Sequential Mapping of the Post-Lung Transplant Metabolome: A Metabolomic Survey of the Respiratory Microbiome

Author(s):
Callie Winters; Johnathan Kent; Ashley Sidebottom; Remzi Bag; Renea Jablonski; Kevin Tsui; Olga Zaborina; John Alverdy; Robert Guzy; Maria Lucia Madariaga

Background:

The potential role of the lung microbiome in post-lung transplant disease is the subject of ongoing investigation, but there has been limited exploration of metabolites as a mediating factor in microbiota-host relationships.

Hypothesis:

We analyzed sequential bronchioalveolar lavage fluid (BALF) samples to correlate the post-transplant lung metabolome and clinical course.

Methods:

Excess BALF was obtained during surveillance bronchoscopies of lung transplant recipients from November 2021 to June 2022. Targeted metabolomics by gas chromatography-mass spectrometry (GC-MS) was performed on the collected fluid. From the GC-MS data, we compared the normalized relative abundance for 86 previously validated compounds between the BALF samples and a saline control. Raw feature peak areas were normalized by the average of two internal standards. Background signal was subtracted, and the peak areas were adjusted for BALF instillation volume. Compounds of interest (CI) were those enriched compared to the saline control; compounds of high interest (CHI) were identified by association with patient health status and BALF culture results.

Results:

Six patients provided nine BALF samples. Of 86 possible compounds, 30 CI were identified. No patients experienced health status changes during the study period, however three patients had asymptomatic culture positive BALF samples yielding Kloeckera sp., Pseudomonas aeruginosa, or Aspergillus sp. There were no metabolite differences between patients with positive vs. negative cultures; however, 11 CHI were identified (5 tryptophan metabolites, 5 other amino acids, and 1 fatty acid) by sequentially comparing one patient whose BALF samples progressed from Kloeckera to Pseudomonal culture and two patients with negative culture samples (Figure).

Conclusions:

We identified 11 CHI associated with microbiome-host cross-talk, dysbiosis, and inflammation in sequential comparison between samples from a patient with positive BALF cultures and two patients with negative cultures which were not identifiable on single time-point analysis. Ongoing studies in additional patients will determine whether this methodology could potentially identify novel biomarkers of post-lung transplant disease.