CCR5Δ32 mutation, Mycoplasma pneumoniae infection, and asthma

CCR5 as a Coreceptor for Human Immunodeficiency Virus and Simian Immunodeficiency Viruses: A Prototypic Love-Hate Affair

CCR5, a chemokine receptor central for orchestrating lymphocyte/cell migration to the sites of inflammation and to the immunosurveillance, is involved in the pathogenesis of a wide spectrum of health conditions, including inflammatory diseases, viral infections, cancers and autoimmune diseases. CCR5 is also the primary coreceptor for the human immunodeficiency viruses (HIVs), supporting its entry into CD4⁺ T lymphocytes upon transmission and in the early stages of infection in humans. A natural loss-of-function mutation CCR5-Δ32, preventing the mutated protein expression on the cell surface, renders homozygous carriers of the null allele resistant to HIV-1 infection. This phenomenon was leveraged in the development of therapies and cure strategies for AIDS. Meanwhile, over 40 African nonhuman primate species are long-term hosts of simian immunodeficiency virus (SIV), an ancestral family of viruses that give rise to the pandemic CCR5 (R5)-tropic HIV-1. Many natural hosts typically do not progress to immunodeficiency upon the SIV infection. They have developed various strategies to minimize the SIV-related pathogenesis and disease progression, including an array of mechanisms employing modulation of the CCR5 receptor activity: (i) deletion mutations abrogating the CCR5 surface expression and conferring resistance to infection in null homozygotes; (ii) downregulation of CCR5 expression on CD4⁺ T cells, particularly memory cells and cells at the mucosal sites, preventing SIV from infecting and killing cells important for the maintenance of immune homeostasis, (iii) delayed onset of CCR5 expression on the CD4⁺ T cells during ontogenetic development that protects the offspring from vertical transmission of the virus. These host adaptations, aimed at lowering the availability of target CCR5⁺ CD4⁺ T cells through CCR5 downregulation, were countered by SIV, which evolved to alter the entry coreceptor usage toward infecting different CD4⁺ T-cell subpopulations that support viral replication yet without disruption of host immune homeostasis. These natural strategies against SIV/HIV-1 infection, involving control of CCR5 function, inspired therapeutic approaches against HIV-1 disease, employing CCR5 coreceptor blocking as well as gene editing and silencing of CCR5. Given the pleiotropic role of CCR5 in health beyond immune disease, the precision as well as costs and benefits of such interventions needs to be carefully considered.

Mycoplasma pneumoniae infection and risk of childhood asthma: A systematic review and meta-analysis

The etiology of childhood asthma is multifactorial, atypical bacterial pathogens, including Mycoplasma pneumoniae, have been proposed as possible risk factors or contributors. This review aims to assess the possible association between M. pneumoniae infection and childhood asthma. We searched major international literature databases (up to January 10, 2021) to identify relevant studies. We used a random-effects meta-analysis (REM) model to generate the pooled odds ratio (OR) and 95% confidence intervals (CIs). Several subgroups analyses were performed concerning the IgG, IgM, and DNA detection of M. pneumoniae infection. We included 22 eligible studies; these studies involved a total of 5064 children. We found that there was a statistically significant association between M. pneumoniae infection, as determined by IgM serology (OR, 3.13; 95% CI, 1.78-5.48), and DNA detection (OR, 1.57; 95% CI, 1.25-1.97) with increased risk of any type of childhood asthma. Moreover, children with acute asthma had significantly higher seropositivity for anti- M. pneumoniae IgM antibodies (OR, 4.43; 95% CI, 2.80-7.02) than children with stable asthma. Although our findings indicate a positive association between M. pneumoniae infection and childhood asthma, well-designed and -controlled studies are need in the future to rigorously test this association and identify the underlying mechanisms.

