Association of specific IgE to staphylococcal superantigens with the phenotype of chronic urticaria

S. aureus and IgE-mediated diseases: pilot or copilot? A narrative review

INTRODUCTION

S. aureus is a major opportunistic pathogen that has been implicated in the pathogenesis of several chronic inflammatory diseases including bronchial asthma, chronic rhinosinusitis with nasal polyps (CRSwNP), chronic spontaneous urticaria (CSU), and atopic dermatitis. S. aureus can induce the production of both polyclonal and specific IgE that can elicit an inflammatory cascade.

AREAS COVERED

The link between the sensitization to S. aureus enterotoxins and the severity of several chronic inflammatory diseases is reviewed in detail, as well as its therapeutic implications.

EXPERT OPINION

An anti-IgE strategy to inhibit S. aureus enterotoxins would be a valid approach to treat several endotypes of severe asthma, CRSwNP and CSU in which IgE against S. aureus enterotoxins should represent, not only a marker of severity of the diseases but also a target of a treatment.

Aeroallergens in Atopic Dermatitis and Chronic Urticaria

PURPOSE OF REVIEW

While aeroallergens are a well-established trigger of asthma and allergic rhinitis, their role in allergic skin diseases such as atopic dermatitis and chronic urticaria remains controversial. This paper reviews the pathophysiology and clinical evidence for aeroallergens in these allergic skin diseases and summarizes current strategies for evaluation and management.

RECENT FINDINGS

Current evidence implicates aeroallergens as triggers of cutaneous reactions in atopic dermatitis. Direct skin contact is the likely route of trigger. Aeroallergens may also trigger chronic urticaria, though mechanistic studies are limited. These allergens may cross the skin barrier and directly trigger neurons to release substance P, resulting in mast cell degranulation and dumping of histamine and prostaglandin D2. Many studies link aeroallergen sensitization to chronic urticaria, and case reports suggest the utility of avoidance strategies. The role of aeroallergens as a trigger is clear in atopic dermatitis and becoming emergent in chronic urticaria. Skin prick testing or serum-specific immunoglobulin E testing may be used to determine sensitivities. Management at this time centers on avoidance, and further studies are necessary to evaluate the efficacy of aeroallergen immunotherapy for both conditions.

Elevated MRGPRX2 Levels Related to Disease Severity in Patients With Chronic Spontaneous Urticaria

Mas-related G-protein coupled receptor-X2 (MRGPRX2), a receptor on mast cells, basophils, and eosinophils associated with immunoglobulin E (IgE)-independent degranulation, has been reported to be highly expressed on cutaneous mast cells in patients with severe chronic spontaneous urticaria (CSU). We sought to investigate whether MRGPRX2 levels in the sera from CSU patients differ from those in healthy control subjects and to evaluate the clinical utility of MRGPRX2 levels in CSU patients. Severe CSU was defined as urticaria activity score over 7 days (UAS7) ≥ 28. Serum samples from 116 (73 severe and 43 non-severe) CSU patients and 50 healthy subjects were screened for MRGPRX2 using enzyme-linked immunosorbent assay. Serum MRGPRX2 levels were significantly higher in patients with severe CSU (median [interquartile range], 16.5 [10.8–24.8]) than in healthy controls (11.7 [6.5–21.2], P = 0.036) and in non-severe CSU patients (8.7 [4.5–18.8], P = 0.002), although they did not differ between healthy subjects and non-severe CSU patients. Serum MRGPRX2 levels in CSU patients showed positive correlations with UAS7 and specific IgE against Dermatophagoides farinae in CSU subjects, whereas no correlations were observed for age, sex, urticaria duration, atopy, combined angioedema, autologous serum skin test positivity, or total IgE levels. Logistic regression analysis identified serum MRGPRX2 ≥ 12 ng/mL (odds ratio, 6.421; P = 0.002) as an independent risk factor for severe CSU, along with increased serum total IgE levels, peripheral basophil percentage, and angioedema. In conclusion, we suggest that serum MRGPRX2 could help indicate severe CSU.

Presence of positive skin prick tests to inhalant allergens and markers of T2 inflammation in subjects with chronic spontaneous urticaria (CSU): a systematic literature review

BACKGROUND

Current guidelines do not recommend performing aeroallergen skin prick testing (SPT) in chronic spontaneous urticaria (CSU).

