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Infect. Immun., Mar 1996, 870-877, Vol 64, No. 3
TP Shanley, D Schrier, V Kapur, M Kehoe, JM Musser and PA Ward
Streptococcus pyogenes infections in humans may be associated with severe
clinical manifestations, including adult respiratory distress syndrome and
a toxic shock-like syndrome. These observations have led to the
investigation of products of group A streptococci that may contribute to
increased virulence. Streptococcal pyrogenic exotoxin B is a highly
conserved precursor of an extracellular cysteine protease that is secreted
by S. pyogenes. We investigated the ability of this streptococcal cysteine
protease (SCP) to act synergistically with either streptococcal cell wall
antigen (SCW) or streptolysin-O (SLO) to augment lung injury in rats.
Intratracheal administration of either SCW or SLO alone caused lung injury,
as measured by pulmonary vascular leak. Bronchoalveolar lavage (BAL) fluid
analysis showed that SCW induced neutrophil accumulation and appearance of
interleukin-1beta and tumor necrosis factor alpha. In contrast, SLO induced
neither neutrophil influx nor significant cytokine elevations in BAL
fluids. Intratracheal administration of SCP with either SCW or SLO resulted
in synergistic augmentation of lung vascular permeability and accumulation
of BAL neutrophils. The synergy was reduced when SCP was either heat
inactivated or coinstilled with a peptide inhibitor of the protease. SCP in
the presence of SCW resulted in a significant increase in BAL fluid tumor
necrosis factor alpha content but not in immunoreactive interleukin-1beta.
Moreover, the copresence of SAP with SAW resulted in increased BAL fluid
nitrite-nitrate levels, indicative of nitric oxide production. These data
demonstrate that SCP acts synergistically with other S. pyogenes products
(SCW or SLO) to increase tissue injury and provide additional evidence that
SCP may function as an important virulence factor in group A streptococcal
infections.
Copyright © 1996, American Society for Microbiology
Streptococcal cysteine protease augments lung injury induced by products of group A streptococci
Department of Pathology, University of Michigan Medical School, Ann Arbor, 48109-0602, USA.
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