No association between asthma or allergy and the CCR5Delta 32 mutation

Is the CCR5 Δ 32 mutation associated with immune system-related diseases?

Hypersensitivity and autoimmunity are the main features of immune system-related diseases such as type 2 diabetes (T2D), multiple sclerosis (MS), and asthma. It has been established that chemokines play key roles in the activation and regulation of immune cell migration which is important in the pathogenesis of the diseases mentioned. CC chemokines receptor 5 or CCR5 is a receptor for RANTES, MIP-1α, and MIP-1β and is expressed by several immune cells including NK cells, T lymphocytes, and macrophages. It plays key roles in the regulation of migration and activation of the immune cells during immune responses against microbe and self-antigens during autoimmunity and hypersensitivity disorders. Therefore, any alteration in the sequence of CCR5 gene or in its expression could be associated with immune system-related diseases. Previous studies revealed that a 32-base pair deletion (Δ 32) in exon 1 of the CCR5 gene led to downregulation of the gene. Previous studies demonstrated that not only CCR5 expression was altered in autoimmune and hypersensitivity disorders, but also that the mutation is associated with the diseases. This review addresses the recent information regarding the association of the CCR5 Δ 32 mutation in immune-related diseases including T2D with and without nephropathy, MS, and asthma. Based on the collected data, it seems that the CCR5 Δ 32 mutation can be considered as a risk factor for MS, but not asthma and T2D with and without nephropathy.

Polymorphisms in recent GWA identified asthma genes CA10, SGK493, and CTNNA3 are associated with disease severity and treatment response in childhood asthma

Recent genome-wide association studies (GWAs) have identified several new genetic risk factors for asthma; however, their influence on disease behavior and treatment response is still unclear. The aim of our study was the association analysis of the most significant single nucleotide polymorphisms (SNPs) recently reported by GWAs in different phenotypes of childhood asthma and analysis of correlation between these SNPs and clinical parameters. We have genotyped 288 children with asthma and 276 healthy controls. We provided here first replication of bivariate associations between CA10 (p = 0.001) and SGK493 (p = 0.011) with asthma. In addition, we have identified new correlation between SNPs in CA10, SGK493, and CTNNA3 with asthma behavior and glucocorticoid treatment response. Asthma patients who carried G allele in SNP rs967676 in gene CA10 were associated with more pronounced airway obstruction, higher bronchial hyper-reactivity, and increased inflammation. Higher bronchial hyper-reactivity was also associated with C allele in SNP rs1440095 in gene SGK493 but only in nonatopic asthmatics. In addition, we found that patients who carried at least one T allele in SNP rs1786929 in CTNNA3 (p = 0.022) and atopic patients who carried at least one G allele in SNP rs967676 in gene CA10 (p = 0.034) had higher increase in pulmonary function after glucocorticoid therapy. Our results suggest genetic heterogeneity between atopic and nonatopic asthma. We provided further evidence that treatment response in childhood asthma is genetically predisposed, and we report here two novel SNPs in genes CA10 and CTNNA3 as potential pharmacogenetic biomarkers that could be used in personalized treatment in childhood asthma.

[CCR5 antagonists and HIV-1 infection: Bases and consequences of this therapeutic approach]

La molécule CCR5 est un récepteur de chimiokines qui joue un rôle important en pathologie infectieuse : corécepteur des souches du VIH-1 à tropisme R5, il est également impliqué dans la défense immunitaire contre certains agents transmissibles. Les antagonistes de CCR5 constituent une nouvelle approche thérapeutique antirétrovirale. Trois inhibiteurs du CCR5 ont atteint les phases IIb et III de développement clinique : aplaviroc (GlaxoSmithKine), vicriviroc (Schering-Plough) et maraviroc (Pfizer). Le développement de l’aplaviroc a été interrompu pour toxicité hépatique. Les essais ACTG 5211 et Motivate ont démontré une amélioration de la réponse antirétrovirale par l’addition respectivement de vicriviroc (actuellement en phase III) et de maraviroc (ayant déjà obtenu l’Autorisation de Mise sur le Marché) à un traitement optimisé chez des patients en échec thérapeutique. Le rôle de cette nouvelle cible thérapeutique dans les stratégies de traitement initial, de substitution ou de sauvetage reste à préciser, de même que leur intérêt chez des patients ayant une réponse immunovirologique dissociée, en immunodépresssion sévère ou infectés par des souches à tropisme non-R5. Plusieurs points sont également à éclaircir comme la tolérance à long terme, le risque d’induire une commutation R5-X4, en particulier dans les tissus, le risque d’interférer avec les réponses immunitaires, ainsi que l’impact d’une discordance de tropisme entre le plasma et les autres compartiments de l’organisme.

