Cutaneous exposure to the superantigen staphylococcal enterotoxin B elicits a T-cell-dependent inflammatory response

Exploring the Role of Staphylococcus Aureus Toxins in Atopic Dermatitis

Atopic dermatitis (AD) is a chronic and inflammatory skin disease with intense pruritus and xerosis. AD pathogenesis is multifactorial, involving genetic, environmental, and immunological factors, including the participation of Staphylococcus aureus. This bacterium colonizes up to 30-100% of AD skin and its virulence factors are responsible for its pathogenicity and antimicrobial survival. This is a concise review of S. aureus superantigen-activated signaling pathways, highlighting their involvement in AD pathogenesis, with an emphasis on skin barrier disruption, innate and adaptive immunity dysfunction, and microbiome alterations. A better understanding of the combined mechanisms of AD pathogenesis may enhance the development of future targeted therapies for this complex disease.

Effect of Montelukast, a Cysteinyl Leukotriene Receptor-1 Antagonist, on a Rat Model of Acute Bacterial Sinonasal Inflammation

Aim

This study aimed to investigate montelukast (MONT), a leukotriene receptor antagonist, as a potential treatment protocol and/or supportive therapy against acute bacterial sinonasal inflammation by histopathological and molecular analyses.

Material and Methods

A total of 30 rats were used in the study. The nasal dorsum was sterilized, and gelatin sponges were inserted into the right nasal cavities. The nostrils were then inoculated with Staphylococcus aureus (SA) for rhinosinusitis (RS) induction. Rats were treated once daily for 7 days with an injection of saline, either cefazolin sodium (CEFA) or MONT. Tissue samples were collected for examination.

Results

To evaluate whether CEFA and MONT were able to attenuate the SA-induced nasal inflammation, we analyzed the proinflammatory cytokine levels in the nasal tissue of rats by real-time polymerase chain reaction (PCR). The inflammatory cytokines tumor necrosis factor-α ( P ≤ .05) and interleukin-1α (IL-1α) ( P ≤ .05) increased in the SA-induced group, when compared with the healthy control. MONT treatment significantly reversed these elevations, especially IL-1α messenger RNA expression levels induced by SA. Also, CEFA administration significantly changed the proinflammatory cytokine levels when compared to the SA group, but this effect was not as strong as MONT. Also, histopathological findings supported the beneficial effects of MONT.

Conclusion

This study histopathologically and molecularly showed that MONT significantly ameliorated the SA-associated sinonasal inflammatory reaction, both alone and in combination with CEFA. These results may suggest that MONT may block the inflammatory reaction underlying RS even more significantly by antioxidative or anti-inflammatory effects. This study suggests MONT as a future potential therapeutic agent for RS treatment.

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.

Presence and Characterization of Sensitization to Staphylococcal Enterotoxins in Patients with Allergic Rhinitis

Exotoxins derived from Staphylococcus aureus appear to be involved in the pathogenesis of allergic diseases, especially atopic dermatitis (AD). However, little is known about sensitization to enterotoxins in cases of respiratory allergies. Because the nasal cavity is a primary site of colonization by S. aureus, we sought to determine the prevalence and role of serum immunoglobulin E (IgE) antibodies against staphylococcal enterotoxin A (SEA) and SEB in patients with allergic rhinitis (AR). The presence of SEA- and SEB-specific IgE was determined in 40 patients with AR and 16 healthy control subjects. In the rhinitis group, nasal symptom score, total serum IgE, sensitization to other inhaled allergens and the presence of sinusitis were determined. Twenty-five percent of patients with AR were sensitized to SEA/SEB whereas 6.3% of controls were sensitized to the toxins. Sensitization to SEB was predominant relative to SEA. There were no significant differences in the severity of nasal symptoms and complications of other allergic diseases including AD and bronchial asthma, between patients with or without sensitization to SEA/SEB. However, patients sensitized to these toxins were likely to show increased total serum IgE and polyvalent sensitization, suggesting that exposure and subsequent sensitization to SEA/SEB may be involved in polyvalent sensitization.

Animal Models Used to Study Superantigen-Mediated Diseases

Superantigens secreted by Staphylococcus aureus and Streptococcus pyogenes interact with the T-cell receptor and major histocompatibility class II molecules on antigen-presenting cells to elicit a massive cytokine release and activation of T cells in higher numbers than that seen with ordinary antigens. Because of this unique ability, superantigens have been implicated as etiological agents for many different types of diseases, including toxic shock syndrome, infective endocarditis, pneumonia, and inflammatory skin diseases. This review covers the main animal models that have been developed in order to identify the roles of superantigens in human disease.

Association between specific IgE to Staphylococcus aureus enterotoxins A and B and asthma control

BACKGROUND

Recent studies have found that serum levels of Staphylococcus aureus enterotoxin (SE)-IgE are higher in patients with severe asthma compared with patients with nonsevere asthma. However, the association between SE-IgE and asthma control is not fully understood. Furthermore, SEA and SEB were the first reported SEs and subdivided into different groups. The influences of SEA-IgE and SEB-IgE on asthma control have not been elucidated.

OBJECTIVE

To determine the relevance of SEA- and SEB-IgE in patients with adult asthma and to investigate the association of SEA-IgE, SEB-IgE, and asthma control, respectively.

METHODS

The serum concentrations of SEA- and SEB-IgE in 172 adults with asthma were measured with a fluorescent enzyme immunoassay.

