Peptide-based ELISA for laboratory diagnosis of sarcoidosis

Project Summary Sarcoidosis is a systemic inflammatory disease of unknown etiology characterized by granuloma formation in the lungs and other organs, affecting about 200,000 patients in the U.S. and over 1 million worldwide, with significantly higher frequency in northern Europeans and African Americans, and in women vs. men. While the disease can be contained with corticosteroids, there is no cure, and some patients progress to irreversible fibrosis. Sarcoidosis remains a diagnostic challenge due to its symptomatic overlap with multiple other disease conditions including lung cancer, tuberculosis, fungal and other infectious and non-infectious diseases. Unfortunately, there is no available test for sarcoidosis due to the lack of a specific biomarker for the disease. Consequently, diagnosis is generally based on exclusion of other causes, and ultimately rests on a tissue biopsy. Biopsy of the lung – the most frequently affected organ – in pulmonary sarcoidosis patients is an invasive procedure; for cardiac or neurosarcoidosis, it is all but impossible. Given the critical need to differentiate patients with sarcoidosis from those with tuberculosis, cancer or other serious conditions, a test for sarcoidosis that would enable diagnosis without a biopsy is an urgent priority. This Direct-to-Phase II project is based on research carried out by co-investigators at Wayne State University who developed a novel T7 phage display library derived from cDNA isolated from BAL and peripheral blood cells of sarcoidosis patients. Immunoscreening of a microarray containing clones from the T7 library identified two peptides that were specifically recognized by sera from sarcoidosis patients but not those from patients with tuberculosis or lung cancer. The two peptides were found to be partially homologous to cofilin, an actin-binding and depolymerizing protein, and methionine aminopeptidase 1, respectively. ELISAs using the two peptides - termed cofilinμ and Chain A based on the divergence in sequence from the native protein at the N terminal – were specifically reactive with sera from sarcoidosis patients, discriminating them from tuberculosis and lung cancer. In Phase II, we will complete the development and optimization of the sarcoidosis ELISA, and will carry out the pivotal clinical study that will support an FDA submission for approval of the ELISA as a diagnostic test for sarcoidosis. In this clinical study, we will evaluate the sensitivity and specificity of the ELISA on retrospective panels of well-characterized sarcoidosis sera and controls, and on prospective sera from patients undergoing evaluation for suspected sarcoidosis. Achievement of this objective will change the paradigm of sarcoidosis diagnosis, as the sarcoidosis ELISA will for the first time enable presumptive diagnosis of this disease based on a simple blood test without requirement for an invasive tissue biopsy.