Functional characterization of streptococcal pyrogenic exotoxin J, a novel superantigen.
Streptococcal toxic shock syndrome (STSS) is a highly lethal, acute-onset illness that is a subset of invasive streptococcal disease. The majority of clinical STSS cases have been associated with the pyrogenic toxin superantigens (PTSAgs) streptococcal pyrogenic exotoxin A or C (SPE A or C), although cases have been reported that are not associated with either of these exotoxins. Recent genome sequencing projects have revealed a number of open reading frames that potentially encode proteins with similarity to SPEs A and C and to other PTSAgs. Here, we describe the cloning, expression, purification, and functional characterization of a novel exotoxin termed streptococcal pyrogenic exotoxin J (SPE J). Purified recombinant SPE J (rSPE J) expressed from Escherichia coli stimulated the expansion of both rabbit splenocytes and human peripheral blood lymphocytes, preferentially expanded human T cells displaying Vbeta2, -3, -12, -14, and -17 on their T-cell receptors, and was active at concentrations as low as 5 x 10(-6) microg/ml. Furthermore, rSPE J induced fevers in rabbits and was lethal in two models of STSS. Biochemically, SPE J had a predicted molecular weight of 24,444 and an isoelectric point of 7.7 and lacked the ability to form the cystine loop structure characteristic of many PTSAgs. SPE J shared 19.6, 47.1, 38.8, 18.1, 19.6, and 24.4% identity with SPEs A, C, G, and H, streptococcal superantigen, and streptococcal mitogenic exotoxin Z-2, respectively, and was immunologically cross-reactive with SPE C. The characterization of a seventh functional streptococcal PTSAg raises important questions relating to the evolution of the streptococcal superantigens.
McCormick
J K
JK
Department of Microbiology, University of Minnesota Medical School, Minneapolis, Minnesota 55455, USA.
Pragman
A A
AA
Stolpa
J C
JC
Leung
D Y
DY
Schlievert
P M
PM
D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins; D003001:Cloning, Molecular; D003429:Cross Reactions; D019143:Evolution, Molecular; D005098:Exotoxins / Q000235:genetics* / Q000633:toxicity; D005334:Fever; D008969:Molecular Sequence Data; D010802:Phylogeny; D011749:Pyrogens / Q000145:classification / Q000235:genetics* / Q000633:toxicity; D011817:Rabbits; D011994:Recombinant Proteins / Q000276:immunology / Q000633:toxicity; D017386:Sequence Homology, Amino Acid; D013210:Staphylococcus / Q000235:genetics / Q000276:immunology / Q000472:pathogenicity; D013297:Streptococcus pyogenes / Q000235:genetics* / Q000276:immunology / Q000472:pathogenicity; D018089:Superantigens / Q000145:classification / Q000235:genetics* / Q000633:toxicity
D001426:Bacterial Proteins; D005098:Exotoxins; D011749:Pyrogens; D011994:Recombinant Proteins; C423447:SpeJ protein, Streptococcus pyogenes; D018089:Superantigens