ABCMdb

PMID: 25769931

Bratcher PE, Rowe SM, Reeves G, Roberts T, Szul T, Harris WT, Tirouvanziam R, Gaggar A
Alterations in blood leukocytes of G551D-bearing cystic fibrosis patients undergoing treatment with ivacaftor.
J Cyst Fibros. 2015 Mar 11. pii: S1569-1993(15)00050-8. doi: 10.1016/j.jcf.2015.02.010., [PubMed]

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No. Mutations Sentence Comment

3 ABCC7 p.Gly551Asp Methods: We examined blood leukocytes from G551D CF subjects prior to and at one and six months after receiving ivacaftor. Login to comment 4 ABCC7 p.Gly551Asp Blood leukocytes from ivacaftor-na&#ef;ve G551D, F508del, and healthy controls were also treated with ivacaftor ex vivo to assess mutation-specific effects. Login to comment 5 ABCC7 p.Gly551Asp Results: Compared to healthy controls, G551D CF subjects had significantly higher expression of active CD11b on PMNs and of CD63 on monocytes, which were normalized by in vivo ivacaftor treatment. Login to comment 6 ABCC7 p.Gly551Asp Ex vivo exposure to ivacaftor of blood cells from G551D, but not F508del and healthy subjects, resulted in changes in CXCR2 and CD16 expression on PMNs. Login to comment 7 ABCC7 p.Gly551Asp Conclusions: In vivo and ex vivo exposure of G551D CF leukocytes to ivacaftor resulted in an altered activation profile, suggesting mutation-specific leukocyte modulation. Login to comment 9 ABCC7 p.Gly551Asp Keywords: CFTR; G551D; Ivacaftor; VX-770; Leukocyte; Blood 1. Login to comment 19 ABCC7 p.Gly551Asp Please cite this article as: Bratcher PE, et al, Alterations in blood leukocytes of G551D-bearing cystic fibrosis patients undergoing treatment with ivacaftor, J Cyst Fibros (2015), http://dx.doi.org/10.1016/j.jcf.2015.02.010 Journal of Cystic Fibrosis xx (2015) xxx-xxx JCF-01171; No of Pages 7 More recently the protean manifestations of CFTR have been realized, including its expression in peripheral leukocytes and other non-epithelial tissues, which have also been postulated to contribute to disease pathogenesis [5,6]. Login to comment 25 ABCC7 p.Gly551Asp Recently, the CFTR potentiator ivacaftor (formerly known as VX-770) was approved for the treatment of CF caused by the G551D gating mutation (but not for the most common folding and gating mutation, F508del) [11]. Login to comment 28 ABCC7 p.Gly551Asp ABCC7 p.Gly551Asp Following approval, CF patients with the G551D mutation were monitored in the G551D Observational (GOAL) Study. Login to comment 33 ABCC7 p.Gly551Asp Based on these findings, we hypothesized that leukocyte function might be improved in G551D CF patients treated with ivacaftor. Login to comment 34 ABCC7 p.Gly551Asp ABCC7 p.Gly551Asp The aim of the present study is to characterize the activation state of peripheral blood leukocytes in G551D CF patients pre/post ivacaftor initiation, and after ex vivo exposure to ivacaftor of blood cells from G551D CF patients compared to F508del CF patients and healthy control subjects. Login to comment 38 ABCC7 p.Gly551Asp Briefly, CF patients age 6 and older carrying at least one copy of the G551D mutation and no recent or sustained exposure to ivacaftor were eligible. Login to comment 47 ABCC7 p.Gly551Asp The median age of the G551D group was 6.5 years (range of 2-18) with 75% Caucasian and 75% male distribution. Login to comment 54 ABCC7 p.Gly551Asp ABCC7 p.Gly551Asp ABCC7 p.Asn1303Lys Subject demographics GOAL study subjects Sex % Male 40 Age Mean (SD); median (range) 20.81 (11.46); 16 (10-40) Race % Caucasian 100 Genotype Genotype (%) G551D/F508del (80), G551D/N1303K (20) ƊFEV1 (% change) Mean (SD); median (range) 1.14 (9.98); 2 (-11-12.4) ƊFVC(% change) Mean (SD); median (range) 2.58 (7.81); 0.2 (-7.4-13.7) ƊSweat Chloride Mean (SD); median (range) -51.9 (17.37); -57 (-75 to -31.5) Healthy controls Sex % Male 40 Age Mean (SD); median (range) 25.6 (4.98); 24 (22-34) Race % Caucasian 100 2 2.2. Login to comment 80 ABCC7 p.Gly551Asp Comparisons of