Allergic Aspergillosis and the Antigens of Aspergillus fumigatus
Bharat Singh, Seema Singh, Abdul R. Asif, Michael Oellerich and Gainda L. Sharma
Affiliation: CSIR-Institute of Genomics and Integrative Biology, University Campus, Mall Road, Delhi-110007, India.
Keywords: Allergic aspergillosis, allergens, desensitization, diagnosis, recombinants.
Incidence of fungal infections has increased alarmingly in past few decades. Of the fungal pathogens, the Aspergillus
fumigatus has been a major cause of allergic bronchopulmonary aspergillosis (ABPA) which has five main
stages - the acute, remission, exacerbation, glucocorticoid dependent and fibrotic stage. The diagnosis of ABPA remains
difficult due to its overlapping clinical and radiological features with tuberculosis and cystic fibrosis. From past few decades,
the crude fractions of A. fumigatus have been used for immunodiagnosis of ABPA. Most of the detection kits based
on crude fractions of A. fumigatus are quite sensitive but have low specificity. Till date 21 known and 25 predicted allergens
of A. fumigatus have been identified. Of these allergens, only five recombinants (rAsp f1-f4 and f6) are commercially
used for diagnosis of allergic aspergillosis. Remaining allergens of A. fumigatus have been restricted for use in specific
diagnosis of ABPA, due to sharing of common antigenic epitopes with other allergens. Complete sequencing of A.
fumigatus genome identified 9926 genes and the reports on the proteome of A. fumigatus have shown the presence of large
number of their corresponding proteins in the pathogen. The analysis of immunoproteomes developed from crude fractions
of A. fumigatus by IgG/IgE reactivity with ABPA patients and animal sera have identified the panel of new antigens.
A brief description on the current status of A. fumigatus antigens is provided in this review. The implementation of advance
recombinant expression and peptidomic approaches on the A. fumigatus antigens may help in the selection of appropriate
molecules for the development of tools for more specific early diagnosis of ABPA, and desensitization therapies
for patients of allergic disorders.
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