Gene Expression Profiling of Bronchoalveolar Lavage Cells during Aspergillus Colonization of the Lung Allograft
Aspergillus colonization after lung transplant is associated with an increased risk of chronic lung allograft dysfunction (CLAD). We hypothesized that gene expression during Aspergillus colonization could provide clues to CLAD pathogenesis.Methods
We examined transcriptional profiles in 3 or 6-month surveillance bronchoalveolar lavage fluid cell pellets from recipients with A. fumigatus colonization (n=12) and without colonization (n=10). Among the Aspergillus colonized, we also explored profiles in those who developed CLAD (n=6) or remained CLAD free (n=6). Transcription profiles were assayed with the HG-U133 Plus 2.0 microarray (Affymetrix). Differential gene expression was based upon an absolute fold difference ≥2.0, and unadjusted P-value <0.05. We used NIH DAVID for functional analyses, with false discovery rates <5% considered significant.Results
Aspergillus colonization was associated with differential expression of 489 probe sets, representing 404 unique genes. “Defense response” genes and genes in the “cytokine-cytokine receptor” KEGG pathway were notably enriched in this list. Among Aspergillus colonized patients, CLAD development was associated with differential expression of 69 probe sets, representing 64 unique genes. This list was enriched for genes involved in “immune response” and “response to wounding”, among others. Notably, both chitinase 3-like-1 and chitotriosidase were associated with progression to CLAD.Conclusion
Aspergillus colonization is associated with gene expression profiles related to defense responses including cytokine signaling. Epithelial wounding, as well as the innate immune response to chitin that is present in the fungal cell wall, may be key in the link between Aspergillus colonization and CLAD.