Possible influences of Staphylococcus aureus on atopic dermatitis — the colonizing features and the effects of staphylococcal enterotoxins

BACKGROUND: Heavy colonization of atopic dermatitis (AD) with Staphylococcus aureus is well documented. This phenomenon suggests that S. aureus in AD lesions influences the disease processes of AD. OBJECTIVE: We describe the importance of the presence of S. aureus and staphylococcal enterotoxins A and B (SEA, SEB) in AD lesions. METHODS: We investigated the colonizing features of S. aureus in AD lesions using electron microscopy, the distribution of SEB in the eczematous skin of AD using immunofluorescence, the effects of SEA and SEB on normal human epidermal keratinocytes in organ culture, and the presence of specific IgE antibodies to SEA and/or SEB in serum of AD patients by enzyme immunoassay. RESULTS: S. aureus in AD lesions colonized on and in the horny layers of the eczematous skin. SEB produced by S. aureus was distributed mainly on the dermal-infiltrated cells, especially on eosinophils. SEA and SEB stimulated expression of ICAM-1 and HLA-DR in normal human keratinocytes. More than half of the AD patients in the present study had specific IgE antibodies to SEA and/or SEB in their serum. CONCLUSION: S. aureus and SEs have important roles in the exacerbation and prolongation of AD.     

Comparative study of the biological properties of plasmid and natural human interferons

A comparative study of biological properties of natural and plasmid human interferons was carried out. Natural and leukocyte interferons: alpha (induced by Newcastle disease virus) and gamma (induced by staphylococcal enterotoxin A) as well as natural fibroblastic beta interferon induced by poly(I) X poly(C) were studied in comparison with plasmid interferons alpha-F and alpha-F/D obtained from recombinant bacteria. Antigenic determinants of plasmid interferons alpha-F and alpha-F/D were found to be identical with those of natural and alpha-interferon of man and to differ from those of natural human alpha- and beta-interferons. Both plasmid interferons demonstrated the kinetics of development of the state of resistance to viruses in a human diploid cell culture typical of alpha-interferon but not of gamma-interferon from human leukocytes. Plasmid and natural alpha-interferons have similar anticellular activity for human tumor HeLa cells, similarly activate natural human killer cells and are similarly stabilized in the presence of 0.01 M lantan chloride. All these data permit a conclusion that plasmid human interferons alpha-F and alpha-F/D are analogous and close to the total preparation of natural alpha-interferon from human leukocytes. On the other hand, the range of cells sensitive to the antiviral effect of alpha-F and alpha-F/D interferons is wider than for leukocyte alpha-interferon, and stability on storage and heating is higher.     

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

It has been well established that bacterial superantigens lead to the induction and aggravation of chronic inflammatory skin diseases. We investigated the clinical significance of serum specific immunoglobulin E (lgE) to the staphylococcal superantigens staphylococcal enterotoxin A (SEA), staphylococcal enterotoxin B (SEB), and toxic shock syndrome toxin (TSST)-1 in patients with chronic urticaria (CU), focusing on the differences in these prevalences between aspirin-intolerant CU (AICU) and aspirin-tolerant CU (ATCU) patients. Aspirin sensitivity was confirmed by oral aspirin provocation test. There were 66 patients AICU and 117 patients ATCU in the study. Serum IgE antibodies specific for SEA, SEB, and TSST-1 were measured by the ImmunoCAP test and the patients were compared with 93 normal controls (NC). The prevalences of serum specific IgE to staphylococcal superantigens were significantly higher in CU than in NC patients (IgE to SEA, 13.7% vs. 5.4%; IgE to SEB, 12.0% vs. 4.3%; IgE to TSST-1, 18.0% vs. 6.5%; p<0.05, respectively). The patients with specific IgE to SEA, SEB, and TSST-1 had higher serum total IgE levels and higher rates of atopy. Significant associations were noted between the prevalence of specific IgE to SEA and SEB and the HLA DQB1*0609 and DRB1*1302 alleles in the AICU group. We confirmed that a sub-population of patients with CU possesses serum IgE antibodies to SEA, SEB, and TSST- 1. Particularly, the IgE immune response to TSST-1 is associated with aspirin sensitivity in CU patients.     

