Superantigens and their potential role in human disease

Immunological Characterization of Superantigen-induced Intrauterine Fetal and Newborn Death

PROBLEM

The present study characterizes the immunological responses induced by superantigen and the underlying pathological mechanism using T-cell receptor-transgenic mice (TCR-Tg) to enable the ligand toxic shock syndrome toxin-1 (TSST-1) to induce a cytokine storm.

METHOD OF STUDY

Three kinds of pregnant mice which could respond to TSST-1 at various levels were injected with TSST-1 on gestation day 17.5 and then the incidence of fetal/newborn death, production of cytokines including serum interleukin-2 (IL-2) and the histological status of the placenta were examined on day 18.5.

RESULTS

The incidence of fetal/newborn death and the concentrations of cytokines such as IL-2 were higher in TCR-Tg mother than those in other strains of mice. Pathological examinations revealed that the placenta was congestive and apoptotic in TCR-Tg mice.

CONCLUSIONS

Superantigen injection into pregnant mice appears to increase the incidence of fetal/newborn death through an IL-2-dependent immunological pathway.

A role for the Tec family kinase ITK in regulating SEB-induced interleukin-2 production in vivo via c-jun phosphorylation

Background

Exposure to Staphylococcal Enterotoxin B (SEB), a bacterial superantigen secreted by the Gram-positive bacteria Staphyloccocus aureus, results in the expansion and eventual clonal deletion and anergy of Vβ8⁺ T cells, as well as massive cytokine release, including Interleukin-2 (IL-2). This IL-2 is rapidly secreted following exposure to SEB and may contribute to the symptoms seen following exposure to this bacterial toxin. The Tec family kinase ITK has been shown to be important for the production of IL-2 by T cells stimulated in vitro and may represent a good target for blocking the production of this cytokine in vivo. In order to determine if ITK represents such a target, mice lacking ITK were analyzed for their response to SEB exposure.

Results

It was found that T cells from mice lacking ITK exhibited significantly reduced proliferative responses to SEB exposure in vitro, as well as in vivo. Examination of IL-2 production revealed that ITK null mice produced reduced levels of this cytokine in vitro, and more dramatically, in vivo. In vivo analysis of c-jun phosphorylation, previously shown to be critical for regulating IL-2 production, revealed that this pathway was specifically activated in SEB reactive Vβ8⁺ (but not non-reactive Vβ6⁺) T cells from WT mice, but not in Vβ8⁺ T cells from ITK null mice. However, toxicity analysis indicated that both WT and ITK null animals were similarly affected by SEB exposure.

Conclusion

These data show that ITK is required for IL-2 production induced by SEB in vivo, and may regulate signals leading IL-2 production, in part by regulating phosphorylation of c-jun. The data also suggest that perturbing T cell activation pathways leading to IL-2 does not necessarily lead to improved responses to SEB toxicity.

Immunization with glutathioneS-transferase and mutant toxic shock syndrome toxin 1 fusion protein protects againstStaphylococcus aureusinfection

To investigate whether immunization with glutathione S-transferase (GST) and mutant toxic shock syndrome toxin 1 (mTSST-1) fusion protein can protect against Staphylococcus aureus infection, we purified a non-toxic mutant GST-mTSST-1 fusion protein. Mice were immunized with the GST-mTSST-1 plus alum adjuvant and then challenged with viable S. aureus. The results showed that the survival rate of GST-mTSST-1-immunized group was higher and the bacteria counts in the organs were significantly lower than those of the non-immunized mice. Immunization with GST-mTSST-1 induced strongly the production of TSST-1 specific antibodies, especially immunoglobulin G1 and immunoglobulin G2b. Furthermore, the serum samples from GST-mTSST-1-immunized mice also significantly inhibited interferon-gamma and tumor necrosis factor-alpha production from murine spleen cells by TSST-1. These results suggest that vaccination with GST-mTSST-1 provides protection against S. aureus infection and that the protection might be mediated by TSST-1-neutralizing antibody.

Managing toxic shock syndrome with antibiotics

Toxic shock syndrome (TSS) is a serious disorder with a worldwide prevalence of approximately 3/100,000 persons. TSS is mainly caused by Streptococcus pyogenes or Staphylococcus aureus. Thus, beta-lactam and lincosamides, such as clindamycin, are the first-line drugs. Yet, the mortality rate remains unacceptably high; highlighting the role of bacterial toxin-mediated activation of the inflammatory cascade in TSS pathogenesis. Further strategies should be targeted towards interfering with the interaction between bacterial toxins and host T cells. This paper aims to provide an overview of the epidemiology, pathomechanisms, and clinical presentation of TSS, and criteria for selecting drugs among available antibiotics.

Heterogeneity of methicillin-resistant Staphylococcus aureus strains at a German university hospital during a 1-year period

Heterogeneous methicillin-resistant Staphylococcus aureus (MRSA) strains, including community-acquired MRSA strains, have been observed in Central Europe. The purpose of this study was to characterize by molecular methods MRSA isolated during the period 2002-2003 at the Otto-von-Guericke University Hospital in Magdeburg, Germany, and at a nearby chronic care facility. Strains were analyzed for their resistance phenotype. Selected isolates were typed by multilocus sequence typing (MLST), by a multiplex polymerase chain reaction (PCR) for the staphylococcal cassette chromosome mec (SCCmec), by an allele-specific PCR for the staphylococcal accessory gene regulator (agr), and by PCR for the presence of toxin genes (sea-sej, tsst-1, hlgA, C, and B, lukE/D, and luk-pvl). Of the 2,731 S. aureus isolates studied, 199 (7.3%) were MRSA, with a prevalence of 21.6%, 19.6%, and 12% in the department of dermatology, the chronic care facility, and the intensive care units. Six different sequence types (ST247, ST228, ST22, ST22a, ST225, and ST45) were observed. Of these, ST22, ST22a, and ST45 dominated (>50%) in the department of dermatology and the chronic care facility. Strains with these sequence types were usually not resistant to gentamicin and were associated with agr group I, the SCCmec type IV element, and the presence of the sec and sed toxin genes. ST228 strains were found mainly in the intensive care units and had a broader resistance phenotype and were associated with agr group II and the SCCmec type I element. All luk-pvl-positive MRSA isolates (n=8) belonged to agr group I and were typed as ST22 or ST45 and contained the SCCmec type I (n=1), type III (n=1), or type IV (n=6) element. The main observations of this study are in concordance with previously reported findings showing dissemination of MRSA in Central Europe. Through the multitude of applied methods, the data from this study contribute to a more precise knowledge about the heterogeneity of MRSA in a clinical setting. Rapid dissemination of MRSA clones at a university hospital was demonstrated, indicating that dissemination may depend on the environmental conditions within the individual departments.

Diagnosis and management of acute myelopathies

BACKGROUND

Acute myelopathies represent a heterogeneous group of disorders with distinct etiologies, clinical and radiologic features, and prognoses. Transverse myelitis (TM) is a prototype member of this group in which an immune-mediated process causes neural injury to the spinal cord, resulting in varying degrees of weakness, sensory alterations, and autonomic dysfunction. TM may exist as part of a multifocal CNS disease (eg, MS), multisystemic disease (eg, systemic lupus erythematosus), or as an isolated, idiopathic entity.

