV, from its discovery to its clinical relevance.
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Acanthamoeba Polyphaga mimivirus Virophage Seroconversion in Travelers Returning from Laos
Emerging Infectious Diseases, 2012Co-Authors: Philippe Parola, Elisabeth Botelho-nevers, Christelle Desnues, Bernard La Scola, Aurelie Renvoise, Didier RaoultAbstract:During January 2010, a husband and wife returned from Laos to France with probable parasitic disease. Increased antibodies against an Acanthamoeba Polyphaga mimivirus virophage indicated seroconversion. While in Laos, they had eaten raw fish, a potential source of the virophage. This virophage, associated with giant viruses suspected to cause pneumonia, could be an emerging pathogen.
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viruses with more than 1 000 genes mamavirus a new Acanthamoeba Polyphaga mimivirus strain and reannotation of mimivirus genes
Genome Biology and Evolution, 2011Co-Authors: Philippe Colson, Catherine Robert, Bernard La Scola, Ghislain Fournous, Didier Raoult, Natalya Yutin, Svetlana A Shabalina, Eugene V KooninAbstract:The genome sequence of the Mamavirus, a new Acanthamoeba Polyphaga mimivirus strain, is reported. With 1,191,693 nt in length and 1,023 predicted protein-coding genes, the Mamavirus has the largest genome among the known viruses. The genomes of the Mamavirus and the previously described Mimivirus are highly similar in both the protein-coding genes and the intergenic regions. However, the Mamavirus contains an extra 5′-terminal segment that encompasses primarily disrupted duplicates of genes present elsewhere in the genome. The Mamavirus also has several unique genes including a small regulatory polyA polymerase subunit that is shared with poxviruses. Detailed analysis of the protein sequences of the two Mimiviruses led to a substantial amendment of the functional annotation of the viral genomes.
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Specific recognition of the major capsid protein of Acanthamoeba Polyphaga mimivirus by sera of patients infected by Francisella tularensis.
Fems Microbiology Letters, 2009Co-Authors: Nicolas Pelletier, Didier Raoult, Bernard La ScolaAbstract:Francisella tularensis, a Gram-negative cocobacillus responsible for tularemia, especially severe pneumonia, is a facultative intracellular bacterium classified as a biological agent of category A. Acanthamoeba Polyphaga mimivirus (APM) is a recently discovered giant virus suspected to be an agent of both community- and hospital-acquired pneumonia. During specificity testing of antibody to APM detection, it was observed that nearly all patients infected by F. tularensis had elevated antibody titers to APM. In the present study, we investigated this cross-reactivity by immunoproteomics. Apart from the detection of antibodies reactive to new immunoreactive proteins in patients infected by F. tularensis, we showed that the sera of those patients recognize specifically two proteins of APM: the capsid protein and another protein of unknown function. No common protein motif can be detected in silico based on genome analysis of the involved protein. Furthermore, this cross-reactivity was confirmed with the recombinant capsid protein expressed in Escherichia coli. This emphasizes the pitfalls of a serological diagnosis of pneumonia.
S.n. Smith - One of the best experts on this subject based on the ideXlab platform.
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Acanthamoeba Polyphaga trophozoite binding of representative fungal single cell forms
Acta Protozoologica, 2010Co-Authors: S.n. Smith, Jamshaid Ali Khan, Bishal Mohindru, Mark Prince, Richard A. Armstrong, John M. WhippsAbstract:Acanthamoeba Polyphaga trophozoites bind yeast cells of Candida albicans isolates within a few hours, leaving few cells in suspension or still attached to trophozoite surfaces. The nature of yeast cell recognition, mediated by an Acanthamoebal trophozoite mannose binding protein is confirmed by experiments utilizing concentration dependent mannose hapten blocking. Similarly, acapsulate cells of Cryptococcus neoformans are also bound within a relatively short timescale. However, even after protracted incubation many capsulate cells of Cryptococcus remain in suspension, suggesting that the capsulate cell form of this species is not predated by Acanthamoebal trophozoites. Further aspects of the association of Acanthamoeba and fungi are apparent when studying their interaction with conidia of the biocontrol agent Coniothyrium minitans. Conidia which readily bind with increasing maturity of up to 42 days, were little endocytosed and even released. Cell and conidial surface mannose as determined by FITC-lectin binding, flow cytometry with associated ligand binding analysis and hapten blocking studies demonstrates the following phenomena. Candida isolates and acapsulate Cryptococcus expose most mannose, while capsulate Cryptococcus cells exhibit least exposure commensurate with yeast cellular binding or lack of trophozoites. Conidia of Coniothyrium, albeit in a localized fashion, also manifest surface mannose exposure but as shown by Bmax values, in decreasing amounts with increasing maturity. Contrastingly such conidia experience greater trophozoite binding with maturation, thereby questioning the primacy of a trophozoite mannose-binding-protein recognition model.
