Evidence for a superantigen mediated process in Kawasaki disease

The throat flora and its mitogenic activity in patients with Kawasaki disease

The etiology of Kawasaki disease (KD) remains unknown, although some infectious organism has been suggested as the cause. Recent studies suggest that some bacterial toxins with superantigen activity are involved in its pathogenesis, but no specific bacterial toxin has yet been identified. Throat swabs for bacterial culture were obtained from 21 patients with KD and 20 with other febrile illnesses as controls. Mitogenic activity in culture supernatants obtained from individual bacterial strains was measured by lymphocyte proliferation assay. Sixty-one bacterial strains were isolated from KD patients, and 62 strains from control patients. There was no apparent difference in bacterial species in the throat flora between KD patients and febrile controls. Moreover, total and individual mitogenic activity of strains from KD patients was no greater than that of strains from febrile controls. The bacterial superantigen activity of throat flora may not play a major role in the pathogenesis of KD.

Serum Anti-Yersinia Antibody in Chinese Patients with Kawasaki Disease

BACKGROUND

Many infectious agents have been implicated as an etiology to develop Kawasaki disease (KD). In Taiwan, studies on the relationship between Yersinia and KD have not been reported.

METHODS

We measured sera for anti-Yersinia antibodies by using enzyme immunoassay (EIA) in 31 patients with KD and 60 healthy children (HC). Yersinia strains included Y. pseudotuberculosis I, II, III, IV, V, VI and Y. enterocolitica O3, O8 and O9.

RESULTS

Data of 31 patients with KD showed that for the IgG antibody, serum anti-Y. pseudotuberculosis II, III, Y. O8 and O9 antibody were significantly higher when compared to the HC. Except for Y. pseudotuberculosis IV, all other Yersinia strains of either IgA or IgM antibodies increased significantly in patients with KD vs. the HC. If we compared the number of patients who had significant elevation of OD and those of HC, we found IgA anti-Yersinia antibodies (PST I, PST II, O3, O8, O9), IgM (PST VI, O8) and IgG (PST II, O8, O9) were significantly elevated in KD patients than in HC. A significant relationship was present between KD with myocarditis and increased anti-Yersinia antibody titer.

CONCLUSIONS

The findings in this study suggest that preceding Yersinia infection may play a role in the pathogenesis of KD. Further study of the relationship between KD with myocarditis and increased anti-Yersinia antibody is needed.

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.

Advances in Kawasaki disease

Recent studies have increased our understanding of the etiopathogenesis of Kawasaki disease (KD). The inflammatory infiltrate in KD coronary artery aneurysms has been shown to consist of CD8 T lymphocytes, macrophages, and IgA plasma cells, consistent with an immune response to an intracellular pathogen with a mucosal portal of entry. The identification of an oligoclonal IgA response in the vascular wall and the detection of a KD-associated antigen in inflamed KD tissues using a synthetic antibody derived from KD oligoclonal IgA antibodies have provided new approaches to identification of the etiologic agent. Highly effective therapy has evolved for KD, even in the absence of identification of the etiologic agent. The existence of incomplete KD cases remains a significant diagnostic dilemma for the clinician.

CONCLUSION

The development of a diagnostic test, more specific therapy, and ultimate prevention of this potentially fatal illness of childhood are dependent upon continued advances in determining the etiopathogenesis of this fascinating disorder.

Vbeta-restricted T cell adherence to endothelial cells: a mechanism for superantigen-dependent vascular injury

OBJECTIVE

To investigate the potential for endothelial cells to operate as superantigen-presenting cells for T cells and the potential for such an interaction to cause endothelial cell activation and injury.

METHODS

Class II major histocompatibility complex (MHC)-positive human umbilical vein endothelial cells (HUVECs) were cocultured for 4 hours with purified T cells and the superantigens staphylococcal enterotoxin B (SEB) or toxic shock syndrome toxin 1 (TSST-1). After staining with fluorescence-conjugated monoclonal antibodies, flow cytometric analysis was performed on the HUVECs and T cells to examine V(beta)-restricted T cell adherence to the endothelial cell monolayer, V(beta)-restricted T cell activation (CD69 up-regulation), surface expression of endothelial cell activation markers, and generation of endothelial microparticles (EMPs).

RESULTS

Coculture of purified T cells with class II MHC-positive HUVECs and either TSST-1 or SEB resulted in V(beta)-restricted CD69 up-regulation by CD4 and CD8 cells (V(beta)2 activation for TSST-1; V(beta)3, V(beta)5.1, and V(beta)12 activation for SEB). Additionally, there was CD4 and CD8 T cell V(beta)-restricted adherence to the HUVEC monolayer at 4 hours. Expression of intercellular adhesion molecule 1, E-selectin, and vascular cell adhesion molecule 1 was up-regulated on the class II MHC-positive HUVECs following exposure to superantigen in the presence of T cells, and there was increased EMP release from activated HUVECs, which occurred earlier and was of greater magnitude than that observed in response to tumor necrosis factor alpha.

CONCLUSION

Class II MHC-positive endothelial cells operate as competent superantigen-presenting cells for CD4 and CD8 lymphocytes in vitro. Dual signaling between endothelial cells and T cells results in V(beta)-restricted activation and adherence to endothelial monolayers and endothelial cell activation and release of EMPs expressing inducible cell adhesion molecules. It is proposed that this mechanism could account in part for the vascular injury associated with superantigen-mediated diseases including Kawasaki disease.

Possible relationship between streptococcal pyrogenic exotoxin A and Kawasaki syndrome in patients older than six months of age

BACKGROUND

We previously investigated antibody titers against four kinds of superantigens [streptococcal pyrogenic exotoxin A (SPEA), streptococcal pyrogenic exotoxin C, toxic shock syndrome toxin-1 and staphylococcal enterotoxin B] in patients with Kawasaki syndrome (KS) younger than 6 months of age and reported a relationship between toxic shock syndrome toxin-1 and KS patients. In this study we have investigated antibody titers in KS patients older than 6 months of age.

