scholarly journals Genetics of Surface Antigen Expression inPneumocystis carinii

2001 ◽  
Vol 69 (2) ◽  
pp. 627-639 ◽  
Author(s):  
James R. Stringer ◽  
Scott P. Keely
Keyword(s):  
Antigenic Variation ◽  
Molecular Genetic ◽  
Pneumocystis Carinii ◽  
Antigen Expression ◽  
Surface Glycoprotein ◽  
Major Surface Glycoprotein ◽  
Molecular Genetic Data ◽  
Surface Variation ◽  
Surface Antigen Expression ◽  
Major Surface

ABSTRACT This article reviews the molecular genetic data pertaining to the major surface glycoprotein (MSG) gene family of Pneumocystis carinii and its role in surface variation and compares this fungal system to antigenic variation systems in the protozoanTrypanosoma brucei and the bacteriaBorrelia spp.

scholarly journals Expression of variants of the major surface glycoprotein of Pneumocystis carinii.

1996 ◽  
Vol 183 (3) ◽  
pp. 1229-1234 ◽  
Author(s):  
C W Angus ◽  
A Tu ◽  
P Vogel ◽  
M Qin ◽  
J A Kovacs
Keyword(s):  
Defense Mechanisms ◽  
Antigenic Variation ◽  
Pneumocystis Carinii ◽  
Amino Acid Sequences ◽  
Surface Glycoprotein ◽  
Immunofluorescent Staining ◽  
Major Surface Glycoprotein ◽  
Major Surface ◽  
Indirect Immunofluorescent ◽  
Focal Expression

Previously, we have shown that a multicopy family of related but unique genes encodes the major surface glycoprotein (MSG) of Pneumocystis carinii. To examine whether different members of this gene family are expressed by P. carinii, antisera were prepared against peptides whose sequences were determined from the deduced amino acid sequences of variants of rat-derived MSG. Immunohistochemical staining of serial sections of rat lungs of infected animals showed that at least three variants of MSG were expressed in an individual lobe, that there was a focal expression of these variants within the lung, and that the relative numbers of these foci were different. Indirect immunofluorescent staining of purified P. carinii organisms using these antisera revealed that at least three variants of MSG were present in organisms isolated from an individual rat and that both cysts and trophozoites reacted with each antiserum. A substantial difference in the fraction of organisms reacting with a specific antipeptide antiserum was seen when comparing organisms isolated from rats raised in a single colony over a period of two years as well as organisms isolated at one time point from rats raised in different colonies. This demonstration of antigenic variation in P. carinii supports the hypothesis that P. carinii utilizes such variation for evading host defense mechanisms.

scholarly journals Effect of Bronchoalveolar Lavage Fluid from Pneumocystis carinii- Infected Hosts on Phagocytic Activity of Alveolar Macrophages

2004 ◽  
Vol 72 (4) ◽  
pp. 2140-2147 ◽  
Author(s):  
Mark E. Lasbury ◽  
Peimao Lin ◽  
Dennis Tschang ◽  
Pamela J. Durant ◽  
Chao-Hung Lee
Keyword(s):  
Bronchoalveolar Lavage ◽  
Concanavalin A ◽  
Alveolar Macrophages ◽  
Phagocytic Activity ◽  
Pneumocystis Carinii ◽  
Surface Glycoprotein ◽  
Suppressive Activity ◽  
Agarose Beads ◽  
Major Surface Glycoprotein ◽  
Major Surface

ABSTRACT Alveolar macrophages from Pneumocystis carinii-infected rats are defective in phagocytosis. To investigate whether this defect is due to a certain factor present in P. carinii-infected lungs, alveolar macrophages from uninfected rats were incubated with bronchoalveolar lavage (BAL) fluid samples from P. carinii-infected rats. Alveolar macrophages treated with these BAL fluid samples became defective in phagocytosis but remained normal when treated with BAL fluid samples from noninfected or Toxoplasma gondii-infected rats. The suppressive activity of the BAL fluid samples from P. carinii-infected rats on phagocytosis was retained when the BAL fluid samples were passed through a filter with a pore size of 0.45 μm but was lost when the BAL fluid samples were digested with proteases such as trypsin, pepsin, papain, or endopeptidase Gly-C. Lipid fractions of these BAL fluid samples had no suppressive activity on phagocytosis. The suppressive activity of these BAL fluid samples was also lost when they were incubated with concanavalin A-agarose beads, suggesting that the inhibitor is a glycoprotein. The inhibitor was estimated to be larger than 100,000 Da by exclusion filtration. After binding to the concanavalin A-agarose beads, the inhibitor in BAL fluid samples and P. carinii lysate could be eluted with 200 mM methylmannose. Treatment of both the crude BAL fluid samples and P. carinii lysate and the 200 mM methylmannose eluate with antibody against the major surface glycoprotein of P. carinii eliminated their suppressive activity. These results suggest that the factor capable of suppressing the phagocytic activity of alveolar macrophages is P. carinii major surface glycoprotein or one or more of its derivatives.

