Immunoprint pattern in patients with allergic bronchopulmonary aspergillosis in different stages

Are allergic fungal rhinosinusitis and allergic bronchopulmonary aspergillosis lifelong conditions?

Aspergillus fumigatus can cause several allergic disorders including Aspergillus-sensitized asthma, allergic bronchopulmonary aspergillosis (ABPA), and allergic fungal rhinosinusitis (AFRS). ABPA is an immunological pulmonary disorder caused by allergic reactions mounted against antigens of A. fumigatus colonizing the airways of patients with asthma (and cystic fibrosis). Allergic bronchopulmonary mycosis is an allergic fungal airway disease caused by thermotolerant fungi other than A. fumigatus On the other hand, AFRS is a type of chronic rhinosinusitis that is also a result of hypersensitivity reactions to the presence of fungi that become resident in the sinuses. The pathogenesis of ABPA and AFRS share several common features, and in fact, AFRS can be considered as the upper airway counterpart of ABPA. Despite sharing similar immunopathogenetic features, the simultaneous occurrence of the two disorders is uncommon. Due to the lacuna in understanding of the causative mechanisms, and deficiencies in the diagnosis and treatment, these disorders unfortunately are lifelong illnesses. This review provides an overview of the pathogenesis, diagnosis, and long-term outcomes of both these disorders.

Allergic bronchopulmonary aspergillosis in asthma: epidemiological, clinical and therapeutic issues

Allergic bronchopulmonary aspergillosis (ABPA) is a complex pulmonary disorder caused by immunologic reactions to antigens released by Aspergillus fumigatus, a ubiquitous fungi colonizing the tracheobronchial tree of asthmatic patients. The clinical presentation is usually poorly controlled asthma, recurrent pulmonary opacities and bronchiectasis. The prevalence of ABPA in asthma clinics may be as high as 13% with a global burden of almost 5 million patients. A. fumigatus-specific IgE level is the most sensitive test in diagnosis of ABPA, and all asthmatic patients should be routinely screened with A. fumigatus-specific IgE levels for early diagnosis. The goals of managing ABPA include control of asthma, prevention and treatment of acute exacerbations, and preventing the development or progression of bronchiectasis. Glucocorticoids are the treatment of choice with itraconazole reserved for those with recurrent exacerbations and glucocorticoid-dependent disease. There is a dire need for newer treatment approaches including oral antifungal agents and immunomodulatory therapy.

Allergic bronchopulmonary aspergillosis

Allergic bronchopulmonary aspergillosis (ABPA) is an immunologic pulmonary disorder caused by hypersensitivity to Aspergillus fumigatus. Clinically, a patient presents with chronic asthma, recurrent pulmonary infiltrates, and bronchiectasis. The population prevalence of ABPA is not clearly known, but the prevalence in asthma clinics is reported to be around 13%. The disorder needs to be detected before bronchiectasis has developed because the occurrence of bronchiectasis is associated with poorer outcomes. Because many patients with ABPA may be minimally symptomatic or asymptomatic, a high index of suspicion for ABPA should be maintained while managing any patient with bronchial asthma whatever the severity or the level of control. This underscores the need for routine screening of all patients with asthma with an Aspergillus skin test. Finally, there is a need to update and revise the criteria for the diagnosis of ABPA. This review summarizes the advances in the diagnosis and management of ABPA using a systematic search methodology.

Identification of vacuolar serine proteinase as a major allergen of Aspergillus fumigatus by immunoblotting and N-terminal amino acid sequence analysis

Aspergillus species are common airborne fungi that have been identified as causative agents of extrinsic bronchial asthma. More than 10 allergens from A. fumigatus have been recently characterized by cDNA cloning. The objective of this study is to identify A. fumigatus allergens through immunoblot analysis using sera from asthmatic patients. IgE-binding components of A. fumigatus and IgE cross-reactivity among allergens of different prevalent airborne fungal species were analysed by immunoblot and immunoblot inhibition, respectively, using sera from asthmatic patients. The N-terminal amino acid sequences of major allergens identified were determined by Edman degradation. Among two batches (70 and 41 sera) of asthmatic sera tested, 19 (27%) and 14 (34%), respectively, have IgE immunoblot reactivity towards components of A. fumigatus. A 34-kDa protein that reacts with IgE antibodies in 15 (79%) and 11 (79%) of the 19 and 14 positive samples, respectively, may be considered a major allergen of A. fumigatus. The N-terminal amino acid sequences of the 34 kDa major allergen and the 30.5 and 30 kDa IgE-binding components of A. fumigatus showed sequence identity to that of the vacuolar serine proteinase from A. fumigatus. The results from immunoblot inhibition show IgE cross-reactivity among major allergens of A. fumigatus, P. notatum and P. oxalicum. Results obtained suggest that the 34 kDa major allergen of A. fumigatus may be a vacuolar serine proteinase. There is IgE cross-reactivity among serine proteinase allergens of A. fumigatus, P. notatum and P. oxalicum.