REVIEW SUMMARY

In this article, we summarize recent classification and diagnostic schemes, which provide a framework for the diagnosis and management of patients with acute myelopathy. Additionally, we review the state of current knowledge about the epidemiology, natural history, immunopathogenesis, and treatment strategies for patients with TM.

CONCLUSIONS

Our understanding of the classification, diagnosis, pathogenesis, and treatment of TM has recently begun to expand dramatically. With more rigorous criteria applied to distinguish acute myelopathies and with an emerging understanding of immunopathogenic events that underlie TM, it may now be possible to effectively initiate treatments in many of these disorders. Through the investigation of TM, we are also gaining a broader appreciation of the mechanisms that lead to autoimmune neurologic diseases in general.

How to diagnose and treat secondary forms of vasculitis

Vasculitis is considered to be secondary when it arises either in the context of a pre-existing connective tissue disease, as a result of direct infection with a limited range of organisms, especially viruses, or when it arises in response to exposure to a number of medications. Rheumatoid vasculitis is probably the most widely recognised form of secondary vasculitis, and in this article we review the incidence, clinical features and management of this condition. Infections may either trigger or cause some types of vasculitis. Drug therapy is a common cause of limited forms of vasculitis and may enhance our understanding of the mechanism of these diseases. The premature development of atherosclerosis in patients with existing connective tissue diseases or indeed primary vasculitis has been recognised for some time, and the underlying mechanisms are currently being studied. An appreciation of the complex and varied pathophysiology of secondary vasculitis may further our understanding of primary vasculitis.

Purpura Fulminans Due toStaphylococcus aureus

BACKGROUND

Purpura fulminans is an acute illness commonly associated with meningococcemia or invasive streptococcal disease, and it is typically characterized by disseminated intravascular coagulation (DIC) and purpuric skin lesions. In this article, we report the first 5 cases (to our knowledge) of purpura fulminans directly associated with Staphylococcus aureus strains that produce high levels of the superantigens toxic shock syndrome toxin-1 (TSST-1), staphylococcal enterotoxin serotype B (SEB), or staphylococcal enterotoxin serotype C (SEC).

METHODS

Cases were identified in the Minneapolis-St. Paul, Minnesota, metropolitan area during 2000-2004. S. aureus infection was diagnosed on the basis of culture results, and susceptibility to methicillin was determined. The ability of the isolated organisms to produce TSST-1, SEB, SEC, and Panton-Valentine leukocidin (PVL) was determined. TSST-1, SEB, and SEC levels were also quantified after in vitro growth of the organisms.

RESULTS

In 3 of the 5 cases, the infecting S. aureus strain was isolated from the blood cultures. In 2 of the 5 cases, the infecting S. aureus strain was isolated only from the respiratory tract, indicating that purpura fulminans and toxic shock syndrome resulted from exotoxin and/or other host factors, rather than septicemia. One of these latter 2 patients also had necrotizing pneumonia, and the isolated S. aureus was a methicillin-resistant strain that produced both SEC and PVL. Only 2 of the 5 patients survived, and 1 of the survivors received activated protein C.

CONCLUSIONS

Staphylococcal purpura fulminans may be a newly emerging illness associated with superantigen production. Medical practitioners should be aware of this illness.

Commensal bacteria (normal microflora), mucosal immunity and chronic inflammatory and autoimmune diseases

Commensal microflora (normal microflora, indigenous microbiota) consists of those micro-organisms, which are present on body surfaces covered by epithelial cells and are exposed to the external environment (gastrointestinal and respiratory tract, vagina, skin, etc.). The number of bacteria colonising mucosal and skin surfaces exceeds the number of cells forming human body. Commensal bacteria co-evolved with their hosts, however, under specific conditions they are able to overcome protective host responses and exert pathologic effects. Resident bacteria form complex ecosystems, whose diversity is enormous. The most abundant microflora is present in the distal parts of the gut; the majority of the intestinal bacteria are Gram-negative anaerobes. More than 50% of intestinal bacteria cannot be cultured by conventional microbiological techniques. Molecular biological methods help in analysing the structural and functional complexity of the microflora and in identifying its components. Resident microflora contains a number of components able to activate innate and adaptive immunity. Unlimited immune activation in response to signals from commensal bacteria could pose the risk of inflammation; immune responses to mucosal microbiota therefore require a precise regulatory control. The mucosal immune system has developed specialised regulatory, anti-inflammatory mechanisms for eliminating or tolerating non-dangerous, food and airborne antigens and commensal micro-organisms (oral, mucosal tolerance). However, at the same time the mucosal immune system must provide local defense mechanisms against environmental threats (e.g. invading pathogens). This important requirement is fulfilled by several mechanisms of mucosal immunity: strongly developed innate defense mechanisms ensuring appropriate function of the mucosal barrier, existence of unique types of lymphocytes and their products, transport of polymeric immunoglobulins through epithelial cells into secretions (sIgA) and migration and homing of cells originating from the mucosal organised tissues in mucosae and exocrine glands. The important role of commensal bacteria in development of optimally functioning mucosal immune system was demonstrated in germ-free animals (using gnotobiological techniques). Involvement of commensal microflora and its components with strong immunoactivating properties (e.g. LPS, peptidoglycans, superantigens, bacterial DNA, Hsp) in etiopathogenetic mechanism of various complex, multifactorial and multigenic diseases, including inflammatory bowel diseases, periodontal disease, rheumatoid arthritis, atherosclerosis, allergy, multiorgan failure, colon cancer has been recently suggested. Animal models of human diseases reared in defined gnotobiotic conditions are helping to elucidate the aetiology of these frequent disorders. An improved understanding of commensal bacteria-host interactions employing germ-free animal models with selective colonisation strategies combined with modern molecular techniques could bring new insights into the mechanisms of mucosal immunity and also into pathogenetic mechanisms of several infectious, inflammatory, autoimmune and neoplastic diseases. Regulation of microflora composition (e.g. by probiotics and prebiotics) offers the possibility to influence the development of mucosal and systemic immunity but it can play a role also in prevention and treatment of some diseases.

Evidence for Restricted Vβ Usage in the Leukemic Phase of Cutaneous T Cell Lymphoma

Antibodies directed against the beta chain of the T cell receptor (anti-Vbeta antibodies) are useful to identify the Vbeta repertoire of T cells in various diseases and to quantify numbers of Vbeta-bearing T cells. The goals of this study were to identify Vbeta+ cases of leukemic phase cutaneous T cell lymphoma (CTCL) and to compare the percentage of positive calls with other measures of blood tumor burden, i.e., lymphocyte subsets with a CD4+CD7- and CD4+CD26- phenotype and Sezary cell counts. Thirty-three of 49 (67%) cases of leukemic CTCL reacted with an anti-Vbeta antibody. When combined with reports from the literature, the frequency of Vbeta5 (probably Vbeta5.1) usage was relatively high when compared with Vbeta2 that is also frequently expressed by normal CD4+ T cells. The percentage of Vbeta+ cells correlated to the percentage of CD4+CD7- and CD4+CD26- cells for cases in which the neoplastic cells were deficient in expression of CD7 and CD26, respectively, but not the Sezary cell count. We hypothesize that the increased Vbeta5.1 usage in CTCL may be the result of depletion of Vbeta2 and other Vbeta-bearing T cells by staphylococcal superantigens prior to neoplastic transformation, resulting in a relative increase in the frequency of Vbeta5.1 usage in CTCL.