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analysis of Acanthamoeba Polyphaga surface carbohydrate exposure by fitc lectin binding and fluorescence evaluation
Journal of Applied Microbiology, 2004Co-Authors: Edward A. G. Elloway, Richard A. Armstrong, Roger Bird, Steven L. Kelly, S.n. SmithAbstract:Aims: Characterization of the representative protozoan Acanthamoeba Polyphaga surface carbohydrate exposure by a novel combination of flow cytometry and ligand-receptor analysis. Methods and Results: Trophozoite and cyst morphological forms were exposed to a panel of FITC-lectins. Population fluorescence associated with FITC-lectin binding to Acanthamoebal surface moieties was ascertained by flow cytometry. Increasing concentrations of representative FITC-lectins, saturation binding and determination of K d and relative Bmax values were employed to characterize carbohydrate residue exposure. FITC-lectins specific for N-acetylglucosamine, N-acetylgalactosamine and mannose/glucose were readily bound by trophozoite and cyst surfaces. Minor incremental increases in FITC-lectin concentration resulted in significant differences in surface fluorescence intensity and supported the calculation of ligand-binding determinants, Kd and relative B max, which gave a trophozoite and cyst rank order of lectin affinity and surface receptor presence. Conclusions: Trophozoites and cysts expose similar surface carbohydrate residues, foremost amongst which is N-acetylglucosamine, in varying orientation and availability. Significance and Impact of the Study: The outlined versatile combination of flow cytometry and ligand-receptor analysis allowed the characterization of surface carbohydrate exposure by protozoan morphological forms and in turn will support a valid comparison of carbohydrate exposure by other single-cell protozoa and eucaryotic microbes analysed in the same manner.
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Analysis of Acanthamoeba Polyphaga surface carbohydrate exposure by FITC–lectin binding and fluorescence evaluation
Journal of applied microbiology, 2004Co-Authors: Edward A. G. Elloway, Richard A. Armstrong, Roger Bird, Steven L. Kelly, S.n. SmithAbstract:Aims: Characterization of the representative protozoan Acanthamoeba Polyphaga surface carbohydrate exposure by a novel combination of flow cytometry and ligand-receptor analysis. Methods and Results: Trophozoite and cyst morphological forms were exposed to a panel of FITC-lectins. Population fluorescence associated with FITC-lectin binding to Acanthamoebal surface moieties was ascertained by flow cytometry. Increasing concentrations of representative FITC-lectins, saturation binding and determination of K d and relative Bmax values were employed to characterize carbohydrate residue exposure. FITC-lectins specific for N-acetylglucosamine, N-acetylgalactosamine and mannose/glucose were readily bound by trophozoite and cyst surfaces. Minor incremental increases in FITC-lectin concentration resulted in significant differences in surface fluorescence intensity and supported the calculation of ligand-binding determinants, Kd and relative B max, which gave a trophozoite and cyst rank order of lectin affinity and surface receptor presence. Conclusions: Trophozoites and cysts expose similar surface carbohydrate residues, foremost amongst which is N-acetylglucosamine, in varying orientation and availability. Significance and Impact of the Study: The outlined versatile combination of flow cytometry and ligand-receptor analysis allowed the characterization of surface carbohydrate exposure by protozoan morphological forms and in turn will support a valid comparison of carbohydrate exposure by other single-cell protozoa and eucaryotic microbes analysed in the same manner.
Didier Raoult - One of the best experts on this subject based on the ideXlab platform.
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Acanthamoeba Polyphaga mimivirus Virophage Seroconversion in Travelers Returning from Laos
Emerging Infectious Diseases, 2012Co-Authors: Philippe Parola, Elisabeth Botelho-nevers, Christelle Desnues, Bernard La Scola, Aurelie Renvoise, Didier RaoultAbstract:During January 2010, a husband and wife returned from Laos to France with probable parasitic disease. Increased antibodies against an Acanthamoeba Polyphaga mimivirus virophage indicated seroconversion. While in Laos, they had eaten raw fish, a potential source of the virophage. This virophage, associated with giant viruses suspected to cause pneumonia, could be an emerging pathogen.
