(143) Bronchoalveolar lavage proteome identifies pathways of disease that segregate lung transplant recipients with versus without bronchiolitis obliterans syndrome

Background: Lung transplantation (LTx) is a treatment option for many end-stage lung diseases, including cystic fibrosis (CF). Proteomic analysis of bronchoalveolar lavage (BAL) fluid from lung transplant (LTx) recipients has not been performed to identify potential biomarkers or pathways that associate with bronchiolitis obliterans syndrome (BOS). We hypothesized that determining the differences in patients with BOS versus those without may shed light on the molecular underpinnings of disease.

Methods: We analyzed BAL fluid from 31 adult LTx recipients with (n=15, 2 females) and without BOS (n=16, 3 females). Samples were collected from patients that received LTx for idiopathic pulmonary fibrosis, chronic obstructive pulmonary disease, or alpha 1 antitrypsin deficiency. Whole BAL protein was precipitated with acetone, resolubilized, fractionated by SDS gel electrophoresis, in-gel trypsin digested, and subjected to mass spectrometer-based proteomic analysis.

Results: Our liquid chromatography mass spectrometry (LCMS) proteomic approach identified 4908 protein isoforms that were present in at least 50% of either cohort, with 227 isoforms (p< 0.01, FDR< 0.1) distinguishing LTx recipients with and without BOS. Pathway analysis of differentially expressed proteins reveal vascular permeability (p=3.31e-3), proliferation/migration (p=5.68e-2), protein localization to ciliary membrane (p=8.02e-4), and prostaglandin E2 (PGE2) immune response (p=4.93e-2). A more stringent percolator-decoy analysis identified 9 isoform differences and reveals changes in platelet degranulation (p=5.36e-8, FDR=6.09e-6), kallikrein-kinin driven inflammation (p=3.37e-4, FDR=3.37e-3), lectin-induced complement pathway (p=6.19e-8, FDR=6.09e-6), blood coagulation (p=6.19e-7, FDR=4.567e-5), and IL-6 mediated inflammation (p=3.98e-3, FDR=9.96e-3). Disease associations of identified differences included connective tissue diseases (p=2.20e-5, FDR=3.26e-3), wounds and injuries (p=3.71e-5, FDR=3.26e-3), and autoimmune disease (p=4.71e-5, FDR=3.26e-3). Strong signals antigen presentation and immunoglobulin mediated immune response (p=9.76e-17) and viral transcription (p=6.41e-11) were also observed in the BOS cohort.

Conclusions: The data suggest that antiviral / antimicrobial, complement inhibition, and antigen presentation are features of disease in LTx patients that developed BOS. Therapies that target these pathways may be of benefit. Furthermore, our proteomic approach may offer an additional tool for the diagnosis of BOS in LTx recipients.

Acknowledgements: R01HL142210 / NHLBI (Ziady)

References: