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Infect. Immun., Sep 1997, 3828-3833, Vol 65, No. 9
Y Kamezawa, T Nakahara, S Nakano, Y Abe, J Nozaki-Renard and T Isono
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.
Copyright © 1997, American Society for Microbiology
Streptococcal mitogenic exotoxin Z, a novel acidic superantigenic toxin produced by a T1 strain of Streptococcus pyogenes
Department of Microbiology, Saitama College of Health, Urawa, Japan.
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