Hypersensitivity Pneumonitis Caused by House Cricket, Acheta domesticus

Hypersensitivity pneumonitis (HP) is characterized by extensive interstitial lung inflammation primarily driven by activated T lymphocytes in response to exogenous antigens. The purpose of this study was to investigate whether chronic exposure to Acheta domesticus commonly known as house cricket was the underlying cause of HP in a 63 year old patient. HP was diagnosed by the history, spirometry high resolution computed tomography (HRCT) of the chest, bronchoalveolar lavage and trans-bronchial biopsy. Ouchterlony double diffusion assay, direct ELISA and Western blotting were used to detect immuno-reactive precipitins/antigens and anti-cricket antibodies. Mass spectrometry was used to identify the major putative antigens. T cell-mediated response to cricket antigens was assessed by in vitro cytokine production assays. HRCT showed extensive bilateral and ground glass opacification throughout the lungs with some sparing at the bases, while bronchoalveolar lavage showed lymphocyte predominant leukocyte infiltration. A lung biopsy showed diffuse chronic interstitial inflammation with poorly defined granulomas consisting lymphocytes and occasional giant cells. There were high titer antibodies against cricket protein extracts and specific antigen-antibody precipitins. Western blotting showed 4 specific immuno-reactive bands. Tryptic peptide digest and mass spectrometry revealed arginine kinase as a potential antigen. Multistep chromatography enriched cricket arginine kinase induced strong in-vitro interferon-γ response by PBMC obtained from the patient but not in other cricket-exposed and non-exposed healthy control subjects. This is the first study to report a case of subacute HP in response to prolonged exposure to house cricket antigens.