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Epitope location in the Cryptococcus neoformans capsule is a determinant of antibody efficacy.

Nussbaum G, Cleare W, Casadevall A, Scharff MD, Valadon P - J. Exp. Med. (1997)

Bottom Line: The IgM mAbs 12A1 and 13F1 originated from the same B cell and differ only by somatic mutations in their variable regions; yet mAb 12A1 protects against serotype D infection, while mAb 13F1 does not.Immunofluorescence and immunoelectron microscopy studies revealed differences in antibody localization within the capsule of serotype D strain; mAb 12A1 bound to the outer rim of the capsule resulting in an annular pattern, whereas mAb 13F1 bound throughout the capsule and had a punctate appearance.Annular binding, but not punctate binding, was associated with increased opsonic efficacy for phagocytosis of C. neoformans by J774.16 macrophage-like cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.

ABSTRACT
Monoclonal antibodies (mAbs) to the polysaccharide capsule of Cryptococcus neoformans can prolong survival in mice. However, the properties of antibodies that mediate protection are not fully understood. The IgM mAbs 12A1 and 13F1 originated from the same B cell and differ only by somatic mutations in their variable regions; yet mAb 12A1 protects against serotype D infection, while mAb 13F1 does not. Phage peptide display libraries were used to analyze the fine specificity of these two mAbs. The selection of distinct peptide motifs from identical libraries confirmed that mAbs 12A1 and 13F1 bound to two distinct epitopes. Immunofluorescence and immunoelectron microscopy studies revealed differences in antibody localization within the capsule of serotype D strain; mAb 12A1 bound to the outer rim of the capsule resulting in an annular pattern, whereas mAb 13F1 bound throughout the capsule and had a punctate appearance. The difference in the binding pattern of mAb 12A1 and 13F1 was not observed on serotype A organisms, where both mAbs bound to the capsule with an annular fluorescence pattern. The fluorescence pattern of binding correlated with protective efficacy; mAb 13F1 prolonged survival of mice infected with the J11 serotype A strain (annular fluorescence), but not serotype D strains (punctate pattern). Annular binding, but not punctate binding, was associated with increased opsonic efficacy for phagocytosis of C. neoformans by J774.16 macrophage-like cells. The correlation between capsular binding pattern, opsonic activity, and ability to prolong survival suggests that the efficacy of anticryptococcal antibodies is dependent upon where they bind in the polysaccharide capsule.

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Opsonic activity of mAbs 12A1 and 13F1 in the presence of  J774.16 macrophages on (A) C. neoformans serotype D strain 24067, and  (B) C. neoformans serotype A strain J11.
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Figure 4: Opsonic activity of mAbs 12A1 and 13F1 in the presence of J774.16 macrophages on (A) C. neoformans serotype D strain 24067, and (B) C. neoformans serotype A strain J11.

Mentions: mAbs 12A1 and 13F1 were tested for their ability to promote opsonization of organisms by macrophages. mAb 12A1 significantly enhanced phagocytosis when added to monolayers of J774.16 and strain 24067 cells (Fig. 4 A). Using the same conditions, 13F1 did not enhance phagocytosis, even at concentrations as high as 25 μg/ml. With the J11 serotype A organisms and low antibody concentrations, 12A1 was still more effective than 13F1. However, above 10 μg/ml, both mAbs promoted significant phagocytosis (Fig. 4 B). Annular binding is therefore associated with more effective opsonization than punctate binding.


Epitope location in the Cryptococcus neoformans capsule is a determinant of antibody efficacy.

Nussbaum G, Cleare W, Casadevall A, Scharff MD, Valadon P - J. Exp. Med. (1997)

Opsonic activity of mAbs 12A1 and 13F1 in the presence of  J774.16 macrophages on (A) C. neoformans serotype D strain 24067, and  (B) C. neoformans serotype A strain J11.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2196155&req=5

Figure 4: Opsonic activity of mAbs 12A1 and 13F1 in the presence of J774.16 macrophages on (A) C. neoformans serotype D strain 24067, and (B) C. neoformans serotype A strain J11.
Mentions: mAbs 12A1 and 13F1 were tested for their ability to promote opsonization of organisms by macrophages. mAb 12A1 significantly enhanced phagocytosis when added to monolayers of J774.16 and strain 24067 cells (Fig. 4 A). Using the same conditions, 13F1 did not enhance phagocytosis, even at concentrations as high as 25 μg/ml. With the J11 serotype A organisms and low antibody concentrations, 12A1 was still more effective than 13F1. However, above 10 μg/ml, both mAbs promoted significant phagocytosis (Fig. 4 B). Annular binding is therefore associated with more effective opsonization than punctate binding.

Bottom Line: The IgM mAbs 12A1 and 13F1 originated from the same B cell and differ only by somatic mutations in their variable regions; yet mAb 12A1 protects against serotype D infection, while mAb 13F1 does not.Immunofluorescence and immunoelectron microscopy studies revealed differences in antibody localization within the capsule of serotype D strain; mAb 12A1 bound to the outer rim of the capsule resulting in an annular pattern, whereas mAb 13F1 bound throughout the capsule and had a punctate appearance.Annular binding, but not punctate binding, was associated with increased opsonic efficacy for phagocytosis of C. neoformans by J774.16 macrophage-like cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.

ABSTRACT
Monoclonal antibodies (mAbs) to the polysaccharide capsule of Cryptococcus neoformans can prolong survival in mice. However, the properties of antibodies that mediate protection are not fully understood. The IgM mAbs 12A1 and 13F1 originated from the same B cell and differ only by somatic mutations in their variable regions; yet mAb 12A1 protects against serotype D infection, while mAb 13F1 does not. Phage peptide display libraries were used to analyze the fine specificity of these two mAbs. The selection of distinct peptide motifs from identical libraries confirmed that mAbs 12A1 and 13F1 bound to two distinct epitopes. Immunofluorescence and immunoelectron microscopy studies revealed differences in antibody localization within the capsule of serotype D strain; mAb 12A1 bound to the outer rim of the capsule resulting in an annular pattern, whereas mAb 13F1 bound throughout the capsule and had a punctate appearance. The difference in the binding pattern of mAb 12A1 and 13F1 was not observed on serotype A organisms, where both mAbs bound to the capsule with an annular fluorescence pattern. The fluorescence pattern of binding correlated with protective efficacy; mAb 13F1 prolonged survival of mice infected with the J11 serotype A strain (annular fluorescence), but not serotype D strains (punctate pattern). Annular binding, but not punctate binding, was associated with increased opsonic efficacy for phagocytosis of C. neoformans by J774.16 macrophage-like cells. The correlation between capsular binding pattern, opsonic activity, and ability to prolong survival suggests that the efficacy of anticryptococcal antibodies is dependent upon where they bind in the polysaccharide capsule.

Show MeSH
Related in: MedlinePlus