METHODS

Serum of 81 patients with KS older than 6 months of age, before intravenous gamma-globulin therapy, and 88 normal age-matched children were used in this study. The IgG antibody titers against four kinds of superantigens were measured with an enzyme-linked immunosorbent assay.

RESULTS

The KS patients showed significantly elevated mean SPEA titer (P = 0.006) and significantly higher incidence of high SPEA (P = 0.0024) compared with the controls. The SPEA titer in KS patients showed a significant positive correlation with the number of days from onset of illness (P = 0.0002).

CONCLUSIONS

The elevated antibody titer against superantigens of KS patients older than 6 months of age was different from that of KS patients younger than 6 months of age. Our results suggest that KS patients' exposure to SPEA occurred a few weeks before the onset of KS. SPEA may be one of the possible etiologic agents of KS among patients older than 6 months of age in Kagoshima, Japan.

T cell Vbeta repertoires in childhood vasculitides

Superantigens (SAgs) are potent stimulators of T cells bearing specific Vbeta T cell receptors (TCR) and may play a role in the aetiopathogenesis of systemic vasculitis, although this remains contentious. To investigate the possible aetiological role of SAgs, this study examined peripheral blood T cell Vbeta repertoires in children with systemic vasculitis. FACS analysis of 17 different peripheral blood T cell Vbeta families was performed in 20 healthy control children, 27 disease control children with nonvasculitic inflammatory disease, 25 children with primary systemic vasculitis, six patients with Kawasaki disease (KD) and six patients with Henoch-Schönlein purpura (HSP). There was a significantly increased variance of CD4 Vbeta12 and Vbeta17, and CD8 Vbeta1 in the primary systemic vasculitis group compared to control and disease controls. Moreover, 80% of the primary systemic vasculitis children had one or more CD4 Vbeta expansions or deletions, compared with 30% of controls (P < 0.002), and 37% of the disease controls (P < 0.002). In the KD group, the mean percentage of CD4 Vbeta2 T cells was higher than in controls or disease controls. In the HSP group, there was no consistent skewing of the T cell Vbeta repertoire. We have observed changes in the T cell Vbeta repertoire in children with vasculitis over and above those observed in disease controls. While these data provide impetus for further research into this contentious field, they do not resolve unequivocally the question of the role of SAgs in childhood vasculitic syndromes.

Relation of streptococcal pyrogenic exotoxin C as a causative superantigen for Kawasaki disease

We previously reported that the frequency of TCRBV2 and TCRBV6S5-bearing T-cells was high in patients in the acute phase of Kawasaki disease (KD) and that streptococcal pyrogenic exotoxin C (SPE-C) was a potent stimulator of these TCRBV-bearing T-cells. To further elucidate the pathogenesis of KD, we examined the T-cell receptor (TCR) repertoire, human leukocyte antigen (HLA)-DRB1 genotype, and antibody responses to recombinant(r) SPE-C in patients with KD. We also performed in vitro stimulation with rSPE-A and rSPE-C of peripheral blood mononuclear cells from healthy donors and characterized the reacting T-cells. The percentage of T-cells bearing TCRBV2 and TCRBV6S5 was high in patients in the acute stage of KD. rSPE-C stimulation of PBMC from healthy donors induced expansion of TCRBV2 and TCRBV6S5-bearing T-cells. Furthermore, serum levels of anti-SPEC antibodies, which did not display antimitogenic activity, were higher in patients with acute KD than in age-matched controls. The frequencies of the DRB1*04051, 0406, and 0901 were high, whereas that of the DRB1*1101 was low among patients with KD as compared with the healthy adults.

Intravenous immunoglobulin for the treatment of Kawasaki disease in children

BACKGROUND

Kawasaki disease is the most common cause of acquired heart disease in children in developed countries. The coronary arteries supplying the heart can be damaged in Kawasaki disease. The principal advantage of timely diagnosis is the potential to prevent this complication with early treatment. Intravenous immunoglobulin (IVIG) is widely used for this purpose.

OBJECTIVES

The objective of this review was to evaluate the effectiveness of IVIG in treating, and preventing cardiac consequences, of Kawasaki disease in children.

SEARCH STRATEGY

Electronic searches of the Cochrane Peripheral Vascular Disease Group Specialised Register, CENTRAL, MEDLINE, EMBASE, and CINAHL were performed (last searched April 2003). We also searched references from relevant articles and contacted authors where necessary. In addition we contacted experts in the field for unpublished works.

SELECTION CRITERIA

Randomised controlled trials of intravenous immunoglobulin to treat Kawasaki disease were eligible for inclusion.

DATA COLLECTION AND ANALYSIS

Fifty-nine trials were identified in the initial search. On careful inspection only sixteen of these met all the inclusion criteria. Trials were data extracted and assessed for quality by at least two reviewers. Data were combined for meta-analysis using relative risk ratios for dichotomous data or weighted mean difference for continuous data. A random effects statistical model was used.

MAIN RESULTS

The meta-analysis of IVIG versus placebo, including all children, showed a significant decrease in new coronary artery abnormalities (CAAs) in favour of IVIG, at thirty days RR (95% CI) = 0.74 (0.61 to 0.90). No statistically significant difference was found thereafter. A subgroup analysis excluding children with CAAs at enrollment also found a significant reduction of new CAAs in children receiving IVIG RR (95%) = 0.67 (0.46 to 1.00). There was a trend towards benefit from IVIG at sixty days (p=0.06). Results of dose comparisons showed a decrease in the number of new CAAs with increased dose. The meta-analysis of 400 mg/kg/day for five days versus 2 gm/kg in a single dose showed statistically significant reduction in CAAs at thirty days RR (95%) = 4.47 (1.55 to 12.86). This comparison also showed a significant reduction in duration of fever with the higher dose. There was no statistically significant difference noted between different preparations of IVIG. There was no statistically significant difference of adverse effects in any group.

