Two Siblings Homozygous for F508del-CFTR Have Varied Disease Phenotypes and Protein Biomarkers

Abstract

Two siblings with CF are homozygous for F508del (referred to as Subject A and Subject B). Despite having the same CFTR genotype and similar environment, these two subjects exhibited different disease phenotypes. We analyzed their medical records and CF Foundation Registry data and measured inflammatory protein mediators in their sputum samples. Then, we examined the longitudinal relationships between inflammatory markers and disease severity for each subject and compared between them. Subject A presented a more severe disease than Subject B. During the study period, Subject A had two pulmonary exacerbations (PEs) whereas Subject B had one mild PE. The forced expiratory volume in 1 s (FEV₁, % predicted) values for Subject A were between 34-45% whereas for Subject B varied between 48-90%. Inflammatory protein mediators associated with neutrophils, Th1, Th2, and Th17 responses were elevated in sputum of Subject A compared with Subject B, and also in samples collected prior to and during PEs for both subjects. Neutrophilic elastase (NE) seemed to be the most informative biomarkers. The infectious burden between these two subjects was different.

Keywords: CFTR; F508del-CFTR; biomarkers; cystic fibrosis (CF); disease phenotypes; infection; inflammation.

Figure 1

IL-8 and NE levels in the sputum samples from Subject A (black bars) and Subject B. (A) IL-8 levels. (B) NE levels. The samples were measured using ELISA kits and the data are presented as Mean ± standard error of mean (SEM). n = 4–6. * admitted into the emergency room (ER) 6 days later for pulmonary exacerbation (PE); ** admitted into ER 5 days later for PE; ^# admitted into ER for PE on this visit.

Figure 2

The levels of neutrophil-associated markers, (A) TNFα, (B) MPO, (C) GM-CSF, and (D) Gro-α in the sputum samples from Subject A (black bars) and Subject B. Cytokines were measured in sputum samples in duplicate using a bead-based multiplex assay. The dotted lines indicate the lower limit of detection for each specific cytokine; the solid line indicates the upper limit of detection for each specific cytokine. * admitted into the emergency room (ER) 6 days later for pulmonary exacerbation (PE); ** admitted into ER 5 days later for PE.

Figure 3

Inflammatory mediators in sputum samples from Subject A (black bars) were increased in comparison to Subject B. (A) IL-6 levels. (B) BAFF levels. (C) TWEAK levels. (D) IL-27 levels. (E) IFNγ levels. (F) IL-13 levels. (G) IL-1Ra levels. (H) MCP-1 levels. Cytokines were measured in sputum samples in duplicate using a bead-based multiplex assay. The dotted lines indicate the lower limit of detection for each specific cytokine; the solid line indicates the upper limit of detection for each specific cytokine. * admitted into the emergency room (ER) 6 days later for pulmonary exacerbation (PE); ** admitted into ER 5 days later for PE.

Figure 4

Cytokines that were elevated in both subjects. Subject A (black bars). (A) IL-1α levels. (B) IL-1β levels. (C) IL-22 levels. (D) IL-9 levels. Cytokines were measured in sputum samples in duplicate using a bead-based multiplex assay. The dotted lines indicate the lower limit of detection for each specific cytokine. * admitted into the emergency room (ER) 6 days later for pulmonary exacerbation (PE); ** admitted into ER 5 days later for PE.