Association of RANTES gene polymorphisms with susceptibility to childhood asthma: A meta-analysis

BACKGROUND

Previous investigations have illustrated that regulated upon activation, normal T-cell expressed and secreted (RANTES) polymorphisms are linked to susceptibility to childhood asthma; nevertheless, the findings continue to be controversial. Accordingly, we conducted the present meta-analysis to clarify the impact of RANTES genetic polymorphisms (-403G/A and -28C/G) on childhood asthma vulnerability.

METHODS

A search for published literature was performed using the PubMed, EMBASE, Chinese National Infrastructure, Cochrane Library, Scopus, Web of Science, and WanFang databases and selected in the form of PICOS (participants, interventions, comparisons, outcomes, and study design) to identify all eligible research works. The link between RANTES genetic polymorphisms and childhood asthma susceptibility was evaluated by a pooled odds ratio with a 95% confidence interval.

RESULTS

In total, 14 case-control studies were included in the analysis. No significant association existed between risk of childhood asthma and the -403G/A polymorphism subjected to any genetic framework in the overall population. In the stratified analysis, according to ethnicity, the -403G/A polymorphism was linked to augmented vulnerability to childhood asthma in Caucasians (allelic model: odds ratio [OR] = 1.63, 95% confidence interval [CI] = 1.04-2.57, P = .034; codominant model: OR = 2.20, 95% CI = 1.28-3.78, P = .004; dominant model: OR = 1.78, 95% CI = 1.01-3.13, P = .047; and recessive model: OR = 1.92, 95% CI = 1.11-3.30, P = .019). For the stratified analysis by atopic status, the -403G/A polymorphism was linked to augmented childhood asthma in the codominant (OR = 1.39, 95% CI = 1.02-1.91, P = .037) and dominant models (OR = 1.43, 95% CI = 1.02-2.01, P = .037) in atopic asthma. For the -28C/G polymorphism, there was a significant association between childhood asthma and the -28C/G variant (allelic model: OR = 1.33, 95% CI = 1.08-1.65, P = .009; codominant framework: OR = 2.14, 95% CI = 1.47-3.10, P < .001; dominant model: OR = 1.44, 95% CI = 1.07-1.93, P = .017; and recessive model: OR = 2.08, 95% CI = 1.44-3.02, P < .001). Stratified analysis based on ethnicity and the -28C/G polymorphism was linked to augmented vulnerability to childhood asthma in Asian and Caucasian populations. For the subgroup analysis by atopic status, no association was found in atopic and non-atopic asthma.

CONCLUSION

The present meta-analysis indicated that the RANTES -403G/A and -28C/G polymorphisms contributed to the development of childhood asthma.

Beyond HIV infection: Neglected and varied impacts of CCR5 and CCR5Δ32 on viral diseases

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CCR5 regulates multiple cell types (e.g., T regulatory and Natural Killer cells) and immune responses.

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The effects of CCR5, CCR5Δ32 (variant associated with reduced CCR5 expression) and CCR5 antagonists vary between infections.

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CCR5 affects the pathogenesis of flaviviruses, especially in the brain.

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The genetic variant CCR5Δ32 increases the risk of symptomatic West Nile virus infection.

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The triad “CCR5, extracellular vesicles and infections” is an emerging topic.

