Aspergillus species recombinant antigens for serodiagnosis of farmer's lung disease

OUP accepted manuscript

Although a high prevalence of COVID-19-associated pulmonary aspergillosis has been reported, it is still difficult to distinguish between colonization with Aspergillus fumigatus and infection. Concomitantly, similarities between severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and hypersensitivity pneumonitis were suggested. The objective of this study was to investigate retrospectively if precipitin assays targeting A. fumigatus could have been useful in the management of SARS-CoV-2 patients hospitalized in an Intensive Care Unit (ICU) in 2020. SARS-CoV-2 ICU patients were screened for Aspergillus co-infection using biomarkers (galactomannan antigen, qPCR) and culture of respiratory samples (tracheal aspirates and bronchoalveolar lavage). For all these patients, clinical data, ICU characteristics and microbial results were collected. Electrosyneresis assays were performed using commercial A. fumigatus somatic and metabolic antigens. ELISA were performed using in-house A. fumigatus purified antigen and recombinant antigens.

Our study population consisted of 65 predominantly male patients, with a median ICU stay of 22 days, and a global survival rate of 62%. Thirty-five patients had at least one positive marker for Aspergillus species detection. The number of arcs obtained by electrosyneresis using the somatic A. fumigatus antigen was significantly higher for these 35 SARS-CoV-2 ICU patients (P 0.01, Welch's t-test). Our study showed that SARS-CoV-2 ICU patients with a positive marker for Aspergillus species detection more often presented precipitins towards A. fumigatus. Serology assays could be an additional tool to assess the clinical relevance of the Aspergillus species in respiratory samples of SARS-CoV-2 ICU patients.

The value of serum precipitins against specific antigens in patients diagnosed with hypersensitivity pneumonitis - retrospective study

INTRODUCTION

Hypersensitivity pneumonitis (HP) is the third most common interstitial lung disease, and is often under-recognized, especially in patients who are not aware of their occupational or environmental contact with organic antigens. The aim of the present study was to assess the results of serum specific IgG antibodies (ssIgG) in HP patients and their correlation with clinical data.

MATERIAL AND METHODS

128 HP patients, median age 53 years, participated in the study. The control group consisted of 102 patients with interstitial lung diseases (ILDs) other than HP. Assessment of pretreatment ssIgG to thermophilic actinomycetes and protein antigens from bird droppings (pigeons, hens, ducks, parrots, turkeys) was performed by double diffusion in agar gel according to Ouchterlony method.

RESULTS

Positive precipitins were obtained in 57% of all HP patients and in 61% of those exposed to above mentioned antigens. Positive results in the control group were obtained in 7% of patients. Sensitivity of ssIgG in HP group was 0.57 and specificity 0.93. Precipitins to at least one bird antigen was confirmed in 64% of HP patients exposed to birds. Precipitins to thermophilic bacteria were found in 29% of HP patients exposed to hay or hay products.

CONCLUSIONS

The results of the study indicate that ssIgG against birds' allergens were the valuable diagnostic tool in HP patients. Low-rate of confirmation of ssIgG to thermophilic bacteria in patients exposed to hay or hay products indicate that other microorganisms, most likely molds, could be responsible for the disease development.

Emphysema in active farmer's lung disease

BACKGROUND

Farmer's lung (FL) is a common type of hypersensitivity pneumonitis. It is often considered that fibrosis is the most frequent finding in chronic FL. Nevertheless, three cohort studies have suggested that some patients with chronic FL may develop emphysema. We aimed to evaluate the current prevalence of emphysema in active FL, to describe the radiological and functional features of emphysema in active FL, and to identify risk factors associated with emphysema in this population.

METHODS

Patients aged over 18 years with active FL were prospectively recruited through the SOPHIA study (CPP Est; P-2009-521), between 2007 and 2015. Each patient had complete medical history screening, clinical examination, high resolution computed tomodensitometry, bronchoalveolar lavage, pulmonary function tests and serum precipitins.

RESULTS

Among 33 patients with active FL, the prevalence of emphysema in this series of incident active FL cases was higher (48.5%) than that of fibrosis (12%) and was not dependent on smoking habits. Most patients with emphysema did not have lung hyperinflation. The possible risk factors for emphysema in active FL were a longer duration of exposure to organic dusts, and at a higher level.

CONCLUSION

Emphysema is found in half of patients with active FL and may be influenced by exposure patterns.

Allergen component analysis as a tool in the diagnosis of occupational allergy

PURPOSE OF REVIEW

Rapid developments have been seen in molecular allergy diagnosis, based on the detection and quantification of specific IgE to single allergens. This review summarizes and discusses studies on allergen component analysis as a tool in the diagnosis of occupational allergy.

