The Lights And The Shadows Of Controlled Sting Challenge With Hymenoptera

Hymenoptera venom immunotherapy (VIT) is a treatment which has been shown to be effective in the protection of individuals with systemic allergic reactions caused by Hymenoptera stings. The need for a tool which shows the degree of protection afforded by VIT and the lack of useful biomarkers, has converted the Sting Challenge Test (SCT) into the gold standard for this disorder although its use has both lights and shadows. SCT with Hymenoptera is a test consisting of causing a real sting in a patient diagnosed with an allergy to the venom of the stinging insect and who normally is undergoing treatment with specific immunotherapy. In Spain, SCT is included in the list of services offered by some hospitals and forms part of their habitual clinical practice. This review aims to analyze the strengths and weaknesses of this test and describe the standardized procedure and necessary resources, based on the experience of a group of Spanish experts and a review of the literature.

Lack of Major Involvement of Common CYP2C Gene Polymorphisms in the Risk of Developing Cross-Hypersensitivity to NSAIDs

Cross-hypersensitivity to non-steroidal anti-inflammatory drugs (NSAIDs) is a relatively common, non-allergic, adverse drug event triggered by two or more chemically unrelated NSAIDs. Current evidence point to COX-1 inhibition as one of the main factors in its etiopathogenesis. Evidence also suggests that the risk is dose-dependent. Therefore it could be speculated that individuals with impaired NSAID biodisposition might be at increased risk of developing cross-hypersensitivity to NSAIDs. We analyzed common functional gene variants for CYP2C8, CYP2C9, and CYP2C19 in a large cohort composed of 499 patients with cross-hypersensitivity to NSAIDs and 624 healthy individuals who tolerated NSAIDs. Patients were analyzed as a whole group and subdivided in three groups according to the main enzymes involved in the metabolism of the culprit drugs as follows: CYP2C9, aceclofenac, indomethacin, naproxen, piroxicam, meloxicam, lornoxicam, and celecoxib; CYP2C8 plus CYP2C9, ibuprofen and diclofenac; CYP2C19 plus CYP2C9, metamizole. Genotype calls ranged from 94 to 99%. No statistically significant differences between patients and controls were identified in this study, either for allele frequencies, diplotypes, or inferred phenotypes. After patient stratification according to the enzymes involved in the metabolism of the culprit drugs, or according to the clinical presentation of the hypersensitivity reaction, we identified weak significant associations of a lower frequency (as compared to that of control subjects) of CYP2C8*3/*3 genotypes in patients receiving NSAIDs that are predominantly CYP2C9 substrates, and in patients with NSAIDs-exacerbated cutaneous disease. However, these associations lost significance after False Discovery Rate correction for multiple comparisons. Taking together these findings and the statistical power of this cohort, we conclude that there is no evidence of a major implication of the major functional CYP2C polymorphisms analyzed in this study and the risk of developing cross-hypersensitivity to NSAIDs. This argues against the hypothesis of a dose-dependent COX-1 inhibition as the main underlying mechanism for this adverse drug event and suggests that pre-emptive genotyping aiming at drug selection should have a low practical utility for cross-hypersensitivity to NSAIDs.

Deep sequencing of prostaglandin-endoperoxide synthase (PTGE) genes reveals genetic susceptibility for cross-reactive hypersensitivity to NSAID

BACKGROUND AND PURPOSE

Cross-reactive hypersensitivity to nonsteroidal anti-inflammatory drugs (NSAIDs) is a relatively common adverse drug event caused by two or more chemically unrelated drugs and that is attributed to inhibition of the COX activity, particularly COX-1. Several studies investigated variations in the genes coding for COX enzymes as potential risk factors. However, these studies only interrogated a few single nucleotide variations (SNVs), leaving untested most of the gene sequence.

EXPERIMENTAL APPROACH

In this study, we analysed the whole sequence of the prostaglandin-endoperoxide synthase genes, PTGS1 and PTGS2, including all exons, exon-intron boundaries and both the 5' and 3' flanking regions in patients with cross-reactive hypersensitivity to NSAIDs and healthy controls. After sequencing analysis in 100 case-control pairs, we replicated the findings in 540 case-control pairs. Also, we analysed copy number variations for both PTGS genes.

KEY RESULTS

The most salient finding was the presence of two PTGS1 single nucleotide variations, which are significantly more frequent in patients than in control subjects. Patients carrying these single nucleotide variations displayed a significantly and markedly lower COX-1 activity as compared to non-carriers for both heterozygous and homozygous patients.

CONCLUSION AND IMPLICATIONS

Although the risk single nucleotide variations are present in a small proportion of patients, the strong association observed and the functional effect of these single nucleotide variations raise the hypothesis of genetic susceptibility to develop cross-reactive NSAID hypersensitivity in individuals with an impairment in COX-1 enzyme activity.

Identification of Novel Biomarkers for Drug Hypersensitivity After Sequencing of the Promoter Area in 16 Genes of the Vitamin D Pathway and the High-Affinity IgE Receptor