The interactions between chemokine receptors and their ligands may affect susceptibility to infectious diseases as well as their clinical manifestations. These interactions mediate both the traffic of inflammatory cells and virus-associated immune responses. In the context of viral infections, the human C-C chemokine receptor type 5 (CCR5) receives great attention from the scientific community due to its role as an HIV-1 co-receptor. The genetic variant CCR5Δ32 (32 base-pair deletion in CCR5 gene) impairs CCR5 expression on the cell surface and is associated with protection against HIV infection in homozygous individuals. Also, the genetic variant CCR5Δ32 modifies the CCR5-mediated inflammatory responses in various conditions, such as inflammatory and infectious diseases. CCR5 antagonists mimic, at least in part, the natural effects of the CCR5Δ32 in humans, which explains the growing interest in the potential benefits of using CCR5 modulators for the treatment of different diseases. Nevertheless, beyond HIV infection, understanding the effects of the CCR5Δ32 variant in multiple viral infections is essential to shed light on the potential effects of the CCR5 modulators from a broader perspective. In this context, this review discusses the involvement of CCR5 and the effects of the CCR5Δ32 in human infections caused by the following pathogens: West Nile virus, Influenza virus, Human papillomavirus, Hepatitis B virus, Hepatitis C virus, Poliovirus, Dengue virus, Human cytomegalovirus, Crimean-Congo hemorrhagic fever virus, Enterovirus, Japanese encephalitis virus, and Hantavirus. Subsequently, this review addresses the impacts of CCR5 gene editing and CCR5 modulation on health and viral diseases. Also, this article connects recent findings regarding extracellular vesicles (e.g., exosomes), viruses, and CCR5. Neglected and emerging topics in “CCR5 research” are briefly described, with focus on Rocio virus, Zika virus, Epstein-Barr virus, and Rhinovirus. Finally, the potential influence of CCR5 on the immune responses to coronaviruses is discussed.

CCR5 and CCR5Δ32 in bacterial and parasitic infections: Thinking chemokine receptors outside the HIV box

The CCR5 molecule was reported in 1996 as the main HIV-1 co-receptor. In that same year, the CCR5Δ32 genetic variant was described as a strong protective factor against HIV-1 infection. These findings led to extensive research regarding the CCR5, culminating in critical scientific advances, such as the development of CCR5 inhibitors for the treatment of HIV infection. Recently, the research landscape surrounding CCR5 has begun to change. Different research groups have realized that, since CCR5 has such important effects in the chemokine system, it could also affect other different physiological systems. Therefore, the effect of reduced CCR5 expression due to the presence of the CCR5Δ32 variant began to be further studied. Several studies have investigated the role of CCR5 and the impacts of CCR5Δ32 on autoimmune and inflammatory diseases, various types of cancer, and viral diseases. However, the role of CCR5 in diseases caused by bacteria and parasites is still poorly understood. Therefore, the aim of this article is to review the role of CCR5 and the effects of CCR5Δ32 on bacterial (brucellosis, osteomyelitis, pneumonia, tuberculosis and infection by Chlamydia trachomatis) and parasitic infections (toxoplasmosis, leishmaniasis, Chagas disease and schistosomiasis). Basic information about each of these infections was also addressed. The neglected role of CCR5 in fungal disease and emerging studies regarding the action of CCR5 on regulatory T cells are briefly covered in this review. Considering the "renaissance of CCR5 research," this article is useful for updating researchers who develop studies involving CCR5 and CCR5Δ32 in different infectious diseases.

Prevalence of CCR5delta32 in Northeastern Iran

Background

A 32-base pair deletion (∆32) in the open reading frame (ORF) of C-C motif chemokine receptor 5 (CCR5) seems to be a protective variant against immune system diseases, especially human immunodeficiency virus type 1 (HIV-1). We aimed to assess the frequency of CCR5∆32 in the healthy Iranian population.

Methods

In this study, 400 normal samples from Khorasan, northeastern Iran, were randomly selected. The frequency of CCR5∆32 carriers was investigated using PCR analysis. Allele prevalence and the fit to the Hardy-Weinberg equilibrium were analyzed.

Results

The prevalence of CCR5∆32 in the northeastern population of Iran was 0.016. Four hundred samples were studied, among which one with CCR5^∆32/∆32 and 11 with CCR5^Wild/∆32 genotype were detected.

Conclusion

This study was the first investigation for an assessment of the prevalence of CCR5∆32 in northeastern Iran. The low prevalence of CCR5∆32 allele in the Iranian population may result in the increased susceptibility to HIV-1. In addition, this prevalence is the same as that of reported in East Asia, while is lower than that in the Europeans.