REVIEWER'S CONCLUSIONS

Children fulfilling the diagnostic criteria for Kawasaki disease should be treated with IVIG (2 gm/kg single dose) within 10 days of onset of symptoms.

Prevalence of superantigen-secreting bacteria in patients with Kawasaki disease

OBJECTIVES

To assess the prevalence of superantigen secreting bacteria in children with acute Kawasaki disease (KD) relative to control patients.

STUDY DESIGN

Bacterial cultures were obtained in a blinded fashion from the throat, rectum, and groin of 45 patients with untreated acute KD and 37 febrile control patients from 6 centers in the United States. Cultures were processed for the presence of superantigen-producing bacteria at a central laboratory.

RESULTS

Staphylococci or streptococci that produced superantigens (TSST-1, SEB, SEC, SPEB, SPEC) were isolated from 25 of 45 patients with KD (56%) as compared with 13 of 37 (35%) control patients (P =.078). Because SEB- and SEC-producing Staphylococcus aureus have not been associated with KD and because they do not induce a Vbeta2+ T-lymphocyte response, we analyzed the difference between groups relative to superantigens TSST-1 or SPEB/SPEC production. TSST-1 secreting S aureus or SPEB/SPEC producing group A streptococci were isolated from 20 of 45 (44%) patients with KD compared with 7 of 37 (19%) control patients (P =.019).

CONCLUSIONS

The overall isolation rates of superantigen (TSST-1, SPEB, SPEC, SEB, SEC) producing bacteria between patients with KD and febrile control patients were not statistically significant. However, future studies should further examine the potential role of Vbeta2-stimulatory superantigens (TSST-1 and SPEB/SPEC) in KD.

Kawasaki disease: an evidence based approach to diagnosis, treatment, and proposals for future research

This article proposes a clinical guideline for the diagnosis and treatment of Kawasaki disease in the UK based on the best available evidence to date, and highlights areas of practice where evidence is anecdotal or based on retrospective data. Future research as proposed by the London Kawasaki Disease Research Group is outlined, and clinicians are invited to prospectively enroll their suspected cases into this collaborative research project.

Pharmacological therapy for patients with Kawasaki disease

Kawasaki disease is a systemic vasculitis of unknown aetiology that has been reported worldwide since its initial description in Japanese children. The most significant sequelae of acute Kawasaki disease are related to the inflammation of small to medium sized arteries and, in particular, the development of coronary artery aneurysms. Because the aetiology is unknown, pharmacological therapy is nonspecific and directed towards modulation of the inflammatory response and inhibition of platelet activation with the aim of preventing coronary artery aneurysms. In the US, the recommended treatment for Kawasaki disease in the acute phase is a single, high dose of intravenous gammaglobulin (2 g/kg) and high dose aspirin (80 to 100 mg/kg/day). Use of this regimen has resulted in a significant decrease in the incidence of coronary artery abnormalities. Although the American Heart Association currently recommends high dose aspirin, moderate doses are used in Japan and the optimal dose of aspirin is not known. There has been renewed interest in the use of corticosteroids in the treatment of acute Kawasaki disease: however, their precise role remains unclear. Newer antiplatelet agents have also shown some promise in the treatment of patients with coronary artery aneurysms. Long term pharmacological therapy consists primarily of anticoagulation in patients with persistent coronary artery abnormalities. In this review, current recommendations for pharmacological therapy in Kawasaki disease are reviewed and some of the controversies in management of this disease, including management of patients who do not respond to initial therapy and the role of corticosteroids in the acute setting, are outlined.

Oligoclonal IgA response in the vascular wall in acute Kawasaki disease

Kawasaki Disease (KD) is a potentially fatal acute vasculitis of childhood. Although KD is the leading cause of acquired heart disease in children in developed nations, its pathogenesis remains unknown. We previously reported the novel observation that IgA plasma cells infiltrate the vascular wall in acute KD. We have now examined the clonality of this IgA response in vascular tissue from three fatal cases of KD to determine whether it is oligoclonal, suggesting an Ag-driven process, or polyclonal, suggesting nonspecific B cell activation or a response to a superantigen. We first sequenced VDJ junctions of 44 alpha genes isolated from a primary, unamplified KD vascular cDNA library. Five sets of clonally related alpha sequences were identified, comprising 34% (15 of 44) of the isolated alpha sequences. Furthermore, point mutations consistent with somatic mutation were detected in the related sequences. Next, using formalin-fixed coronary arteries from two additional fatal KD cases, we sequenced VDJ junctions of alpha genes isolated by RT-PCR, and a restricted pattern of CDR3 usage was observed in both. We conclude that the vascular IgA response in acute KD is oligoclonal. The identification of an oligoclonal IgA response in KD strongly suggests that the immune response to this important childhood illness is Ag-driven.

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

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

Vasculitis from the pediatric perspective

This article reviews the spectrum of vasculitic illness affecting children. Apart from the relatively common vasculitides (Henoch-Schönlein purpura, Kawasaki disease, and in worldwide terms Takayasu disease) there are a number of important but comparatively rare disorders affecting children. As in adults, there is a considerable degree of overlap between the various vasculitic syndromes in childhood. With modern therapeutic agents, the prognosis for many of the childhood vasculitides has improved; however, in spite of this, there remains a not inconsequential morbidity and mortality. It is anticipated that as our knowledge of the immunopathogenesis of this group of disorders expands, classification and treatment of vasculitis in both children and adults will improve.