Severe atopic dermatitis is associated with sensitization to staphylococcal enterotoxin B (SEB)

BACKGROUND: Staphylococcus aureus has been identified as a possible trigger factor in atopic dermatitis (AD). Some 30-60% of S. aureus strains isolated from patients with AD are able to produce exotoxins with superantigenic properties, mostly staphylococcal enterotoxins A, B, C, and D (SEA-D) and toxic shock syndrome toxin-1 (TSST-1). Recently, it was demonstrated that the presence of IgE antibodies to SEA and SEB is correlated with the severity of skin lesions in children with AD. To determine the relevance of staphylococcal enterotoxins in adult patients with AD, we investigated the relationship between the severity of skin lesions and sensitization to SEA and SEB. METHODS: Clinical severity was determined by the SCORAD index. Circulating IgE antibodies to SEA and SEB, serum eosinophil cationic protein (ECP) levels, and urine eosinophil protein X (EPX) levels were measured. RESULTS: The skin condition was significantly worse in patients sensitized to SEB than in unsensitized patients. Serum ECP and urine EPX levels were found to be significantly higher in SEB-sensitized patients, confirming the higher degree of cutaneous inflammation. CONCLUSIONS: Our results demonstrate a relationship between severity of skin lesions and sensitization to SEB in adult patients with AD, but a relationship between disease activity and sensitization to SEA could not be shown.     

Antiproliferative effects of recombinant alpha- and gamma-interferons on cultured human keratinocytes

To extend our initial observation that recombinant gamma-interferon induced expression of class II major histocompatibility (HLA-DR) antigen on normal cultured human keratinocytes, we studied the antiproliferative effects of recombinant alpha- and gamma-interferons. Both interferons reduced the number of attached cells (dose range 10-10(3) units/ml; 7.1 X 10(-11) to 7.1 X 10(-9) M) and gamma-interferon was 100 times more potent than alpha. This effect did not require the presence of Langerhans cells. gamma-Interferon reduced total cell production during the first week without increasing the percentage of cells shed. During the second week, gamma-interferon also increased the percentage of cell shedding. Although 10(2) units/ml of gamma-interferon was maximal for HLA-DR expression by cultured keratinocytes, there was increasing reduction of attached cells between 10(2) to 10(3) units/ml. The demonstration that recombinant gamma-interferon induces HLA-DR expression and also inhibits keratinocyte proliferation in vitro at nanomolar concentration expands the growing list of normal cells whose biologic function may be influenced by this lymphokine in vivo.     

Prevalence of serum IgE antibodies to the Staphylococcus aureus enterotoxins (SAE, SEB, SEC, SED, TSST-1) in patients with persistent allergic rhinitis