Contribution of Cytokines to Tissue Damage During Human Respiratory Syncytial Virus Infection

The human respiratory syncytial virus (hRSV) remains one of the leading pathogens causing acute respiratory tract infections (ARTIs) in children younger than 2 years old, worldwide. Hospitalizations during the winter season due to hRSV-induced bronchiolitis and pneumonia increase every year. Despite this, there are no available vaccines to mitigate the health and economic burden caused by hRSV infection. The pathology caused by hRSV induces significant damage to the pulmonary epithelium, due to an excessive inflammatory response at the airways. Cytokines are considered essential players for the establishment and modulation of the immune and inflammatory responses, which can either be beneficial or harmful for the host. The deleterious effect observed upon hRSV infection is mainly due to tissue damage caused by immune cells recruited to the site of infection. This cellular recruitment takes place due to an altered profile of cytokines secreted by epithelial cells. As a result of inflammatory cell recruitment, the amounts of cytokines, such as IL-1, IL-6, IL-10, and CCL5 are further increased, while IL-10 and IFN-γ are decreased. However, additional studies are required to elicit the mediators directly associated with hRSV damage entirely. In addition to the detrimental induction of inflammatory mediators in the respiratory tract caused by hRSV, reports indicating alterations in the central nervous system (CNS) have been published. Indeed, elevated levels of IL-6, IL-8 (CXCL8), CCL2, and CCL4 have been reported in cerebrospinal fluid from patients with severe bronchiolitis and hRSV-associated encephalopathy. In this review article, we provide an in-depth analysis of the role of cytokines secreted upon hRSV infection and their potentially harmful contribution to tissue damage of the respiratory tract and the CNS.

Novel genes in Human Asthma Based on a Mouse Model of Allergic Airway Inflammation and Human Investigations

Purpose

Based on a previous gene expression study in a mouse model of asthma, we selected 60 candidate genes and investigated their possible roles in human asthma.

Methods

In these candidate genes, 90 SNPs were genotyped using MassARRAY technology from 311 asthmatic children and 360 healthy controls of the Hungarian (Caucasian) population. Moreover, gene expression levels were measured by RT PCR in the induced sputum of 13 asthmatics and 10 control individuals. t-tests, chi-square tests, and logistic regression were carried out in order to assess associations of SNP frequency and expression level with asthma. Permutation tests were performed to account for multiple hypothesis testing.

Results

The frequency of 4 SNPs in 2 genes differed significantly between asthmatic and control subjects: SNPs rs2240572, rs2240571, rs3735222 in gene SCIN, and rs32588 in gene PPARGC1B. Carriers of the minor alleles had reduced risk of asthma with an odds ratio of 0.64 (0.51-0.80; P=7×10^-5) in SCIN and 0.56 (0.42-0.76; P=1.2×10^-4) in PPARGC1B. The expression levels of SCIN, PPARGC1B and ITLN1 genes were significantly lower in the sputum of asthmatics.

Conclusions

Three potentially novel asthma-associated genes were identified based on mouse experiments and human studies.

Lack of association between chemokine receptor 5 (CCR5) δ32 mutation and pathogenesis of asthma in Iranian patients

BACKGROUND

Chemokines and their receptors are clinically important mediators, as the chemokine receptors are expressed on almost all immune cells. They play pivotal roles in pathogenesis of almost all clinical situations including asthma. Correspondingly, MIP-1α (CCL3), MIP-1β (CCL4), and RANTES (CCL5) are among the important chemokines involved in the pathogenesis of asthma. These chemokines bind to the CCR5 (their related receptor) on the cell surfaces. Attachment of related chemokine ligands to CCR5 plays an important role in the pathogenesis of asthma; hence, this study aimed to analyze δ32 mutations in CCR5 in asthmatic patients.

MATERIAL AND METHODS

This experimental study was undertaken on 162 asthmatic patients and 200 healthy controls during February to June 2008 at Rafsanjan University of Medical Sciences. The Gap-PCR method was applied to analyze the δ32 mutation in the CCR5 gene, and demographic data (eg, age, sex, occupation, socio-economic status) were collected using a questionnaire.

RESULTS

The findings of this study indicated that none of the asthmatic patients exhibited δ32 mutation in CCR5 chemokine receptor while only 3 (1.5%) of controls had the heterozygotic form of this mutation.