Superantigens: mechanisms by which they may induce, exacerbate and control autoimmune diseases

Superantigens are polypeptide molecules produced by a broad range of infectious microorganisms which elicit excessive and toxic T-cell responses in mammalian hosts. In light of this property and the fact that autoimmune diseases are frequently the sequelae of microbial infections, it has been suggested that superantigens may be etiologic agents of autoreactive immunological responses resulting in initiation, exacerbation or relapse of autoimmune diseases. This article relates the biology of superantigens to possible mechanisms by which they may exert these activities and reviews the evidence for their roles in various human and animal models of autoimmune disease. Finally, a mechanism of active suppression by superantigen-activated CD4+ T-cells that could be exploited for therapy as well as prophylaxis of human autoimmune diseases is proposed.

Overview of pharmacological treatment of Kawasaki disease

Kawasaki disease has been researched for 32 years but its aetiology is still unknown. Conventional therapy for the disease includes corticosteroids and aspirin (acetylsalicylic acid) as anti-inflammatory and/or antithrombotic agents but they have not been proven to prevent coronary artery aneurysms. Although a high incidence of liver dysfunction in Japanese patients with Kawasaki disease receiving high dose aspirin (> or =80 mg/kg/day) suggests racial differences in salicylate sensitivity, the duration of fever in patients receiving high dose aspirin is shorter than that in patients receiving moderate dosages (30 to 50 mg/kg/day). Furthermore, most corticosteroid-resistant patients were found to develop coronary artery aneurysms, many of which were large. With the clarification of the pathogenesis and clinical features of Kawasaki disease, advances in its treatment have been achieved. The introduction of high-dose intravenous gamma-globulin (IVGG) was an epoch in this field and IVGG is now a standard therapy with the incidence of persistent coronary aneurysms 1.9% in children with the disease receiving IVGG. Today, research is mainly directed toward the treatment of IVGG-resistant patients. One to 3 days of pulsed doses of methylprednisolone (30 mg/kg/day) or readministration of IVGG 1 g/kg (once to several times) has been recommended for patients with IVGG-resistant Kawasaki disease.

Staphylococcus aureus isolates from patients with Kawasaki disease express high levels of protein A

Kawasaki disease (KD) is an acute vasculitis of young children that can be complicated by coronary artery abnormalities. Recent findings suggest that a superantigen(s) may play an important role in stimulating the immune activation associated with the disease, although the origin of this superantigen(s) is unclear. Staphylococcus aureus, isolated from the rectum or pharynx of patients with KD, secretes toxic shock syndrome toxin 1 (TSST-1). The KD isolates express low levels of other exoproteins compared to isolates from patients with toxic shock syndrome (TSS). Thus, it was previously suggested that the KD isolates may be defective in the global regulatory locus agr (for accessory gene regulator), which positively regulates these factors (D. Y. M. Leung et al., Lancet 342:1385-1388, 1993). Here we describe another characteristic of KD isolates. When considered collectively, the KD isolates were found to express higher levels of staphylococcal protein A than the TSS isolates, another characteristic of an agr-defective phenotype. This correlated with a higher level of spa mRNA in these isolates. In contrast, the KD and TSS isolates expressed comparable levels of TSST-1, consistent with previous findings (D. Y. M. Leung et al., Lancet 342:1385-1388, 1993). Analysis of RNAIII transcript levels and nucleotide sequence analysis of the RNAIII-coding region suggested that the KD isolates are not defective in RNAIII, the effector molecule of the agr regulatory system. However, induction of RNAIII transcription in the KD isolates did not result in a dramatic decrease in the amount of spa mRNA, as has been reported for other strains (F. Vandenesch, J. Kornblum, and R. P. Novick, J. Bacteriol. 173:6313-6320, 1991).

Activation of mouse liver natural killer cells and NK1.1(+) T cells by bacterial superantigen-primed Kupffer cells

Although bacterial superantigens have been well characterized as potent stimulators of T cells, their role in natural killer (NK)-type cells remains largely unknown. In the present study, we examined the effect of bacterial superantigens on mouse liver NK cells and NK1.1 Ag(+) (NK1(+)) T cells. C57BL/6 mice were intravenously injected with staphylococcal enterotoxin B (SEB) or streptococcal pyrogenic exotoxin A (SPE-A), and mononuclear cells (MNC) of various organs were obtained from mice 4 hours after being injected with superantigen. MNC were cultured for 48 hours, and interferon gamma (IFN-gamma) levels of supernatants were measured. The antitumor cytotoxicities of the liver and spleen MNC were also evaluated 24 hours after the mice were injected with superantigen. Liver MNC produced more IFN-gamma than did splenocytes, and peripheral blood and lung MNC did not produce any detectable IFN-gamma. In addition, liver MNC acquired a potent antitumor cytotoxicity by the SEB injection, and both NK cells and NK1(+)T cells but not cluster of differentiation (CD)8(+) T cells were responsible for the cytotoxicity as demonstrated by either in vivo or in vitro cell depletion experiments, and the NK-type cells were partly responsible for the increased serum IFN-gamma. Activation of liver NK-type cells was also supported by the fact that liver NK cells proportionally increased and NK1(+) T cells augmented their CD11a expressions after SEB injection. The pretreatment of mice with anti-IFN-gamma Ab and/or with anti-interleukin-12 (IL-12) Ab diminished the SEB-induced cytotoxicity of liver MNC. Furthermore, the in vivo depletion of Kupffer cells decreased the SEB-induced cytotoxicity of liver MNC. Consistent with these results, liver MNC stimulated with superantigens in the presence of Kupffer cells in vitro produced a greater amount of IFN-gamma than did the liver MNC without Kupffer cells or splenocytes. Our results suggest that bacterial superantigen-primed Kupffer cells produce IL-12 and other monokines, while also nonspecifically activating both NK cells and NK1(+) T cells to produce IFN-gamma.