Aspergillus fumigatus and aspergillosis

Aspergillus fumigatus is one of the most ubiquitous of the airborne saprophytic fungi. Humans and animals constantly inhale numerous conidia of this fungus. The conidia are normally eliminated in the immunocompetent host by innate immune mechanisms, and aspergilloma and allergic bronchopulmonary aspergillosis, uncommon clinical syndromes, are the only infections observed in such hosts. Thus, A. fumigatus was considered for years to be a weak pathogen. With increases in the number of immunosuppressed patients, however, there has been a dramatic increase in severe and usually fatal invasive aspergillosis, now the most common mold infection worldwide. In this review, the focus is on the biology of A. fumigatus and the diseases it causes. Included are discussions of (i) genomic and molecular characterization of the organism, (ii) clinical and laboratory methods available for the diagnosis of aspergillosis in immunocompetent and immunocompromised hosts, (iii) identification of host and fungal factors that play a role in the establishment of the fungus in vivo, and (iv) problems associated with antifungal therapy.

Display of expression products of cDNA libraries on phage surfaces. A versatile screening system for selective isolation of genes by specific gene-product/ligand interaction

Techniques for cloning cDNAs from bacteriophage libraries immobilised on solid supports are well established. However, these techniques do not allow selective enrichment of clones expressing proteins of interest. Screening of cDNA libraries would be simplified if the proteins encoded by cDNAs could be expressed on the surface of phage. Phage carrying genes encoding proteins for which a ligand is available can be selected directly by affinity interaction [Crameri, R. & Suter, M. (1993) Gene (Amst.) 137, 69-75]. The expression products from a cDNA library from Aspergillus fumigatus have been displayed on the surface of the filamentous phage M13 and screened for gene products binding to human serum IgE. The physical linkage of cDNA-encoded proteins to the genetic information required for their production, achieved by exploiting the high-affinity interaction of the Jun and Fos leucine zippers, allows screening of up to 1 x 10(10) independent clones in 50-microliters aliquots applied to a well of a microtiter plate coated with the ligand. Phage displaying IgE-binding proteins were selectively enriched 10(5)-10(6)-fold over non-specific phage after six rounds of growth and selection. The apparent molecular mass of the proteins selected from the cDNA library was in the range 20-40 kDa. Restriction enzyme analysis and preliminary sequence determination of 12 selected inserts revealed different sequences. The ability of the proteins to bind to human serum IgE was corroborated by enzyme-linked immunosorbent assay and by Western-blot analysis. The developed cloning strategy allows isolation of cDNAs encoding proteins for which a ligand is available and circumvents immobilisation of the libraries on solid-phase supports which hamper selective enrichment of clones expressing the desired protein.

Recombinant expression and antigenic properties of a 32-kilodalton extracellular alkaline protease, representing a possible virulence factor from Aspergillus fumigatus

A 32-kDa nonglycosylated alkaline protease (EC 3.4.1.14) with elastolytic activity, secreted by the opportunistic pathogen Aspergillus fumigatus ATCC 42202, is suggested to be a virulence factor of this fungus. The enzyme is a serine protease of the subtilisin family, and its cDNA nucleotide sequence has recently been reported. We have cloned the cDNA encoding the mature protease into a high-level Escherichia coli expression plasmid and produced the recombinant protease as a fusion protein with a six-adjacent-histidine affinity tag at the carboxy terminus. Subsequently, the recombinant protease was purified to homogeneity, with affinity chromatography yielding 30 to 40 mg of recombinant protease per liter of E. coli culture. Refolded recombinant protease, in comparison with native protease, demonstrated weak enzymatic activity but similar immunochemical characteristics as analyzed by antigen-specific enzyme-linked immunosorbent assay (ELISA), competition ELISA, and immunoblotting assays. To assess the allergenic potential of the protease, sera from patients with allergic bronchopulmonary aspergillosis and sera from healthy control individuals were analyzed by ELISA and immunoblotting techniques. Sera from patients with allergic bronchopulmonary aspergillosis did not have protease-specific immunoglobulin E (IgE) antibodies and, remarkably, did not show significantly elevated protease-specific IgG antibody levels compared with those in sera from healthy control individuals. This suggests that the alkaline protease from A. fumigatus does not elicit IgE antibodies and has weak immunogenicity, a property which may explain fungus persistence in allergic individuals.

Specific serum immunopatterns in clinical phases of allergic bronchopulmonary aspergillosis