Superantigen hypothesis for the early development of chronic hyperplastic sinusitis with massive nasal polyposis

PURPOSE OF REVIEW

The pathogenesis, pathophysiology, and immunobiology of chronic hyperplastic sinusitis with massive nasal polyposis are starting to become unraveled. Allergy, viral infection, bacterial infection, fungal infection, and environmental pollution have all been suggested as possible initial triggers that may upregulate inflammation of the lateral wall of the nose to develop nasal polyposis. The purpose of this review is to present data from our laboratory that suggest that one of the possible early events in the development of inflammation of the lateral wall of the nose in chronic hyperplastic sinusitis with massive nasal polyposis is the production of exotoxins from Staphylococcus aureus. The exotoxins may act as superantigens and cause activation and clonal expansion of lymphocytes with specific Vbeta regions, resulting in massive cytokine production.

RECENT FINDINGS

Recent published studies suggest that S. aureus is the most common organism isolated from the mucus adjacent to massive nasal polyposis. Staphylococci produce exotoxins. These exotoxins, sometimes known as enterotoxins, include SEA, SEB, and TSST-1. These exotoxins are capable of acting as superantigens and therefore, reacting with T lymphocytes with specific Vbetas in the lateral wall of the nose. Thereafter, it is possible that these lymphocytes are stimulated to produce both TH1 and TH2 cytokines, which have also been demonstrated in the nasal polyp. The consequence of these findings may be the upregulation and increased survival of eosinophils in the nasal polyp.

SUMMARY

Staphylococcus aureus is present in the mucin adjacent to nasal polyps in about 60 to 70% of cases of massive nasal polyposis. These organism, as studied up to the present, always produce exotoxins, which may act as superantigens, causing activation and clonal expansion of lymphocytes with specific Vbeta region in the lateral wall of the nose. The present review suggests that activation of these lymphocytes produce both TH1 and TH2 cytokines. The potential damage to the nasal mucosa from eosinophils is briefly discussed. Theoretically, topical antibiotics to suppress the colonization of S. aureus may be a logical approach to downregulate the production of superantigen in the lateral wall of the nose after appropriate endoscopic sinus surgery.

Caspase inhibitors attenuate superantigen-induced inflammatory cytokines, chemokines, and T-cell proliferation

Proinflammatory cytokines mediate the toxic effect of superantigenic staphylococcal exotoxins (SE). A pan-caspase inhibitor suppressed SE-stimulated T-cell proliferation and the production of cytokines and chemokines by human peripheral blood mononuclear cells. These data suggest that caspase inhibitors may represent a novel therapeutic modality for treating SE-induced toxic shock.

Environmental Influences in Experimental Autoimmune Encephalomyelitis

Environmental factors, in particular infectious agents, are thought to have a major influence on the development and course of MS. Some of these influences are also reflected in the animal model, EAE. In this chapter, the role of infectious agents in the development and course of autoimmunity in EAE is discussed. Other environmental agents including trauma, solar radiation exposure, temperature, stress, toxins, are discussed in terms of their relevance to MS and EAE.

Peptide antagonists of superantigen toxins

Superantigens produced by Staphylococcus aureus and Streptococcus pyogenes are among the most lethal of toxins. Toxins in this large family trigger an excessive cellular immune response leading to toxic shock. Superantigens are secreted by the bacteria as diverse natural mixtures, a complexity that demands development of broad-spectrum countermeasures. We used a rational approach to design short peptides with homology to various domains in a typical superantigen (staphylococcal enterotoxin B) and screened each peptide for its ability to antagonize, in human peripheral blood mononuclear cells, superantigen-mediated induction of the genes encoding T helper 1 cytokines that mediate shock: interleukin-2, interferon-gamma and tumor necrosis factor. A dodecamer peptide proved a potent antagonist against widely different superantigens. This peptide protected mice from killing by superantigens and it was able to rescue mice undergoing toxic shock. The antagonist peptide shows homology to a beta-strand-hinge-alpha-helix domain that is structurally conserved among superantigens, yet currently of unknown function and remote from the binding sites for the known ligands essential for T cell activation, the major histocompatibility complex class II molecule and T cell receptor. The antagonist activity of this peptide thus identifies a novel domain in superantigens that is critical for their toxic action. The antagonist peptide provides a new tool for understanding the mechanism of excessive human immune response activation by superantigens that occurs during toxic shock and for identification of a novel target ligand that may interact with this superantigen domain.

Clinical latency and reactivation of AIDS-related mycobacterial infections

The immune mechanisms associated with the evolution from latent to clinically active mycobacterial coinfection in human immunodeficiency virus type 1 (HIV-1)-infected humans remain poorly understood. Previous work has demonstrated that macaques infected with simian immunodeficiency virus (SIVmac) can develop persistent Mycobacterium bovis BCG coinfection and a fatal SIV-related tuberculosis-like disease by 4 months after BCG inoculation. In the present study, SIVmac-infected monkeys that developed clinically quiescent mycobacterial infection after BCG inoculation were followed prospectively for the reactivation of the BCG and the development of SIV-related tuberculosis-like disease. The development of clinically latent BCG coinfection in these SIVmac-infected monkeys was characterized by a change from high to undetectable levels of bacterial organisms, with or without measurable BCG mRNA expression in lymph node cells. The reactivation of clinically latent BCG coinfection and development of SIV-related tuberculosis-like disease were then observed in these SIVmac-BCG-coinfected monkeys during a 21-month period of follow-up. The reactivation of SIV-related tuberculosis-like disease in these animals coincided with a severe depletion of CD4 T cells and a loss of BCG-specific T-cell responses. Interestingly, bacterial superantigen challenge of the SIVmac-BCG-coinfected monkeys resulted in an up-regulation of clinically latent BCG coinfection, suggesting that infection with superantigen-producing microbes may increase the susceptibility of individuals to the reactivation of AIDS-related mycobacterial coinfection. Thus, reactivation of latent mycobacterial infections in HIV-1-infected individuals may result from a loss of T-cell immunity or from a superimposed further compromise of the immune system.

Immunoglobulin E to staphylococcal and streptococcal toxins in patients with chronic sinusitis/nasal polyposis

BACKGROUND

The role of infectious agents and their contribution to the inflammation in chronic sinusitis/nasal polyposis (CS/NP) is not clear. Staphylococcal and streptococcal toxins have superantigen activity and have been implicated in inflammatory conditions such as atopic dermatitis, psoriasis, and asthma.

OBJECTIVE

We investigated the presence of immunoglobulin (Ig)E antibodies to staphylococcal and streptococcal toxins in the serum of individuals with CS/NP.

METHOD

IgE antibodies to staphylococcal exotoxins, A, B, and toxic shock syndrome toxin-1 and streptococcal pyrogenic exotoxin A, B, and C were measured in 23 individuals with CS/NP before functional endoscopic sinus surgery and in controls (7 atopic and 6 nonatopic) individuals without chronic sinusitis. Presence of IgE to the toxins was also correlated with disease severity on sinus computed tomography (CT) scans.