RESULTS

The prevalence of SEA- and SEB-IgE was 16.2% and 22.1%, respectively. Total IgE levels and the prevalence of atopic dermatitis were higher in SEA-IgE- and SEB-IgE-positive patients than in SEA-IgE- and SEB-IgE-negative patients, respectively; more SEA-IgE- and SEB-IgE-positive patients owned pets. Sensitization to SEA was associated with a younger mean age and a younger mean age at asthma onset. Multiple regression analysis indicated an association between total IgE levels and SEB-IgE. The prevalence of poorly uncontrolled asthma was significantly higher in SEA-IgE-positive patients than in SEA-IgE-negative patients. In addition, fractional exhaled nitric oxide levels were higher in SEA-IgE-positive patients than in SEA-IgE-negative patients. Logistic regression analysis also identified an association between SEA-IgE and poor asthma control.

CONCLUSION

Our findings indicate that sensitization to SE, in particular SEA rather than SEB, is associated with poor asthma control in adults with asthma.

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.

Potential Immunoinflammatory Role of Staphylococcal Enterotoxin A in Atopic Dermatitis: Immunohistopathological Analysis and in vitro Assay

Background

The underlying mechanism of atopic dermatitis (AD) exacerbated by Staphylococcus aureus has not been established. However, we demonstrated recently that the majority of S. aureus strains colonized in the skin of Korean AD patients carried genes encoding staphylococcal enterotoxin A (SEA) and/or toxic shock syndrome toxin-1 (TSST-1).

Objective

To clarify the role of staphylococcal superantigen, SEA in AD.

Methods

With the lesional skin of 9 AD patients and normal looking skin of one healthy adult, we examined first the expression of SEA, staphylococcal enterotoxin B (SEB), and TSST-1 using immunohistochemical analysis. In addition, we investigated the effects of SEA on the expression of inflammation-related adhesion molecules and cytokines in human HaCaT keratinocytes and Human Umbilical Vein Endothelial Cells (HUVECs) by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis and enzyme-linked immunosorbent assay.

Results

Staphylococcal protein A (SPA) and SEA were detected with increased immunoreactivity in AD patients. However, TSST-1 showed mild-to-moderate immunoreactivity in AD patients, whereas SEB was minimally detected. In the double immunofluorescence investigation, SEA and SPA were well co-localized. SEA induced upregulation of adhesion molecules and elicited inflammatory responses in HaCaT keratinocytes and HUVECs.

Conclusion

This study demonstrates the importance of SEA as an immunoinflammatory triggering factor of AD in Koreans.

Staphylococcal enterotoxin B causes proliferation of sensory C-fibers and subsequent enhancement of neurogenic inflammation in rat skin

BACKGROUND

Staphylococcal enterotoxin B (SEB) may be associated with the exacerbation of atopic dermatitis. We investigated whether SEB causes proliferation of sensory C-fibers and subsequent enhancement of plasma leakage induced by sensorineural stimulation in rat skin.

METHODS

SEB was applied intracutaneously to the abdomen of preweaning and adult rats. Evans blue dye leakage into the skin induced by topical 10% formalin was measured as an index of neurogenic skin vascular permeability. Local expression of substance P, tachykinin NK1 receptors, and nerve growth factor was assessed immunohistochemically. In addition, we assessed the effects of topical tacrolimus on these skin responses induced by SEB.

RESULTS

Increased neurogenic skin plasma leakage was seen 7 days after SEB treatment in 2 different age groups. Innervation of substance P-immunoreactive nerves and expression of tachykinin NK1 receptors and nerve growth factor were also promoted by SEB, peaking at 7 days, 7 days, and 56 h after SEB treatment, respectively. Tacrolimus markedly inhibited these skin changes.

CONCLUSIONS

SEB increased the innervation of sensory C-fibers and tachykinin NK1 receptors in rat skin, probably because of upregulated production of neurotrophins, including nerve growth factor, leading to enhancement of neurogenic skin inflammation. T cell activation induced by SEB may initiate these changes.

Staphylococcal enterotoxin B is involved in aggravation and recurrence of murine experimental autoimmune uveoretinitis via Vbeta8+CD4+ T cells

Endogenous uveitis is a common cause of visual disability and blindness. The etiology of uveitis remains largely unknown but reasonable etiologic factors include infections. Superantigens are regarded as one of the leading causes of infectious etiology in autoimmune disease. However, the role of superantigens in uveitis remains unclear. In the present study, we investigated the effect of Staphylococcal enterotoxin B (SEB), a member of the superantigens, using an experimental model of autoimmune uveoretinitis (EAU). C57BL/6 mice were immunized with human interphotoreceptor retinoid binding protein (IRBP) peptide, and the severity of EAU disease was scored. Vehicle (PBS) alone or SEB dissolved in PBS was administered by intravenous injection on post-immunization day 10 or on post-immunization day 24. In addition, a systemic immune response study was performed to address the effects of SEB on systemic immunity. EAU was aggravated significantly by the injection of SEB at post-immunization day 10. Furthermore, relapse was induced by the injection of SEB at day 24. On the other hand, SEB injection without IRBP peptide immunization elicited no inflammatory changes in the uvea or retina. Furthermore, SEB enhanced not only the IRBP-specific T-cell proliferative responses but also IFN-gamma and IL-17 production. Moreover, the intraocular expression levels of these cytokines was also enhanced by SEB injection. Both anti-CD4 and -Vbeta8 Ab administration suppressed disease aggravation and the enhancement of IRBP-specific T-cell responses caused by SEB. These results suggest that SEB is involved significantly in the aggravation or recurrence of endogenous uveitis through activation of autoreactive uveitogenic T cells.