BACKGROUND: Enterotoxins produced by Staphylococcus aureus and their specific IgE antibodies were thought to be important in worsening atopic dermatitis. However, few studies have documented an association between S. aureus or its exotoxins and exacerbations of upper airway/nasal disease. In the current study, we determined the prevalence of serum-specific IgE towards staphylococcal enterotoxin A, B, C, D (SEA, SEB, SEC, SED) and toxic shock syndrome toxin 1 (TSST-1) in patients suffering from rhinitis and/or asthma due to allergy. Therefore, we examined whether SEA, SEB, SEC, SED and TSST-1 were important in worsening the clinical status of patients allergic to house dust mites by means of assessing serum eosinophil cationic protein (ECP), which is thought to be a reliable marker of asthma and rhinitis severity. METHODS: 198 patients with persistent allergic rhinitis and/or asthma due to house dust mites were evaluated. Specific IgE towards SEA, SEB, SEC, SED, TSST-1, timothy grass and birch pollen recombinant allergens, and other aeroallergen extracts from common allergen sources were evaluated by the Pharmacia CAP System. Serum ECP was assessed, too. RESULTS: The percentages of sensitization to staphylococcal enterotoxins of 198 house dust mite-allergic patients were as follows: TSST-1-specific IgE 24.7% (n=49), SEC-specific IgE 22.2% (n=44), SEB-specific IgE 15.1% (n=30), SEA-specific IgE 9.1% (n=18), and SED-specific IgE 5.5% (n=11). Out of 198 individuals allergic to house dust mites 136 patients suffering from persistent rhinitis were subdivided into two subgroups: 53 patients with serum-specific IgE to at least one staphylococcal enterotoxin and 83 patients without specific IgE towards staphylococcal enterotoxins. Patients sensitive to staphylococcal enterotoxins had higher serum ECP levels than patients lacking specific IgE to SEA, SEB, SEC, SED and TSST-1(geometric mean 24.3 vs. 16.6 microg/100 ml; p=0.029), as well as total IgE levels (geometric mean 564 vs. 161 kU/l, p=0.00063) and specific IgE to Dermatophagoides pteronyssinus (geometric mean 16.7 vs. 6.6 kU/l; p=0.0235) and Dermatophagoides farinae (geometric mean 18.6 vs. 7.8 kU/l; p=0.0246). CONCLUSION: A status of sensitization to staphylococcal enterotoxins seems to be a factor increasing serum ECP, which is thought to be a reliable marker of clinical severity of allergic disease. Therefore, the evaluation of SEA, SEB, SEC, SED and TSST-1-specific IgE antibodies may have additional significance for the prognosis of persistent allergic diseases of the upper airway.     

Induction of clonal anergy by oral administration of staphylococcal enterotoxin B

The staphylococcal enterotoxin is a major cause of food poisoning. The bacterial substance stimulates T cells expressing specific Vβ T cell receptors (TcR) and is termed “the superantigen”. We have previously demonstrated that intravenous injection of staphylococcal enterotoxin B (SEB) induces functional unresponsiveness (anergy) of reactive T cells as well as a partial deletion by activationinduced programmed cell death. In the present study, we examined the effect of oral administration of SEB in mice. Our results indicate that spleen T cells from SEB-primed mice are hyporesponsive to SEB stimulation in vitro, but the response to SEA was normal. Vβ8⁺ T cells purified from SEB-primed mice did not respond to stimulation of TcR. This SEB-specific unresponsiveness could not be reversed by exogenous interleukin-2, but was partially reversed by phorbol 12-myristate 13-acetate. Activation of mitogen-activated protein kinase during TcR-mediated stimulation was significantly inhibited in anergic T cells. Although the mechanisms of oral tolerance are not well understood, these results show that oral administration of SEB induce clonal anergy in peripheral T cells.     

双抗体夹心ELISA检测SEB方法的建立及在不同基质中检测的应用

目的:建立检测SEB的双单克隆抗体(mAb)夹心ELISA,并检测在多种基质中SEB的敏感性。方法:制备、纯化抗SEBmAbB4和D6。D6mAb标记辣根过氧化物酶(HRP)作为检测抗体,B4mAb作为包被抗体。结果:成功建立了敏感、特异检测SEB的ELISA方法,检测抗体稀释液和小牛血清中SEB,检测灵感度0.2μg/L,定量线性范围0.78～12.5μg/L,r2=0.992,批间变异系数(CV)<10%,回收率80%～110%。检测50g/L脱脂牛奶、尿液和自来水中的SEB,灵敏度0.39μg/L,定量线性范围0.78～25μg/L,r2=0.997。与SEA和SECl无交叉反应。结论:本方法测量准确,灵敏度高,特异性好,在食品工业和临床标本检测中有广阔的应用前景。     