RESULTS

Staphylococcal and streptococcal toxin specific IgE antibodies were detected in 18 of 23 (78%) and 7 of 21 (33.3%) patients, respectively. None of the controls had IgE to the staphylococcal or streptococcal toxins (P <.0001). There was no association between radiographic severity of sinus disease and the presence of IgE antibody to the toxins.

CONCLUSION

A significantly greater proportion of CS/NP patients had IgE to staphylococcal or streptococcal toxins. Evidence of IgE antibodies directed against staphylococcal and streptococcal toxins in the sera of patients with CS/NP suggests a potential role of these toxins with established superantigen effects in the pathogenesis of CS/NP.

Crystal structure of Mycoplasma arthritidis mitogen complexed with HLA-DR1 reveals a novel superantigen fold and a dimerized superantigen-MHC complex

Mycoplasma arthritidis-derived mitogen (MAM) is a superantigen that can activate large fractions of T cells bearing particular TCR Vbeta elements. Here we report the crystal structure of MAM complexed with a major histocompatibility complex (MHC) antigen, HLA-DR1, loaded with haemagglutinin peptide 306-318 (HA). The structure reveals that MAM has a novel fold composed of two alpha-helical domains. This fold is entirely different from that of the pyrogenic superantigens, consisting of a beta-grasped motif and a beta barrel. In the complex, the N-terminal domain of MAM binds orthogonally to the MHC alpha1 domain and the bound HA peptide, and to a lesser extent to the MHC beta1 domain. Two MAM molecules form an asymmetric dimer and cross-link two MHC antigens to form a plausible, dimerized MAM-MHC complex. These data provide the first crystallographic evidence that superantigens can dimerize MHC molecules. Based on our structure, a model of the TCR2MAM2MHC2 complex is proposed.

Crystallographic and Mutational Data Show That the Streptococcal Pyrogenic Exotoxin J Can Use a Common Binding Surface for T-cell Receptor Binding and Dimerization

The protein toxins known as superantigens (SAgs), which are expressed primarily by the pathogenic bacteria Staphylococcus aureus and Streptococcus pyogenes, are highly potent immunotoxins with the ability to cause serious human disease. These SAgs share a conserved fold but quite varied activities. In addition to their common role of cross-linking T-cell receptors (TCRs) and major histocompatibility complex class II (MHC-II) molecules, some SAgs can cross-link MHC-II, using diverse mechanisms. The crystal structure of the streptococcal superantigen streptococcal pyrogenic exotoxin J (SPE-J) has been solved at 1.75 A resolution (R = 0.209, R(free) = 0.240), both with and without bound Zn(2+). The structure displays the canonical two-domain SAg fold and a zinc-binding site that is shared by a subset of other SAgs. Most importantly, in concentrated solution and in the crystal, SPE-J forms dimers. These dimers, which are present in two different crystal environments, form via the same face that is used for TCR binding in other SAgs. Site-directed mutagenesis shows that this face is also used for TCR binding SPE-J. We infer that SPE-J cross-links TCR and MHC-II as a monomer but that dimers may form on the antigen-presenting cell surface, cross-linking MHC-II and eliciting intracellular signaling.

Kawasaki disease and toxic shock syndrome--at last the etiology is clear?

A decade after the superantigen hypothesis for KD was first suggested, it has still not been either proven or refuted conclusively. Although initial optimism for the hypothesis was quashed by a series of published papers apparently refuting the idea, in the last few years there have been a number of good studies providing evidence in support of the superantigen hypothesis. Whether this renewed enthusiasm is justified will hopefully become clear in the near future. Ultimately, accurate diagnosis, more targeted treatment, and preventative strategies depend on the unraveling of the immunopathogenesis of this disease.

Essential Role of the E3 Ubiquitin Ligase Cbl-b in T Cell Anergy Induction

Antigen-specific immunotolerance limits the expansion of self-reactive T cells involved in autoimmune diseases. Here, we show that the E3 ubiquitin ligase Cbl-b is upregulated in T cells after tolerizing signals. Loss of Cbl-b in mice results in impaired induction of T cell tolerance both in vitro and in vivo. Importantly, rechallenge of Cbl-b mutant mice with the tolerizing antigen results in massive lethality. Moreover, ablation of Cbl-b resulted in exacerbated autoimmunity. Mechanistically, loss of Cbl-b rescues reduced calcium mobilization of anergic T cells, which was attributed to Cbl-b-mediated regulation of PLCgamma-1 phosphorylation. Our results show a critical role for Cbl-b in the regulation of peripheral tolerance and anergy of T cells.

Superantigens: structure-function relationships

Superantigens are a class of highly potent immuno-stimulatory molecules produced by Staphylococcus aureus and Streptococcus pyogenes. These toxins possess the unique ability to interact simultaneously with MHC class II molecules and T-cell receptors, forming a trimolecular complex that induces profound T-cell proliferation. The resultant massive cytokine release causes epithelial damage and leads to capillary leak and hypotension. The staphylococcal superantigens are designated staphylococcal enterotoxins A, B, C (and antigenic variants), D, E, and the recently discovered enterotoxins G to Q, and toxic shock syndrome toxin-1. The streptococcal superantigens include the pyrogenic exotoxins A (and antigenic variants), C, G-J, SMEZ, and SSA. Superantigens are implicated in several diseases including toxic shock syndrome, scarlet fever and food poisoning; and their function appears primarily to debilitate the host sufficiently to permit the causation of disease. Structural studies over the last 10 years have provided a great deal of information regarding the complex interactions of these molecules with their receptors. This, combined with the wealth of new information from genomics initiatives, have shown that, despite their common molecular architecture, superantigens are able to crosslink MHC class II molecules and T-cell receptors by a variety of subtly different ways through the use of various structural regions within each toxin.

A toroid model for in vitro investigations of toxic shock syndrome toxin-1 production

Human behaviours and consumer products may affect vaginal microbial ecology, thereby influencing women's health. Relevant experimentation systems are needed to understand such possible links. Here, we describe the development of a practical semi-solid in vitro model to assess the effects of interactions between vaginal environment and the presence of tampons, on bacterial communities, including the production of toxic shock syndrome toxin-1 (TSST-1) by Staphylococcus aureus.

Allergic fungal sinusitis

AFS is an increasingly recognized form of HSD, now reported throughout the world. It is probably the most frequently occurring fungal rhinosinusitis disorder. The term fungal sinusitis is no longer appropriate because the five categories of fungal rhinosinusitis can now be differentiated. Each category of fungal rhinosinusitis disorder carries different treatment approaches and prognosis. Diagnostic error can be minimized by adhering to strict diagnostic criteria. The analogy (but not identity) of AFS to ABPA has been supported by histopathology, immunopathology, and the clinical response to OCS treatment. AFS represents a true medical surgical disorder in which both surgery and postoperative medical treatment, if properly coordinated between medical and surgical specialists, leads to the best patient outcomes. Continued advances in the understanding of the immunogenetics and immunopathogenesis of AFS may provide fundamental insights into molecular mechanisms operant in other chronic inflammatory disorders, including other chronic eosinophilic-lymphocytic respiratory mucosal disorders such as common forms of HSD and chronic severe asthma.

