Molecular Characterization of a Glycoprotein Allergen of Aspergillus Fumigatus

Shailly Nigam*, P VGK Sarmaf. PC Ghosh#, Vsha P. Sarma*

Author address: 

*Centre for Biochemical Technology. Delhi,India tSri Venkateshwara College.University of Delhi, Delhi, India *Department of Biochemistry, University of Delhi South Campus, Delhi, India


Allergens and antigens of A.fumigatus are extremely complex macromolecules with multifunctional properties and some of them are proposed to be virulent factors in Aspergillus mediated disorders. A.fumigatus secretes ribonucleases, catalases. elastases and proteases with IgG and IgE binding activity with the sera of patients of aspergillosis. A number of allergens and antigens of A.fumigatus in the molecular weight range of 14-70kD exhibit specific IgG and IgE binding with the sera of aspergillosis patients. This suggests the possible presence of homologous sequential or conformational epitopes among various immunodominant allergens. Such analysis on the structural and biological functional aspects of Aspergillus antigens would further shed light on their mechanism of action in the pathogenesis of fungal diseases. Earlier work in our laboratory focussed on an l8kD allergen with respect to its cloning, expression and structure functional aspects (GenBank accession number:AF181859).With this in view, in the current study the gene encoding an immunodominant 55kD glycoprotein allergen was cloned and expressed. The gene encoding this allergen was amplified by Polymerase Chain Reaction using A.fumigatus genomic DNA of an Indian clinical strain isolated from an aspergilloma patient (Af-285). This product was then cloned in the SmaI site of pUCl8. The recombinants were selected and the fusion protein was expressed in E.coli JM 109 cells. The immunological activity ( IgG & IgE ) of the expressed fusion protein was observed using specific hyperimmune rabbit sera and also with the sera obtained from aspergillosis patients. The biological activity of the recombinant protein was examined with respect to the protease and cytotoxic activity. The cloned fragment and the PCR product have been sequenced. A synthetic peptide of this 55kD allergen has been observed to be allergenic. Further its N-terminal twenty amino acid sequence is homologous to the deduced sequence of Aspf 2 which is one of the immunodominant allergens. The identification of presence of such common sequential epitopes and their characterization at molecular level would enhance our knowledge on structural homology among these fungal aller-gens

abstract No: 


Full conference title: 

2000 American Academy of Allergy, Asthma, and Immunology Annual Meeting
    • AAAAI 2000 (56th)