Group A streptococcal pyrogenic exotoxin (scarlet fever toxin) type A and blastogen A are the same protein

Early intravenous immunoglobulin therapy for group A β-haemolytic streptococcal meningitis with toxic shock syndrome

A woman in her forties was transferred to a Sydney (Australia)-based tertiary hospital, following presentation to a regional hospital with group A Streptococcus (GAS) otomastoiditis; complicated by meningitis, venous sinus thrombosis, haemorrhagic cerebral infarction and subdural empyema. She rapidly deteriorated with profound cardiovascular collapse. Despite initiation of high dose vasoactive therapy, she remained shocked and developed multiorgan dysfunction syndrome. Early intravenous immunoglobulin therapy (140 g in two doses) was initiated as an adjunct to antimicrobial, surgical and supportive care for refractory streptococcal toxic shock syndrome. Over the course of a twelve-day intensive care unit stay she made good progress with de-escalation of her vasoactive supportive care and reversal of her organ injuries. She was subsequently discharged to ward-based care. At her three-month follow-up appointment she had significantly reduced neurological deficit. Five months following her presentation to hospital she had returned to full-time work.

Staphylococcal and streptococcal superantigen exotoxins

SUMMARY This review begins with a discussion of the large family of Staphylococcus aureus and beta-hemolytic streptococcal pyrogenic toxin T lymphocyte superantigens from structural and immunobiological perspectives. With this as background, the review then discusses the major known and possible human disease associations with superantigens, including associations with toxic shock syndromes, atopic dermatitis, pneumonia, infective endocarditis, and autoimmune sequelae to streptococcal illnesses. Finally, the review addresses current and possible novel strategies to prevent superantigen production and passive and active immunization strategies.

Do cardiomyocytes mount an immune response to Group A Streptococcus?

Some patients with Group A Streptococcal toxic shock syndrome (StrepTSS) develop a unique form of cardiomyopathy characterized by global hypokinesia and reduced cardiac index. Here we investigated the immune responses of cardiomyocytes to Group A Streptococcus both in vivo and in vitro. Our data demonstrate that cardiomyocyte-derived cytokines are produced following both direct GAS stimulation and after exposure to GAS-activated inflammatory cells. These locally produced, cardiomyocyte-derived cytokines may mediate cardiac contractile dysfunction observed in patients with StrepTSS-associated cardiomyopathy and may hold the key to our ability to attenuate this severe complication.

Toxic shock syndrome and bacterial superantigens: an update

Toxic shock syndrome (TSS) is an acute onset illness characterized by fever, rash formation, and hypotension that can lead to multiple organ failure and lethal shock, as well as desquamation in patients that recover. The disease is caused by bacterial superantigens (SAGs) secreted from Staphylococcus aureus and group A streptococci. SAGs bypass normal antigen presentation by binding to class II major histocompatibility complex molecules on antigen-presenting cells and to specific variable regions on the beta-chain of the T-cell antigen receptor. Through this interaction, SAGs activate T cells at orders of magnitude above antigen-specific activation, resulting in massive cytokine release that is believed to be responsible for the most severe features of TSS. This review focuses on clinical and epidemiological aspects of TSS, as well as important developments in the genetics, biochemistry, immunology, and structural biology of SAGs. From the evolutionary relationships between these important toxins, we propose that there are five distinct groups of SAGs.

Streptococcal mitogenic exotoxin Z, a novel acidic superantigenic toxin produced by a T1 strain of Streptococcus pyogenes

Streptococcus pyogenes T1 was previously found to produce an acidic mitogenic exotoxin, designated A beta, antigenically distinct from erythrogenic toxin type A (ETA) of strains T1 and NY5. Following chemical analysis and biological characterization, we have renamed this toxin streptococcal mitogenic exotoxin Z (SMEZ). Physicochemical separation of SMEZ from ETA was successfully performed on a hydrophobic chromatograph. The isoelectric point was pH 5.3, and the molecular size was estimated to be 28 kDa. These values were similar to those of ETA, but the amino acid composition and the NH2-terminal sequence of SMEZ were distinct from those of any mitogenic exotoxins hitherto described. Its mitogenic activity was found to be more potent than that of ETA in rabbit lymphocyte cultures. A specific antiserum raised against SMEZ did not cross-react with ETA, ETB, or ETC in the neutralization tests of mitogenic and erythrogenic activities. Its superantigenic nature was evident from the reverse transcriptase PCR findings of the T-cell receptor Vbeta profiles of rabbit lymphocytes stimulated in vitro. The Vbeta 8 subfamily was unique to SMEZ, while the Vbeta 2 and 6 subfamilies were found to be common among lymphocytes stimulated with ETA, ETB, ETC, or SMEZ. The results from this study provide an additional example of the diversity that exists among mitogenic or superantigenic exotoxins of streptococcal origin.

Antibody levels and in vitro lymphoproliferative responses to Streptococcus pyogenes erythrogenic toxin A and mitogen of patients with rheumatic fever

We investigated the in vitro lymphoproliferative responses to a streptococcal mitogen and erythrogenic toxin A of children with acute rheumatic fever (ARF) and patients with chronic rheumatic heart disease (CRHD). Antibody levels to the streptococcal products were also analyzed in the sera of those with ARF or chronic rheumatic heart disease as well as in the sera of children with streptococcal pharyngitis or poststreptococcal glomerulonephritis. Our results demonstrated that the individuals had depressed lymphoproliferative responses during the active stage of rheumatic fever. The depressed responses were not found either to be induced by time-sensitive mitogen-specific suppressor cells or to be related to a dose-response phenomenon. On the other hand, antibody levels to the extracellular mitogens were significantly elevated in the sera of children with ARF compared with the levels in the rest of the groups. The hyperresponsiveness noted among children with ARF was found to be at a quantitative level and was not due to recognition of more epitopes, as determined by Western blotting (immunoblotting). The profile of immune responsiveness in children with ARF to the streptococcal extracellular mitogens is discussed in relation to the pathogenesis of disease.

Frequency of the erythrogenic toxin B and C genes (speB and speC) among clinical isolates of group A streptococci

DNA probes corresponding to the internal region of the erythrogenic toxin B and C genes, speB and speC, were used in hybridization studies with clinical isolates of Streptococcus pyogenes to determine the frequency of occurrence of these genes in a large population of group A streptococci. More than 500 strains from different geographical locations throughout the world were used in this study. The results from colony-lift hybridization experiments indicated that the frequency of occurrence of each toxin gene among all of these strains was 100% for speB and 50% for speC. Division of these strains into subgroups of general group A strains and strains associated with scarlet fever or rheumatic fever resulted in a frequency of occurrence of speC of about 50% for all subgroups. The speC gene was found to be more frequently associated with serotype M2, M4, and M6 strains and less frequently associated with serotype M1, M3, and M49 strains. The results from a similar study with the speA gene have been previously reported (C.-E. Yu and J.J. Ferretti, Infect. Immun. 57:3715-3719, 1989).