OBJECTIVE

The objective of this review was to investigate the presence of aeroallergen sensitization and markers of T2 inflammation in subjects with CSU.

METHODS

Systematic literature reviews to identify all studies that evaluated the presence of T2 markers of allergic inflammation in CSU subjects were performed.

RESULTS

In 16 studies that assessed the prevalence of positive SPT to multiple aeroallergens in CSU, 38.5% of CSU subjects had positive SPT. In three controlled studies, 34.2% of CSU subjects had positive SPT to multiple aeroallergens, compared to 13.6% of controls (p = 0.047). In 18 studies that assessed the prevalence of house dust mite (HDM) positive SPT in CSU, 27.5% of CSU subjects had positive SPT. In three controlled studies, 27.5% of CSU subjects had positive SPT to HDM, compared to 2.1% of controls (p = 0.047). Overall, CSU subjects were 3.1 times more likely to be aeroallergen-sensitized (95% CI 1.7-5.8, p = 0.0002) and 6.1 times more likely to be HDM-sensitized (95% CI 3.7-9.9, p < 0.00001) than controls. Mean total serum IgE (tIgE) levels were 238 kU/L and median tIgE levels were 164 kU/L, which was greater than the upper 90th percentile of normal (< 137 kU/L). Compared to healthy controls, CSU subjects were 6.5 times more likely to have IgG autoantibody against FcεR1α (p = 0.001), 2.4 times more likely to have IgG anti-IgE antibody (p = 0.03) and 5 times more likely to have anti-thyroid peroxidase (anti-TPO) antibody (p = 0.02). When corticosteroids were withheld for ≥ 28 days, mean blood eosinophil percentage was elevated at 5.9% (normal < 4%), but other studies reporting absolute count found the mean was in the normal range, 239 × 10 6 / L (normal < 400 × 10 6 / L).

CONCLUSION

Increased aeroallergen sensitization, tIgE, autoantibodies and blood eosinophil percentage in the CSU subjects indicates the possible importance of T2 inflammation in the pathogenesis of CSU. Further studies may be warranted to determine if specific allergen avoidance, desensitization or improvement in the mucosal allergic inflammation present in asthma and/or rhinitis has any benefit in the management of CSU.

In chronic spontaneous urticaria, IgE against staphylococcal enterotoxins is common and functional

BACKGROUND

Chronic spontaneous urticaria (CSU) is a frequent disorder with recurrent itchy wheals and/or angioedema. Despite the known effectiveness of omalizumab therapy, the relevant IgE antigens are largely unknown. Recently, increased rates of elevated levels of IgE towards Staphylococcus aureus enterotoxins (SEs) were described in CSU.

AIM

To assess the prevalence and functional relevance of IgE to SEs in CSU.

METHOD

We investigated serum levels of IgE against SEs in 49 CSU patients and in 15 CSU patients additional specific IgE to SE components and basophil histamine release (BHR). Sera of 15 healthy controls (HCs) served as control group.

RESULTS

Twenty-five (51%) of the CSU patients had detectable levels of SE-IgE as compared to 5 (33%) of HCs. Specific IgE to one of the SEs, Staphylococcus enterotoxin B (SEB), was present in 5 (33%) of 15 randomly selected CSU patients vs 3 (20%) of HC. Total IgE serum levels in CSU patients were significantly correlated with SE-IgE (r = .52, P < .001) and SEB-IgE (r = .54, P = .04) serum concentrations. Interestingly, SEB-IgE levels were strongly correlated with disease activity (UASday) in CSU patients (r = .657, P = .01). Furthermore, BHR in response to SEB was significantly higher in basophils loaded with the serum of CSU patients compared to HC (P < .05) and was clinically correlated with duration of disease (r > .51, P < .05).

DISCUSSION

IgE against SEs may contribute to the pathogenesis of CSU in a subpopulation of patients. Its role and relevance in the pathophysiology of CSU need to be further analysed.

Approaches to target IgE antibodies in allergic diseases

IgE is the antibody isotype found at the lowest concentration in the circulation. However IgE can undeniably play an important role in mediating allergic reactions; best exemplified by the clinical benefits of anti-IgE monoclonal antibody (omalizumab) therapy for some allergic diseases. This review will describe our current understanding of the interactions between IgE and its main receptors FcεRI and CD23 (FcεRII). We will review the known and potential functions of IgE in health and disease: in particular, its detrimental roles in allergic diseases and chronic spontaneous urticaria, and its protective functions in host defense against parasites and venoms. Finally, we will present an overview of the drugs that are in clinical development or have therapeutic potential for IgE-mediated allergic diseases.