The prevalence of allergic diseases and drug hypersensitivity reactions (DHRs) during recent years is increasing. Both, allergic diseases and DHRs seem to be related to an interplay between environmental factors and genetic susceptibility. In recent years, a large effort in the elucidation of the genetic mechanisms involved in these disorders has been made, mostly based on case-control studies, and typically focusing on isolated SNPs. These studies provide a limited amount of information, which now can be greatly expanded by the complete coverage that Next Generation Sequencing techniques offer. In this study, we analyzed the promoters of sixteen genes related to the Vitamin D pathway and the high-affinity IgE receptor, including FCER1A, MS4A2, FCER1G, VDR, GC, CYP2R1, CYP27A1, CYP27B1, CYP24A1, RXRA, RXRB, RXRG, IL4, IL4R, IL13, and IL13RA1. The study group was composed of patients with allergic rhinitis plus asthma (AR+A), patients with hypersensitivity to beta-lactams (BLs), to NSAIDs including selective hypersensitivity (SH) and cross-reactivity (CR), and healthy controls without antecedents of atopy or adverse drug reactions. We identified 148 gene variations, 43 of which were novel. Multinomial analyses revealed that three SNPs corresponding to the genes FCER1G (rs36233990 and rs2070901), and GC (rs3733359), displayed significant associations and, therefore, were selected for a combined dataset study in a cohort of 2,476 individuals. The strongest association was found with the promoter FCER1G rs36233990 SNP that alters a transcription factor binding site. This SNP was over-represented among AR+A patients and among patients with IgE-mediated diseases, as compared with control individuals or with the rest of patients in this study. Classification models based on the above-mentioned SNPs were able to predict correct clinical group allocations in patients with DHRs, and patients with IgE-mediated DHRs. Our findings reveal gene promoter SNPs that are significant predictors of drug hypersensitivity, thus reinforcing the hypothesis of a genetic predisposition for these diseases.

Asthma and allergic rhinitis associate with the rs2229542 variant that induces a p.Lys90Glu mutation and compromises AKR1B1 protein levels

Asthma and rhinitis are two of the main clinical manifestations of allergy, in which increased reactive oxygen or electrophilic species can play a pathogenic role. Aldose reductase (AKR1B1) is involved in aldehyde detoxification and redox balance. Recent evidence from animal models points to a role of AKR1B1 in asthma and rhinitis, but its involvement in human allergy has not been addressed. Here, the putative association of allergic rhinitis and asthma with AKR1B1 variants has been explored by analysis of single-strand variants on the AKR1B1 gene sequence in 526 healthy subjects and 515 patients with allergic rhinitis, 366 of whom also had asthma. We found that the rs2229542 variant, introducing the p.Lys90Glu mutation, was significantly more frequent in allergic patients than in healthy subjects. Additionally, in cells transfected with expression vectors carrying the wild-type or the p.Lys90Glu variant of AKR1B1, the mutant consistently attained lower protein levels than the wild-type and showed a compromised thermal stability. Taken together, our results show that the rs2229542 variant associates with asthma and rhinitis, and hampers AKR1B1 protein levels and stability. This unveils a connection between the genetic variability of aldose reductase and allergic processes.

A Nonsynonymous FCER1B SNP is Associated with Risk of Developing Allergic Rhinitis and with IgE Levels

Allergic rhinitis is associated with elevated serum IgE levels. IgE response is mediated by the high-affinity IgE receptor (FcεRI), which is polymorphic. Studies analyzing the association between allergic rhinitis and FcεRI variants have been conducted with controversial results. The objective of this study is to analyze, in 1,041 individuals, the putative clinical association of allergic rhinitis with common polymorphisms in FcεRI subunits genes. These SNPs included FECR1A rs2494262, rs2427837 and rs2251746; FECR1B rs1441586, rs569108 and rs512555; FCER1G rs11587213, rs2070901 and rs11421. Statistically significant differences were observed for the FCER1B rs569108 and rs512555 polymorphisms frequencies when comparing patients with allergic rhinitis without asthma and controls. The OR (95% CI) value for the 237Gly allele (rs569108) is equal to 0.26 (0.08–0.86, P = 0.017) and for the G allele (rs512555) it is equal to 0.27 (0.08–0.88, P = 0.020). These two SNPs are linked (D’ = 1.0, LOD = 56.05). Also observed was a statistically significant trend towards lower IgE values among allergic rhinitis patients with variant alleles for both SNPs. In conclusion, in patients with allergic rhinitis without asthma, the FCER1B rs569108 and rs512555 polymorphisms are associated with increased risk of developing allergic rhinitis and with lower IgE levels.

Variability of the L-Histidine decarboxylase gene in allergic rhinitis

BACKGROUND

Nonsynonymous polymorphisms in genes coding for histamine-metabolizing enzymes, diamine oxidase and histamine N-methyltransferase are related to the risk of developing allergic diseases. The role of polymorphisms in the histidine decarboxylase gene remains unexplored. The objective of this study is to identify novel polymorphisms in the human histidine decarboxylase gene and to analyse the clinical association of nonsynonymous polymorphisms with rhinitis.

METHODS

We performed a single-strand conformational polymorphism analysis of the histidine decarboxylase gene sequence. The presence of two nonsynonymous polymorphisms Thr31Met (rs17740607) and Glu644Asp (rs2073440) was analysed in 442 unrelated patients with allergic rhinitis, 233 of whom also had asthma, and in 486 healthy subjects.

RESULTS

We observed three novel polymorphisms designated as ss50402829, ss50402830 and ss50402831-(rs17740607) with allele frequencies = 0.005, 0.208 and 0.073, respectively. Statistically significant differences were observed for the histidine decarboxylase Glu644Asp (rs2073440) polymorphism, with OR (95% CI) values for homozygous carriers of the Glu644 allele equal to 3.12 (1.75-5.56, P < 0.00005) for all patients, 3.38 (1.54-7.44, P = 0.002) for patients with rhinitis alone, and 2.92 (1.43-5.95), P = 0.003 for patients with rhinitis + asthma, when compared with healthy controls. A significant Glu644 gene-dose effect was observed for overall patients (P = 0.0001), for patients with rhinitis alone (P = 0.005) and for patients with rhinitis + asthma (P = 0.010).

CONCLUSIONS

The HDC allele Glu644 in homozygosity increases the risk of developing rhinitis in the studied population. This adds to increasing evidence supporting a prominent role of genetic variations related to histamine homeostasis in the risk to develop allergic diseases.