Humoral and cellular immune responses in Aspergillus fumigatus pulmonary disease

IgE in the diagnosis and treatment of allergic disease

Traditionally, the concept of allergy implied an abnormal response to an otherwise benign agent (eg, pollen or food), with an easily identifiable relationship between exposure and disease. However, there are syndromes in which the relationship between exposure to the relevant allergen and the "allergic" disease is not clear. In these cases the presence of specific IgE antibodies can play an important role in identifying the relevant allergen and provide a guide to therapy. Good examples include chronic asthma and exposure to perennial indoor allergens and asthma related to fungal infection. Finally, we are increasingly aware of forms of food allergy in which the relationship between exposure and the disease is delayed by 3 to 6 hours or longer. Three forms of food allergy with distinct clinical features are now well recognized. These are (1) anaphylactic sensitivity to peanut, (2) eosinophilic esophagitis related to cow's milk, and (3) delayed anaphylaxis to red meat. In these syndromes the immunology of the response is dramatically different. Peanut and galactose α-1,3-galactose (alpha-gal) are characterized by high- or very high-titer IgE antibodies for Ara h 2 and alpha-gal, respectively. By contrast, eosinophilic esophagitis is characterized by low levels of IgE specific for milk proteins with high- or very high-titer IgG4 to the same proteins. The recent finding is that patients with alpha-gal syndrome do not have detectable IgG4 to the oligosaccharide. Thus the serum results not only identify relevant antigens but also provide a guide to the nature of the immune response.

Innate immunity to Aspergillus species

All humans are continuously exposed to inhaled Aspergillus conidia, yet healthy hosts clear the organism without developing disease and without the development of antibody- or cell-mediated acquired immunity to this organism. This suggests that for most healthy humans, innate immunity is sufficient to clear the organism. A failure of these defenses results in a uniquely diverse set of illnesses caused by Aspergillus species, which includes diseases caused by the colonization of the respiratory tract, invasive infection, and hypersensitivity. A key concept in immune responses to Aspergillus species is that the susceptibilities of the host determine the morphological form, antigenic structure, and physical location of the fungus. In this review, we summarize the current literature on the multiple layers of innate defenses against Aspergillus species that dictate the outcome of this host-microbe interaction.

Failure to detect deposition of complement and immunoglobulin in allergen-induced late-phase skin reaction in atopic subjects

There still remains some controversy regarding the possible role of immune complexes in the pathogenesis of the late-phase skin reaction (LPSR). To assess this, skin biopsies were obtained from LPSR induced in atopic human subjects 6, 24 and 48 h after allergen challenge. Cryostat sections were stained by direct immunofluorescence for the presence of fibrinogen, immunoglobulin classes IgM and IgG and for the complement components C1q and C3c. Complement components were observed in only two of the 29 biopsies studied. In both instances, only C3c was detected. One of these subjects also had unequivocal IgG staining at 6 h. IgM staining was detected in two out of 10 subjects at 6 h but no significant deposition of immunoglobulins could be found at 24 or 48 h. Fibrinogen deposition was observed in about half of the biopsies at each time-point. This study suggests that substantial complement and immunoglobulin deposition are not overt features of the allergen-induced LPSR, although the presence of small amounts of immune complexes, below the sensitivity of the method employed cannot be excluded. Fibrin deposition occurs in the LPSR but does not appear to be a prerequisite for LPSR development.

T- and B-cell dysregulation of IgE synthesis in cystic fibrosis patients with allergic bronchopulmonary aspergillosis

Since Aspergillus fumigatus (Af)-specific and polyclonal serum IgE levels are characteristically elevated in patients with allergic bronchopulmonary aspergillosis (ABPA), we evaluated in vitro regulation of IgE synthesis in cystic fibrosis (CF) patients with ABPA. We studied 11 CF patients with ABPA, 37 patients with positive Af prick skin tests and/or IgG precipitating antibodies (ST/PPT+), and 35 patients with no humoral or skin responses to Aspergillus (ST/PPT-). Mean serum IgE concentration was significantly elevated in CF subjects with ABPA compared to ST/PPT+ and ST/PPT- patients, 2866 vs 303 and 61 IU/ml, respectively (P less than 0.01). In vitro studies demonstrated that ABPA patients' B cells spontaneously synthesized significantly increased amounts of IgE compared to ST/PPT positive and negative subjects, 1980 vs 220 and 13 pg/ml, respectively (P less than 0.01). In addition, preformed B-cell-associated IgE was also significantly elevated in ABPA subjects (P less than 0.01), indicating prior in vivo activation. Supernatant cultures of Af-stimulated T cells from ABPA subjects significantly induced allogeneic B-cell IgE synthesis compared to ST/PPT positive and negative CF subjects, 206 vs 13 and 4 pg/ml, respectively (P less than 0.01). Thus T cells stimulated with Aspergillus antigens secrete cytokines that induce B-cell IgE synthesis in ABPA subjects. B-cell IgE hyperactivity is manifested by in vivo and in vitro increased IgE concentrations. Analyses of T-cell regulation and B-cell IgE synthesis distinguish CF subjects with ABPA from Aspergillus sensitive non-ABPA subjects.