Isolation of alpha-toxin-producing Staphylococcus aureus from the skin of highly sensitized adult patients with severe atopic dermatitis

BACKGROUND

Staphylococcus aureus (S. aureus) is a well-known trigger factor of atopic dermatitis (AD). Besides staphylococcal superantigens, alpha-toxin may influence cutaneous inflammation via induction of T-cell proliferation and cytokine secretion.

OBJECTIVES

To investigate the association between sensitization to inhalant allergens and skin colonization with alpha-toxin-producing S. aureus in AD.

PATIENTS AND METHODS

We investigated 127 patients with AD, aged 14-65 years, who were on standard anti-inflammatory and antiseptic treatment before investigation. We evaluated skin colonization, medical history, severity of AD and sensitization to inhalant allergens.

RESULTS

Forty-eight of 127 patients were colonized with S. aureus, suffered from more severe AD, had asthma more often and showed higher sensitization levels to inhalant allergens. Thirty of 48 patients with S. aureus skin-colonizing strains produced alpha-toxin and had higher total IgE and specific IgE to birch pollen and timothy grass pollen.

CONCLUSIONS

Under topical treatment with antiseptic and anti-inflammatory agents the colonization of lesional skin with S. aureus was clearly lower than commonly found in untreated patients with AD. Colonization with S. aureus was associated with a higher severity of AD, higher degree of sensitization, and a higher frequency of asthma. The proportion of patients whose skin was colonized with alpha-toxin-producing S. aureus was higher than expected from a former study. Cutaneous colonization with alpha-toxin-producing S. aureus was associated with a higher sensitization level to birch pollen allergen in AD. This may point to a higher susceptibility of patients with higher T-helper 2 polarization towards alpha-toxin-producing S. aureus.

Rat model of staphylococcal enterotoxin B-induced rhinosinusitis

Objectives

It has been proposed that microbial persistence, superantigen (SA) production, and host T-cell response may be involved in the development of chronic rhinosinusitis. According to the SA hypothesis, a single intranasal application of SA such as staphylococcal enterotoxin B (SEB) may induce chronic eosinophilic rhinosinusitis. This study aimed to develop a rat model of rhinosinusitis induced by intranasally applied SEB.

Methods

Forty µL of SEB (100 µg/mL) or phosphate buffered saline was applied intranasally through each naris in 4 week-old Sprague-Dawley test rats (N=36) and controls (N=16), respectively. Following sacrifice at 1, 5, 14, and 28 days, the obtained nasal cavity and sinuses were prepared for histologic investigation. The histologic sections were examined in a blind manner for the ratio of the sinus spaces occupied by inflammatory cell clusters and the number of inflammatory cells in the lamina propria.

Results

Infiltration of neutrophils in the lamina propria and appearance of neutrophil clusters in the sinus spaces were observed in the SEB-applied rats. The ratio of the sinus spaces occupied by neutrophil clusters and the number of neutrophils infiltrated in the lamina propria increased significantly at day 1 as compared with the control rats.

Conclusion

Intranasally applied SEB induces acute neutrophilic rhinosinusitis in rats. Eosinophilic inflammation was not demonstrated. The mere presence of SA in the nose does not necessarily induce SA-induced inflammation, as suggested by the SA hypothesis.

In vivo pharmacological disease models for psoriasis and atopic dermatitis in drug discovery

In order to perform relevant in vivo pharmacological investigations in drug discovery within dermatology it is fundamental to master or have access to relevant skin disease models that makes it possible to identify and validate targets and to screen and discover drugs in vivo. There is a strong need for highly predictive in vivo models in order to introduce the right drug candidates into the clinical phases of development. Recent advances in dermatological in vivo pharmacological disease models for psoriasis and atopic dermatitis are reviewed together with a discussion of the rationale for their application in drug discovery.

Topical superantigen exposure induces epidermal accumulation of CD8+ T cells, a mixed Th1/Th2-type dermatitis and vigorous production of IgE antibodies in the murine model of atopic dermatitis

Patients with atopic dermatitis (AD) have repeated cutaneous exposure to both environmental allergens and superantigen-producing strains of Staphylococcus aureus. We used a murine model of AD to investigate the role of staphylococcal enterotoxin B (SEB) in the modulation of allergen-induced skin inflammation. Mice were topically exposed to SEB, OVA, a combination of OVA and SEB (OVA/SEB), or PBS. Topical SEB and OVA/SEB exposure induced epidermal accumulation of CD8+ T cells and TCRVbeta8+ cells in contrast to OVA application, which induced a mainly dermal infiltration of CD4+ cells. SEB and OVA/SEB exposure elicited a mixed Th1/Th2-associated cytokine and chemokine expression profile within the skin. Restimulation of lymph node cells from OVA- and OVA/SEB-exposed mice with OVA elicited strong production of IL-13 protein, whereas substantial amounts of IFN-gamma protein were detected after SEB stimulation of cells derived from SEB- or OVA/SEB-exposed mice. Topical SEB treatment elicited vigorous production of SEB-specific IgE and IgG2a Abs and significantly increased the production of OVA-specific IgE and IgG2a Abs. The present study shows that topical exposure to SEB provokes epidermal accumulation of CD8+ T cells, a mixed Th2/Th1 type dermatitis and vigorous production of specific IgE and IgG2a Abs, which can be related to the chronic phase of atopic skin inflammation.