Deficiency of CD11b or CD11d Results in Reduced Staphylococcal Enterotoxin-Induced T Cell Response and T Cell Phenotypic Changes

The beta(2) integrin CD11a is involved in T cell-APC interactions, but the roles of CD11b, CD11c, and CD11d in such interactions have not been examined. To evaluate the roles of each CD11/CD18 integrin in T cell-APC interactions, we tested the ability of splenocytes of CD11-knockout (KO) mice to respond to staphylococcal enterotoxins (SEs), a commonly used superantigen. The defect in T cell proliferation with SEA was more severe in splenocytes from mice deficient in CD18, CD11b, or CD11d than in CD11a-deficient splenocytes, with a normal response in CD11c-deficient splenocytes. Mixing experiments showed that the defect of both CD11b-KO and CD11d-KO splenocytes was, unexpectedly, in T cells rather than in APC. Cytometric analysis failed to detect CD11b or CD11d on resting or activated T cells or on thymocytes of wild-type adult mice, nor did Abs directed to these integrins block responses in culture, suggesting that T cells educated in CD11b-KO or CD11d-KO mice were phenotypically altered. Consistent with this hypothesis, T cells from CD11b-KO and CD11d-KO splenocytes exhibited reduced intensity of CD3 and CD28 expression and decreased ratios of CD4/CD8 cells, and CD4(+) T cells were reduced among CD11b-KO and CD11d-KO thymocytes. CD11b and CD11d were coexpressed on a subset of early wild-type fetal thymocytes. We postulate that transient thymocyte expression of both CD11b and CD11d is nonredundantly required for normal thymocyte and T cell development, leading to phenotypic changes in T cells that result in the reduced response to SE stimulation.

Microbial superantigens induce glucocorticoid receptor beta and steroid resistance in a nasal explant model

OBJECTIVE

To study the role of superantigen (SAg) in inducing glucocorticoid (GC) receptor beta and steroid resistance in an explant model of nasal tissue.

METHODS

Nasal tissue was obtained from inferior turbinates of controls and ragweed (RW)-sensitive patients. Tissue samples were incubated with SAg of staphylococcal enterotoxin B. In addition, tissue samples from RW-sensitive patients were incubated with RW allergen in the presence and absence of both SAg and dexamethasone (DEX). The expression of GC receptor beta was assessed by immunocytochemistry. The expression of interleukin (IL)-2 and IL-4 mRNA was assessed by in situ hybridization.

RESULTS

SAg induced an increase in the expression of GC receptor beta in atopic tissue and to a lesser extent in nonatopic tissue. The most significant induction of GC receptor beta was observed in response to SAg and RW in atopic tissue. Stimulation of atopic tissue with RW alone and SAg alone induced IL-4 and IL-2 mRNA, respectively. Incubation of atopic tissue with both SAg and RW induced both IL-2 and IL-4 mRNA. The increase in IL-4 mRNA expression was blunted by the addition of DEX to atopic tissue stimulated with RW alone but not to tissue stimulated by both RW and SAg.

CONCLUSION

Our results demonstrate that SAgs induce steroid resistance in atopic nasal explant tissue by up-regulating the expression of GC receptor beta. Furthermore, we have shown that the up-regulation of GC receptor beta is a local event that is associated with the coexpression of IL-2 and IL-4 mRNA.

Allergic fungal sinusitis: pathogenesis and management strategies

Allergic fungal sinusitis (AFS) is a noninvasive form of highly recurrent chronic allergic hypertrophic rhinosinusitis that can be distinguished clinically, histopathologically and prognostically from the other forms of chronic fungal rhinosinusitis. There are three invasive (acute necrotising, chronic invasive and granulomatous invasive) and two noninvasive (fungal ball and allergic fungal) forms of fungal rhinosinusitis currently recognised. Confusion in differentiating between the various forms of fungal rhinosinusitis and between other forms of chronic hypertrophic sinus disease (HSD) can be eliminated by adhering to strict diagnostic criteria. Although there are characteristic presenting clinical history and physical examination findings, laboratory test results, including elevated total serum IgE and positive inhalant allergy skin tests, and sinus computed tomography scans showing chronic rhinosinusitis (often with the presence of hyperattenuating sinus contents) diagnosis of AFS is essentially based on histopathology obtained from sinus surgery. Histopathology shows the presence of eosinophilic-lymphocytic sinus mucosal inflammation, extramucosal allergic mucin (that is also seen grossly at surgery as a characteristic 'peanut-buttery' material), and scattered silver stain positive fungal hyphae within the allergic mucin but not in the mucosa. Treatment and follow up of AFS has been based on its immunopathological analogy to allergic bronchopulmonary aspergillosis, a similar noninvasive fungal hypersensitivity disorder of the lung, and its clinical and pathophysiological relationship to other forms of HSD and asthma. Treatment involves aggressive sinus surgery followed by medical management that includes allergen immunotherapy, topical and systemic corticosteroids, antihistamines and antileukotrienes. Total serum IgE levels should be followed postoperatively as they can be prognostic for recurrent disease. Close follow up and coordination of treatment by both medical and surgical physicians as a team leads to the best clinical outcomes. Ongoing studies are being directed at furthering our understanding of the pathophysiological relationships and treatment options for AFS, and other common forms of chronic hypertrophic rhinosinusitis disorders.

Chronic sinusitis: defective T-cells responding to superantigens, treated by reduction of fungi in the nose and air

In this study, the author used endoscopic sinus photography to study the effects of reduction of fungi in the nose, and in environmental air, on the sinus mucosa of 639 patients diagnosed with chronic rhinosinusitis. Sinus mucosal photographs were taken before and after reduction of fungal load in the nose and air, to determine if there was an optimum environmental air fungal load associated with sinus mucosal recovery to normal appearance. Systemic symptoms associated with fungal exposure, which resolved when fungus was removed from the patient and the environmental air and reappeared with recurrent environmental fungal exposure, are also discussed and are termed systemic fungal symptoms. Interventions consisted of nasal fungal load reduction with normal saline nasal irrigations and antimicrobial nasal sprays, and environmental air fungal load reduction with high-efficiency particulate air (HEPA) filtration in combination with ionizers or evaporation of a solution of botanical extract. Main outcome measures were obtained with environmental air 1-hr gravity-plate fungal colony counts, laser air particle counts, and endoscopic sinus photography. Blood levels of immunoglobulins IgG and IgE for 7 common molds were also determined. After intervention, 94% of patients who used antimicrobial nasal sprays and who reduced their environmental fungal air count to 0-4 colonies per 1-hr agar gravity-plate exposure (n = 365) exhibited normal sinus mucosa by endoscopic exam. Environmental air fungal counts that exceeded 4 colonies resulted in sinus mucosal abnormalities ranging from edema, to pus and/or nasal polyps at higher counts. Neutralization of allergy, and/or surgery, were used as appropriate following implementation of environmental measures. On the basis of these observations, as well as detailed clinical experience and a review of the current literature, the author hypothesizes that the pathogenesis of chronic rhinosinusitis, allergic fungal sinusitis, and systemic fungal symptoms is a genetic defect at the variable beta chain helper T-cell receptor (TCR Vbeta) site which requires the presence of an antigen (fungus). Chronic sinusitis patients who have recurring exposure to environmental air that contains fungal concentrations in excess of 4 colonies per 1-hr agar plate exposure appear to have an increased risk of persistent chronic sinusitis and/or systemic symptoms, regardless of the medical treatment provided.