The structural basis of T cell activation by superantigens

Superantigens (SAGs) are a class of immunostimulatory and disease-causing proteins of bacterial or viral origin with the ability to activate large fractions (5-20%) of the T cell population. Activation requires simultaneous interaction of the SAG with the V beta domain of the T cell receptor (TCR) and with major histocompatibility complex (MHC) class II molecules on the surface of an antigen-presenting cell. Recent advances in knowledge of the three-dimensional structure of bacterial SAGs, and of their complexes with MHC class II molecules and the TCR beta chain, provide a framework for understanding the molecular basis of T cell activation by these potent mitogens. These structures along with those of TCR-peptide/MHC complexes reveal how SAGs circumvent the normal mechanism for T cell activation by peptide/MHC and how they stimulate T cells expressing TCR beta chains from a number of different families, resulting in polyclonal T cell activation. The crystal structures also provide insights into the basis for the specificity of different SAGs for particular TCR beta chains, and for the observed influence of the TCR alpha chain on SAG reactivity. These studies open the way to the design of SAG variants with altered binding properties for TCR and MHC for use as tools in dissecting structure-activity relationships in this system.

Kawasaki syndrome

Kawasaki syndrome is a fascinating worldwide illness of young children. This acute self-limited vasculitis has become the most common cause of acquired heart disease in children in the United States and Japan. KS causes significant coronary artery disease that may lead to myocardial infarction and sudden death. Clinical and epidemiologic features of KS support an infectious cause, but the etiology remains unknown. Clearly, additional research on the cause of KS and its pathogenesis is needed urgently to allow for improved diagnosis; more specific therapy; and, ultimately, prevention of the disorder.

Polyclonal expansion of TCRBV2- and TCRBV6-bearing T cells in patients with Kawasaki disease

We examined T-cell receptor (TCR) usage, cytokine production and antibody responses to superantigens in patients with Kawasaki disease (KD) to facilitate a better understanding of the immunopathogenesis of KD. The mean percentage of VB2- or VB6. 5-bearing T cells in peripheral blood mononuclear cells (PBMC) of patients with acute-phase KD was significantly higher than that of patients in the convalescent phase of KD or in healthy donors. Expansion of VB2- or VB6.5-bearing T cells was polyclonal because DNA sequences in the complementarity determining region 3 of VB2- and VB6.5-positive cDNA clones were all different from each other. The plasma levels of interleukin (IL)-1beta, IL-2, IL-6, IL-8, IL-10, interferon-gamma (IFN-gamma), tumour necrosis factor-alpha (TNF-alpha) and granulocyte colony-stimulating factor (G-CSF) were elevated in the acute phase of KD. We previously reported that streptococcal pyrogenic exotoxin C (SPEC) was a potent stimulator of VB2- and VB6.5-positive T cells and, furthermore, serum levels of anti-SPEC antibodies were significantly higher in patients with acute and convalescent KD than in age-matched controls. The results of the present study, together with those of our previous report, suggest that SPEC induces activation and polyclonal expansion of VB2- and VB6.5-positive T cells, and that SPEC-induced activation of T cells may lead to the pathogenesis of KD.

The role of superantigens in vasculitis

Multiple risk factors are involved in susceptibility to vasculitis. Inherited determinants may increase the risk but are insufficient to induce the disease. Environmental factors, such as infections, are important modulators and probably trigger the disease in most cases. One of the possible triggers may be a bacterial superantigen (SAg). SAgs may activate autoreactive T cells that mediate autoimmune vessel wall destruction. Furthermore, SAgs may activate autoreactive B cells to produce autoantibodies that are involved in the pathophysiology of vasculitis, such as antineutrophil cytoplasmic autoantibodies or anti-endothelial cell antibodies. In patients with Kawasaki disease, Wegener's granulomatosis, and infection-related forms of vasculitis, SAg-producing microorganisms have regularly been found. Activation of circulating T cells and skewing of the T-cell repertoire have been reported in most forms of vasculitis. In the past year, for the first time, patients were described in which T-cell receptor V beta expansions were documented simultaneously with the typing of the microbial SAgs, providing evidence that the observed changes in the T-cell repertoire could be caused by these bacterial SAgs. In the future, elucidation of the immunologic mechanisms by which SAgs may play a role in the pathophysiology of vasculitis will provide more effective methods for the treatment of vasculitis.

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

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

Inhibition of IL-12 synthesis of peripheral blood mononuclear cells (PBMC) stimulated with a bacterial superantigen by pooled human immunoglobulin: implications for its effect on Kawasaki disease (KD)

The aim of this study was to further assess the role of pooled human immunoglobulin (PHIG) on cytokine production from PBMC stimulated with a bacterial superantigen. Human PBMC were cultured with Streptococcus pyrogenic exotoxin A (SPE-A) with or without PHIG and several proinflammatory cytokine levels of culture supernatants were measured. Serum cytokine levels of KD patients before and after PHIG therapy were also examined. PHIG greatly reduced the production of IL-12, interferon-gamma (IFN-gamma) and other cytokines from SPE-A-stimulated PBMC, while exogenous IL-12, but neither IL-1 nor tumour necrosis factor-alpha (TNF-alpha), restored IFN-gamma production inhibited by PHIG. Although PHIG partially adsorbed SPE-A, its inhibitory effect on cytokine production was not played by anti-SPE-A antibody. Although purified CD4+ T cells cultured with human HLA-DR-transfected mouse L cells and SPE-A could not effectively produce IFN-gamma, they produced large amounts of IFN-gamma if exogenous IL-12 was introduced. KD patients in the acute phase had higher levels of serum IFN-gamma than did controls and patients with bacterial infection. Although IL-12 levels of children with or without KD were not significantly different, IL-12 levels of children were much higher than those of adults. However, serum levels of IL-12 of KD patients were transiently but significantly decreased by PHIG therapy and IFN-gamma amounts subsequently reverted to basal levels thereafter. These findings indicate that PHIG inhibits IL-12 production of SPE-A-activated monocytes and thereby decreases IFN-gamma synthesis by T cells and suggest that inhibition of IL-12 and IFN-gamma production is an important part of the mechanisms underlying PHIG therapy on KD.