Alpha-toxin is produced by skin colonizing Staphylococcus aureus and induces a T helper type 1 response in atopic dermatitis

BACKGROUND

Staphylococcus aureus is a well known trigger factor of atopic dermatitis (AD). Besides the superantigens, further exotoxins are produced by S. aureus and may have an influence on the eczema.

OBJECTIVE

To explore the impact of staphylococcal alpha-toxin on human T cells, as those represent the majority of skin infiltrating cells in AD.

METHODS

Adult patients with AD were screened for cutaneous colonization with alpha-toxin producing S. aureus. As alpha-toxin may induce necrosis, CD4(+) T cells were incubated with sublytic alpha-toxin concentrations. Proliferation and up-regulation of IFN-gamma on the mRNA and the protein level were assessed. The induction of t-bet translocation in CD4(+) T cells was detected with the Electrophoretic Mobility Shift Assay.

RESULTS

Thirty-four percent of the patients were colonized with alpha-toxin producing S. aureus and alpha-toxin was detected in lesional skin of these patients by immunohistochemistry. Sublytic alpha-toxin concentrations induced a marked proliferation of isolated CD4(+) T cells. Microarray analysis indicated that alpha-toxin induced particularly high amounts of IFN-gamma transcripts. Up-regulation of IFN-gamma was confirmed both on the mRNA and the protein level. Stimulation of CD4(+) T cells with alpha-toxin resulted in DNA binding of t-bet, known as a key transcription factor involved into primary T helper type 1 (Th1) commitment.

CONCLUSION

alpha-toxin is produced by S. aureus isolated from patients with AD. We show here for the first time that sublytic alpha-toxin concentrations activate T cells in the absence of antigen-presenting cells. Our results indicate that alpha-toxin is relevant for the induction of a Th1 like cytokine response. In AD, this facilitates the development of Th1 cell dominated chronic eczema.

Deficiency in immunoglobulin G2 antibodies against staphylococcal enterotoxin C1 defines a subgroup of patients with atopic dermatitis

BACKGROUND AND AIM

Atopic dermatitis (AD) is a common chronic inflammatory skin disease often accompanied by cutaneous Staphylococcus aureus colonization and, in this regard, especially complicated by the presence of superantigen-producing strains. Because IgG antibodies comprise an important defence mechanism of the adaptive immune system against bacteria, it was investigated whether AD patients have an abnormal pattern or distribution of superantigen-specific IgG subclass antibodies in association with disease severity and activity.

METHODS

Staphylococcal enterotoxin B (SEB) and staphylococcal enterotoxin C1 (SEC1) specific IgG antibody subclasses were assessed in n=89 adult AD patients with mild to severe disease activity as determined by the SCORAD score and in n=28 healthy age-matched controls. Results were correlated with the current status of bacterial skin colonization and severity score.

RESULTS

Thirty-eight per cent of the AD patients showed a selective deficiency in IgG2 antibodies against SEC1 compared with only 14% in the control group. The absence of these antibodies was found in both currently colonized and non-colonized AD patients and was associated with a severe phenotype (SCORAD more than 40 points in two-thirds of the deficient patients). However, these patients had normal production levels of IgG2 antibodies against pneumococcal capsular polysaccharide (PCP) and SEB, but higher IgG1 and IgG4 titres against SEC1. Except for elevated total IgG1, total IgG subclass levels were normal in this AD subgroup. Yet, peripheral blood mononuclear cells (PBMCs) derived from these patients clearly produced IL-4 and IL-5 upon SEC1 re-stimulation whereas PBMCs from those providing SEC1-specific IgG2 antibodies failed in the production of these cytokines.

CONCLUSION

A subgroup of AD patients suffers from a selective deficiency to produce anti-SEC1 IgG2 antibodies. This patient group is characterized by a severe AD phenotype.

Nasal exposure to Staphylococcal enterotoxin enhances the development of allergic rhinitis in mice

BACKGROUND

Staphylococcal enterotoxins (SEs) appear to play a role in the pathogenesis of allergic disease. However, little is known whether the nasal exposure to SE affects the development of allergic rhinitis (AR).

OBJECTIVE

We sought to determine the in vivo effect of nasal exposure to SE on the development of AR using mouse model.

METHODS

BALB/c mice were intranasally sensitized with Schistosoma mansoni egg antigen (SmEA) in the presence or absence of staphylococcal enterotoxin B (SEB). Control mice were intranasally sensitized with either SEB or SmEA alone. The production of antigen-specific antibodies including IgE, nasal eosinoplilia and cytokines by nasal mononuclear cells was compared among mice that had or had not received SEB treatment.

RESULTS

Nasal exposure to SEB enhanced the development of AR in SmEA-sensitized mice, as manifested by SmEA-specific IgE production, nasal eosinophilia, and IL-4 and IL-5 production by nasal mononuclear cells after Ag challenge. This treatment also elicited IFN-gamma production by SmEA-primed cells. In addition, these mice produced SEB-specific IgE whereas mice treated with SEB without SmEA sensitization did not produce SEB-specific IgE or demonstrate nasal eosinophilia.