Polyclonal expansion of T cells with the TCR Vbeta type of the tumour cell in lesions of cutaneous T-cell lymphoma: evidence for possible superantigen involvement

The involvement of superantigens in the pathology of cutaneous T-cell lymphomas (CTCL) has been suggested before, but without unequivocal evidence for superantigen activity in the patients. Seeking evidence for superantigen activity we analysed clones and microdissected single cells isolated from the epidermis of early-stage lesions of a CTCL patient for their T-cell receptor (TCR) V beta expression and TCR V gamma gene rearrangements. The vast majority of these T cells expressed the TCR V beta family type of the tumour. From their TCR gamma gene rearrangements, however, these cells were polyclonal. The tumour cell clone accounted for about 60% of these cells, about 40% were of heterogeneous origin. This dominance of a single V beta family in the polyclonally expanded dermal T-cell populations implies superantigen activity in the CTCL lesions.

T regulatory cells in atopic dermatitis and subversion of their activity by superantigens

BACKGROUND

Atopic dermatitis (AD) is a chronic inflammatory skin disease involving colonization by superantigen (SAg)-secreting Staphylococcus aureus. CD4+CD25+ T regulatory (Treg) cells are thought to play an important role in controlling inflammatory responses.

OBJECTIVE

In this study we examined whether Treg cells might be deficient in patients with AD.

METHODS

CD4+CD25+ and CD4+CD25- T cells were isolated from PBMCs by using immunomagnetic beads. Cells were cultured with anti-CD3 or SAg, staphylococcal enterotoxin B (SEB), for 72 hours. Proliferation was measured by means of tritiated thymidine incorporation. CD4, CD8, CD25, and cutaneous lymphocyte-associated antigen expression on PBMCs was assessed by means of flow cytometry. RNA was extracted from isolated subsets of T cells, and the results of real-time PCR for FoxP3 mRNA were determined.

RESULTS

Surprisingly, CD4+CD25+ T cells were significantly (P <.01) increased in patients with AD (6.68%+/-0.99%, n=15) compared with in asthmatic patients (3.42%+/-0.58%, n=12) or nonatopic healthy control subjects (3.34%+/-0.43%, n=14). Patients with AD also had a higher expression of CD25+ in skin-homing, CD4+, cutaneous lymphocyte-associated antigen-positive T cells than asthmatic and nonatopic subjects, with values of 35.95% versus 22.44% versus 23.03%, respectively (P <.006). Only CD4+CD25+ cells expressed FoxP3, whereas CD4+CD25- T cells and CD4- cells did not. Consistent with known properties of Treg cells, CD4+CD25+ cells were anergic to anti-CD3 stimulation. When CD4+CD25+ cells from each study group were mixed with CD4+CD25- cells, proliferative responses were equally suppressed after anti-CD3 stimulation. In contrast, after SEB stimulation, CD4+CD25+ cells were no longer anergic. Furthermore, when CD4+CD25+ cells were mixed with CD4+CD25- cells and stimulated with SEB, the suppressive function of Treg cells was reversed.

CONCLUSION

Patients with AD have significantly increased numbers of peripheral blood Treg cells with normal immunosuppressive activity. However, after SAg stimulation, Treg cells lose their immunosuppressive activity. These data suggest a novel mechanism by which SAgs could augment T-cell activation in patients with AD.

Crystal and Solution Structures of a Superantigen from Yersinia pseudotuberculosis Reveal a Jelly-Roll Fold

Superantigens are a class of microbial proteins with the ability to excessively activate T cells by binding to the T cell receptor. The staphylococcal and streptococcal superantigens are closely related in structure and possess an N-terminal domain that resembles an OB fold and a C-terminal domain similar to a beta-grasp fold. Yersinia pseudotuberculosis produces superantigens, YPMa, YPMb, and YPMc, which have no significant amino acid similarity to other proteins. We have determined the crystal and solution structures of YPMa, which show that the protein has a jelly-roll fold. The closest structural neighbors to YPMa are viral capsid proteins and members of the tumor necrosis factor superfamily. In the crystal structure, YPMa packs as a trimer, another feature shared with viral capsid proteins and TNF superfamily proteins. However, in solution YPMa behaves as a monomer, and any functional relevance of the trimer observed in the crystals is yet to be established.

Leishmanial Amastigote Antigen P-2 Induces Major Histocompatibility Complex Class II-Dependent Natural Killer-Cell Reactivity in Cells from Healthy Donors

Innate mechanisms involving natural killer cells have been implied to play an important role in immunity against Leishmania infection. Previous studies have evaluated responses to three purified amastigote antigens, P-2, P-4 and P-8, of Leishmania pifanoi. The P-4 and P-8 antigens have been demonstrated to induce protection in mouse models, as well as to induce cellular responses in American cutaneous leishmaniasis patients. Cells from Leishmania aethiopica-infected leishmaniasis patients preferentially responded to P-8 and, to a lesser extent, to the cysteine proteinase, P-2. In this study, it is shown that cells from healthy donors, including cells from truly naïve donors (cord blood), could be stimulated to proliferation and cytokine production by P-2. The main proliferating cell types in healthy adult donors were CD16/56(+) and the CD8(+) cells. Blocking of major histocompatibility complex (MHC) class II with alpha-MHC class II antibodies markedly inhibited proliferation and interferon-gamma (IFN-gamma) production, whereas interleukin-10 production was not affected. Experimental evidence indicates that CD4(+) cells were not necessary for the proliferative and IFN-gamma responses; however, an adherent cell population was required. Furthermore, CD16/56(+) cells expressing MHC class II were expanded following P-2 stimulation. The responses to P-2 show a striking similarity to responses induced by the vaccine candidate Leishmania homologue of receptors for activated C-kinase (LACK) in healthy donors. The responses described here may not be desirable when aiming at inducing protective immune responses with a vaccine, and the implications of these results for the development of vaccines against leishmaniasis are discussed.

Crystallization and preliminary crystallographic analysis of Mycoplasma arthritidis-derived mitogen complexed with peptide/MHC class II antigen

Mycoplasma arthritidis-derived mitogen (MAM), a bacterial superantigen, has been crystallized in complex with its human receptor, major histocompatibility complex (MHC) class II antigen, by the hanging-drop vapor-diffusion method. Crystals were obtained under three conditions, with ammonium sulfate, phosphate salt and PEG 8000 as the precipitant. The crystals grown under these conditions all belong to space group I222, with the same unit-cell parameters: a = 137.4, b = 178.2, c = 179.6 A. Diffraction data were collected to 3.3 and 3.4 A resolution from crystals of native and selenomethionylated MAM-MHC complexes, respectively. Self- and cross-rotation function calculations suggest the presence of two complex molecules in the asymmetric unit, resulting in a V(M) of 4.0 and a solvent content of 69%. An interpretable electron-density map was produced using a combination of molecular replacement and SAD phasing.

Superantigen-SEA gene modified tumor vaccine for hepatocellular carcinoma: An in vitro study

AIM: To construct an eukaryotic superantigen gene expression vector containing the recombinant gene of SEA and CD80 molecule transmembrane region (CD80TM), and to express staphylococcus enterotoxin A (SEA) on the membrane of hepatocellular carcinoma (HCC) cell to form a superantigen gene modified tumor vaccine for HCC.