responses between G551D Fig. 1. Login to comment 91 ABCC7 p.Gly551Asp GOAL patient demographics This study enrolled 5 CF patients with at least one G551D allele, each of whom participated in the GOAL study. Login to comment 93 ABCC7 p.Gly551Asp As shown in Table 1, all five G551D patients responded to ivacaftor treatment with a significant improvement in sweat chloride. Login to comment 96 ABCC7 p.Gly551Asp Cell surface markers of activation are reduced on blood leukocytes in patients after in vivo treatment with ivacaftor To examine the phenotype of leukocytes from CF patients with the G551D mutation, blood was stained for flow cytometric analysis before ivacaftor treatment and at one and six months post drug treatment. Login to comment 115 ABCC7 p.Gly551Asp ABCC7 p.Gly551Asp Ex vivo ivacaftor treatment results in changes in surface CXCR2 and CD16 expression on G551D PMNs The change in inflammatory activation and PMA response of blood leukocytes in G551D CF patients after ivacaftor treatment in vivo may be due to a direct effect of ivacaftor on leukocytes or due to a decrease in airway inflammation and its systemic manifestations (i.e. an indirect effect of ivacaftor). Login to comment 116 ABCC7 p.Gly551Asp To begin to address this question, we examined the effect of direct exposure of leukocytes from G551D CF patients to ivacaftor ex vivo. Login to comment 117 ABCC7 p.Gly551Asp We found that short-term ex vivo treatment of blood with ivacaftor resulted in the emergence of a subpopulation of PMNs in G551D CF patients, but not in F508del CF patients and healthy controls (Fig. 3). Login to comment 120 ABCC7 p.Gly551Asp This subpopulation of PMNs (CXCR2int CD16int ) may be generated by a direct effect of ivacaftor on G551D CFTR in PMNs. Login to comment 121 ABCC7 p.Gly551Asp One possible explanation is that G551D CFTR induction by ivacaftor may affect membrane recycling, which, on the one hand, is known to be regulated by CFTR [3], and, on the other hand, has been previously linked to changes in surface CXCR2 and CD16 expression in PMNs [20,21]. Login to comment 125 ABCC7 p.Gly551Asp Our studies highlight changes in the baseline activation status of monocytes and PMNs in CF subjects with the G551D mutation over a Fig. 3. Login to comment 127 ABCC7 p.Gly551Asp A: Histograms of surface CD16 (top row), CXCR2 (middle row), and CD63 (bottom row) expression on PMNs treated with either ivacaftor (black line) or vehicle (DMSO, shaded gray) from representative G551D, F508del and healthy control subjects. Login to comment 131 ABCC7 p.Gly551Asp The G551D group showed a significant difference compared to other groups, as tested using the Kruskal-Wallis method (for CD16, p = 0.0376 and for CXCR2, p = 0.0302). Login to comment 133 ABCC7 p.Gly551Asp 5 6 month period of treatment with the G551D-specific potentiator, ivacaftor. Login to comment 135 ABCC7 p.Gly551Asp While these results are limited due to the small cohort of ivacaftor-treated G551D CF patients enrolled in this study, they contribute to mounting evidence of changes in leukocyte activation after treatment in vivo with a CFTR potentiator. Login to comment 136 ABCC7 p.Gly551Asp Our ex vivo findings are particularly interesting as they demonstrate that direct treatment with ivacaftor of PMNs from CF patients with the G551D mutation (in contrast to F508del homozygous CF patients or healthy controls) leads to changes in CXCR2 and CD16 expression. Login to comment 141 ABCC7 p.Gly551Asp In particular, this study showed that PMNs from CF patients exhibited impaired release of secondary and tertiary granules, and that this impairment was no longer present in PMNs from patients with the G551D mutation who were undergoing treatment with ivacaftor. Login to comment 145 ABCC7 p.Gly551Asp In conclusion, this study presents evidence for alterations in leukocyte activation observed in G551D CF subjects treated with the CFTR potentiator ivacaftor. Login to comment