Cellular and humoral immune responses in experimental aspergillosis in mice

Invasive aspergillosis was established in a naive murine model. Both humoral and cellular aspects of the immunological mechanism responded to invasion. Circulating immune complexes containing IgG in the infected group of animals were detected by both the C1q and conglutinin solid phase assays. Attempts to identify these complexes as Aspergillus antigen-specific complexes were unsuccessful. Cellular responses, as measured by blastogenic activity and inhibition of migration of sensitized cells were significantly elevated in the infected group.

Aspergillus fumigatus-specific antibodies in allergic bronchopulmonary aspergillosis and aspergilloma: evidence for a polyclonal antibody response

Patients with the Aspergillus-induced diseases allergic bronchopulmonary aspergillosis (ABPA), aspergilloma (fungus ball), and Aspergillus skin test-positive asthma were differentiated immunologically by radioimmunoassay based on their total immunoglobulin E (IgE) and Aspergillus fumigatus-specific IgE levels. In this study, a new, highly sensitive biotin-avidin-linked immunosorbent assay was used to evaluate A. fumigatus-specific antibodies of all immunoglobulin classes. Studied populations included 13 patients with ABPA, 12 with aspergilloma, 9 with Aspergillus skin test-positive asthma, and 9 normal individuals without asthma. A. fumigatus-specific antibodies of all classes were elevated in patients with ABPA, variably elevated in those with aspergilloma, and lowest in the other two groups. This assay demonstrated significantly higher specific IgE antibody levels in the ABPA group over those of the other groups, even with 1:1,000 dilutions of the sera. This study demonstrated that ABPA is a disease characterized by a polyclonal antibody response to Aspergillus antigen and not just a response to IgE and IgG antibody classes. The measurement of other antibody classes, particularly IgD and IgA, could enhance the immunodiagnosis of ABPA. The biotin-avidin-linked immunosorbent assay was found to be a highly sensitive assay that can be a clinically useful alternative to radioimmunoassay in the measurement of A. fumigatus-specific antibodies.

Serum antibodies and their role in antibody-dependent cell-mediated cytotoxicity in aspergillosis

A total of 22 sera from patients with aspergilloma and allergic bronchopulmonary aspergillosis (ABPA) were examined concomitantly for specific antibody against Aspergillus fumigatus antigen and for their activity in antibody-dependent cell-mediated cytotoxicity (ADCC) against Aspergillus antigen-coated target cells. These sera demonstrated significant precipitin bands in agar gel double diffusion test (78% of ABPA and 75% of aspergilloma sera), while in indirect immunofluorescence studies all sera showed positive reactivity with a titer distribution of 1:40 to 1:160 and 1:40 to 1:320, respectively, for ABPA and aspergilloma sera. In enzyme-linked immunosorbent assay all sera demonstrated titers varying from 1:200 to 1:6400. Several sera also displayed marked cytotoxic reactions against A. fumigatus antigen-coated SB target cells in ADCC assays using normal lymphocytes as effector cells (35% of aspergilloma and 25% of ABPA sera). These findings suggest a role for ADCC activity in patients with Aspergillus infections.

Detection of class-specific antibodies against Aspergillus fumigatus antigens in various pulmonary diseases

Using an enzyme-linked immunosorbent assay (ELISA) and a radioimmunoassay (RAST), the specific IgA, IgG, IgM and IgE antibody levels against Aspergillus fumigatus antigens were determined in sera from patients with either chronic bronchitis or non-allergic bronchial asthma, allergic asthma, allergic bronchopulmonary aspergillosis or aspergilloma. These levels were compared with those in serum samples from healthy controls. The results showed statistical differences in specific antibody levels between the five groups of patients. It was not possible, however, to reliably classify a subject in one of the studied pathological groups on the sole basis of the assays used.