甲胎蛋自对H－22腹水肝癌小鼠脾淋巴细胞增殖的影响

用抗甲胎蛋白（ａｎｔｉ－ＡＦＰ）的单克隆抗体亲和层析柱从脐带血中提纯ＡＦＰ。通过ＭＴＴ法体外观察人ＡＦＰ对Ｈ－２２腹水肝癌小鼠脾淋巴细胞增殖的影响。结果表明，Ｈ－２２小鼠脾淋巴细胞经不同浓度ＡＦＰ（１２．５－１００μｇ／ｍｌ）处理后，对刀豆素Ａ（ＣｏｎＡ）诱导的增殖反应明显减弱，抑制率达３９．８％－６６％，并有一定的浓度依赖关系；而用不同浓度的人血清白蛋白（ＨＳＡ，３．１～１００μｇ／ｍｌ）体外处理，则无明显抑制作用。另外，我们用反证法证实，ＡＦＰ抗体（５５、１１０μｇ／ｍｌ）能明显阻断人ＡＦＰ（５０、１００μｇ／ｍｌ）对Ｈ－２２小鼠脾淋巴细胞增殖的抑制作用。     

IL-5 Promoter Polymorphism Enhances IgE Responses to Staphylococcal Superantigens in Adult Asthmatics

Interleukin 5 (IL-5) is a key cytokine involved in the induction of T-helper type 2 (Th2) responses in the asthmatic airway. We investigated IL-5 genetic polymorphisms associated with asthma phenotypes, including IgE responses to staphylococcal enterotoxins A and B (SEA and SEB, respectively), in asthmatics. Adult asthmatics (n=310) and normal controls (n=160) were enrolled in the present study. Serum total and specific IgE to SEA and SEB were measured. Two IL-5 polymorphisms, -746A>G and +4499T>G, were genotyped using the primer-extension method. There were no significant differences in genotype or haplotype frequencies of these polymorphisms between the two groups. Asthmatics carrying the AG/GG genotype at -746A>G had a significantly higher prevalence of serum specific IgE to SEA (P=0.008), higher total IgE levels (P=0.014), and lower PC20 methacholine levels (P=0.002) compared to those with the AA genotype. These findings suggest that the IL-5 promoter polymorphism at -746A>G enhances serum total and specific IgE responses to SEA, which may augment airway hyperresponsiveness in adult asthmatics.     

The Prevalence of Serum Specific IgE to Superantigens in Asthma and Allergic Rhinitis Patients

Staphylococcus aureus is the most common bacterium present in upper respiratory tract, and the toxins it produced are involved in allergic inflammation pathogenesis. In this study, we investigated the clinical significance of IgE in association with staphylococcal superantigens in allergic asthma with rhinitis (BAwAR) and allergic rhinitis alone (AR). We recruited 100 patients with BAwAR (group I), 100 patients with AR (group II), and 88 healthy controls (group III). Patients were clinically diagnosed by physicians, and were sensitized to house dust mites. Specific IgE antibodies to staphylococcal superantigen A (SEA), B (SEB), and toxic shock syndrome toxin-1 (TSST-1) were measured using the ImmunoCAP system. Other clinical parameters were retrospectively analyzed. All specific IgE antibodies to SEA, SEB, and TSST-1 were detected most frequently in group I (22%, 21%, and 27%), followed by group II (11%, 14%, and 21%) and group III (4.5%, 3.4%, and 2.3%). Absolute values of serum specific IgE to SEA, SEB, and TSST-1 were also significantly higher in group I (0.300±1.533 kU/L, 0.663±2.933 kU/L, and 0.581±1.931 kU/L) and group II (0.502±2.011 kU/L, 0.695±3.337 kU/L, and 1.067±4.688 kU/L) compared to those in group III (0.03±0.133 kU/L, 0.03±0.14 kU/L, and 0.028±0.112 kU/L). The prevalence of serum specific IgE to SEA was significantly higher in group I compared to group II (P=0.025). Blood eosinophil counts were significantly higher in patients with specific IgE to SEA or SEB, and higher serum levels of specific IgE to house dust mites were noted in patients with specific IgE to TSST-1. In conclusion, the present study suggested that IgE responses to staphylococcal superantigens are prevalent in the sera of both BAwAR and AR patients. This may contribute to an augmented IgE response to indoor allergens and eosinophilic inflammation.     