Characterization of Human Type C Enterotoxin Produced by Clinical S. epidermidis Isolates

Staphylococcal Enterotoxins (SEs) are superantigens (SAg) originally produced by S. aureus, but their presence in coagulase negative staphylococci (CNS) has long been suspected. This study aims to better characterize a novel C-like enterotoxin expressed by clinical S. epidermidis strains, called SEC_epi. We isolated and characterized SEC_epi for its molecular and functional properties. The toxin was structurally modeled according to its significant similarity with S. aureus SEC3. Most of SEC amino acid residues important for the formation of the trimolecular Major Histocompatibility Complex II MHCII-SEC-T Cell Receptor TCR complex are conserved in SEC_epi. The functional properties of SEC_epi were estimated after cloning, expression in E. coli, and purification. The recombinant SEC_epi toxin exhibits biological characteristics of a SAg including stimulation of human T-cell mitogenicity, inducing and releasing high cytokines levels: IL-2, -4, -6, -8, -10, IFN-γ, TNF-α and GM-CSF at a dose as low as 3.7 pM. Compared to SEC_aureus, the production of pro-sepsis cytokine IL-6 is significantly higher with SEC_epi-activated lymphocytes. Furthermore, SEC_epi is stable to heat, pepsin or trypsin hydrolysis. The SEC_epi superantigen produced by CNS is functionally very close to that of S. aureus, possibly inducing a systemic inflammatory response at least comparable to that of SEC_aureus, and may account for S. epidermidis pathogenicity.

Prognostic Factors for Chronic Spontaneous Urticaria: A 6-Month Prospective Observational Study

Purpose

Chronic urticaria (CU) has a substantial impact on the quality of life. Little clinical data on the prognosis of CU has been reported. This study aimed to investigate the control status and remission rate of CU and to explore potential predictors of good responses to the treatment during a 6-month treatment period.

Methods

A total of 75 patients with chronic spontaneous urticaria (CSU) were enrolled from 3 university hospitals in Korea. Urticaria control state was classified into 2 groups: group I (remission and well-controlled) and group II (partly and uncontrolled). CU-specific quality of life (CU-QoL) and the urticaria activity score (UAS) were measured before and after the treatment. Autologous serum skin test (ASST), and anti-nuclear and anti-thyroid antibodies were measured at the enrollment into the study. Aspirin intolerance was confirmed by an oral provocation test.

Results

Of 59 patients completing the study, 21 (35.6%) arrived at well-controlled status and only 2 (3.4%) achieved remission, whereas 26 (44.1%) remained at partly controlled status and 10 (16.9%) were at uncontrolled status. Mean changes in CU-QoL (36.5±2.7 vs 20.6±4.3, P=0.017) and UAS (-7.9±0.8 vs -3.0±1.0, P=0.001) were significantly different between groups I and II. The presence of serum autoantibodies and aspirin intolerance had no influence on the control of urticaria in this study. However, ASST positivity was identified as a significant predictor of CU control in multivariate analysis (OR=6.106, P=0.017).

Conclusions

The proportion of CSU patients that achieved remission or a well-controlled state was 39% for the 6 months of stepwise treatment. Longer observations are necessary to assess the exact prognosis of CSU. ASST results may be a useful parameter for predicting a better response to treatment and both UAS and CU-QoL are helpful to monitor therapeutic response.

Clinical features of elderly chronic urticaria

BACKGROUND/AIMS

Chronic urticaria (CU) is defined as itchy wheals lasting 6 weeks or more. As the aged population increases worldwide, it is essential to identify the specific features of this disease in the elderly population.

METHODS

We investigated the prevalence and clinical features of CU in elderly patients. Medical records of 837 CU patients from the outpatient Allergy Clinic of Ajou University Hospital, Korea were analyzed retrospectively. Patients with chronic spontaneous urticaria according to the EAACI/GA2LEN/EDF/WAO guidelines were included. Patients older than 60 years were defined as elderly.