CONCLUSION

These results suggest that the nasal exposure to SEB enhances susceptibility to AR although the exposure to SE solely does not induce AR.

Superantigens and nasal polyps

Nasal polyps represent an often severe T-cell-orchestrated eosinophilic upper airway disease with currently unknown pathogenesis, often associated with lower airway disease, such as asthma. Superantigens, predominantly derived from Staphylococcus aureus, are potent activators of T cells, induce the synthesis of IgE in B cells, and have direct effects on pro-inflammatory cells, such as eosinophils. IgE antibodies to S. aureus enterotoxins have been described in polyp tissue, linked to a local polyclonal IgE production and an aggravation of eosinophilic inflammation. Furthermore, such IgE antibodies have also been described in the sera of patients with asthma, and linked to severity of disease and steroid insensitivity. This review summarizes our current understanding of the possible role of S. aureus enterotoxins in chronic severe airway disease, such as nasal polyposis.

Epicutaneous sensitization with superantigen induces allergic skin inflammation

BACKGROUND

Atopic dermatitis (AD) is characterized by skin infiltration with eosinophils and lymphocytes and expression of Th2 cytokines in acute skin lesions. The skin of patients with AD is frequently colonized with enterotoxin-secreting strains of Staphylococcus aureus. Staphylococcal enterotoxins have been implicated in the exacerbations of the inflammatory skin lesions in patients with AD.

OBJECTIVE

We sought to determine whether epicutaneous (EC) sensitization of mice with staphylococcal enterotoxin B (SEB) results in allergic skin inflammation.

METHODS

BALB/c mice were EC-sensitized with SEB. Their skin was examined for allergic inflammation and cytokine expression, and their splenocytes were examined for cytokine secretion in response to SEB.

RESULTS

EC sensitization with SEB elicited a local, cutaneous, inflammatory response characterized by dermal infiltration with eosinophils and mononuclear cells and increased mRNA expression of the Th2 cytokine IL-4 but not of the Th1 cytokine IFN-gamma. EC-sensitized mice mounted a systemic Th2 response to SEB evidenced by elevated total and SEB-specific IgG1 and IgE. Although EC sensitization with SEB resulted in selective depletion of SEB-specific T-cell receptor Vbeta8+ cells from the spleen and sensitized skin, splenocytes from SEB-sensitized mice secreted relatively more IL-4 and less IFN-gamma than did saline-sensitized controls, consistent with Th2 skewing of the systemic immune response to the superantigen.

CONCLUSION

These results suggest that EC exposure to superantigens skews the immune response toward Th2 cells, leading to allergic skin inflammation and increased IgE synthesis that are characteristic of AD.

Therapy and prophylaxis of inhaled biological toxins

This review highlights the current lack of therapeutic and prophylactic treatments for use against inhaled biological toxins, especially those considered as potential biological warfare (BW) or terrorist threats. Although vaccine development remains a priority, the use of rapidly deployable adjunctive therapeutic or prophylactic drugs could be life-saving in severe cases of intoxication or where vaccination has not been possible or immunity not established. The current lack of such drugs is due to many factors. Thus, methods involving molecular modelling are limited by the extent to which the cellular receptor sites and mode of action and structure of a toxin need to be known. There is also our general lack of knowledge of what effect individual toxins will have when inhaled into the lungs - whether and to what extent the action will be cell specific and cytotoxic or rather an acute inflammatory response requiring the use of immunomodulators. Possible sources of specific high-affinity toxin antagonists being investigated include monoclonal antibodies, selected oligonucleotides (aptamers) and derivatized dendritic polymers (dendrimers). The initial selection of suitable agents of these kinds can be made using cytotoxicity assays involving cultured normal human lung cells and a range of suitable indicators. The possibility that a mixture of selected antibody, aptamer or dendrimer-based materials for one or more toxins could be delivered simultaneously as injections or as inhaled aerosol sprays should be investigated.

Flare-up reaction on murine contact hypersensitivity. III. Effect of staphylococcal enterotoxin B

Staphylococcal enterotoxin B (SEB), a bacterial superantigen, is known as an immunomodulator because it activates an extremely large number of T-cells, and induces the production of large amounts of cytokines. In this study, we examined the effects of SEB on the contact hypersensitivity reaction (CHR). BALB/c mice were first sensitized through haptens applied to the back, and CHR was then induced through challenge to the left ear using the same haptens. SEB was administered intravenously 4 weeks later, causing a flare-up, peaking at 24 h post-administration, in the left ear that had previously exhibited CHR. This flare-up reaction was hapten non-specific, and was inhibited by anti-mouse tumor necrosis factor (TNF)-alpha antibodies. The flare-up was also suppressed by the oral administration of cyclosporin A prior to the administration of SEB. These results suggest that SEB induces a flare-up of CHR via the production of TNF-alpha.

Staphylococcus aureus: colonizing features and influence of an antibacterial treatment in adults with atopic dermatitis

BACKGROUND

The skin of up to 100% of patients with atopic dermatitis (AD) is colonized with Staphylococcus aureus. Of all S. aureus strains isolated from lesional skin, up to 65% have been shown to produce exotoxins with superantigenic properties. Patients colonized with S. aureus have been treated with antibiotics in several open and double-blind placebo-controlled studies, with conflicting results. These studies did not consider the anterior nares as a reservoir of S. aureus, or the possibility of transmission between patients and their contacts. Moreover, adult patients have not so far been investigated.