scholarly journals Characterization of Major Surface Glycoprotein Genes of Human Pneumocystis carinii and High-Level Expression of a Conserved Region

1998 ◽  
Vol 66 (9) ◽  
pp. 4268-4273 ◽  
Author(s):  
Qin Mei ◽  
Ross E. Turner ◽  
Vivian Sorial ◽  
Diane Klivington ◽  
C. William Angus ◽  
...  
Keyword(s):  
Genomic Library ◽  
Pneumocystis Carinii ◽  
Surface Glycoprotein ◽  
High Level Expression ◽  
Serum Samples ◽  
Major Surface Glycoprotein ◽  
Adult Humans ◽  
Major Surface ◽  
High Level

ABSTRACT To facilitate studies of Pneumocystis cariniiinfection in humans, we undertook to better characterize and to express the major surface glycoprotein (MSG) of human P. carinii, an important protein in host-pathogen interactions. Seven MSG genes were cloned from a single isolate by PCR or genomic library screening and were sequenced. The predicted proteins, like rat MSGs, were closely related but unique variants, with a high level of conservation among cysteine residues. A conserved immunodominant region (of approximately 100 amino acids) near the carboxy terminus was expressed at high levels in Escherichia coli and used in Western blot studies. All 49 of the serum samples, which were taken from healthy controls as well as from patients with and withoutP. carinii pneumonia, were reactive with this peptide by Western blotting, supporting the hypothesis that most adult humans have been infected with P. carinii at some point. This recombinant MSG fragment, which is the first human P. carinii antigen available in large quantities, may be a useful reagent for investigating the epidemiology of P. cariniiinfection in humans.

scholarly journals Identification of a Putative Precursor to the Major Surface Glycoprotein of Pneumocystis carinii

1998 ◽  
Vol 66 (2) ◽  
pp. 741-746 ◽  
Author(s):  
Susan M. Sunkin ◽  
Michael J. Linke ◽  
Francis X. McCormack ◽  
Peter D. Walzer ◽  
James R. Stringer
Keyword(s):  
Insect Cells ◽  
Pneumocystis Carinii ◽  
Recombinant Baculovirus ◽  
Polyclonal Antiserum ◽  
Surface Glycoprotein ◽  
Messenger Rnas ◽  
Conserved Sequence ◽  
Amino Acid Peptide ◽  
Major Surface Glycoprotein ◽  
Major Surface

ABSTRACT The major surface glycoprotein (MSG) of Pneumocystis cariniif. sp. carinii is a family of proteins encoded by a family of heterogeneous genes. Messenger RNAs encoding different MSGs each begin with the same 365-bp sequence, called the Upstream Conserved Sequence (UCS), which is in frame with the contiguous MSG sequence. The UCS contains several potential start sites for translation. To determine if translation of MSG mRNAs begins in the UCS, polyclonal antiserum was raised against the 123-amino-acid peptide encoded by the UCS. The anti-UCS serum reacted with a P. carinii protein that migrated at 170 kDa; however, it did not react with the mature MSG protein, which migrates at 116 kDa. A 170-kDa protein was immunoprecipitated with anti-UCS serum and shown to react with a monoclonal antibody against a conserved MSG epitope. To explore the functional role of the UCS in the trafficking of MSG, the nucleotide sequence encoding the UCS peptide was ligated to the 5′ end of an MSG gene and incorporated into a recombinant baculovirus. Insect cells infected with the UCS-MSG hybrid gene expressed a 160-kDa protein which was N-glycosylated. By contrast, insect cells infected with a baculovirus carrying an MSG gene lacking the UCS expressed a nonglycosylated 130-kDa protein. These data suggest that in P. carinii, translation begins in the UCS to produce a pre-MSG protein, which is subsequently directed to the endoplasmic reticulum and processed to the mature form by proteolytic cleavage.

Characterization of Major Surface Glycoprotein Genes of Human Pneumocystis carinii and High-Level Expression of a Conserved Region

1998 ◽  
Vol 66 (9) ◽  
pp. 4268-4273
Author(s):  
Qin Mei ◽  
Ross E. Turner ◽  
Vivian Sorial ◽  
Diane Klivington ◽  
C. William Angus ◽  
...  
Keyword(s):  
Pneumocystis Carinii ◽  
Surface Glycoprotein ◽  
High Level Expression ◽  
Major Surface Glycoprotein ◽  
Conserved Region ◽  
Major Surface ◽  
High Level
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