DISCUSSION

Several research groups analyzed δ32 mutations in CCR5 in different diseases, including asthma. Some investigations reported a significant relation between asthma and δ32 mutations in CCR5, but there are also many reports which failed to find a relation between asthma and this mutation. Based on the results of this study and others, it seems that the δ32 mutation does not affect the pathogenesis of asthma.

Association of Q551R polymorphism in the interleukin 4 receptor gene with nonatopic asthma in Slovenian children

BACKGROUND

Asthma is one of the most common chronic diseases of childhood and results from the interaction of several genes and environmental influences. Interleukin 4 (IL4) and its receptor IL4R have a central role in the regulation of immunoglobulin E (IgE) production and thereby in the induction and maintenance of allergy and asthma. The single nucleotide polymorphisms (SNPs) Q551R in the IL4RA gene and C-33T in the IL4 gene probably influence IL4/IL4R pathway signaling; however, findings in association studies exploring the role of these two genes in asthma pathogenesis are contradictory. We have studied the association of IL4RA Q551R and IL4 C-33T SNPs with asthma, asthma phenotypes, and clinical and laboratory parameters.

METHODS

The study group comprised 106 children aged between 5 and 18 years with mild or moderate persistent asthma: 78 children were atopic and 28 had nonatopic asthma. The children underwent allergy and spirometry tests, a bronchoprovocation test with methacholine, measurement of exhaled nitric oxide in expired air and genotyping for IL4RA Q551R and IL4 C-33T SNPs. Genotype data from 89 nonatopic nonasthmatics served as a control group.

RESULTS

The frequency of the IL4RA Arg551 allele in the children with nonatopic asthma was 7.1%, significantly lower than 21.9% in the control group (P = 0.01, OR: 0.33, 95% CI: 0.12-0.87). Allelic and genotype frequencies in IL4 C-33T polymorphism in the asthma group and the control group were not significantly different. The mean value of total IgE in asthmatics with the IL4-33C allele was 556.0 IU/l, significantly higher than 371.6 IU/l in those with the T allele (P = 0.02). In an interaction study we did not find significant differences in the frequencies of any combinations of IL4RA Q551R and IL4 C-33T alleles between asthmatics and controls.

CONCLUSIONS

The IL4RA Q551R SNP is associated with nonatopic asthma in Slovenian children. This finding contributes to knowledge about an important asthma phenotype pathogenesis and could serve in future research into new strategies for asthma management.

Personalized medicine: a pediatric perspective

The aim of pediatric personalized medicine is to uniquely combine genetic variation with developmental stage and environmental exposure to provide a tailored preventive, diagnostic, and therapeutic regimen. Recent advances in genomic research have identified many genetic variants that may be related to allergic and inflammatory disease and therapeutic response. These include variants involved in immune response, barrier proteins, and medication response. Current evidence also suggests that the effect of genetic variation often depends on the developmental stage of a child and environmental exposure such as infection or tobacco smoke during a specific stage. Personalized medicine is a new and exciting field with the potential to significantly improve medical care for children and adults.

Common promoter deletion is associated with 3.9-fold differential transcription of ovine CCR5 and reduced proviral level of ovine progressive pneumonia virus

