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Updated: Aug 11, 2026
Passive Administration of Monoclonal Antibodies Against H. capsulatum and Others Fungal Pathogens
Published on: February 15, 2011
Immunochemical studies of heat-shock protein 80 of Histoplasma capsulatum
L Jeavons1, L Hunt, A Hamilton
1Dermatology Unit, St Johns Institute of Dermatology, Guy's Hospital, London, UK.
Insights
Researchers developed a monoclonal antibody targeting an 80 kDa O-glycosylated glycoprotein in Histoplasma capsulatum. This heat-inducible molecule, homologous to heat-shock protein 70, is found in cytoplasm and cell membranes, and in other fungi.
Area of Science:
- Medical Mycology
- Immunology
- Molecular Biology
Background:
- Histoplasma capsulatum is a fungal pathogen causing histoplasmosis.
- Understanding fungal antigens is crucial for developing diagnostics and therapeutics.
- Monoclonal antibodies (MAbs) are valuable tools for antigen characterization.
Purpose of the Study:
- To characterize a novel antigen recognized by a MAb raised against Histoplasma capsulatum.
- To investigate the molecular properties and localization of this antigen.
- To assess the cross-reactivity of the antigen with other fungal species.
Main Methods:
- Production and characterization of a specific monoclonal antibody (MAb 69F).
- Immunoblotting, enzymatic deglycosylation, and Western blotting to identify and analyze the antigen.
- Immunofluorescence microscopy for cellular localization studies.
- ELISA and Western blotting for cross-reactivity analysis.
- Isoelectric focusing (pI) and N-terminal amino acid sequencing.
Main Results:
- A MAb (IgG1 subclass) was generated with higher activity against the yeast phase of H. capsulatum.
- The MAb predominantly recognized an 80 kDa O-glycosylated glycoprotein.
- The antigen is heat-inducible, localized in the cytoplasm and possibly cell membrane, not the cell wall.
- The antigen's culture filtrate was reactive with the MAb.
- A similar epitope was detected in other fungal species.
- N-terminal sequencing indicated homology to heat-shock protein 70 family and a known H. capsulatum antigen.
Conclusions:
- A novel, heat-inducible, O-glycosylated glycoprotein of H. capsulatum was identified and characterized.
- This antigen shares homology with heat-shock proteins and exhibits cross-reactivity with other fungi.
- The findings provide insights into H. capsulatum antigens and potential targets for immunodiagnostics or therapies.
Abstract:
A monoclonal antibody (MAb) of the IgG1 subclass, with greater activity to the yeast than the mycelial phase of Histoplasma capsulatum was raised and was found to predominantly recognize a molecule of 80 kDa by immunoblot. Enzymatic deglycosylation and chemical degradation, followed by reaction with MAb 69F on Western blots showed the molecule to be O-glycosylated, and immunofluorescence studies showed it to be heat-inducible and its distribution to be cytoplasmic and possibly cell membraneous. There was no apparent staining of the cell wall. Culture filtrate was positive by ELISA and Western blot when reacted with MAb 69F. In addition, ELISA and Western blot demonstrated that a similar epitope was present in other fungal species. The glycoprotein had a pI of approximately 4.7. N-terminal amino acid sequencing revealed this molecule to be homologous to members of the heat-shock protein 70 family and to a recently described antigen from H. capsulatum.