Immunoblotting, radioallergosorbent test (RAST), and enzyme-linked immunosorbent assay (ELISA) were performed to determine specific IgE and IgG responses to Aspergillus fumigatus (Af) allergens (IgE-Af; IgG-Af). Serology results were compared in patients with allergic bronchopulmonary aspergillosis (ABPA) (n = 43), patients with Aspergillus fumigatus-associated asthma (Af-asthma) (n = 26), and healthy individuals (n = 3). In patients with different clinical phases of ABPA, three specific immunopatterns were found by immunoblotting. It is proposed to classify ABPA into the active, intermediate, and remission phase with respect to the specific immunoresponse to Af-allergens and asthma symptoms. First, the active phase of ABPA is characterized by a fully developed specific immunoresponse to Af-allergens and severe asthma. Second, the intermediate phase includes patients with elevated specific immunologic findings without asthma symptoms. Third, the remission phase is characterized by a weak specific immunoresponse to Af-allergens after a long-term asymptomatic period. No correlation occurred between specific immunopatterns and irreversible brochopulmonary lesions. The IgE-Af RAST and IgG-Af ELISA titers of patients with ABPA in the active and intermediate phase were significantly higher compared with patients with ABPA in remission phase and with patients with Af-asthma. In particular, the demonstration of positive IgG-Af ELISA titer generally allows the serologic discrimination of patients with asthma and ABPA from patients with Af-asthma in clinical practice. The present study revealed that immunoblots of most patients with Af-asthma were negative. Immunoblotting demonstrated an IgG reactivity exclusively to low molecular weight (MW) Af-allergens in 8 out of 26 patients with Af-asthma and in the three healthy individuals, and this IgG response may reflect naturally occurring antibodies.

Heat shock protein 88 and Aspergillus infection

Immunoblotting was used to dissect the antibody responses in the sera of 50 patients with proven invasive aspergillosis, 28 patients with suspected invasive aspergillosis, 35 patients with allergic bronchopulmonary aspergillosis, and 10 patients with an aspergilloma. This demonstrated the immunodominance of antigenic bands at 88, 84, 51, and 40 kDa. Monoclonal antibodies against the heat shock protein 90 complexes of Candida albicans and the water mold Achlya ambisexualis identified these four antigenic bands as homologous proteins. Similar antigens have been described in humans, mice, Saccharomyces cerevisiae, chickens, and Drosophila species. The antibody against A. ambisexualis has previously been shown to cross-react with antigens belonging to the human heat shock protein 90 complex. Aspergillus heat shock protein 90 was extracted from the sera of patients with invasive aspergillosis by affinity chromatography. This was done with both a rabbit hyperimmune antiserum raised against an extract of Aspergillus fumigatus NCPF 2109 and a monoclonal antibody against the heat shock protein 90 of C. albicans. In vivo expression of the antigen was demonstrated in an aspergilloma surgically removed from a patient. The role of the antigen as an allergen in allergic bronchopulmonary aspergillosis is also discussed.

Immunodiagnosis of aspergillosis

Aspergillus species are ubiquitous fungi and have been implicated as the causative agents of a variety of lung disorders in humans. These disorders include allergic, saprophytic, and systemic manifestations. The allergic disorders mainly affect atopic persons, and invasive or systemic diseases affect immunosuppressed individuals. Immunodiagnosis can help the practitioner diagnose these diseases. Demonstration of circulating antibodies is a useful criterion, but the lack of dependable and standardized antigens is a limiting factor in the diagnosis of most Aspergillus-induced diseases. Despite this limitation, however, immunodiffusion and enzyme-linked immunosorbent assays have been widely used for the detection of antibodies in the sera of patients with aspergillosis. Similarly, crude and semipurified antigens are being used to demonstrate skin hypersensitivity in patients, and several methods have been useful in the detection of antigenemia in patients with invasive aspergillosis. With a growing number of reports on the incidence of aspergillosis and an increase in the number of immunosuppressed individuals in the population, more rapid methods and more reliable reagents for immunodiagnosis are needed. With recent attempts at obtaining reliable reagents for through hybridoma technology and molecular biological techniques, substantial progress toward efficient immunodiagnosis may be achieved.

The 18-kilodalton antigen secreted by Aspergillus fumigatus

One of the major antigens secreted in vitro by Aspergillus fumigatus is an 18-kDa basic protein which has been purified by cation-exchange chromatography. It is recognized by sera from aspergilloma patients. It is also the major circulating antigen found in urine of patients with invasive aspergillosis. Our results indicated that this antigen has potential for the diagnosis of both aspergilloma and invasive aspergillosis.

Detection of circulating galactomannan by Pastorex Aspergillus in experimental invasive aspergillosis

The performance of Pastorex Aspergillus, a new latex agglutination test for the detection of circulating galactomannan in the serum of patients with invasive aspergillosis, was evaluated in a blind trial in standardized guinea-pig models of invasive aspergillosis and other invasive mycoses. In these animal models, the invasive nature of the fungal infection was confirmed by re-isolation of the etiologic agent from the organs of every animal. Ninety-two plasma samples from 42 animals with invasive aspergillosis were submitted to the test. In 41 of these animals, at least one plasma sample was positive with the latex test (sensitivity 97.6%), titers ranging from 1/1 to 1/512. In general, antigen titers increased as a function of time, reaching the highest values shortly before death. Guinea-pigs infected with Penicillium marneffei also yielded positive agglutination reactions but antigen titers were lower (maximal titer 1/8). Plasma samples from animals with invasive candidosis (23), disseminated trichophytosis (11) and cryptococcosis (23) were all negative with the latex test. In 80 guinea-pigs without fungal infection, 3 false positive results (titers 1/1) were observed, which means a specificity of 96.2% in this control group.