Chemokine (C-C motif) Receptor 5 (CCR5) is a chemokine receptor that regulates immune cell recruitment in inflammation and serves as a coreceptor for human immunodeficiency virus (HIV). A human CCR5 coding deletion (termed delta-32) results in strong resistance to HIV infection, and sequence variants in CCR5 regulatory regions have been implicated in delayed progression to acquired immune deficiency syndrome. Both ovine progressive pneumonia virus (OPPV), also known as maedi-visna, and HIV are macrophage-tropic lentiviruses, have similar genomic structures, and cause lifelong persistent host infection, suggesting CCR5 may have a role in regulating OPPV provirus levels. Therefore, the ovine CCR5 genomic sequence was determined, and sequence variants were obtained from the open reading frame and surrounding regulatory sites. One CCR5 variant contained a 4-base deletion within a binding site for octamer transcription factors in the promoter region. A test for differential transcription from each allele in heterozygous animals showed a 3.9-fold transcription difference (P < 0.0001). OPPV proviral levels were also measured in 351 naturally exposed Rambouillet, Polypay and Columbia sheep. Deletion homozygotes showed reduced OPPV proviral levels among these animals (P < 0.01). The association of this CCR5 promoter deletion with OPPV levels will need to be validated in additional populations before the deletion can be recommended for widespread use in marker-assisted selection. However, because of the large impact on transcription and because CCR5 has roles in inflammation, recruitment of effector cells, and cell-mediated immunity, this deletion may play a role in the control of infections of many diverse pathogens of sheep.

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.

Advances in asthma and allergy genetics in 2007

This review discusses the main advances in the genetics of asthma and allergy published in the Journal in 2007. The association studies discussed herein addressed 3 main topics: the effect of the environment and gene-environment interactions on asthma/allergy susceptibility, the contribution of T(H)2 immunity gene variants to allergic inflammation, and the role of filaggrin mutations in atopic dermatitis and associated phenotypes. Other articles revealed novel, potentially important candidate genes or confirmed known ones. Collectively, the works published in 2007 reiterate that allergy and asthma are typical complex diseases; that is, they are disorders in which intricate interactions among environmental and genetic factors modify disease susceptibility by altering the fundamental structural and functional properties of target organs at critical developmental windows.

Asthma from a pharmacogenomic point of view

Pharmacogenomics, a fascinating, emerging area of biomedical research is strongly influenced by growing availability of genomic databases, high-throughput genomic technologies, bioinformatic tools and artificial computational modelling approaches. One main area of pharmacogenomics is the discovery of new drugs and drug targets with molecular genetic, genomic or even bioinformatic methods; the other is the study of how genomic differences influence the variability in patients' responses to drugs. From a genetic point of view, asthma is multifactorial, which means that the susceptibility to the disease is determined by interactions between multiple genes, and involves important non-genetic factors such as the environment for their expression. In this review, we summarize collective evidence from linkage and association studies that have consistently reported suggestive linkage or association of asthma or its associated phenotypes to polymorphic markers and single nucleotide polymorphisms in selected chromosomes. Genes that have been found implicated in the disease are potential new drug targets and several pharmacological investigations are underway to utilize these new discoveries. Next, we will focus on the inter-individual variability in anti-asthmatic drug responses and review the recent results in this topic.

Inhibition of message for FcepsilonRI alpha chain blocks mast cell IL-4 production induced by co-culture with Mycoplasma pneumoniae

We have previously described the activation of RBL-2H3 mast cells for IL-4 production by Mycoplasma pneumoniae but the mechanism remains unclear. M. pneumoniae binds eukaryotic cells primarily through sialoglycoproteins on the target cell surface. This study was undertaken to determine whether the sialated FcepsilonRI alpha chain on RBL cells is important for M. pneumoniae-induced IL-4 production. We found that IgE-mediated IL-4 release by a series of RBL sublines correlated with the release induced by M. pneumoniae. Further, aggregation of FcgammaRII (CD32) in RBL cells using a monoclonal antibody inhibited both IgE-mediated and mycoplasma-induced IL-4 production, providing further evidence for an Fc receptor-mediated mechanism of activation. To examine the role of FcepsilonRI in mycoplasma-induced IL-4 release, we created stably transfected RBL sublines using a vector expressing a short hairpin sequence designed to inhibit message for the FcepsilonRI alpha chain. IgE-induced IL-4 production by the transfected sublines was reduced in similar proportion to the degree of message suppression. M. pneumoniae-induced IL-4 production in the four transfected sublines was completely blocked in contrast to results with the controls or parent RBL cells. We conclude that the heavily glycosylated FcepsilonRI alpha chain is required for activation of mast cells for IL-4 production by M. pneumoniae.