Pyrogenicity and Cytokine-Inducing Properties ofStreptococcus pyogenesSuperantigens: Comparative Study of Streptococcal Mitogenic Exotoxin Z and Pyrogenic Exotoxin A

Abstract

Streptococcal mitogenic exotoxin Z (SMEZ), a superantigen derived from Streptococcus pyogenes, provoked expansion of human lymphocytes expressing the V␤ 2, 4, 7 and 8 motifs of T-cell receptor. SMEZ was pyrogenic in rabbits and stimulated the expression of the T-cell activation markers CD69 and cutaneous lymphocyteassociated antigen. A variety of cytokines was released by human mononuclear leukocytes stimulated with SMEZ, which was 10-fold more active than streptococcal pyrogenic exotoxin A. Th2-derived cytokines were elicited only by superantigens and not by streptococcal cells.Group A streptococci (Streptococcus pyogenes) provoke a wide spectrum of diseases ranging from skin infections and pharyngitis to more severe diseases such as scarlet fever, deep tissue infections, streptococcal toxic shock syndrome (STSS), and probably chronic diseases such as Kawasaki syndrome and guttate psoriasis (1,2,22,23,31,33,44). Several lines of evidence suggest that these diseases are at least partially mediated by extracellular mitogens that belong to the family of the superantigens (SAgs) (2, 33, 47). These effectors trigger polyclonal expansion of T lymphocytes by simultaneous binding to major histocompatibility complex class II molecules on antigen-presenting cells and T-cell receptor via its V␤ domain (37). The V␤ motifs recognized vary from one SAg to another (7). This process leads to the release of high levels of cytokines by antigen-presenting cells and lymphocytes as widely investigated for streptococcal SAgs (6,8,11,12,16,[26][27][28]34,35,41,42). Cytokine accumulation in vivo results in acute shock and other disorders (16,19,20,41,47). In this respect, significant levels of SAg (43) and cytokines in the biological fluids were detected in patients with STSS (6,11,20,32,36,43).S. pyogenes SAgs comprise the classical erythrogenic (pyrogenic) exotoxins A and C (SPEA and SPEC), encoded by bacteriophage speA and speC genes (2, 31); other novel SAgs (2,17,25,33,34,38,46); and the streptococcal mitogenic exotoxin Z (SMEZ) (3, 18, 38), encoded by the gene smez, which displays 24 allelic forms (39). Four newly discovered genes speG, speH, speJ, and smez-2, were identified (reference 38 and genomic database at Oklahoma University [www .genome.ou.edu/strep.html]). Their corresponding recombinant proteins were highly mitogenic for human peripheral blood mononuclear cells (PBMC). We describe here some immunological and biological properties of a potent mitogen released in the culture supernatant of an S. pyogenes strain (strain L) lacking both speA and speC genes, isolated from a French patient with STSS. This strain was selected among a number of speA-and speC-lacking isolates (40). The mitogen was identified as an SAg corresponding to SMEZ. The pyrogenic and superantigenic properties and the cytokine and skin homing antigen-inducing capacities of SMEZ were investigated in parallel with those of purified SPEA (10) used as a control. The cytokine response of PBMC challenged with heatkilled streptococci was also studied for compa...

The Bacterial Superantigen Streptococcal Mitogenic Exotoxin Z Is the Major Immunoactive Agent ofStreptococcus pyogenes

“…This may be because SMEZ is the only significant stimulus present in supernatant which can lead to cytokine production, or, more likely, because SMEZ is an essential cofactor which synergizes with other streptococcal proteins. Very recently, it was reported that a native preparation of the SMEZ-16 allele was 10-fold more active than a native preparation of SPEA when cytokine production from human mononuclear cells was quantified (20). The cytokine-stimulating role of a range of streptococcal secreted proteins has been extensively reported (21,22); data from the current study underpin the value of examining protein function in a physiological context, using supernatants from isogenic strains which are free of endotoxin contamination.…”

Longitudinal analysis of the group A Streptococcus transcriptome in experimental pharyngitis in cynomolgus macaques

“…The smeZ transcript level was 24 times higher than the speA2 level ( Fig. 8 C and D), a very important finding given that SmeZ has been reported to be at least 10 times more potent than other GAS PTSAgs in the ability to stimulate cytokine release by human T cells (29). Together, the data suggest that these three PTSAgs act sequentially to assist colonization, with speJ contributing early when GAS densities are low and smeZ and speA2 contributing preferentially to a rapid increase in CFUs.…”

Histone-like DNA binding protein of Streptococcus intermedius induces the expression of pro-inflammatory cytokines in human monocytes via activation of ERK1/2 and JNK pathways

“…Recognition of PAMP by the involved host cells, primarily neutrophils, monocytes and dendritic cells, leads to pro-inflammatory responses, including the release of cytokines, chemokines and other mediators, which are required for an effective host response (Medzhitov and Janeway, 1997); however, a range of other molecules from bacteria also has the capacity to induce cytokine production (Henderson et al, 1996). Streptococci have several functional proteins which are involved in the host proinflammatory response, such as pneumolysin of S. pneumoniae (Houldsworth et al, 1994;Rogers et al, 2003;Thornton and McDaniel, 2005), mitogenic exotoxin Z, pyrogenic exotoxin A and M protein of S. pyogenes (Muller-Alouf et al 2001;Pahlman et al, 2006), and antigen I/II of S. mutans (Soell et al, 1994) and other streptococci (Chatenay-Rivauday et al, 2000). This study is the first report showing that the histone-like DNA binding protein of S. intermedius (Si-HLP), a highly conserved structural protein within streptococci, is a potent activator upregulating pro-inflammatory cytokines in human monocytes.…”