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A new glycoprotein allergen/antigen with the protease activity from Aspergillus fumigatus
Shailly Nigam1, P C Ghosh, P Usha Sarma
1Molecular Biochemistry and Diagnostics Division, Centre for Biochemical Technology, Delhi, India.
Background:
Aspergillus fumigatus is an opportunistic fungus causing allergic and invasive aspergillosis in humans and animals. It secretes an array of complex biologically active glycoprotein antigens and allergens. It is important to identify and characterize probable potential virulent factors playing a major role in the pathogenesis of aspergillosis.
Methods:
Using protein purification techniques (lectin affinity chromatography, gel filtration, electroelution and high-pressure liquid chromatography), a major antigen/allergen with a molecular weight of 56 kD (gp56) from A. fumigatus was purified to homogeneity. The protein was characterized by immunoblot, ELISA and protease assays. The N-terminal amino acid sequencing was performed.
Results:
The gp56 protein showed a single band on silver staining and isoelectric focussing. The protein to carbohydrate ratio was 1.5:1 and gp56 gave a protein band at a molecular weight of 34 kD on enzymatic deglycosylation. It also exhibited IgG and IgE immunobinding with antibodies present in sera of allergic bronchopulmonary aspergillosis patients. The gp56 exhibited protease activity and N-terminal seven-amino acid sequence showed homology with fungal serine proteases.
Conclusions:
The gp56 protein by virtue of its proteolytic activity could be one of the virulent factors of A. fumigatus involved in establishing infection in the host along with other factors.
Insights
A 56 kD glycoprotein (gp56) from Aspergillus fumigatus, a fungus causing aspergillosis, was identified as a potential virulence factor. This allergen exhibits protease activity, aiding in infection establishment.
Area of Science:
- Mycology
- Immunology
- Biochemistry
Background:
- Aspergillus fumigatus is an opportunistic pathogen responsible for allergic and invasive aspergillosis in humans and animals.
- This fungus releases various glycoprotein antigens and allergens that contribute to disease pathogenesis.
- Identifying virulence factors is crucial for understanding and combating aspergillosis.
Purpose of the Study:
- To isolate and characterize a major antigen/allergen from Aspergillus fumigatus.
- To investigate the potential role of this molecule as a virulence factor in aspergillosis.
Main Methods:
- Purification of a 56 kD glycoprotein (gp56) using lectin affinity chromatography, gel filtration, electroelution, and HPLC.
- Characterization through immunoblot, ELISA, protease assays, and N-terminal amino acid sequencing.
Main Results:
- Purified gp56 showed a single band on silver staining and isoelectric focusing.
- Enzymatic deglycosylation yielded a 34 kD protein band, indicating a protein to carbohydrate ratio of 1.5:1.
- gp56 demonstrated IgG and IgE immunobinding and exhibited protease activity, with N-terminal sequencing showing homology to fungal serine proteases.
Conclusions:
- The gp56 protein, due to its proteolytic activity, is identified as a potential virulence factor of Aspergillus fumigatus.
- This enzyme may play a significant role in the pathogenesis of aspergillosis, contributing to host infection.
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