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viruses with more than 1 000 genes mamavirus a new Acanthamoeba Polyphaga mimivirus strain and reannotation of mimivirus genes
Genome Biology and Evolution, 2011Co-Authors: Philippe Colson, Catherine Robert, Bernard La Scola, Ghislain Fournous, Didier Raoult, Natalya Yutin, Svetlana A Shabalina, Eugene V KooninAbstract:The genome sequence of the Mamavirus, a new Acanthamoeba Polyphaga mimivirus strain, is reported. With 1,191,693 nt in length and 1,023 predicted protein-coding genes, the Mamavirus has the largest genome among the known viruses. The genomes of the Mamavirus and the previously described Mimivirus are highly similar in both the protein-coding genes and the intergenic regions. However, the Mamavirus contains an extra 5′-terminal segment that encompasses primarily disrupted duplicates of genes present elsewhere in the genome. The Mamavirus also has several unique genes including a small regulatory polyA polymerase subunit that is shared with poxviruses. Detailed analysis of the protein sequences of the two Mimiviruses led to a substantial amendment of the functional annotation of the viral genomes.
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Is Acanthamoeba Polyphaga Mimivirus an Emerging Causative Agent of Pneumonia
Emerging Infections 9, 2010Co-Authors: Philippe Colson, Didier RaoultAbstract:Acanthamoeba Polyphaga mimivirus (APMV) is the first member of a new family of nucleocytoplasmic large DNA viruses called the Mimiviridae. Another giant virus, named mamavirus, was discovered in 2008 and is considered another APMV strain. Moreover, nosocomially acquired pneumonias account for 10 to 15% of all hospital-acquired infections, and pneumonia is actually the leading cause of nosocomial infection in intensive care units (ICU), where ventilator-associated pneumonias (VAP) are the most frequently observed hospital-acquired infections and are associated with high morbidity and mortality. Mimivirus was one of the agents investigated by serological testing, among other conventional pneumonia agents. Among pneumonia patients with amoeba-associated pathogens, more had seroconversion to mimivirus (5 cases) than to any other pathogen. In addition, mimivirus was second among the four most frequently encountered agents of pneumonia diagnosed with high levels of evidence (3.8%), behind Pseudomonas aeruginosa (4.8%) but before Escherichia coli (1.9%) and Legionella pneumophila (1.4%). It should be noted that only one-third of the therapeutic regimens are effective in pneumonia patients needing ventilators. Serology linked APMV to pneumonia, but infection was documented by PCR in only one patient. current data prompt us to consider APMV and its relatives as biosafety level 2 pathogens and to enforce the respiratory care protocols aimed at limiting exposure to amoeba-associated microorganisms (AAMs).
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Specific recognition of the major capsid protein of Acanthamoeba Polyphaga mimivirus by sera of patients infected by Francisella tularensis.
Fems Microbiology Letters, 2009Co-Authors: Nicolas Pelletier, Didier Raoult, Bernard La ScolaAbstract:Francisella tularensis, a Gram-negative cocobacillus responsible for tularemia, especially severe pneumonia, is a facultative intracellular bacterium classified as a biological agent of category A. Acanthamoeba Polyphaga mimivirus (APM) is a recently discovered giant virus suspected to be an agent of both community- and hospital-acquired pneumonia. During specificity testing of antibody to APM detection, it was observed that nearly all patients infected by F. tularensis had elevated antibody titers to APM. In the present study, we investigated this cross-reactivity by immunoproteomics. Apart from the detection of antibodies reactive to new immunoreactive proteins in patients infected by F. tularensis, we showed that the sera of those patients recognize specifically two proteins of APM: the capsid protein and another protein of unknown function. No common protein motif can be detected in silico based on genome analysis of the involved protein. Furthermore, this cross-reactivity was confirmed with the recombinant capsid protein expressed in Escherichia coli. This emphasizes the pitfalls of a serological diagnosis of pneumonia.
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Specific recognition of the major capsid protein of Acanthamoeba Polyphaga mimivirus by sera of patients infected by Francisella tularensis.
Fems Microbiology Letters, 2009Co-Authors: Nicolas Pelletier, Didier Raoult, Bernard La ScolaAbstract:Francisella tularensis, a Gram-negative cocobacillus responsible for tularemia, especially severe pneumonia, is a facultative intracellular bacterium classified as a biological agent of category A. Acanthamoeba Polyphaga mimivirus (APM) is a recently discovered giant virus suspected to be an agent of both community- and hospital-acquired pneumonia. During specificity testing of antibody to APM detection, it was observed that nearly all patients infected by F. tularensis had elevated antibody titers to APM. In the present study, we investigated this cross-reactivity by immunoproteomics. Apart from the detection of antibodies reactive to new immunoreactive proteins in patients infected by F. tularensis, we showed that the sera of those patients recognize specifically two proteins of APM: the capsid protein and another protein of unknown function. No common protein motif can be detected in silico based on genome analysis of the involved protein. Furthermore, this cross-reactivity was confirmed with the recombinant capsid protein expressed in Escherichia coli. This emphasizes the pitfalls of a serological diagnosis of pneumonia.