RECENT FINDINGS

More than 400 agents are identified as sensitizers of occupational asthma, but only very few are characterized on the molecular level and available for routine diagnosis. Baker's asthma is one of the most frequently occurring forms of occupational asthma caused by workplace-related inhalation of cereal flour mainly wheat. Wheat sensitization profiles of bakers show great interindividual variability and no wheat allergen could be classified as the major allergen. Component-resolved diagnosis is a useful tool for diagnosing natural rubber latex (NRL) allergy. In cases with unexpected high-latex IgE but without clinical symptoms application of crossreactive carbohydrate determinants are helpful to clarify the cause of IgE binding.

SUMMARY

Latex is an excellent model for component-resolved diagnosis and demonstrates well how to improve the diagnosis by using single allergens. For diagnosis of baker's asthma, a whole wheat extract is still the best option for specific IgE determination, but single wheat allergens might help to discriminate between wheat-induced food allergy, grass-pollen allergy, and baker's asthma. New diagnostic tools and platforms are promising, but further knowledge of molecules relevant for occupational asthma (as in wood dust allergens, enzymes, laboratory animal allergens, etc.) and for occupational hypersensitivity pneumonitis is necessary to improve and standardize the diagnostic tools.

Fungal peptides from pneumonitis hypersensitivity etiologic agents are able to induce specific cellular immune response

PURPOSE

Hypersensitivity pneumonitis (HP) is an immunoallergic disease due to chronic exposure to high quantities of different microorganisms such as Mycobacterium immunogenum (Mi), a mycobacterium, and Lichtheimia corymbifera (Lc), a filamentous fungus. It has recently been demonstrated that the protein DLDH (dihydrolipoyl dehydrogenase), is common to these microorganisms. This study aimed to investigate the immune potential of overlapping peptide pools covering the MiDLDH and LcDLDH.

EXPERIMENTAL DESIGN

A selection of 34 peptides, from the MiDLDH and LcDLDH, able to interact with Major Histocompatibility Complex (MHC) 1 and MHC 2, was obtained using three different epitope prediction websites. By means of ELISPOT assays, we compared the frequency of Interferon gamma (IFNγ) secreting peripheral blood mononuclear cells (PBMC) after stimulation with overlapping peptide pools. Tests were performed using cells from 35 healthy blood donors.

RESULTS

One peptide pool containing five peptides from MiDLDH and able to interact with MHC 2 induced a marked IFNγ specific immune response (Pool F, p<0.001, Wilcoxon signed-rank test).

CONCLUSION

This study demonstrated that peptides from microorganisms involved in HP were able to induce a high IFNγ specific immune response after stimulation of PBMCs from healthy blood donors which could be useful to develop an effective prevention strategy.

Identification of Antigenic Proteins from Lichtheimia corymbifera for Farmer's Lung Disease Diagnosis

The use of recombinant antigens has been shown to improve both the sensitivity and the standardization of the serological diagnosis of Farmer’s lung disease (FLD). The aim of this study was to complete the panel of recombinant antigens available for FLD serodiagnosis with antigens of Lichtheimia corymbifera, known to be involved in FLD. L. corymbifera proteins were thus separated by 2D electrophoresis and subjected to western blotting with sera from 7 patients with FLD and 9 healthy exposed controls (HEC). FLD-associated immunoreactive proteins were identified by mass spectrometry based on a protein database specifically created for this study and subsequently produced as recombinant antigens. The ability of recombinant antigens to discriminate patients with FLD from controls was assessed by ELISA performed with sera from FLD patients (n = 41) and controls (n = 43) recruited from five university hospital pneumology departments of France and Switzerland. Forty-one FLD-associated immunoreactive proteins from L. corymbifera were identified. Six of them were produced as recombinant antigens. With a sensitivity and specificity of 81.4 and 77.3% respectively, dihydrolipoyl dehydrogenase was the most effective antigen for discriminating FLD patients from HEC. ELISA performed with the putative proteasome subunit alpha type as an antigen was especially specific (88.6%) and could thus be used for FLD confirmation. The production of recombinant antigens from L. corymbifera represents an additional step towards the development of a standardized ELISA kit for FLD diagnosis.

Occupational hypersensitivity pneumonitis: an EAACI position paper

The aim of this document was to provide a critical review of the current knowledge on hypersensitivity pneumonitis caused by the occupational environment and to propose practical guidance for the diagnosis and management of this condition. Occupational hypersensitivity pneumonitis (OHP) is an immunologic lung disease resulting from lymphocytic and frequently granulomatous inflammation of the peripheral airways, alveoli, and surrounding interstitial tissue which develops as the result of a non-IgE-mediated allergic reaction to a variety of organic materials or low molecular weight agents that are present in the workplace. The offending agents can be classified into six broad categories that include bacteria, fungi, animal proteins, plant proteins, low molecular weight chemicals, and metals. The diagnosis of OHP requires a multidisciplinary approach and relies on a combination of diagnostic tests to ascertain the work relatedness of the disease. Both the clinical and the occupational history are keys to the diagnosis and often will lead to the initial suspicion. Diagnostic criteria adapted to OHP are proposed. The cornerstone of treatment is early removal from exposure to the eliciting antigen, although the disease may show an adverse outcome even after avoidance of exposure to the causal agent.