Epithelial ion transport and barrier abnormalities evoked by superantigen-activated immune cells are inhibited by interleukin-10 but not interleukin-4

Many studies have indicated an association between bacteria and the severity of enteric secretory or inflammatory disorders. We previously showed that monolayers of human T84 epithelial cells display altered ion transport and permeability after coculture with Staphylococcus aureus enterotoxin B (SEB, a model superantigen)-activated immune cells, where interferon-gamma and tumor necrosis factor-alpha were key mediators in the pathophysiology. Here we examined whether the regulatory Th2-type cytokines, interleukin (IL)-10 and IL-4, could prevent these epithelial irregularities. T84 monolayers were cocultured with human peripheral blood mononuclear cells (PBMC) or T cell-enriched, monocyte-depleted PBMC (T + B cells) +/- SEB for 20 hr in the presence or absence of IL-10 or IL-4. Subsequently, T84 monolayers were mounted in Ussing chambers and ion transport (short-circuit current (Isc) and DeltaIsc evoked by forskolin) and permeability (ion resistance and probe fluxes) were assessed. IL-10 dose-dependently inhibited the increased T84 permeability and the reduced responsiveness to forskolin that were evoked by coculture with SEB-activated PBMC or T + B cells. Similar changes in T84 function occurred in response to conditioned medium from SEB-activated immune cells; however, addition of IL-10 to the conditioned medium did not prevent the changes in epithelial function. In contrast, when PBMC were stimulated with SEB in the presence of IL-10, the subsequent conditioned medium was less effective in evoking altered epithelial function. These data suggest that the affect of IL-10 was due to effects on the immune cells and not directly on the epithelium. In contrast to IL-10, IL-4 did not ameliorate any of the immune-mediated changes in T84 function. We conclude that IL-10 can reduce the epithelial functional changes caused by SEB-activated immune cells and this data adds further support for IL-10 immunotherapy in the treatment of intestinal secretory or inflammatory disorders.

Characterization of the T-cell receptor V-beta repertoire in Kawasaki disease

Kawasaki disease (KD) is a paediatric multisystem necrotizing vasculitis constituting the most frequent cause of acquired heart disease in childhood. Conflicting data have been reported regarding expanded T-cell populations using particular T-cell receptor (TCR) beta-chain variable (BV) gene segments, suggesting either a superantigen- or a conventional antigen-mediated immune response in this disease. In order to further investigate the role of T lymphocytes, cells were stained with an extensive panel of 21 different TCRBV specific monoclonal antibodies (MoAbs) covering almost 70% of all T-cells. Flow cytometry was employed to analyse the expression of the TCRBV repertoire in the CD4+ and CD8+ subsets separately, and of activation markers, in freshly isolated peripheral blood lymphocytes of 25 Kawasaki disease patients during the acute and convalescent phases of the disease. No abnormal usage of any TCRBV family was found, neither acutely nor during convalescence, compared with a control group of healthy children. However, a significant increase in interleukin-2 receptor (IL-2R)-expressing T lymphocytes restricted to the CD4+ subset was observed in KD patients. Our data confirm a strong immune activation in KD that might be of importance in the pathogenesis of the disease.

Toxin-mediated streptococcal and staphylococcal disease

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

Transient low T cell response to streptococcal pyrogenic exotoxin-C in patients with Kawasaki disease

Superantigens (SAs) are known to induce transient anergy followed by T cell activation. Recent reports have suggested that SAs are involved in the pathogenesis of Kawasaki disease (KD). In the present study, we investigated the peripheral T cell response to SAs by measuring proliferation and IL-2 production to determine whether the T cell anergy is induced by SAs in patients with KD. T cells were obtained from 45 Japanese patients with KD in different stages of the disease and were stimulated by streptococcal pyrogenic exotoxin (SPE)-A, SPE-C, and toxic shock syndrome toxin-1 (TSST-1). T cells from patients with KD in the acute or convalescent stage up to 2 mo showed significantly lower proliferation and IL-2 production than did T cells from healthy control subjects stimulated by SPE-C, but not SPE-A or TSST-1. The T cell response to SPE-C normalized within 1 y. The low T cell response to SPE-C in the acute stage correlated with a peak platelet count and the C-reactive protein-positive period. These findings suggest that the transient low T cell response to SPE-C in patients with KD may have been related to SA-induced anergy or disappearance of SPE-C-responding cells from the circulation. The present results suggested that SPE-C may be involved in the pathogenesis of KD.

Kawasaki syndrome

Kawasaki syndrome (KS) is an acute, sometimes fatal vasculitis of young children. KS has replaced acute rheumatic fever as the most common cause of acquired heart disease in children in the United States. The illness is manifested by prolonged fever, conjunctival injection, enanthem, exanthem, erythema and swelling of the hands and feet, and cervical adenopathy. These acute features of illness are self-limiting, but coronary artery abnormalities occur in 20% of untreated patients. The etiology of the illness is unknown, but its clinical and epidemiologic features are most consistent with an infectious cause. Common cardiovascular manifestations of the illness include myocarditis, pericardial effusion, and coronary artery aneurysm formation. Treatment with intravenous gamma globulin (IVGG) and aspirin within the first 10 days of illness reduces the prevalence of coronary artery abnormalities from 20% in those treated with aspirin alone to 4%. Patients who develop coronary artery aneurysms, particularly those who develop giant coronary artery aneurysms, may suffer myocardial infarction secondary to thrombosis or stenosis in the abnormal vessel. Additional research to determine the cause of KS is urgently needed to allow for improved diagnosis, more specific therapy, and prevention of the disorder.

