scholarly journals The mouse antibody response to infection with Cryptococcus neoformans: VH and VL usage in polysaccharide binding antibodies.

1991 ◽  
Vol 174 (1) ◽  
pp. 151-160 ◽  
Author(s):  
A Casadevall ◽  
M D Scharff
Keyword(s):  
Antibody Response ◽  
Cryptococcus Neoformans ◽  
Capsular Polysaccharide ◽  
Light Chains ◽  
Serious Infections ◽  
Vh Gene ◽  
Kappa Light Chains ◽  
Precursor B Cells ◽  
Mouse Antibody ◽  
Responder Mouse

Cryptococcus neoformans is a ubiquitous fungus that can cause serious infections in humans. The fungus has a polysaccharide (C. neoformans capsular polysaccharide; CNPS) capsule that contributes to its pathogenicity and can elicit an antibody response. Nevertheless, only 4 of 60 BALB/c mice chronically infected with C. neoformans had a detectable increase in serum anti-CNPS. The sera of three responder mice contained both IgM and IgG anti-CNPS antibody, and the titers of lambda and kappa anti-CNPS antibody were approximately equal. Eight IgM and one IgG3 monoclonal antibodies (mAbs) were generated from the spleen of one responder mouse, and one IgA was generated from the spleen of another mouse. Seven of the IgMs, the IgG3, and the IgA mAb had lambda light chains and were specific for serotype D CNPS. Molecular analysis confirmed that this was a highly restricted antibody response. All of the D-specific antibodies used VH441, JH3, and either V lambda 2/J lambda 2 or V lambda 1/J lambda 1, and all had the same heavy chain CDR3 amino acid sequence, even though there were differences in the nucleotide sequence of the N/D segment. One IgM mAb reacted with both serotype A and D CNPS, and this mAb used different VH and JH genetic elements and had kappa light chains. All the anti-CNPS mAbs used J proximal VH gene elements that have previously been shown to bind dextran and other polysaccharides. Sequence and Southern blot analysis indicate that the serotype-D CNPS-specific mAbs arose from only a few precursor B cells.

scholarly journals Immunogenicity and Efficacy of Cryptococcus neoformans Capsular Polysaccharide Glucuronoxylomannan Peptide Mimotope-Protein Conjugates in Human Immunoglobulin Transgenic Mice

2004 ◽  
Vol 72 (1) ◽  
pp. 196-208 ◽  
Author(s):  
Robert W. Maitta ◽  
Kausik Datta ◽  
Andrew Lees ◽  
Shelley Sims Belouski ◽  
Liise-anne Pirofski
Keyword(s):  
Transgenic Mice ◽  
Antibody Response ◽  
Cryptococcus Neoformans ◽  
Capsular Polysaccharide ◽  
Serum Antibody ◽  
Human Immunoglobulin ◽  
Enzyme Linked Immunosorbent Assay ◽  
Human Antibody ◽  
Human Antibodies ◽  
Risk Of Death

ABSTRACT Peptide mimotopes of capsular polysaccharides have been proposed as antigens for vaccines against encapsulated pathogens. In this study, we determined the antibody response to and efficacy of P13, a peptide mimetic of the Cryptococcus neoformans capsular polysaccharide glucuronoxylomannan (GXM), in mice that produce human antibodies. P13 was conjugated to tetanus toxoid (TT) or diphtheria toxoid (DT) and administered subcutaneously in Alhydrogel with or without CpG to mice transgenic for human immunoglobulin loci (XenoMouse mice) and expressing either immunoglobulin G2 (IgG2) (G2 mice) or IgG4 (G4 mice). Mice were vaccinated and revaccinated two or three times. The serum antibody responses of the mice to GXM and P13 and antibody idiotype expression were analyzed by an enzyme-linked immunosorbent assay. The results showed that both P13-TT and P13-DT were antigenic, inducing a mimetic response to P13 in both G2 and G4 mice, and immunogenic, inducing a mimotope response including VH3 (idiotype)-positive antibodies to GXM in G2 but not G4 mice. CpG led to higher titers of IgG to P13 and GXM in P13-TT-vaccinated G2 mice. C. neoformans challenge of P13-protein conjugate-vaccinated and control G2 mice induced anamnestic IgG- and VH3-positive responses to GXM and was associated with a significantly decreased risk of death and a prolongation of survival in P13-DT-vaccinated mice compared to phosphate-buffered saline-treated or protein carrier-vaccinated mice. These findings reveal that P13 elicited a human antibody response with VH3 expression in human immunoglobulin transgenic mice that has been observed for human antibodies to GXM and support the concept that peptide mimotope-based vaccines may hold promise for the treatment of C. neoformans infections.

scholarly journals Murine Immune Response to Neisseria meningitidis Group C Capsular Polysaccharide: Analysis of Monoclonal Antibodies Generated in Response to a Thymus-Independent Antigen and a Thymus-Dependent Toxoid Conjugate Vaccine

2000 ◽  
Vol 68 (1) ◽  
pp. 239-246 ◽  
Author(s):  
Pablo A. García-Ojeda ◽  
Martha E. Monser ◽  
Leonard J. Rubinstein ◽  
Harold J. Jennings ◽  
Kathryn E. Stein
Keyword(s):  
Monoclonal Antibody ◽  
Immune Response ◽  
Gene Family ◽  
Neisseria Meningitidis ◽  
Capsular Polysaccharide ◽  
Immunoglobulin M ◽  
Light Chains ◽  
Dot Blot ◽  
Fine Specificity ◽  
Kappa Light Chains

ABSTRACT Antibody (Ab) responses to polysaccharides (PSs) such asNeisseria meningitidis group C PS (MCPS) are characterized as being thymus independent (TI) and are restricted with regard to clonotype and isotype expression. PS conjugated to proteins, e.g., MCPS coupled to tetanus toxoid (MCPS-TT), elicits a thymus-dependent (TD) response. In order to understand the influence of the form of a vaccine (TI versus TD) on the Ab repertoire, we generated monoclonal antibody (MAb) panels from mice immunized and boosted with MCPS or MCPS-TT in different ways. The panels of MAbs were examined for isotype, fine specificity, affinity, and VH gene family usage. The use of MCPS-TT resulted in a shift in the isotype from immunoglobulin M (IgM) and IgG3 elicited in response to the MCPS to primarily IgG1. This isotype shift was accompanied by a change in the fine specificity of the response to the conjugate compared to that of PS. New fine specificities and increased affinity were observed in response to the TD antigen (Ag). Dot blot and Northern analyses of MCPS MAbs revealed that VH gene family usage is dominated by VHJ558, used by 23 of 39 MAbs. VH3609 was seen in three MAbs of restricted fine specificity. VHQ52, VH7183, and VHVGAM3-8 were seen in more than one MAb across these panels, while VH10 and VHX24 were detected only once in response to the TI-2 Ag. All MAbs in the panels utilized kappa light chains, and all functional Jκ genes were expressed.

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.

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