New Commercially Available IgG Kits and Time-Resolved Fluorometric IgE Assay for Diagnosis of Allergic Bronchopulmonary Aspergillosis in Patients with Cystic Fibrosis

Allergic bronchopulmonary aspergillosis (ABPA) is difficult to diagnose; diagnosis relies on clinical, radiological, pathological, and serological criteria. Our aim was to assess the performance of two new commercially available kits and a new in-house assay: an Aspergillus fumigatus enzyme-linked immunosorbent assay (ELISA) IgG kit (Bordier Affinity Products), an Aspergillus Western blotting IgG kit (LDBio Diagnostics), and a new in-house time-resolved fluorometric IgE assay (dissociation-enhanced lanthanide fluorescent immunoassay, or DELFIA) using recombinant proteins from an Aspergillus sp. recently developed by our laboratory for ABPA diagnosis in a retrospective study that included 26 cystic fibrosis patients. Aspergillus fumigatus-specific IgG levels measured by a commercial ELISA kit were in accordance with the level of precipitins currently used in our lab. The ELISA kit could accelerate and help standardize ABPA diagnosis. Aspergillus fumigatus-specific IgE levels measured by ImmunoCAP (Phadia) with A. fumigatus M3 antigen and by DELFIA with a purified protein extract of A. fumigatus were significantly correlated (P < 10(-6)). The results with recombinant antigens glucose-6-phosphate isomerase and mannitol-1-phosphate dehydrogenase were encouraging but must be confirmed with sera from more patients. The DELFIA is an effective tool that can detect specific IgE against more fungal allergens than can be detected with other commercially available tests.

Evaluation of the applicability of the Immuno-solid-phase allergen chip (ISAC) assay in atopic patients in Singapore

Background/Objective

Molecular-based allergy diagnostics are gaining popularity in clinical practice. Our aim was to evaluate their role in the tropics, given the inherent genetic and environmental differences.

Methods

We recruited subjects with history of atopy and collected data on demographics and atopic symptoms using validated questionnaires. Subjects underwent a series of skin prick tests (SPT). Serum total and specific IgE levels were measured using ImmunoCAP FEIA and ImmunoCAP ISAC®, respectively. We describe their pattern of sensitization and agreement between test methods.

Results

A total of 135 subjects were recruited; mean ± SD age of 31.18 ± 12.72 years, 52.7% female. Allergic rhinitis (AR) was the most prevalent clinical manifestation of atopy (70.7%), followed by atopic dermatitis (AD) (50.5%) and asthma (26.2%). Polysensitization was seen in 51.1% of subjects by both SPT and ISAC. House dust mites (HDM) were the dominant allergen, with sensitization in 67.8% and 62% of subjects on SPT and ISAC, respectively. A group of subjects with monosensitization to B. tropicalis was identified. HDM sensitization was strongly associated with AR, while AD and asthma were not associated with sensitization to any allergen. Agreement between SPT and ISAC was mostly suboptimal. Greatest agreement was documented for the measurement of HDM sensitization with both methods (κ = 0.64). Sensitization to the bulk of the remaining allergens in the ISAC panel was infrequent.

Conclusion

Multiplex methods should not be used as a screening tool, especially in a population with lower rates of polysensitization and a dominant sensitizing allergen. There may be a role in adjusting the antigen spectrum in the ISAC panel to regional differences.

Electronic supplementary material

The online version of this article (doi:10.1186/s13601-015-0053-z) contains supplementary material, which is available to authorized users.

Western blotting as a tool for the serodiagnosis of farmer's lung disease: validation with Lichtheimia corymbifera protein extracts

Electrosyneresis and double diffusion are immunoprecipitation techniques commonly used in the serological diagnosis of Farmer's lung disease (FLD). These techniques are reliable but lack standardization. The aim of this study was to evaluate Western blotting for the serodiagnosis of FLD. We carried out Western blotting with an antigenic extract of Lichtheimia corymbifera, an important aetiological agent of the disease. The membranes were probed with sera from 21 patients with FLD and 21 healthy exposed controls to examine the IgG antibody responses against purified somatic antigens. Given the low prevalence of the disease, 21 patients could be considered as a relevant series. Four bands were significantly more frequently represented in membranes probed with FLD sera (bands at 27.7, 40.5, 44.0 and 50.5 kDa) than those probed with control sera. We assessed the diagnostic value of different criteria alone or in combination. The diagnostic accuracy of the test was highest with the inclusion of at least two of the following criteria: at least five bands on the strip and the presence of one band at 40.5 or 44.0 kDa. Sensitivity, specificity and positive and negative predictive values were all 81%, and the odds ratio was 18.06. Inclusion of bands of high intensity diminished rather than improved the diagnostic value of the test. We concluded that Western blotting is a valuable technique for the serodiagnosis of FLD. The industrial production of ready-to-use membranes would enable the routine use of this technique in laboratories, and provide reliable and standardized diagnostic results within a few hours.

Immunoreactive proteins of Saccharopolyspora rectivirgula for farmer's lung serodiagnosis

PURPOSE

Saccharopolyspora rectivirgula is the principal cause of farmer's lung disease (FLD). Serodiagnosis is based on immunoprecipitation techniques or enzyme immunoassays with homemade crude antigens and is not standardized. We aimed to produce specific recombinant antigens for the development of a standardized ELISA.

EXPERIMENTAL DESIGN

We recruited 41 patients and 43 healthy exposed controls from five university hospital pneumology departments in France and Switzerland. S. rectivirgula proteins were extracted, separated by 2D electrophoresis, and subjected to Western blotting, with sera from FLD patients or controls. FLD-specific proteins were identified by MS and were produced as recombinant antigens. The diagnostic performance of ELISA tests using the recombinant antigens was assessed with all the sera from FLD patients and controls.

RESULTS

We identified 25 FLD-specific proteins, some of which play important roles in transport, nutrition, or virulence. We produced 17 of these proteins as recombinant antigens and assessed their suitability for inclusion in the ELISA test. A combination of three of these proteins (SR1FA, SR17, and SR22) proved remarkably effective at discriminating between patients and controls, with a sensitivity of 83% and a specificity of 77%.

CONCLUSIONS AND CLINICAL RELEVANCE

The recombinant antigens produced in this study constitute a major step toward the improvement of diagnostic performance and the standardization of FLD serodiagnosis.

A murine inhalation model to characterize pulmonary exposure to dry Aspergillus fumigatus conidia

Most murine models of fungal exposure are based on the delivery of uncharacterized extracts or liquid conidia suspensions using aspiration or intranasal approaches. Studies that model exposure to dry fungal aerosols using whole body inhalation have only recently been described. In this study, we aimed to characterize pulmonary immune responses following repeated inhalation of conidia utilizing an acoustical generator to deliver dry fungal aerosols to mice housed in a nose only exposure chamber. Immunocompetent female BALB/cJ mice were exposed to conidia derived from Aspergillus fumigatus wild-type (WT) or a melanin-deficient (Δalb1) strain. Conidia were aerosolized and delivered to mice at an estimated deposition dose of 1×10⁵ twice a week for 4 weeks (8 total). Histopathological and immunological endpoints were assessed 4, 24, 48, and 72 hours after the final exposure. Histopathological analysis showed that conidia derived from both strains induced lung inflammation, especially at 24 and 48 hour time points. Immunological endpoints evaluated in bronchoalveolar lavage fluid (BALF) and the mediastinal lymph nodes showed that exposure to WT conidia led to elevated numbers of macrophages, granulocytes, and lymphocytes. Importantly, CD8⁺ IL17⁺ (Tc17) cells were significantly higher in BALF and positively correlated with germination of A. fumigatus WT spores. Germination was associated with specific IgG to intracellular proteins while Δalb1 spores elicited antibodies to cell wall hydrophobin. These data suggest that inhalation exposures may provide a more representative analysis of immune responses following exposures to environmentally and occupationally prevalent fungal contaminants.

Advances in in vitro diagnostics in allergy, asthma, and immunology in 2012

Laboratory tests play an increasing role in risk assessment, diagnostics, and disease monitoring. Great advances have been achieved lately, particularly in the field of clinical immunology and allergy. These include neonatal screening of immunodeficiencies and asthma biomarkers and investigation into the role of recombinant allergens in in vitro testing. The latter area has implications for the diagnostics of food allergy, pollen-induced allergies, asthma, and insect allergies.

Advances in environmental and occupational disorders in 2012

The year 2012 produced a number of advances in our understanding of the effect of environmental factors on allergic diseases, identification of new allergens, immune mechanisms in host defense, factors involved in asthma severity, and therapeutic approaches. This review focuses on the articles published in the Journal in 2012 that enhance our knowledge base of environmental and occupational disorders. Identification of novel allergens can improve diagnostics, risk factor analysis can aid preventative approaches, and studies of genetic-environmental interactions and immune mechanisms will lead to better therapeutics.