Elevated levels of circulating CD4(+) CRTh2(+) T cells characterize severe asthma

BACKGROUND

Chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTh2) is a receptor for PGD2 and expressed by T cells, eosinophils, basophils, and ILC2 cells. CRTh2 expression by CD4(+) T cells identifies the Th2 subset, and these cells have been characterized as allergen-specific central memory Th2 cells. Recently, activation of the PGD2 -CRTh2 pathway in the lungs was associated with severe asthma.

OBJECTIVE

To assess circulating levels of Th2 cells and related mediators in severe asthma and those who experience asthma exacerbations.

METHODS

Peripheral blood cells expressing CRTh2 were characterized by flow cytometry and qRT-PCR. Serum IL-13 and PGD2 were measured by ELISA and compared with asthma severity and tendency to exacerbate.

RESULTS

Severe asthmatics had more circulating CD4(+) CRTh2(+) T cells, CRTh2 and GATA3 mRNA, and a higher level of serum IL-13 compared to mild/moderate asthmatics. The proportion of CD4(+) CRTh2(+) T cells was associated with lower lung function and was highest in severe asthmatics that exacerbated in the last year. Circulating CD4(+) CRTh2(+) T cells, unlike eosinophils, were positively correlated with inhaled steroid dose.

CONCLUSIONS AND CLINICAL RELEVANCE

Elevated levels of circulating CD4(+) CRTh2(+) T cells are a feature of severe asthma, despite high-dose corticosteroids. Tracking the systemic level of these cells may help identify type 2 severe asthmatics at risk of exacerbation.

The single nucleotide polymorphism CRTh2 rs533116 is associated with allergic asthma and increased expression of CRTh2

BACKGROUND

CRTh2 (chemoattractant-receptor homologous molecule expressed on Th2 cells) is expressed by Th2 cells and other cells involved in allergic inflammation. Single nucleotide polymorphisms (SNPs) in CRTh2 (rs11571288, rs545659, rs634681) have been associated with various phenotypes of allergy in ethnically distinct populations. Here, we assessed the association between CRTh2 rs533116 and allergic asthma, expression of CRTh2 and Th2 cytokine production.

METHODS

CRTh2 rs533116 was genotyped in an ethnically diverse population (n = 1282). The proportion of cells expressing CRTh2 was determined in peripheral blood from subjects with allergic airways disease and controls as well as with in vitro differentiated Th2 cells. Receptor function was assessed by stimulating Th2 cells with the CRTh2-specific agonist 13,14-dihydro-15-keto-PGD(2) (DK-PGD(2) ) and measuring IL-4 and IL-13 by intracellular staining and ELISA.

RESULTS

CRTh2 rs533116 was associated with allergic asthma in White people (2.67 [1.09-6.55], P < 0.05), and expression of CRTh2 was higher in subjects with allergic airways disease compared to controls (P < 0.05). Among allergic individuals, the AA genotype was significantly associated with more eosinophils and higher expression of CRTh2 by both CD4(+) T cells and eosinophils (P < 0.05). In vitro, the AA genotype was associated with a higher proportion of CRTh2(+) cells during Th2 differentiation as well as more IL-4 and IL-13 expression following DK-PGD(2) stimulation (P < 0.05).

CONCLUSIONS

These findings show an association between CRTh2 rs533116 and allergic asthma and suggest this may be mediated by elevated expression of CRTh2, leading to higher numbers of circulating eosinophils and Th2 cytokine production.

Association of thromboxane A2 receptor (TBXA2R) gene polymorphism in patients with aspirin-intolerant acute urticaria

BACKGROUND

The thromboxane A2 receptor (TBXA2R) is a potent broncho- and vaso-constrictor and is associated with leukotriene synthesis. Polymorphisms in the TBXA2R gene have been linked to atopy, asthma, and atopic dermatitis. This study evaluated the association between genetic TBXA2R variants and the development of acetyl salicylic acid (ASA)-intolerant acute urticaria (AIAU).

METHODS

AIAU patients (n=167), ASA-intolerant chronic urticaria (AICU) patients (n=149), and healthy controls (NC) (n=265) were included. All patients were enrolled at Ajou University Hospital in Suwon, Korea. Two TBXA2R polymorphisms (-4684T>C and 795T>C) were genotyped by primer extension using a SNAPshot ddNTP primer extension kit. Luciferase activity was measured using a dual-luciferase reporter assay kit. An electrophoretic mobility shift assay (EMSA) was performed using a nuclear extract from a human mast cell line (HMC-1).

RESULTS

Genetic association data demonstrated that compared with NC subjects, AIAU patients had a significantly higher frequency of the homozygous TT genotype of TBXA2R-4684T>C (P=0.005, P(corr) =0.03). No differences were identified between the AICU and the NC groups. Luciferase activity, reflecting promoter activity, was significantly lower with the TBXA2R-4684T-containing construct than with the -4684C-containing construct (P<0.001); the activity decreased further upon co-transfection with ETS-like gene transcription factor-1 (ELK-1) (P=0.012). EMSA revealed that the -4684T allele produced a specific shifted band, with a greater affinity than that produced by the -4684C allele.