超抗原对NK细胞CD226分子表达与功能的调节

目的研究超抗原对NK细胞CD226分子表达与功能的调节。方法以超抗原金黄色葡萄球菌肠毒素A/B(SEA/B)活化PBMC为模型,应用双重免疫荧光染色和流式细胞术分析,观察CD226分子在NK细胞上的变化;采用51Cr释放实验,观察NK细胞在超抗原作用下杀伤功能的改变;利用激光共聚焦显微镜,观察CD226分子在NK细胞杀伤相的分布。结果在静止PBMC中,CD56 NK细胞的百分率为12.3%,CD56 CD226 细胞仅为1.4%。当效靶比为5∶1时,NK细胞对K562细胞的杀伤率为(3.2±0.2)%。当0.1mg/LSEA或SEB刺激PBMC1d后,CD56 NK细胞的百分率分别为13.5%和14.1%,CD226在NK细胞上的表达水平明显升高,且主要表达在CD56dim细胞上。在刺激第2天,SEA组CD56 CD226 占CD56 细胞69.1%,SEB组CD56 CD226 占CD56 细胞64.3%。刺激第3天,CD226在NK细胞上的表达水平均较第2天明显下降。在超抗原0.1mg/L作用3d中,SEA组和SEB组NK细胞杀伤率均明显高于同期未刺激组NK细胞的杀伤率及新鲜分离NK细胞的杀伤率(P<0.05),在作用的第2天,SEA组和SEB组杀伤率均达到峰值分别为(82.3±6.9)%和(80.6±7.5)%。激光共聚焦结果显示,CD226分子与LFA-1分子共定位于NK细胞与K562细胞的接触部位。结论超抗原SEA和SEB可提高NK细胞杀伤活性,可能与其促进CD226分子在NK细胞上的表达相关,CD226分子可能参与NK细胞免疫突触的形成。     

Comparison of serum specific IgE antibodies to staphylococcal enterotoxins between atopic children with and without atopic dermatitis

BACKGROUND: The skin of patients with atopic dermatitis (AD) exhibits a striking susceptibility to colonization and infection by Staphylococcus aureus. The exotoxins secreted by S. aureus can act as superantigens and classic allergens, inducing the production of functionally relevant specific IgE antibodies. The aim of this study was to compare the levels and positive rates of serum staphylococcal enterotoxin A (SEA)- and staphylococcal enterotoxin B (SEB)-specific IgE between atopic children with and without AD. METHODS: Sixty children with AD, 55 children with respiratory allergy without AD, and 24 nonatopic healthy children were studied. The levels and positive rates of serum SEA- and SEB-specific IgE were compared among three groups. The correlation between the levels or positive rates of serum SEA/SEB-specific IgE and the severity of AD or the presence of previous skin infections was studied. RESULTS: The children with AD had significantly higher levels and positive rates of serum SEA- and SEB-specific IgE than the atopic children without AD (P < 0.001) and the nonatopic children (P < 0.001). There was no significant difference in the levels and positive rates of serum SEA- and SEB-specific IgE between the atopic children without AD and the nonatopic children. With or without adjustment for the potential confounding effect of total serum IgE levels, the levels and positive rates of serum SEA- and SEB-specific IgE were significantly correlated with severity of AD (P <0.005), but they were not significantly different between AD children with and without previous skin infections. CONCLUSIONS: SEA and SEB may contribute to chronic inflammation and exacerbation of AD through the IgE-mediated immune response.     