Steven L. Kelly - One of the best experts on this subject based on the ideXlab platform.
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Azole antifungal agents to treat the human pathogens Acanthamoeba castellanii and Acanthamoeba Polyphaga through inhibition of sterol 14α-demethylase (CYP51)
Antimicrobial agents and chemotherapy, 2015Co-Authors: David C. Lamb, Andrew G. S. Warrilow, Nicola J. Rolley, Josie E. Parker, W. David Nes, Stephen N. Smith, Diane E. Kelly, Steven L. KellyAbstract:In this study, we investigate the amebicidal activities of the pharmaceutical triazole CYP51 inhibitors fluconazole, itraconazole, and voriconazole against Acanthamoeba castellanii and Acanthamoeba Polyphaga and assess their potential as therapeutic agents against Acanthamoeba infections in humans. Amebicidal activities of the triazoles were assessed by in vitro minimum inhibition concentration (MIC) determinations using trophozoites of A. castellanii and A. Polyphaga. In addition, triazole effectiveness was assessed by ligand binding studies and inhibition of CYP51 activity of purified A. castellanii CYP51 (AcCYP51) that was heterologously expressed in Escherichia coli. Itraconazole and voriconazole bound tightly to AcCYP51 (dissociation constant [Kd] of 10 and 13 nM), whereas fluconazole bound weakly (Kd of 2,137 nM). Both itraconazole and voriconazole were confirmed to be strong inhibitors of AcCYP51 activity (50% inhibitory concentrations [IC50] of 0.23 and 0.39 μM), whereas inhibition by fluconazole was weak (IC50, 30 μM). However, itraconazole was 8- to 16-fold less effective (MIC, 16 mg/liter) at inhibiting A. Polyphaga and A. castellanii cell proliferation than voriconazole (MIC, 1 to 2 mg/liter), while fluconazole did not inhibit Acanthamoeba cell division (MIC, >64 mg/liter) in vitro. Voriconazole was an effective inhibitor of trophozoite proliferation for A. castellanii and A. Polyphaga; therefore, it should be evaluated in trials versus itraconazole for controlling Acanthamoeba infections.
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analysis of Acanthamoeba Polyphaga surface carbohydrate exposure by fitc lectin binding and fluorescence evaluation
Journal of Applied Microbiology, 2004Co-Authors: Edward A. G. Elloway, Richard A. Armstrong, Roger Bird, Steven L. Kelly, S.n. SmithAbstract:Aims: Characterization of the representative protozoan Acanthamoeba Polyphaga surface carbohydrate exposure by a novel combination of flow cytometry and ligand-receptor analysis. Methods and Results: Trophozoite and cyst morphological forms were exposed to a panel of FITC-lectins. Population fluorescence associated with FITC-lectin binding to Acanthamoebal surface moieties was ascertained by flow cytometry. Increasing concentrations of representative FITC-lectins, saturation binding and determination of K d and relative Bmax values were employed to characterize carbohydrate residue exposure. FITC-lectins specific for N-acetylglucosamine, N-acetylgalactosamine and mannose/glucose were readily bound by trophozoite and cyst surfaces. Minor incremental increases in FITC-lectin concentration resulted in significant differences in surface fluorescence intensity and supported the calculation of ligand-binding determinants, Kd and relative B max, which gave a trophozoite and cyst rank order of lectin affinity and surface receptor presence. Conclusions: Trophozoites and cysts expose similar surface carbohydrate residues, foremost amongst which is N-acetylglucosamine, in varying orientation and availability. Significance and Impact of the Study: The outlined versatile combination of flow cytometry and ligand-receptor analysis allowed the characterization of surface carbohydrate exposure by protozoan morphological forms and in turn will support a valid comparison of carbohydrate exposure by other single-cell protozoa and eucaryotic microbes analysed in the same manner.