METHODS: SEA and linker-CD80TM gene were amplified through PCR from plasmid containing cDNA of SEA and CD80. Gene fragments were then subcloned into the multiple cloning sites of retroviral vector pLXSN. Recombinant plasmid was transferred into HepG2 cells mediated with lipofectamine, positive clones were selected in culture medium containing G418. RT-PCR and indirect immunofluorescence studies confirmed that SEA was expressed specifically on HCC cell membrane. INFγ -ELISPOT study demonstrated that SEA protein was expressed on the membrane of HCC cells. Cytotoxicity of HepG2-SEA primed CTLs (SEA-T) was analyzed by ⁵¹Cr release assay. T cells cultured with rhIL-2 (IL-2-T) were used as control.

RESULTS: Restriction digestion and sequence analyses confirmed the correctness of length, position and orientation of inserted fusion genes. SEA was expressed on the surface of HepG2 cells, HepG2-SEA had strong stimulating effect on production of HepG2 specific CTL (P < 0.001). SEA-T had enhanced cytotoxicity to HepG2 cells (P < 0.05).

CONCLUSION: Tumor cell membrane expressed superantigen can be used to reinforce the immune effect of tumor cell vaccine for HCC, which provides a new method of the enhanced active immunotherapy for HCC.

HIV-1-suppressive factors are secreted by CD4+ T cells during primary immune responses

CD4+ T cells are required for immunity against many viral infections, including HIV-1 where a positive correlation has been observed between strong recall responses and low HIV-1 viral loads. Some HIV-1-specific CD4+ T cells are preferentially infected with HIV-1, whereas others escape infection by unknown mechanisms. One possibility is that some CD4+ T cells are protected from infection by the secretion of soluble HIV-suppressive factors, although it is not known whether these factors are produced during primary antigen-specific responses. Here, we show that soluble suppressive factors are produced against CXCR4 and CCR5 isolates of HIV-1 during the primary immune response of human CD4+ T cells. This activity requires antigenic stimulation of naïve CD4+ T cells. One anti-CXCR4 factor is macrophage-derived chemokine (chemokine ligand 22, CCL22), and anti-CCR5 factors include macrophage inflammatory protein-1 alpha (CCL3), macrophage inflammatory protein-1 beta (CCL4), and RANTES (regulated upon activation of normal T cells expressed and secreted) (CCL5). Intracellular staining confirms that CD3+CD4+ T cells are the source of the prototype HIV-1-inhibiting chemokines CCL22 and CCL4. These results show that CD4+ T cells secrete an evolving HIV-1-suppressive activity during the primary immune response and that this activity is comprised primarily of CC chemokines. The data also suggest that production of such factors should be considered in the design of vaccines against HIV-1 and as a mechanism whereby the host can control infections with this virus.

Doxycycline is anti-inflammatory and inhibits staphylococcal exotoxin-induced cytokines and chemokines

Proinflammatory cytokines mediate the toxic effect of superantigenic staphylococcal exotoxins (SE). Doxycycline inhibited SE-stimulated T-cell proliferation and production of cytokines and chemokines by human peripheral blood mononuclear cells. These results suggest that the antibiotic doxycycline has anti-inflammatory effects and is therapeutically useful for mitigating the pathogenic effects of SE.

Three-dimensional structural location and molecular functional effects of missense SNPs in the T cell receptor V? domain

The mechanisms by which human single nucleotide polymorphisms (SNPs) influence susceptibility to disease are not yet well understood. In a previous study, we developed a structure-based model that may be used to identify which missense SNPs are neutral and which are deleterious to protein function and so potentially involved in disease (Wang and Moult, Hum Mutat 2001;263-270). The model has now been applied to a set of 54 missense cSNPs in the 46 functional T-cell receptor Vbeta-genes. Most of these missense cSNPs are found to be neutral, but 10 are identified as likely deleterious to protein function. Only one was previously associated with disease. We suggest that the others may be disease related but that redundancy in the T-cell response prevents any simple, monogenic effect. Therefore, these SNPs are the most likely contributors to complex, polygenic disease traits. It has been noted that there is a surprisingly high (74%) fraction of nonsynonymous SNPs in these genes. Contrary to expectation, the analysis shows that these are not associated with an unusually high fraction of deleterious SNPs, nor do they significantly contribute to a larger range of antigen recognition or a reduced superantigen-binding repertoire.

Functional analysis of the TCR binding domain of toxic shock syndrome toxin-1 predicts further diversity in MHC class II/superantigen/TCR ternary complexes

Superantigens (SAGs) aberrantly alter immune system function through simultaneous interaction with lateral surfaces of MHC class II molecules on APCs and with particular variable regions of the TCR beta-chain (Vbeta). To further define the interface between the bacterial SAG toxic shock syndrome toxin-1 (TSST-1) and the TCR, we performed alanine scanning mutagenesis within the putative TCR binding region of TSST-1 along the central alpha helix adjacent to the N-terminal alpha helix and the beta7-beta9 loop as well as with two universally conserved SAG residues (Leu(137) and Tyr(144) in TSST-1). Mutants were analyzed for multiple functional activities, and various residues appeared to play minor or insignificant roles in the TCR interaction. The locations of six residues (Gly(16), Trp(116), Glu(132), His(135), Gln(136), and Gln(139)), each individually critical for functional activity as well as direct interaction with the human TCR Vbeta2.1-chain, indicate that the interface occurs in a novel region of the SAG molecule. Based on these data, a model of the MHC/TSST-1/TCR ternary complex predicts similarities seen with other characterized SAGs, although the CDR3 loop of Vbeta2.1 is probably involved in direct SAG-TCR molecular interactions, possibly contributing to the TCR Vbeta specificity of TSST-1.

Customized mitogen or antibody treatments enhance the sensitivity of lymphoid tumors to 5-fluorouracil in vitro and in vivo

Despite impressive cure rates for certain leukemias and lymphomas, lymphoid tumors are responsible for thousands of deaths per year. Refractory disease remains difficult to control, encouraging the development of new treatment options. 5-fluorouracil (5-FU) has been successfully used to control (or cure) a variety of tumors, but has been only rarely applied to tumors of the lymphoid lineage. Here we demonstrate that the effects of 5-FU on lymphoid tumors can be enhanced by the concomitant binding of cellular membrane molecules with mitogen or antibody. When used in combination with 5-FU, mitogen treatments: (i) enhance the association of drug with cells, (ii) reduce cell proliferation in vitro and (iii) inhibit cell growth in a mouse B-cell tumor model.

Maturation of adult peripheral blood CD38(+)CD4(+) T cells demonstrated by cytokine production in response to a superantigen, TSST-1

This study looks at immunoincompetent CD4(+) T cells in adult peripheral blood (APB) using cytokine production in response to a superantigen as a measure of function. We compared the function of APB CD38(+)CD4(+) and CD38(-/low)CD4(+) T cells to that of cord blood (CB) CD4(+) T cells. APB CD4(+) T cell blasts produce substantial amounts of IL-2 in response to TSST-1 restimulation, while CB CD4(+) T cell blasts produce less. APB CD38(+)CD4(+) T cells produce low levels of IL-4 and IFN-gamma in response to TSST-1, even after activation, while APB CD38(-/low)CD4(+) T cells retain their ability to produce high levels of these cytokines despite high CD38 expression. These results suggest that the developmental stage of APB CD38(+)CD4(+) T cells lies between that of CB CD4(+) T cells and APB CD38(-/low)CD4(+) T cells and that APB CD38(+)CD45RO(-)CD4(+) T cells gradually cease to express CD38 as they acquire full function. We reconsider CD4(+) cell maturation and response to TSST-1 and discuss the implications of T cell maturity on infectious diseases.