Schistosoma japonicum soluble egg antigens: Separation by con a chromatography and immunoaffinity purification

A crude soluble egg antigen (SEA) preparation from Schistosoma japonicum eggs was used for immunoabsorbent fractionation of anti-SEA antibody. Anti-SEA antibodies were isolated from serum pooled from mice infected with S. japonicum for 7 weeks and from mice infected for 12 weeks. These anti-SEA immunoglobulins were then used for immunoabsorbent fractionation of specific SEA antigens. Crude SEA was also partially purified by Con A chromatography. Crude SEA, the Con A fraction, an antigen isolated with 7 week infection serum, and antigens isolated with 12 week infection serum were analysed by immunoprecipitation and SDS polyacrylamide gel electrophoresis.     

Locally superantigen-activated peritoneal cytolytic T lymphocytes belong to the CD8+ CD45RC- subset and lyse MHC class II+ tumor cells.

Bacterial encoded superantigens (SA) are capable of activating and targeting cytolytic human and mouse T lymphocytes (CTL) to lyse major histocompatibility complex class II positive (MHC class II+) target cells. In this study both in vitro and in vivo activated rat CTL were directed against MHC II+ tumor targets by bacterial encoded SA. Polyclonal in vitro activation of rat peripheral blood T lymphocytes generated CTL capable of killing MHC class II+ human BSM cells coated by staphylococcal enterotoxin (SE) -A, -E, -D, and TSST-1 but not by SEB or SEC1-3. Allo selective peritoneal CTL generated by intraperitoneal stimulation with allogeneic spleen cells were directed against BSM cells by SEA, -D, and -E but not by SEB, SEC1-3 or TSST-1. Based on the above observations, and in order to locally activate CTL, SEA was chosen for in vivo priming of rats by intraperitoneal inoculation of the toxin. SEA injection generated highly cytolytic CTL, and maximum cytolytic responses were seen at 50-250 micrograms SEA per animal with a peak in response 48-72 hours after injection of the toxin. The cytolytic activity of peritoneal SEA reactive effector cells was confined to the TCR alpha beta+ CD4- CD8+ CD45RC- cell population. MHC class II- colon carcinoma cells were insensitive to lysis by SEA reactive CTL but colon carcinoma cells induced to express MHC class II by interferon-gamma (IFN-gamma) treatment were efficiently lysed in the presence of SEA. Comparison of rat and human MHC II+ colon carcinomas revealed a peak in sensitivity to lysis at 10-100 ng SEA/ml for both tumor targets. These findings suggest that superantigens can be used in local immunotherapy of peritoneal tumors such as ovarian and colorectal carcinomatosis, with inducible or constitutive expression of MHC class II.     

Mycobacterium bovis BCG-infected mice are more susceptible to staphylococcal enterotoxin B-mediated toxic shock than uninfected mice despite reduced in vitro splenocyte responses to superantigens

Type 1 T-cell responses against intracellular pathogens play a crucial role in mediating protection. We examined whether the induction of a strong type 1 T-cell response during a chronic bacterial infection influences responses to superantigens capable of inducing acute shock. Intravenous infection of mice with Mycobacterium bovis BCG appeared to induce a progressive anergy towards staphylococcal enterotoxin B (SEB) and towards antigen preparation of BCG (BCG-Ag) itself, based on diminished gamma interferon (IFN-gamma) production by SEB- and BCG-Ag-stimulated splenocytes from infected mice. In contrast to these in vitro results, injection of SEB into BCG-infected mice led to a dramatic increase in the serum IFN-gamma levels and the death of infected but not of control mice. In vitro hyporesponsiveness towards SEB and BCG-Ag occurred only with unfractionated splenocyte cultures, as purified T cells from infected mice produced higher levels of IFN-gamma. Hyporesponsiveness towards SEB and BCG-Ag in unfractionated splenocyte cultures was not due to suppressive antigen-presenting cells (APCs), as APCs from infected mice stimulated higher levels of IFN-gamma from purified T cells. The diminished IFN-gamma levels observed with bulk splenocytes appear to be due to changes in the T-cell-to-APC ratio that result in a decreased proportion of T cells, coupled to reduced proliferative responses and an increased susceptibility of effector T cells to activation-induced cell death in vitro. Our results indicate that the reported phenomena of T-cell anergy during mycobacterial infection may be an in vitro consequence of the development of a strong type 1 response in vivo.     