Allergic bronchopulmonary aspergillosis

Allergic bronchopulmonary aspergillosis (ABPA) occurs as a complication of asthma. It presents as an infiltrative pulmonary disorder with respiratory and systemic symptoms, eosinophilia, elevated total serum IgE, and skin sensitizing, as well as precipitating antibodies to Aspergillus fumigatus. Sputum cultures are not always positive for the organism. If unchecked, the disease may lead to bronchiectasis and ultimately pulmonary fibrosis. Therapy consists mainly of corticosteroids.

Aspergillomas complicating sarcoidosis. A prospective study in 100 patients

During a ten-year study period, we evaluated 100 histologically-proven sarcoid patients for the development of aspergillomas. Serum precipitins against Aspergillus antigens were used to screen all patients regardless of sarcoid stage. Twelve patients had serum precipitins and were further investigated with tomography and serial serum precipitins testing. Ten of these 12 patients had aspergillomas and two patients died of massive hemoptysis. No aspergillomas occurred in stages I, II, or non-cystic stage III patients. All ten aspergillomas developed in the 19 stage III patients with cystic parenchymal damage. We believe that aspergillomas in sarcoidosis are not as rare as previously reported, but occur commonly in chronic cystic sarcoidosis. Additionally, we found serial testing for serum precipitins to be valuable both for the screening of cystic sarcoid patients for aspergillomas and for the management of this complication.

Mould counts and exacerbations of allergic bronchopulmonary aspergillosis

The purpose of this study was to determine whether exacerbations of allergic bronchopulmonary aspergillosis (ABPA) were associated with the total outdoor mould counts in the Chicago area. From 1976-1980, forty-nine flares of ABPA (new pulmonary infiltrate with elevation in total serum IgE) occurred in nineteen patients. Thirty-eight (77.5%) of flares occurred during months June through November in association with increased outdoor mould counts in Chicago. This association confirms earlier observations from the U.K. where during the peak mould season which occurs in winter months, there was an increased number of pulmonary infiltrates and average prednisone doses required in ABPA.

The rapid development of an aspergilloma secondary to allergic bronchopulmonary aspergillosis

A patient with allergic bronchopulmonary aspergillosis who developed a cavitary lung lesion suggestive of neoplasm is presented. At thoracotomy an aspergilloma was found. Although coexistence of these two forms of aspergillosis has been reported, the brief history of preceding asthma and the rapid development of the aspergilloma in the absence of typical roentgenographic features are unusual. Aspergilloma should be considered when a patient with allergic bronchopulmonary aspergillosis develops a cavitary pulmonary lesion.

Antibodies to Aspergillus fumigatus in farmers' lung patients measured by enzyme-linked immunosorbent assay (ELISA)

Enzyme-linked immunosorbent assay (ELISA) was used to measure antibodies against Aspergillus fumigatus in farmers' lung patients, various other pulmonary diseases and healthy controls. Both the prevalence and the mean titre of antibodies were significantly higher in farmers' lung patients than in the other groups. There was no difference between controls and patients with bronchial asthma or non-allergic pulmonary diseases. On the other hand, in the group of patients with respiratory diseases of undefined aetiology the mean antibody titre was significantly higher than that of the controls. Comparison of ELISA and the precipitin test showed the higher sensitivity of ELISA, but otherwise the two tests were in a close agreement.

A guide to the recent literature on aspergillosis as caused by Aspergillus fumigatus, a fungus frequently found in self-heating organic matter

Spores of Aspergillus fumigatus have been found to be abundantly present in the outdoor air at a site where large scale experimental composting of sewage sludge is in progress at Beltsville, Maryland. The health significance of this finding, for that site and for others in the future, is still only incompletely understood. Further studies are in progress to characterize absolute concentrations of the spores of the fungus in air at the site, spore dispersal by air from composting operations, and background environmental spore levels in air. The present paper contains a list of references to papers on health effects of A. fumigatus, many published in the past ten years, along with a review of the same designed to assist the reader in finding information on particular aspects of the subject in the literature. It is intended primarily as an aid to individuals interested in sludge composting and wishing to attain an insight into the A. fumigatus-composting situation, but it may also interest others concerned with other substrates which become moldy at 40--50 C. A. fumigatus has been found in great numbers in naturally and artificially heated environments such as decaying leaves, compost heaps, solar heated sloughs, cooling canals for nuclear power generators, silos, grain storage bins, boiler rooms, detritus around steam turbines and sauna baths. The evident practical merits of sludge composting have been described elsewhere; the information presented here has its main significance in respect to requirements for choice of locations for composting sites and to process and design criteria.