Association of CCR5-delta32 mutation with reduced risk of nonatopic asthma in Slovenian children

Asthma is one of the most common chronic diseases of childhood. Asthma results from the interaction of several genes and environmental influences. Viral infections are common triggers of asthma attacks, especially in nonatopic asthmatics. CCR5 is a chemokine receptor involved in the immune response against a number of viruses. A 32 base pair deletion (delta32) in the CCR5 receptor gene causes loss of gene function and is associated with several chronic diseases due to the resulting altered immunity. The results of the association studies exploring the role of the CCR5 receptor gene in asthma pathogenesis are contradictory. We studied 111 children aged between 5 and 18 years with mild or moderate persistent asthma; 75 of them were atopic and 36 had nonatopic asthma. We carried out allergy and spirometry tests, a bronchoprovocation test with methacholine and performed measurement of exhaled nitric oxide and genotyping for CCR5-delta32 mutation. Compared with 365 nonatopic, nonasthmatic controls we found significantly lower CCR5-delta32 allelic frequency in nonatopic asthmatics (p = 0.016, OR 0.139, 95% CI 0.02 to 0.984) but not in atopic asthmatics. CCR5-delta32 mutation protects against nonatopic asthma. This association offers new insights into the pathogenesis of an important asthma phenotype and could serve as useful information for the future research of new asthma management strategies.

Candidate gene association studies and evidence for gene-by-gene interactions

Candidate gene studies in asthma are a powerful and valuable tool in asthma genetics. Although the quality of small-scale, freely associating studies has been questionable, increasingly serious efforts are made to establish, replicate, and verify association results. Association studies may help us to better understand the mechanisms underlying asthma. They may create hypotheses and help to direct functional studies to targets that are likely to give valuable results. However, they should not be over-interpreted; only biologic proof can verify associations between genetic variations and a certain disease outcome. The insight that gene-by-gene and gene-by-environment interactions may be crucial for understanding and pinpoint the complex mechanisms of genetic regulation of multifactorial diseases has gained momentum in the last years when technical improvement allowed for the effective genotyping and analysis of great numbers of polymorphisms in large populations. It can be expected that from this area of research new and exciting results will follow soon.

Association of interleukin-8 receptor α polymorphisms with chronic obstructive pulmonary disease and asthma

Chronic obstructive pulmonary disease (COPD) and asthma are common complex diseases characterized by airflow obstruction and inflammatory processes in the small airways. lnterleukin 8 (IL-8) is a potent proinflammatory cytokine which interacts with the IL-8 receptor alpha (IL8RA, CXCR1) and beta (IL8RB, CXCR2), leading to activation and migration of leukocytes. In order to evaluate the role of the IL8RA gene in the pathogenesis of COPD and asthma, we screened the coding region of IL8RA for mutations by means of single-strand conformation polymorphism analysis in 50 COPD patients and identified three exchanges (M31R, S276T and R335C). These three polymorphisms were subsequently genotyped in 182 adult patients with COPD, 68 adult patients and 130 children with asthma as well as 454 healthy controls. The frequencies of the IL8RA 31R and 335C alleles were significantly increased in patients with COPD and in children with asthma compared to healthy controls (P=0.0073 and 0.023, respectively). Thus, these polymorphisms may play a role in the pathogenesis of COPD and asthma.

Association studies for asthma and atopic diseases: a comprehensive review of the literature

Hundreds of genetic association studies on asthma-related phenotypes have been conducted in different populations. To date, variants in 64 genes have been reported to be associated with asthma or related traits in at least one study. Of these, 33 associations were replicated in a second study, 9 associations were not replicated either in a second study or a second sample in the same study, and 22 associations were reported in just a single published study. These results suggest the potential for a great amount of heterogeneity underlying asthma. However, many of these studies are methodologically limited and their interpretation hampered by small sample sizes.