CONCLUSION AND CLINICAL RELEVANCE

These results suggest that the TBXA2R-4684T allele may be associated with lower TBXA2R expression, which may contribute to the development of the AIAU phenotype.

Genetic variability in CRTH2 polymorphism increases eotaxin-2 levels in patients with aspirin exacerbated respiratory disease

INTRODUCTION

CRTH2 is expressed on the surface of eosinophils and has been shown to mediate PGD2-induced eosinophil migration in vitro. Eosinophilic infiltration in the upper and lower airways is the key feature of asthma. Considering the fact that eosinophil infiltration is prominent in the upper and lower airways of aspirin exacerbated respiratory disease (AERD) compared to aspirin-tolerant asthma (ATA) patients, we hypothesized that activation of eosinophils via dysregulation of the CRTH2 gene may play an important role and be an important marker for AERD.

METHODS

The three study groups - 107 with AERD, 115 with ATA and 133 normal healthy controls (NC) - were recruited from Ajou University Hospital, South Korea. Two polymorphisms of the CRTH2 gene at -466T>C and -129C>A were genotyped using primer extension methods.

RESULTS

AERD patients had significantly higher serum eotaxin-2 levels than did those with ATA (P = 0.034). A significant difference in the genotype frequencies of CRTH2 -466T>C was detected between AERD and ATA patients (P < 0.05). The serum eotaxin-2 level was significantly higher in AERD patients carrying the TT genotype of CRTH2 -466T>C than those with the CT and CC (P < 0.05). In vitro functional study demonstrated that the -466T allele had lower luciferase activity (P < 0.001) and lower mRNA expression with higher production of eotaxin-2 (P = 0.003) in human lung epithelial cells. EMSA showed that CRTH2 -466T produced a specific band with a higher affinity than CRTH2 -466C had.

CONCLUSION

The CRTH2 -466T>C polymorphism increases serum and cellular eotaxin-2 production through lowered CRTH2 expression, leading to eosinophilic infiltration in AERD patients.

Serum lactoferrin level as a serologic biomarker for allergic rhinitis

BACKGROUND

Allergic rhinitis (AR) is a very common disease and a risk factor for allergic asthma. The discovery of new biomarkers for the early detection of AR would improve the clinical outcomes and reduce socio-economic burden. We sought to identify a novel serologic marker for detection of AR using a proteomic approach.

METHODS

To identify the proteins involved in AR, comparative proteomics was applied using nasal lavage fluids (NLFs) taken before and after a nasal provocation test (NPT) with Dermatophagoides pteronyssinus (Dpt) in a subject with AR sensitized to Dpt. The clinical relevance of the identified proteins was evaluated by ELISA using NLFs and sera from the three study groups: Dpt-sensitive AR; asymptomatic Dpt-sensitive controls; and non-atopic healthy controls. The sensitivities and specificities of the candidate proteins for predicting AR were determined using receiver operating characteristic (ROC) curves.

RESULTS

In proteomic analysis, lactoferrin expression was up-regulated after NPT. The validation study using ELISA showed a significantly lower serum lactoferrin level in the AR group than those of the other two groups (P<0.05, respectively). To discriminate between subjects with or without AR, the optimal serum cut-off level of lactoferrin was set at <307 ng/mL using the ROC curve. The sensitivity and specificity for predicting AR were 81.4% and 58%. When combined with serum Dpt-specific IgE level, the sensitivity and specificity for predicting AR were 76.7% and 79.2%.

CONCLUSION

These results suggest that the serum lactoferrin level is associated with the phenotype of Dpt-sensitive AR, and in combination with the serum Dpt-specific IgE level, may be a potential serologic marker for early detection of AR.

What do we know about the genetics of aspirin intolerance?

Although acetylsalicylic acid is prescribed for a broad range of diseases, it can induce a wide array of clinically recognized hypersensitivity reactions, including aspirin-intolerant asthma (AIA) with rhinitis and aspirin-intolerant urticaria (AIU) with anaphylaxis. Altered eicosanoid metabolism is the generally accepted mechanism of aspirin intolerance; the overproduction of cysteinyl leucotrienes has been suggested to play a causative role in both AIA and AIU. Genetic markers suggested for AIA include HLA-DPBI*0301, leucotriene C4 synthase (LTC4S), ALOX5, CYSLT, PGE2, TBXA2R and TBX21. Similarly, HLA-DB1*0609, ALOX5, FCER1A and HNMT have been identified as possible genetic markers for AIU. An additional low-risk genetic marker for AIA is MS4A2, which encodes the beta-chain of FCER1. Other single and sets of two or more interacting genetic markers are currently being investigated. Analyses of the genetic backgrounds of patients with AIA and AIU will promote the development of early diagnostic and therapeutic interventions, which may reduce the incidence of AIA and AIU.