Increased levels of serum-specific immunoglobulin e to staphylococcal enterotoxin a and B in patients with allergic rhinitis and bronchial asthma

BACKGROUND: The association between staphylococcal enterotoxins and atopic dermatitis (AD) is well characterized. We aim to evaluate the association between sensitization to staphylococcal enterotoxin A (SEA) and/or B (SEB) and the development of allergic airway disease. METHODS: Two hundred and seventy-four patients were grouped into allergic rhinitis (AR) and/or bronchial asthma (BA) only, AD only and AR/BA+AD. The AR/BA only group was further divided into AR only, AR and airway hyperresponsiveness (AR+AHR) and BA. The allergen-specific and total immunoglobulin E (IgE) antibodies were determined by the CAP system. The associations of sensitization to SEA/SEB with allergic airway disease were analyzed by logistic regression analysis. RESULTS: The overall rate of sensitization to SEA/SEB was 25.7%, whereas the rate of the AD only group (45.5%) was significantly higher than that of the AR/BA only group (24.5%, chi2=8.1). After sensitization to SEA/SEB, the geometric mean total IgE levels were significantly elevated in patients with AR+AHR and BA, but not in those with AR only. BA patients had higher geometric mean values of SEA- and SEB-specific IgE than AR only and AR+AHR patients. Logistic regression revealed that AR/BA only was more associated with sensitization to SEA/SEB (odds ratio 6.57) than AD only and AR/BA+AD (odds ratio 2.44 and 1.72). CONCLUSIONS: Atopic status after sensitization to SEA/SEB was more closely associated with BA than with other airway allergy, implying that SEA/SEB may play a role in exacerbating airway allergy and increasing the risk of allergic airway disease. Our study suggests that staphylococcal enterotoxins play a prominent role in the pathogenesis of allergic airway disease as well as AD.     

Kinetics of cellular and cytokine responses in a chimeric mouse model for the study of staphylococcal enterotoxin B pathogenesis

The mechanisms by which superantigens, such as staphylococcal enterotoxin B (SEB), contribute to microbial pathogenicity have been poorly defined. The study of such pathogenic processes has been hampered by the lack of an adequate animal model. We utilized a previously described murine chimeric model to determine the cytokines and cell populations that might be involved in SEB toxicity. In the absence of bone marrow transplantation (BMT), all total body irradiated (TBI) mice died, while all transplanted mice survived up to 6 months. Compared with non-TBI and non-BMT mice, chimeric mice had an increased percentage of CD11b (Mac-1)-positive splenocytes (17 vs. 59%, P < 0.05) and decreased CD45R-positive (B) cells (33 vs. 6%, P < 0.05) at 6 weeks after BMT. The relative numbers of splenocyte CD4 and CD8 cells were similar in chimeric and normal mice. Susceptibility of chimeric animals to 10 or 100 microg SEB was time-dependent: no mice challenged at 2 weeks post-BMT died, but 15% of mice challenged at 4 weeks and 50% of those challenged at 6-8 weeks died. Compared with TBI and non-BMT C3H/HeJ mice, SEB-challenged chimeric mice at 6-8 weeks had (1) increased splenocyte mRNA expression for: IFN-gamma (3.5 x optimally at 1 h), TNF-alpha (6.5 x at 2 h), IL-6 (4.8 x at 4 h), IL-1beta (8.4 x at 4 h), IL-2 (4.7 x at 4 h), and IL-10 (3 x at 16 h), and (2) increased and earlier peak serum levels of IFN-gamma, IL-6, IL-1beta and IL-2, but no increase in serum TNF-alpha or IL-4. These data support the hypothesis that the decreased percentage of B cells and increased macrophages in chimeric mice lead to enhanced T cell-macrophage interactions after SEB administration and a lethal burst of T cell and macrophage cytokine release. This model will provide insight into cell populations and mechanisms that mediate superantigen-induced toxicity.     