Childhood vasculitis

Vasculitis can and does occur in childhood. Apart from the relatively common vasculitides (Henoch-Schönlein purpura, Kawasaki disease and in world wide terms Takayasu disease) there are a number of important but comparatively rare disorders affecting children. These include macroscopic and microscopic polyarteritis, cutaneous polyarteritis, Wegener's granulomatosis, Churg-Strauss syndrome, primary angiitis of the central nervous system, hypersensitivity angiitis, hypocomplimentaemic urticarial vasculitis, vasculitis associated with various connective tissue disorders and vasculitis associated with conditions such as Behçets syndrome, familial Mediterranean fever and Cogan's syndrome. Distinguishing these conditions from other disorders is often difficult and requires clinical acumen and appropriate investigative procedures. With modern therapeutic agents, it is possible to implement appropriate therapy but in spite of this, there remains a not inconsequential morbidity and mortality.

Kawasaki disease and the T-cell antigen receptor

We investigated the evidence for an infectious etiology of Kawasaki disease (KD), an acute vasculitis of unknown etiology, by assessing the effects of KD on the T cell antigen receptor variable beta region families (V beta). Using 3-color flow cytometry, we studied KD patients pre- and post-intravenous gamma globulin (IVIG) therapy and at > 40 days post therapy, additionally comparing them to matched pediatric control patients (PCC) and their own healthy parents (one parent/KD child). Of all the V beta families examined, only V beta 2 exhibited statistically significant differences, between the pre- and post-IVIG samples and preIVIG and parent samples. No associations were found between V beta 2 findings and T cell memory, activation, or adhesion markers. For 2 KD patients, 4 parents, and 1 PCC participant, > 15% of resting CD8+ lymphocytes and > 15% of blastic CD8+ lymphocytes expressed a single V beta family, which varied by individual, without similar expansions in the CD4+ cell populations. One of the participants with this abnormality was the only one with significant cardiac abnormalities. For all participants with the V beta abnormality, other T-cell abnormalities were extensive and involved both CD4+ and CD8+ cells. We suggest that V beta 2 changes do occur in KD, as previously reported. However, these may not be involved in disease pathogenesis. Other V beta changes also occur. Those occurring in parents may reflect asymptomatic reinfection with an infectious agent causing KD. Further, some KD patients may have restricted cytotoxic T-cell responses to that as yet unidentified agent; this restricted response may be associated with more severe cardiac involvement.

Kawasaki disease in Australia, 1993-95

AIM

To describe the epidemiology, management, and rate of cardiac sequelae of Kawasaki disease in Australia.

DESIGN

Cases were notified to the Australian Paediatric Surveillance Unit, an active national surveillance scheme, from May 1993 to June 1995.

RESULTS

139 cases of Kawasaki disease were confirmed. In 1994, the annual incidence was 3.7/100,000 children < 5 years old. Sixteen children were not admitted to hospital. Coronary artery abnormalities were reported in 35 (25%) children. Two patients were diagnosed at postmortem examination. Sixty six per cent of patients were diagnosed within 10 days of onset and 81% of these received intravenous gammaglobulin within 10 days. Forty five of the notified children did not fulfil the study criteria because of streptococcal infection or insufficient clinical criteria. One child with streptococcal infection had coronary artery dilatation.

CONCLUSION

Diagnosis of Kawasaki disease was delayed beyond 10 days in one third of patients, and almost 20% of children who could have received gammaglobulin within 10 days did not. The distinction between Kawasaki disease, streptococcal infection, and other possible diagnoses is problematic in some children.

Kawasaki disease. The mystery continues

Kawasaki disease is an acute systemic vasculitis of unknown cause first described in Japan in 1967. It affects children younger than 10 years, predominantly those younger than 3 years. Children of Asian ancestry are more commonly affected than white children. The diagnosis is made when 4 of the following 5 signs or symptoms are present with fever for at least 5 days: polymorphous rash; conjunctival injection; oral mucosal changes; cervical lymphadenitis; and erythema, swelling, or desquamation of the hands and feet. Various symptoms may be seen also, among them pronounced irritability, arthralgia, and abdominal pain. No diagnostic test exists, and clinicians must carefully exclude diseases that mimic Kawasaki disease. In addition to the above clinical findings, Kawasaki disease causes aneurysm formation in medium-sized arteries, particularly the coronary arteries. Found in about a fourth of patients, these lesions may persist, scar with stenosis, or resolve angiographically. The treatment consists of administering high-dose aspiring and intravenous immune globulin, with the goal of relieving acute illness and minimizing sequelae. Although most respond rapidly, almost 10% of children do not improve clinically with treatment. Complications of Kawasaki disease include myocardial infarction, which may occur during acute illness or later, as a result of coronary abnormalities.