RESULTS

Of the 837 patients, 37 (4.5%) were elderly. In elderly versus nonelderly CU patients, the prevalence of atopic dermatitis (AD) was significantly higher (37.8% vs. 21.7%, respectively; p = 0.022), while that of aspirin intolerance was lower (18.9% vs. 43.6%, respectively; p = 0.003) in terms of comorbid conditions. The prevalences of serum specific immunoglobulin E antibodies to staphylococcal enterotoxin A and staphylococcal enterotoxin B were considerably higher in elderly CU patients with AD than in those without AD (37.5% vs. 0%, respectively).

CONCLUSIONS

Elderly patients with CU had a higher prevalence of AD. Therefore, there is a need to recognize the existence of AD in elderly CU patients.

Association Between PTPN22 Polymorphisms and IgE Responses to Staphylococcal Superantigens in Chronic Urticaria

Protein tyrosine phosphatase-22 (PTPN22) gene encodes lymphoid-specific tyrosine phosphatase (Lyp), an inhibitor of T cell activation. A polymorphism of the PTPN22 gene has been found to be associated with chronic urticaria (CU). We investigated the associations between PTPN22 gene polymorphisms and CU characteristics, including serum specific IgE antibodies response to toxic shock syndrome toxin-1 (TSST-1) and staphylococcal enterotoxin A (SEA). CU patients (n=409) and normal healthy controls (n=388) were enrolled in the present study. Serum specific IgE to TSST-1 and SEA were measured by ImmunoCAP®. Five PTPN22 single nucleotide polymorphisms, -1123G>C, 1858C>T, 13145A>G, 14943C>T, and 20628A>G, were genotyped. There were no significant differences in genotype or haplotype frequencies of these polymorphisms between the 2 groups. CU patients carrying the GG genotype at 20628A>G (P=0.035) or haplotype 3 [GGG] (P=0.047) had a significantly higher prevalence of serum specific IgE to TSST-1 compared to non-carriers. Similarly, CT/TT genotype at 14943C>T had a significantly higher prevalence of serum specific IgE to SEA (P=0.045). The findings suggest that the PTPN22 gene polymorphisms at 20628A>G and 14943C>T may enhance serum specific IgE responses to TSST-1 and SEA, which may contribute to CU pathogenesis.

Molecular genetic mechanisms of chronic urticaria

Chronic urticaria (CU) is a common allergic skin disease that requires long-term pharmacological treatment. Some patients with severe CU suffer a poor quality of life. Although the pathogenic mechanisms of CU are not clearly understood, several groups have suggested that genetic mechanisms are involved in various CU cohorts. To further understand the molecular genetic mechanisms of CU, we summarize recent genetic data in this review. Although a few HLA alleles were suggested to be candidate markers in different ethnic groups, further replication studies that apply the recent classification are needed. Genetic polymorphisms in histamine-related genes, including FcεRI and HNMT, were suggested to be involved in mast cell activation and histamine metabolism. Several genetic polymorphisms of leukotriene-related genes, such as ALOX5, LTC4S, and the PGE2 receptor gene PTGER4, were suggested to be involved in leukotriene overproduction, a pathogenic mechanism. Further investigations using candidate gene approaches and genome-wide association studies (GWAS) will provide new insights into the molecular genetic mechanisms of CU, which will provide new marker genes for differentiation of CU phenotypes and identification of potential therapeutic targets.

Clinical significance of immunoglobulin E responses to staphylococcal superantigens in patients with aspirin-exacerbated respiratory disease

BACKGROUND

Previous studies have reported a higher prevalence of immunoglobulin E (IgE) specific for staphylococcal superantigens (SAg) in the nasal mucosa of patients with aspirin-exacerbated respiratory disease (AERD), associated with eosinophilic inflammation and leukotriene production. However, the role of SAg-specific IgE in the pathogenesis of AERD is not well understood. We evaluated the clinical significance of serum IgE specific for three types of SAg, namely staphylococcal enterotoxins A and B (SEA and SEB) and toxic shock syndrome toxin-1 (TSST-1) in AERD.

METHODS

We enrolled 147 patients with AERD confirmed by a lysine-acetyl salicylic acid bronchoprovocative test and compared them with 147 patients with aspirin-tolerant asthma (ATA) and 141 healthy controls (NC). The levels of serum total IgE and SAg-specific IgE were measured using an ImmunoCAP system. Other clinical parameters were analyzed retrospectively.