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Analysis of Acanthamoeba Polyphaga surface carbohydrate exposure by FITC–lectin binding and fluorescence evaluation
Journal of applied microbiology, 2004Co-Authors: Edward A. G. Elloway, Richard A. Armstrong, Roger Bird, Steven L. Kelly, S.n. SmithAbstract:Aims: Characterization of the representative protozoan Acanthamoeba Polyphaga surface carbohydrate exposure by a novel combination of flow cytometry and ligand-receptor analysis. Methods and Results: Trophozoite and cyst morphological forms were exposed to a panel of FITC-lectins. Population fluorescence associated with FITC-lectin binding to Acanthamoebal surface moieties was ascertained by flow cytometry. Increasing concentrations of representative FITC-lectins, saturation binding and determination of K d and relative Bmax values were employed to characterize carbohydrate residue exposure. FITC-lectins specific for N-acetylglucosamine, N-acetylgalactosamine and mannose/glucose were readily bound by trophozoite and cyst surfaces. Minor incremental increases in FITC-lectin concentration resulted in significant differences in surface fluorescence intensity and supported the calculation of ligand-binding determinants, Kd and relative B max, which gave a trophozoite and cyst rank order of lectin affinity and surface receptor presence. Conclusions: Trophozoites and cysts expose similar surface carbohydrate residues, foremost amongst which is N-acetylglucosamine, in varying orientation and availability. Significance and Impact of the Study: The outlined versatile combination of flow cytometry and ligand-receptor analysis allowed the characterization of surface carbohydrate exposure by protozoan morphological forms and in turn will support a valid comparison of carbohydrate exposure by other single-cell protozoa and eucaryotic microbes analysed in the same manner.
Edward A. G. Elloway - One of the best experts on this subject based on the ideXlab platform.
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analysis of Acanthamoeba Polyphaga surface carbohydrate exposure by fitc lectin binding and fluorescence evaluation
Journal of Applied Microbiology, 2004Co-Authors: Edward A. G. Elloway, Richard A. Armstrong, Roger Bird, Steven L. Kelly, S.n. SmithAbstract:Aims: Characterization of the representative protozoan Acanthamoeba Polyphaga surface carbohydrate exposure by a novel combination of flow cytometry and ligand-receptor analysis. Methods and Results: Trophozoite and cyst morphological forms were exposed to a panel of FITC-lectins. Population fluorescence associated with FITC-lectin binding to Acanthamoebal surface moieties was ascertained by flow cytometry. Increasing concentrations of representative FITC-lectins, saturation binding and determination of K d and relative Bmax values were employed to characterize carbohydrate residue exposure. FITC-lectins specific for N-acetylglucosamine, N-acetylgalactosamine and mannose/glucose were readily bound by trophozoite and cyst surfaces. Minor incremental increases in FITC-lectin concentration resulted in significant differences in surface fluorescence intensity and supported the calculation of ligand-binding determinants, Kd and relative B max, which gave a trophozoite and cyst rank order of lectin affinity and surface receptor presence. Conclusions: Trophozoites and cysts expose similar surface carbohydrate residues, foremost amongst which is N-acetylglucosamine, in varying orientation and availability. Significance and Impact of the Study: The outlined versatile combination of flow cytometry and ligand-receptor analysis allowed the characterization of surface carbohydrate exposure by protozoan morphological forms and in turn will support a valid comparison of carbohydrate exposure by other single-cell protozoa and eucaryotic microbes analysed in the same manner.
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Analysis of Acanthamoeba Polyphaga surface carbohydrate exposure by FITC–lectin binding and fluorescence evaluation
Journal of applied microbiology, 2004Co-Authors: Edward A. G. Elloway, Richard A. Armstrong, Roger Bird, Steven L. Kelly, S.n. SmithAbstract:Aims: Characterization of the representative protozoan Acanthamoeba Polyphaga surface carbohydrate exposure by a novel combination of flow cytometry and ligand-receptor analysis. Methods and Results: Trophozoite and cyst morphological forms were exposed to a panel of FITC-lectins. Population fluorescence associated with FITC-lectin binding to Acanthamoebal surface moieties was ascertained by flow cytometry. Increasing concentrations of representative FITC-lectins, saturation binding and determination of K d and relative Bmax values were employed to characterize carbohydrate residue exposure. FITC-lectins specific for N-acetylglucosamine, N-acetylgalactosamine and mannose/glucose were readily bound by trophozoite and cyst surfaces. Minor incremental increases in FITC-lectin concentration resulted in significant differences in surface fluorescence intensity and supported the calculation of ligand-binding determinants, Kd and relative B max, which gave a trophozoite and cyst rank order of lectin affinity and surface receptor presence. Conclusions: Trophozoites and cysts expose similar surface carbohydrate residues, foremost amongst which is N-acetylglucosamine, in varying orientation and availability. Significance and Impact of the Study: The outlined versatile combination of flow cytometry and ligand-receptor analysis allowed the characterization of surface carbohydrate exposure by protozoan morphological forms and in turn will support a valid comparison of carbohydrate exposure by other single-cell protozoa and eucaryotic microbes analysed in the same manner.