OBJECTIVES

To investigate the colonizing features of S. aureus in adults with AD and in their contacts, and the effect of an antimicrobial treatment of the patients and their partners.

METHODS

Swabs were taken from the skin and anterior nares of 66 adults with AD. S. aureus strains were screened for the production of exotoxins in 32 patients. Ten patients (two with toxigenic strains, eight with non-toxigenic strains) were treated orally with cefalexin, chlorhexidine ointment was applied to the skin, and the anterior nares were treated with mupirocin ointment. A bath containing potassium permanganate was taken daily. In addition, their partners were treated topically.

RESULTS

Sixty-two of 66 patients (94%) were carriers of S. aureus, and mostly harboured the bacteria on both skin and anterior nares. Ten of 32 (31%) patients were colonized with toxigenic strains. The Severity Scoring in AD (SCORAD) score decreased in nine of 10 patients who received antimicrobial treatment (P < 0.001), and this effect was more pronounced in patients with a baseline SCORAD > 50.

CONCLUSIONS

S. aureus may play an important role as an aggravating factor in adults with AD, as antimicrobial treatment leads to a significant improvement of AD in patients who are colonized with the bacterium.

Staphylococcal exotoxins exert proinflammatory effects through inhibition of eosinophil apoptosis, increased surface antigen expression (CD11b, CD45, CD54, and CD69), and enhanced cytokine-activated oxidative burst, thereby triggering allergic inflammatory reactions

BACKGROUND

Staphylococcus aureus colonization of the skin represents a potent trigger factor of atopic dermatitis. Our previous studies demonstrated that in atopic dermatitis eosinophil apoptosis is significantly delayed.

OBJECTIVE

We sought to investigate the effect of staphylococcal exotoxins (SETs) on eosinophil apoptosis and functional activities.

METHODS

Apoptotic eosinophils were investigated by determining their hypodiploid DNA peak. Eosinophil surface-antigen expression and intracellular production of hydrogen peroxide were assessed by means of flow cytometric analysis and respiratory burst by lucigenin-dependent chemiluminescence.

RESULTS

The SETs SEA, SEB, SEC, and toxic shock syndrome toxin 1 significantly inhibited eosinophil apoptosis in a manner comparable with that of high concentrations of IL-3. The LPS inhibitor polymyxin B was found to significantly inhibit LPS-mediated, but not SET-mediated, inhibition of apoptosis. Neither SETs nor LPS was able to modulate eosinophil surface expression of CD9, CD11a, CD16, CD40, CD44, or CD63. However, 24- and 48-hour incubation with all SETs, but not with LPS, significantly upregulated expression of CD11b and CD45 in a manner similar to that of IL-3, whereas dexamethasone induced a downregulation. Moreover, all SETs resulted in a significant upregulation of CD54 after 24 hours but not after 48 hours. Interestingly, CD69 was upregulated by means of IL-3 and SEB only. Neither direct stimulation of eosinophils nor 24-hour incubation with SETs or stimulation with SETs after a 24-hour prestimulation with IL-3, IL-5, or GM-CSF resulted in a significant extracellular production of reactive oxygen species or in a significant production of intracellular hydrogen peroxide. However, SEB and toxic shock syndrome toxin 1 were able to enhance cytokine-induced respiratory burst.

CONCLUSION

Taken together, our data demonstrate that SETs may modulate the course of the allergic inflammatory response through modulation of potent eosinophil effector functions. This may be of particular importance in atopic dermatitis, in which the skin is regularly colonized with SET-producing S aureus.

Evidence for the involvement of bacterial superantigens in psoriasis, atopic dermatitis, and Kawasaki syndrome

A growing body of evidence implicates streptococcal and staphylococcal superantigens in the development of psoriasis, atopic dermatitis and Kawasaki syndrome. In each of these illnesses, an abnormal state of immunologic activity is observed. Superantigens, which have a unique ability to activate large numbers of lymphocytes, are likely to contribute to these disorders in a number of ways. The demonstrated activities of bacterial superantigens include increasing the number of circulating lymphocytes, with activation of autoreactive subsets, upregulation of tissue homing receptors on circulating lymphocytes, and local activation of immune cells within affected tissues. Through these and other mechanisms, superantigens have a proven ability to induce high levels of inflammatory cytokines and/or initiate autoimmune responses that contribute to the development of skin and vascular disorders. Though development of the illnesses discussed in this review are highly complex processes, superantigens may well play a critical role in their onset or maintenance. Understanding superantigen function may elucidate potential therapeutic strategies for these disorders.

Role of staphylococcal superantigens in atopic dermatitis: from colonization to inflammation

OBJECTIVE

This review article has been prepared in order to enable the readers to understand the role of staphylococcal superantigens (SsAgs) in atopic dermatitis (AD).

DATA SOURCES

MEDLINE literature search was performed for obtaining references. Recent reviews, research articles, poster presentations, and letters (to the editor) were meticulously reviewed.

