PROJECT SUMMARY/ABSTRACT
Streptococcus pyogenes (Spy; group A Streptococcus) is the most prolific pathogen in the number of distinct
diseases it is responsible for. Most commonly Spy is a cause of childhood acute pharyngitis (strep throat), but it
is also a top-10-pathogen in mortality that results in more than half a million deaths annually through invasive
infections and immune diseases that include necrotizing fasciitis, toxic shock syndrome, and acute rheumatic
fever. Despite their public health importance, the pathogenesis of these severe diseases is poorly understood,
and they remain challenging to treat. Our long-term goal seeks to determine how Spy virulence factors contribute
to the development of these more severe forms of disease so that effective therapeutic countermeasures can
be developed. Our previous studies show that the streptococcal protease SpeB acts directly on the host cytokine
pro-IL-1ß to induce inflammatory pathology during invasive infection. We hypothesize that additional proteins
targeted by SpeB, from both host and microbe, contribute to the proinflammatory responses we see during
infection. In our preliminary data, we have characterized the biochemical activity of SpeB and identified two of
its substrates that cooperatively lead to fundamental shifts in pathogenesis. In our first aim, we examine how
SpeB regulates the activities of M protein, a pleiotropic virulence factor with numerous host targets. By
eliminating domains specific for the binding of some host molecules or anchoring of M protein to the Spy surface,
SpeB directly contributes to pathological complications of infection like glomerulonephritis and toxic shock
syndrome. In our second aim, we define the molecular determinates of how SpeB blocks signaling by the
CovR/CovS two-component regulator by targeting its agonist, the host defense peptide LL-37. This mechanism
results in a positive-feedback loop for SpeB production and repression of capsule and other cell surface factors
that alter antimicrobial resistance, detection by the host, and promotes inflammation and disease complications.
Both aims take advantage of new genetic and biochemical tools we developed for targeted control and specific
detection of SpeB and its substrates. These innovations allow us for the first time to separate activities for these
multifunctional proteins and examine in vivo dramatic switch in the virulence strategy of Spy regulated by SpeB.
The expected contribution of the proposed research is an expanded understanding of how Spy pathogenesis is
regulated that provides attractive therapeutic targets for the prevention and treatment of severe Spy disease and
insights into orthologous systems of other pathogens highly relevant to the NIAID mission.