Neonatal toxic shock syndrome-like exanthematous disease (NTED)

The author and colleagues recently discovered an emerging neonatal infectious disease: neonatal toxic shock syndrome-like exanthematous disease (NTED), which is induced by the superantigen toxic shock syndrome toxin-1 (TSST-1), produced by methicillin-resistant Staphylococcus aureus (MRSA). The massively expanded Vbeta2+ T cells were rapidly deleted in the peripheral blood of patients with NTED. A marked depletion of Vbeta2+ T cells was also observed in the peripheral blood before the expansion of these T cells. Anergy is specifically induced in the TSST-1 reactive T cells of patients with NTED. Rapid recovery from NTED without complications is expected to be related to the induction of immunologic tolerance in neonatal patients. Anti-TSST-1 IgG antibody of maternal origin was found to play a protective role in preventing the development of NTED. The number of hospitals that have experience caring for patients with NTED has increased threefold in the past 5 years. Most MRSA isolates from neonatal intensive care units in Japan were found to be a single clone of coagulase type II and to possess TSST-1 and staphylococcal enterotoxin C genes. The timing and increased incidence of NTED suggest the emergence of a new MRSA clone. By recognizing that TSST-1 can induce NTED, healthcare providers may give increased attention to this disease in neonatal wards.

Streptococcus dysgalactiae-derived mitogen (SDM), a novel bacterial superantigen: characterization of its biological activity and predicted tertiary structure

A mitogenic substance, designated Streptococcus dysgalactiae-derived mitogen (SDM), was purified from S. dysgalactiae culture supernatant, and the gene encoding the mitogen was cloned. Both native and recombinant SDM expressed in Escherichia coli significantly activated human V beta 1+ and V beta 23+ T cells in association with major histocompatibility complex (MHC) class II molecules on accessory cells, indicating that SDM possesses superantigenic properties. The sdm gene consists of two segments encoding a signal peptide and a mature 25 kDa protein composed of 212 amino acids. Three of 34 S. dysgalactiae strains but none of 28 Streptococcus pyogenes strains examined carried sdm. Phylogenetic analysis indicated that SDM belongs to a family distinct from established bacterial superantigens. SDM showed around 30% homology with other superantigens at the amino acid sequence level. The tertiary structure of SDM was predicted by modelling onto streptococcal pyrogenic exotoxin C and streptococcal mitogenic exotoxin Z-2, both of which share highly homologous structure-determining regions. SDM showed overall structural similarity to both these superantigens. This is the first study to characterize fully a bacterial superantigen from S. dysgalactiae.

Early and definitive diagnosis of toxic shock syndrome by detection of marked expansion of T-cell-receptor VBeta2-positive T cells

We describe two cases of early toxic shock syndrome, caused by the superantigen produced from methicillin-resistant Staphylococcus aureus and diagnosed on the basis of an expansion of T-cell-receptor VBeta2-positive T cells. One case-patient showed atypical symptoms. Our results indicate that diagnostic systems incorporating laboratory techniques are essential for rapid, definitive diagnosis of toxic shock syndrome.

Two novel superantigens found in both group A and group C Streptococcus

Two novel streptococcal superantigen genes (speL(Se) and speM(Se)) were identified from the Streptococcus equi genome database at the Sanger Center. Genotyping of 8 S. equi isolates and 40 Streptococcus pyogenes isolates resulted in the detection of the orthologous genes speL and speM in a restricted number of S. pyogenes isolates (15 and 5%, respectively). Surprisingly, the novel superantigen genes could not be found in any of the analyzed S. equi isolates. The results suggest that both genes are located on a mobile element that enables gene transfer between individual isolates and between streptococci from different Lancefield groups. S. equi pyrogenic exotoxin L (SPE-L(Se))/streptococcal pyrogenic exotoxin L (SPE-L) and SPE-M(Se)/SPE-M are most closely related to SMEZ, SPE-C, SPE-G, and SPE-J, but build a separate branch within this group. Recombinant SPE-L (rSPE-L) and rSPE-M were highly mitogenic for human peripheral blood lymphocytes, with half-maximum responses at 1 and 10 pg/ml, respectively. The results from competitive binding experiments suggest that both proteins bind major histocompatibility complex class II at the beta-chain, but not at the alpha-chain. The most common targets for both toxins were human Vbeta1.1 expressing T cells. Seroconversion against SPE-L and SPE-M was observed in healthy blood donors, suggesting that the toxins are expressed in vivo. Interestingly, the speL gene is highly associated with S. pyogenes M89, a serotype that is linked to acute rheumatic fever in New Zealand.

Serological markers in inflammatory bowel diseases

This chapter is an overview of the literature on serological markers of inflammatory bowel diseases (IBD), focusing on anti-neutrophil cytoplasm autoantibodies (ANCA) and anti- Saccharomyces cerevisiae mannan antibodies (ASCA). The methodology for ANCA and ASCA testing is first introduced. The value of these markers as diagnostic tools is then discussed. Other chapters are devoted to the potential role of ANCA and ASCA in disease monitoring, disease stratification and as subclinical markers in families. Finally reviewed are other antibodies recently tested in clinical trials such as pancreatic antibodies and antibodies directed against bacterial antigens. The role of these antibodies in the pathophysiology of IBD still needs to be assessed. We also need to identify the ASCA immunogen(s) eliciting the antibody response.

A serine/threonine phosphorylation site in the ectodomain of a T cell receptor beta chain is required for activation by superantigen

The presence of consensus phosphorylation sites in the ectodomains of cell surface proteins suggests that such post-translational modification may be important in regulation of surface receptor activity. To date, the only cell surface receptor for which such ectodomain phosphorylation has been conclusively demonstrated is the clonally expressed T cell antigen receptor (TCR). Attempts to conclusively identify individual phosphorylated residues in TCR alpha and beta chains and determine their functional significance by biochemical approaches failed due to insufficient quantities of purified molecules. Here we present the results of an alternative approach where survey of phosphorylation sites in the TCR alpha and beta chains was accomplished using site-directed mutagenesis and retroviral vector expression, as well as in vitro phosphorylation of synthetic peptide substrates. All mutants studied directed the cell surface expression of normal amounts of TCR, and all transfectants could be stimulated to produce IL-2 in response to substrate-immobilized antibody to TCR. However, mutation of serine-88 in the protein kinase A phosphorylation site of the TCR beta chain resulted in a complete lack of response to the superantigen staphylococcal enterotoxin B (SEB). In addition, this mutation abolished TCR-associated tyrosine phosphorylation, consistent with the impairment of cell signaling. Reversion of the serine-88/alanine mutation with phosphorylatable threonine completely restored the SEB recognition by TCR. These results, interpreted in the context of the known three-dimensional structure of the complex of SEB and TCR, are consistent with the view that serine-88 is important for the contact of the TCR beta chain with SEB.