RESULTS

(1) SsAgs contribute to the pathogenesis of cutaneous inflammation in AD with five potential mechanisms: Direct stimulation of antigen presenting cells (APCs) and keratinocytes. Stimulation of T cell proliferation [superantigenic binding to T cell receptor (TCR)]. Expansion of skin-homing cutaneous lymphocyte antigen (CLA) (+) T cells. The role of superantigens as allergens. Reduction of apoptosis. (2) Effectiveness of antibiotic therapy in AD patients without signs of bacterial infection is still under discussion. If signs of skin infection are present, antibiotic therapy (topical/oral) may help exacerbations of AD. Prolonged topical/oral antibiotic therapy, however, may cause development of antibiotic-resistant strains of Staphylococcus aureus (SA).

CONCLUSIONS

Atopic dermatitis is a genetically determined, chronically relapsing, inflammatory skin disease which has many aspects and a complex immunopathogenesis involving both immediate and cellular immune responses. While the pathogenic role of SsAgs may not be of primary importance, SsAgs appear to be one of the important triggering factors that contribute to the cutaneous inflammation in AD. We suggest that staphylococcal colonization does not always mean SsAg-mediated inflammation, and anti-staphylococcal treatment should be considered in cases with signs of bacterial infection.

Nitric Oxide Participates in the Recovery of Normal Jejunal Epithelial Ion Transport Following Exposure to the Superantigen, Staphylococcus aureus Enterotoxin B

Bacterial superantigens (SAgs) are potent T cell activators. Mice treated 4 h previously with the SAg, Staphylococcus aureus enterotoxin B (SEB), display reduced ion transport (assessed by short circuit current) responses to prosecretory stimuli, which normalize 24 h posttreatment. Here, mice were treated with SEB alone or in combination with an inhibitor of the inducible form of NO synthase (iNOS), l-NIL. Subsequently, jejunal iNOS expression was detected by immunohistochemistry, ion transport was evaluated in Ussing chambers, and serum levels of TNF-α and IFN-γ were measured by ELISA. SEB-treated mice had increased epithelial iNOS immunoreactivity, and numerous iNOS-positive CD3+ T cells occurred in their mucosa and submucosa. Concomitant treatment with l-NIL did not affect the reduced short circuit current responsiveness to electrical nerve stimulation or the prosecretory agents, carbachol and forskolin, that occurred 4 h post-SEB (5 μg) treatment. However, Isc responses in l-NIL- plus SEB-treated mice were still significantly reduced 24 h posttreatment, indicating a role for NO in the restoration of normal ion transport following exposure to SAgs. The prolongation of epithelial ion transport abnormalities correlated with elevated serum levels of TNF-α and IFN-γ in mice treated 24 h previously with l-NIL plus SEB compared with those in controls and SEB-only-treated mice. Additionally, mice treated with l-NIL plus SEB and TNF-α- or IFN-γ-neutralizing Abs displayed normal jejunal ion transport characteristics 24 h posttreatment. We conclude that NO mobilization is important in the homeostatic recovery response following immune stimulation by SAgs and that the beneficial effect of NO in this model system is probably via regulation of TNF-α and IFN-γ production.

The role of superantigens in human diseases: therapeutic implications for the treatment of skin diseases

Although it is well established that immune mechanisms contribute to the pathogenesis of chronic inflammatory skin diseases such as atopic dermatitis (AD) and psoriasis, the actual events that trigger the immunological pathways resulting in these skin diseases are not well understood. Colonization and infection with Staphylococcus aureus and streptococci has been reported to exacerbate AD and psoriasis. Recent studies demonstrating that bacterial toxins can act as superantigens provide mechanism(s) by which S. aureus and streptococci could mediate an inflammatory skin lesion that consists predominantly of activated T-cells and monocytes. This review will explore the diverse mechanisms by which bacterial superantigens can induce skin inflammation following systemic or local infection. These observations provide a new direction for the development of novel approaches for the treatment of skin inflammation.

Toxin-mediated streptococcal and staphylococcal disease

After several decades of seemingly decreasing virulence, streptococcal and staphylococcal infections have reemerged as a major source of morbidity and mortality. Within the past 2 decades, not only have well-established diseases such as rheumatic fever begun to reappear. but also many new entities, such as toxic shock syndrome, streptococcal toxic shock syndrome, recurrent toxin-mediated perineal erythema, and recalcitrant erythematous desquamating disorder have been described. Central to the renewed importance of these bacteria has been the production of circulating toxins, which often function as superantigens in causing the clinical manifestations, morbidity and mortality associated with these diseases.

Staphylococcal enterotoxin B inhibits the production of interleukin-4 in a human mast-cell line HMC-1

Staphylococcal enterotoxins belong to the recently characterized group of immunocytotropic bacterial superantigens that are potent mitogens for human T cells. Superantigens are presented, but without intracellular processing, to T cells by monocyte/macrophages, Langerhans' cells and keratinocytes via the class II major histocompatibility complex (MHC) molecules. Superantigens have been demonstrated to act as potent inducers of several proinflammatory cytokines in the antigen-presenting cells such as interleukin-1 (IL-1) and tumour necrosis factor-alpha (TNF-alpha). As mast cells participate in the pathogenesis of several inflammatory skin disorders such as atopic dermatitis (AD), which is often aggravated by staphylococcal infections, we studied the effect of staphylococcal enterotoxin B (SEB) superantigen on the histamine release and IL-4 expression in a human mast-cell line (HMC-1). Incubation of SEB (50 micrograms/ml) with HMC-1 cells for 45 min, could not induce any histamine release. The HMC-1 cells were also stimulated with various concentrations of SEB (0, 1, 10, 20, 50 micrograms/ml) for 1, 2, 3 and 4 days. Clear dose-dependent inhibition of IL-4 protein production and release was observed on day 4 without any observed effect on cell viability. Compared with unstimulated HMC-1 cells, after 50 micrograms/ml SEB stimulation, the IL-4 mRNA levels decreased steadily in the 2, 6, 18 and 24 hr samples in repeated experiments as measured with the reverse transcription polymerase chain reaction (RT-PCR) method. In comparison, a biphasic decrease in TNF-alpha expression was found. Our results show that an human leukaemic mast cells, superantigen stimulation downregulates the production of IL-4.