RESULTS

The prevalences of SEA-, SEB- and TSST-1-specific IgE in the AERD and ATA groups were significantly higher than those in the NC group (p < 0.05, respectively). The total IgE level was significantly higher in patients with AERD with high levels of SEA-specific IgE than in those with lower levels (p < 0.05), with significant positive correlations between total and SAE-specific IgE levels (p < 0.05). The PC20 methacholine level was significantly lower in patients with AERD with high levels of SEA-specific IgE, while a significantly higher eosinophil count was noted in patients with AERD with high levels of SEB-specific IgE (p < 0.05, respectively).

CONCLUSIONS

Specific IgE responses to SAg may increase the serum total IgE level, airway hyperresponsiveness and eosinophil activation, leading to more severe clinical symptoms in AERD.

Staphylococcal enterotoxin A: a candidate for the amplification of physiological immunoregulatory responses in the gut

Staphylococcal enterotoxin A (SEA) is one of the bacterial products tested for modulation of unwanted immune responses. Of all the staphylococcal enterotoxins, SEA is the most potent stimulator of T cells. When administered orally, SEA acts as a superantigen (SA), producing unspecific stimulation of intra-epithelial lymphocytes (IELs) in the intestinal mucosa. This stimulation results in amplification of the normal local immunologic responses, which are mainly regulatory. This amplification is based on increased local production of IFN-γ by IELs, which acts on the nearby enterocytes. As a result, the enterocytes produce large amounts of tolerosomes, cellular corpuscles which detach themselves from the basal poles of the enterocytes and contain antigenic peptides that are conditioned to be interpreted as tolerogenic by the gut immune system. Tolerosomes are physiologically produced as a response to dietary peptides; it is already known that enterocytes posses the molecular mechanisms for processing peptides in a similar manner to lymphocytes. The fate of tolerosomes is not precisely known, but it seems that they merge with intestinal dendritic cells, conveying to them the information that orally administered peptides must be interpreted as tolerogens. SEA can stimulate this mechanism, thus favoring the development of tolerance to peptides/proteins administered subsequently via the oral route. This characteristic of SEA might be useful in therapy for regulating immune responses. The present paper reviews the current status of research regarding the impact of SEA on the enteric immune system and its potential use in the treatment of allergic and autoimmune diseases.

Urticaria and infections

Urticaria is a group of diseases that share a distinct skin reaction pattern. Triggering of urticaria by infections has been discussed for many years but the exact role and pathogenesis of mast cell activation by infectious processes is unclear. In spontaneous acute urticaria there is no doubt for a causal relationship to infections and all chronic urticaria must have started as acute. Whereas in physical or distinct urticaria subtypes the evidence for infections is sparse, remission of annoying spontaneous chronic urticaria has been reported after successful treatment of persistent infections. Current summarizing available studies that evaluated the course of the chronic urticaria after proven Helicobacter eradication demonstrate a statistically significant benefit compared to untreated patients or Helicobacter-negative controls without urticaria (p < 0.001). Since infections can be easily treated some diagnostic procedures should be included in the routine work-up, especially the search for Helicobacter pylori. This review will update the reader regarding the role of infections in different urticaria subtypes.

In vitro cell-based assay for activity analysis of staphylococcal enterotoxin A in food

Staphylococcal enterotoxins (SEs) are a leading cause of food poisoning and have two separate biological activities; it causes gastroenteritis and functions as a superantigen that activates large numbers of T cells. In vivo monkey or kitten bioassays were developed for analysis of SEs emetic activity. To overcome the inherent limitations of such bioassays, this study describes an in vitro splenocyte proliferation assay based on SEs superantigen activity as an alternative method for measuring the activity of staphylococcal enterotoxin A (SEA). After incubation of splenocytes with SEA, cell proliferation was measured by labeling the proliferating cells' DNA with bromodeoxyuridine (5-bromo-2-deoxyuridine, BrdU) and quantifying the incorporated BrdU by immunohistochemistry. BrdU labeling is shown to be highly correlated with SEA concentration (R(2)=0.99) and can detect 20 pg mL(-1) of SEA, which is far more sensitive than most enzyme-linked immunosorbent assays. Our assay can also distinguish between active toxin and inactive forms of the toxin in milk. By applying immunomagnetic beads that capture and concentrate the toxin, our assay was able to overcome matrix interference. These results suggest that our in vitro cell-based assay is an advantageous practical alternative to the in vivo monkey or kitten bioassays for measuring SEA and possibly other SEs activity in food.