The bacterial superantigen Staphylococcal enterotoxin B stimulates lymphocyte locomotor capacity during culture in vitro.

The bacterial superantigen Staphylococcal enterotoxin B (SEB) was investigated for its effects on lymphocyte locomotion in vitro. Culture of peripheral blood mononuclear cells (PBMC) for 24-72 hr in SEB (1-100 micrograms/ml) increased the proportion of lymphocytes in locomotor (polarized) morphology and capable of invading collagen gels, to the same extent as the established locomotor activator, anti-CD3 (alpha-CD3), though the conventional antigen, tetanus toxoid was ineffective. The cells responding to SEB were predominantly T cells. SEB had no effect on lymphocyte locomotion in short-term (45 min) assays, thus its effect is to stimulate growth-related locomotor capacity and it does not act as a chemoattractant. During culture of PBMC in SEB, the chemokines interleukin-8 (IL-8) and macrophage chemotactic protein-1 (MCP-1) were released into the culture medium. The presence of anti-IL-8, but not of anti-MCP-1, either during culture or added to SEB culture supernatants and tested in short-term assays, inhibited the development of polarization suggesting that IL-8, which is a lymphocyte chemoattractant, also plays a key role in SEB-induced locomotor activation. Among SEB-activated lymphocytes, CD45RO+CD45RA- lymphocytes showed enhanced locomotor responses, but a relation was not found between locomotor activity and the presence of cell surface CD69.     

Enhanced killing of Blastomyces dermatitidis by gamma interferon-activated murine peripheral blood polymorphonuclear neutrophils

Normal peripheral blood polymorphonuclear neutrophils (PB-PMNs), challenged in vitro with yeast form Blastomyces dermatitidis, reduced inoculum colony-forming units of a virulent strain by 37.5 +/- 9.5%. Pre-incubation of PB-PMNs with 10-100,000 U/ml of purified recombinant murine gamma-interferon (IFN) for 1 h prior to challenge with fungi resulted in significant enhancement of PB-PMN fungicidal activity. No direct fungicidal activity by IFN alone was observed. Pretreatment of selected concentrations of IFN shown to have PMN-enhancing activity (100 or 1000 U/ml) with rabbit hyperimmune anti-IFN antiserum for 1 h before addition to PB-PMNs abrogated the enhancement of fungicidal activity. Isolated peripheral blood mononuclear cells failed to kill B. dermatitidis, even when mononuclear cells were present at a concentration ten times greater than that normally used in killing assays, and failed to be activated by IFN. Treatment of unstimulated or IFN-activated PB-PMNs with complement and hybridoma-derived monoclonal antibody specific for PMNs eliminated PB-PMN fungicidal activity. Exogenously added lipopolysaccharide (0.0005-50,000 ng/ml) did not activate PB-PMNs, whether added alone or in conjunction with IFN. The PB-PMN activating capacity of IFN could be destroyed by heat treatment (100 degrees C, 15 min) or by acid treatment with HCl (pH 2). These results demonstrate that recombinant gamma-interferon can stimulate PB-PMNs to kill B. dermatitidis, that the PB-PMN activating moiety is IFN and that PB-PMNs are responsible for fungal killing in this assay system.(ABSTRACT TRUNCATED AT 250 WORDS)