Follicular mucinosis associated with scarring alopecia, oligoclonal T-cell receptor V beta expansion, and Staphylococcus aureus: when does follicular mucinosis become mycosis fungoides?

A diagnosis of alopecia mucinosa, occurring as a single scalp lesion, was made in a 40-year-old white woman who had a history of trauma. Follicular mucinosis, Staphylococcus aureus, and oligoclonal expansion of the T-cell receptor V beta chain genes 6 and 7 were present in the skin. Epidermotropic T-cell skin diseases with oligoclonal T-cell proliferations may be the result of HLA- and cytokine-determined reaction patterns to persistent antigens.

Streptococcal pyrogenic exotoxin A (SPE A) superantigen induced production of hematopoietic cytokines, IL-12 and IL-13 by human peripheral blood mononuclear cells

A quantitative and kinetic study of the release of the hematopoietic cytokines IL-3, IL-5 and GM-CSF, the immunoregulatory cytokine IL-12 heterodimer (and its p40 subunit) and IL-13 by human peripheral blood mononuclear cells (PBMC) stimulated in vitro with the superantigen streptococcal pyrogenic (erythrogenic) exotoxin A (SPE A) from Streptococcus pyogenes is reported. PBMC were stimulated in parallel with heat-killed group A streptococcal cells, E. coli lipopolysaccharide (LPS) and with concanavalin A (Con A) in certain experiments for comparative purposes. The cytokines were assayed in the supernatant fluids by ELISA. IL-13 expression was also determined by a quantitative competitive PCR. IL-3, IL-5, GM-CSF, IL-12 p40, IL-12 heterodimer and IL-13 expression was induced by SPE A in a time- and dose-dependent manner in rather substantial amounts except the IL-12 heterodimer, which was released in small quantities. In contrast to SPE A, IL-3, IL-5 and IL-13 were not or poorly elicited by streptococcal cells or LPS whereas these two stimulants induced relatively high amounts of GM-CSF. Interestingly, both IL-12 p40 and IL-12 heterodimer were released in much higher amounts by streptococcal cells. Con A induced IL-3, IL-5, GM-CSF and IL-13 production in amounts comparable to those elicited by SPE A. The possible pathophysiological relevance of the elicitation by SPE A and streptococcal cells of these cytokines is discussed.

Expression of bacterial superantigen genes in mice induces localized mononuclear cell inflammatory responses

Bacterial superantigens are potent T cell activators, and superantigen proteins have been injected into mice and other animals to study T cell responses in vivo. When superantigen proteins are injected, however, the T cell stimulatory effects cannot be confined to specific tissues. Therefore, to target superantigen expression to specific tissues, we used gene transfer techniques to express bacterial superantigen genes in mammalian cells in vitro and in tissues in vivo. Murine, human, and canine cells transfected with superantigen genes in vitro all produced superantigen proteins both intracellularly and extracellularly, as assessed by bioassay, immunocytochemistry, and antigen ELISA. Superantigens produced by transfected eukaryotic cells retained their biologic specificity for T cell receptor binding. Intramuscular injection of superantigen plasmid DNA in vivo induced an intense intramuscular mononuclear cell infiltrate, an effect that could not be reproduced by intramuscular injection of superantigen protein. Intradermal and intravenous injection of superantigen DNA induced cutaneous and intrapulmonary mononuclear cell inflammatory responses, respectively. Thus, superantigen genes can be expressed by mammalian cells in vivo. Superantigen gene therapy represents a novel method of targeting localized T cell inflammatory reactions, with potential application to treatment of cancer and certain infectious diseases.

An immunohistochemical study of the lesions of demodicosis in the dog

Histopathological and immunohistochemical examination of skin biopsies from 32 dogs with demodicosis is reported. There was no association between the different clinical presentations of the disease and the histopathological character of the biopsies, which included absence of inflammation (n = 2), dominant perifolliculitis (n = 11), interface mural folliculitis (n = 7), mural folliculitis (n = 1), furunculosis (n = 10) and nodular dermatitis (n = 1). In eight of 32 biopsies colonies of coccoid bacteria or Malassezia pachydermatis-like yeasts were observed. IgG-bearing plasma cells were found in similar numbers in the inflammatory infiltrates of all types of histological lesion, and were invariably more numerous than IgM or IgA plasma cells. The IgG plasma cells were largely IgG4 in lesions of perifolliculitis, but consisted of a mixture of IgG2 and IgG4 where folliculitis or furunculosis was present. CD3+T lymphocytes were prominent within the interface infiltrates of follicular epithelium and also within the lesions of furunculosis. Dermal inflammatory cells and epidermal Langerhans cells expressing MHC Class II were observed in similar number in all types of lesion. The study demonstrated an active local cutaneous immune response in canine demodicosis, which increased as the dermal pathology progressed from perifolliculitis to furunculosis.