Immunoregulatory changes in Kawasaki disease

Kawasaki disease (KD) is an acute vasculitis of unknown etiology, occurring in young children and treated with intravenous gamma globulin (IVIG) to prevent significant cardiac morbidity and mortality. We studied KD patients pre- and post-IVIG therapy and at >40 days posttherapy, additionally comparing them with matched pediatric control patients and parents. Using three-color flow cytometry, we examined immune changes in KD, especially previously unassessed markers of T-lymphocyte activation, memory, and adhesion. The percentage of cells positive for CD19, CD25, CD38, and CD71 was significantly lower during convalescence compared with pre-IVIG (medians: CD19, 18% vs 26%, P = 0.0004; CD25, 6% vs 9% for CD3(+) cells, P = 0.0074; CD38, 78% vs 89% for CD8(+) cells, P = 0.0015; CD71, 1% vs 6% for CD4(+) cells, P = 0.0024). The proportion of CD3(+) cells increased (medians: CD3, 66% vs 45%, P < 0.0001). Values for all parameters varied greatly pre- and post-IVIG, but not in a consistent direction. The sole patient with cardiac abnormalities had the greatest pre-/post-IVIG variability. These changes support the involvement of T-lymphocytes in the acute KD vasculitic process. They also suggest that T-lymphocytes involved in endothelial damage during acute KD may be subsequently removed or eliminated from the peripheral blood.

Association of toxic shock syndrome toxin-secreting and exfoliative toxin-secreting Staphylococcus aureus with Kawasaki syndrome complicated by coronary artery disease

Kawasaki syndrome (KS) has been reported to be associated with selective expansion of Vbeta2+ T cells and either staphylococcal toxic shock syndrome toxin-1 or streptococcal pyrogenic exotoxin C in uncomplicated cases. However, there have been no previous studies on the role of superantigens in KS associated with coronary artery disease, the major complication of this illness. The present study characterized bacteria isolated from three acute KS patients who developed coronary artery disease. Staphylococcus aureus secreting either TSST-1 (n = 3) or exfoliative toxin A (n = 1), both known to stimulate expansion of Vbeta2+ T cells, were isolated from all three patients. The percent Vbeta2+ T cells was determined in three patients with coronary artery disease. On presentation, one patient demonstrated reduction, whereas the other two showed expansion, of Vbeta2+ T cells. Repeat analyses of the latter two children showed their percent Vbeta2+ T cells to decrease toward normal. These observations suggest that coronary artery disease in KS may result from superantigenic stimulation of Vbeta2+ T cells. This is also the first demonstration of an association of staphylococcal exfoliative toxin with acute KS. The observation that three different bacterial toxins associated with KS are potent activators of Vbeta2+ T cells suggests an important role for this T cell subset in the pathogenesis of this autoimmune disease.

A case of Kawasaki disease with coronary artery aneurysms documenting Yersinia pseudotuberculosis infection

A case of a 5-year-old boy who fulfilled all the criteria for Kawasaki disease (KD) was described. He had associated bilateral coronary artery aneurysms. Our study revealed the isolation of Yersinia pseudotuberculosis in stool cultures, and the elevation and seroconversion of the agglutination antibody titres, and hence he was diagnosed as Y. pseudotuberculosis infection-positive. We also demonstrated the positive mitogenic activity of the culture supernatant of the isolated bacterium from the patient and detected Y. pseudotuberculosis-derived mitogen by PCR. This case therefore suggests that Y. pseudotuberculosis might be closely related to the cause of KD.

New aspects of exanthematous diseases of childhood

The childhood exanthems include a spectrum of common and uncommon disorders caused by a variety of pathogens. In this article, timely issues relating to immunization for measles and varicella are discussed. Recently reported exanthematous illnesses, including papular-purpuric gloves and socks syndrome, unilateral laterothoracic exanthem, and eruptive pseudo-angiomatosis, are described. The current research and debate about bacterial toxins as the cause of Kawasaki syndrome are presented.

Tuberculin skin test reactivity in Kawasaki disease

A strongly positive tuberculin skin reaction (> 1.5 cm2) was observed during the acute phase of the illness in 11 children with Kawasaki disease (KD), but not in control pediatric patients with other febrile infections (41 patients) or diseases similar to KD (9 patients). The cutaneous sensitivity to intermediate strength [5 tuberculin units (TU)] purified protein derivative (PPD) inoculation had completely disappeared by the second monthly checkup. Peripheral blood T lymphocytes from KD subjects proliferated vigorously and produced significant amounts of IL-2 in response to the stimulation elicited by 0.05 TU/mL of PPD. In contrast, the proliferative response of, and IL-2 release by, control T cells was within background values. Mounting laboratory evidence suggests that heat shock proteins (HSP) may be involved in the pathogenesis of KD. Our clinical and experimental data may, therefore, have been due to immunologic cross-reactivity between mycobacterial derived HSP65 and its human homologue HPS63 (self P1 antigen). Despite the low number of patients investigated, our findings suggest that the tuberculin skin test and its in vitro correlates (T cell mitogenesis and IL-2 production) could provide simple and reliable diagnostic tools for identifying atypical forms of KD, or vice versa, in subjects not vaccinated against tuberculosis.

Kawasaki disease: clustering in infants and pre-school children in Kuwait

We report five children who presented within a 2-month period and who all fulfilled at least four of the five criteria essential for the diagnosis of Kawasaki disease. They were three girls and two boys aged between 5 months and 3 years. Two of them had atypical presentations; one mimicked infectious mononucleosis and the other had severe abdominal pain and was later found to have hydrops of the gall bladder. Although treatment was started within the 1st 10 days of the illness, echocardiographic changes were found in three cases: one had myocarditis and the other two showed in the coronary arteries. The occurrence of five cases in such as short period of time is similar to the clusterings of Kawasaki disease reported in Japan and the USA, and strongly suggests the presence of a causative infectious agent.

Soluble CD30 serum antigen in Kawasaki disease

Very high levels of sCD30, a glycoprotein surface antigen expressed by T lymphocytes and other mononuclear cells of the immune system, were found in serum samples from 10 children with typical Kawasaki disease (KD), but not in blood specimens from a vast cohort of paediatric control subjects. These data strongly support an involvement of CD30 T cells in the immune processes which take place at the level of lymphoid organs during the acute phase of KD.