Decreased Immune Activation in Cystic Fibrosis Airway Epithelium Following Lung Transplant

Abstract

End-stage cystic fibrosis (CF) can be managed by lung transplantation (LT), but chronic allograft dysfunction (CLAD) limits long-term survival. While Pseudomonas aeruginosa airway infection (PsA) is a risk factor for CLAD for most lung allograft recipients, this association does not hold for CF recipients. We hypothesized that differences in host epithelial immune responses and the composition of airway microbial communities could contribute to protection from CLAD in CF recipients with PsA. We compared transcriptomes from clinical airway brushes following LT for 28 subjects, grouped by CF status and PsA culture result (CF+PsA+, n=8; CF+PsA-, n=6; CF-PsA+, n=5; and CF-PsA-, n=9) using DEseq2. For in vitro analysis of immune responses, airway epithelial cells (AEC) were isolated from lung explants (pre-LT) or surveillance airway brushes (post-LT) and grown at air-liquid interface until polarized and differentiated. Gene expression differences and DNA methylation were compared by CF status using quantitative PCR and DNA methylation array. For subjects with a positive PsA culture following LT, there were 193 differentially expressed genes between CF and non-CF airways. Pathway analysis demonstrated suppression of interferon response in CF airways. Relative to non-CF referents, CF AEC in vitro transitioned from increased expression of neutrophil-associated genes (Cxcl8 and Lcn2) pre-LT, to decreased expression of interferon-associated genes (Mx1 and Oas1) post-LT. DNA methylation analysis showed hypermethylation of promoters in type I interferon responsive genes (p = 0.002). All CF+PsA+ subjects had mucoid PsA strains while 72% of non-CF subjects had non-mucoid PsA (p <0.001). The combination of attenuated interferon responses and prevalence of mucoid strains may explain the differential outcomes in CF LT recipients with PsA.