Bird fancier's lung serodiagnosis by automated r-IgLL1 ELISA

CONTEXT

Bird fancier's lung (BFL) is the most prevalent form of hypersensitivity pneumonitis (HP) worldwide. The current techniques used for the serological diagnosis of BFL all use crude extracts from feathers, droppings, and blooms as test antigens, which is associated with a lack of standardization and variability of the results. An antigenic protein, immunoglobulin lambda-like polypeptide-1 (IgLL1), isolated from pigeon droppings, was recently identified to be associated with BFL. We used genetic engineering to produce IgLL1 as a recombinant antigen.

AIM

We aimed to prospectively validate the use of an automated ELISA based on recombinant IgLL1 protein (r-IgLL1) as the test antigen for the serological diagnosis of BFL.

METHODS

Immunoprecipitation (IP) techniques (immunodiffusion (ID), immunoelectrophoresis (IEP)) and ELISA using r-IgLL1 were performed concomitantly over 10 months on 634 sera from patients with a BFL serodiagnosis request. Questionnaires were sent to obtain details on the avian exposure, clinical data, and final diagnosis. Concordance, sensitivity (Se), and specificity (Sp) of the two techniques were compared.

RESULTS

In total, 72 completed questionnaires were returned with 18 cases of BFL diagnosed and 54 of non-BFL. The concordance between the ELISA and ID+IEP precipitation techniques was 71%. The combination of immunoprecipitation techniques showed a Se of 78% and a Sp of 67%. The ELISA using r-IgLL1 showed a Se of 89% and a Sp of 91%. The automated r-IgLL1 ELISA test is sufficiently efficient to be used alone for the diagnosis of patients exposed solely to Columbidae. In cases of other avian exposure, the Se and Sp of the r-IgLL1 ELISA used for screening combined with the immunodiffusion test for confirmation were 89% and 93%, respectively.

CONCLUSIONS

The automated ELISA using r-IgLL1 is a promising tool for BFL serodiagnosis. Replacing immunodiffusion by the automated ELISA using r-IgLL1 as a screening technique will be the basis of our future strategy for BFL serodiagnosis.

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.

Pilot Study Using Recombinant Antigens r-PROE and r-IGLL1 for the Serodiagnosis of Feather Duvet Lung

BACKGROUND

Feather duvet lung (FDL) is an underestimated form of acute and chronic hypersensitivity pneumonitis. Serological tests for FDL need to be validated. We investigated the ability of recombinant pigeon Proproteinase E (r-PROE) and Immunoglobulin-lambda-like-polypeptide-1 (r-IGLL1) proteins to support the serological diagnosis of FDL, and propose them as a serological tool for clinicians to differentiate cases from FDL and Bird fancier's lung (BFL).

METHODS

Specific IgG antibodies against r-PROE and r-IGLL1, analyzed with ELISA, were measured in patients diagnosed with FDL (n=31), BFL (n=15) controls exposed (n=15) and unexposed to feathers (n=15).

RESULTS

The sensitivity and specificity of the r-PROE ELISA for the serological diagnosis of FDL cases versus exposed and unexposed controls were 74.2% and 86.7% respectively, with an index threshold of 0.5 (AUC: 0.89). In addition, this serological test was effective to support the serological diagnosis of FDL and BFL cases with significantly different thresholds. The r-IGLL1 ELISA was only effective for the serological diagnosis of BFL. Also, these two serological tests were useful for the diagnosis of both chronic and acute forms.

CONCLUSIONS

The new diagnostic test for FDL using r-PROE protein should help to detect overt and hidden cases of FDL. The combination of both test will help the clinician in distinguish between the etiology of birds or feathers duvet.

Hypersensitivity pneumonitis: A new strategy for serodiagnosis and environmental surveys

We propose a strategy for serodiagnosis of hypersensitivity pneumonitis (HP): 1) question patients about their private or occupational activity, or visit him on site; 2) select panels of six somatic specific antigens appropriate for each type of exposure; 3) and use ELISA to test concomitantly two recombinant antigens highly specific to Farmer's lung, Metalworking-fluid HP, and for Bird fancier's lung. The serodiagnosis provides an immunological argument that may complete radiological, functional lung exploration and clinical features; 4) If the serodiagnosis is negative but the suspicion of HP is strong, a microbial analysis of the patient's specific exposure is conducted; 5) "A la carte" antigens are produced from the microorganisms isolated in the patient's environment sample and tested; 6) Finally, the patient may be asked to undergo a specific inhalation challenge with the offending antigens in a safety cabin, or to avoid his usual environment for a few days.

Immunogenic proteins specific to different bird species in bird fancier's lung

Bird fancier's lung (BFL) is a disease produced by exposure to avian proteins present in droppings, blooms, and serum of a variety of birds. Although serological test results are currently used to confirm clinical diagnosis of the disease, bird species specificity is poorly understood. This study aimed to contribute to a better understanding of the specificity of immunogenic proteins revealed from the droppings of three bird species. Sera from four patients with BFL and two controls without exposure were analyzed by Western blotting with antigens from droppings of two pigeon and budgerigar strains and two hen species. When the antigens from the droppings of the three bird species were compared, the profile of immunogenic proteins was different and there were similarities between strains of the same species. Only one 68-kD protein was common to pigeon and budgerigar droppings, while proteins of 200, 175, 140, 100, and 35 kD were detected as specific in one bird species. These results provide insight to further characterize these proteins, and to design new serological tests specific to different bird species. These tests may help to refine strategies of antigenic exclusion and also to allow a patient compensation in case of BFL of occupational origin.