GAS is a preeminent Gram+ bacterial pathogen causing a wide spectrum of diseases in the human host. While the common outcome of a GAS encounter is asymptomatic colonization or self-limited mucosal infection, the propensity of particular GAS strains to produce systemic infection in otherwise healthy individuals defines a capacity to resist host innate immune clearance mechanisms that normally function to prevent dissemination beyond epithelial surfaces. A clone of the GAS M1T1 serotype has spread globally over the last 30 years as the leading cause of invasive infections including necrotizing fasciitis. Our laboratory has adopted a multifaceted approach to understanding those GAS and host factors that explain the diverse outcomes of this important host-pathogen interaction, using the invasive M1T1 GAS clone as a model. Our methodology has coupled precise, targeted mutagenesis and heterologous expression of candidate virulence factor genes with in vitro, ex vivo and in vivo models of disease pathogenesis, including WT, knockout and human transgenic mouse lines. We hypothesize that the outcome of GAS infection is dictated by the action and regulation of these GAS virulence factors in response to selective pressures exerted by host innate immunity. In this proposal, we will define the repertoire of bacterial virulence factors that promote the shift of GAS M1T1 strains to an invasive disease phenotype in response to innate immune selection.
In Aim 1, we will test a unique and extensive panel of isogenic M1T1 GAS virulence factor mutants for neutrophil resistance, invasive phenotype switching, and systemic infection in the humanized plasminogen mouse, defining those innate immune resistance factors necessary for systemic virulence. In parallel, we will constitutively express specific virulence factors to identify if any are sufficient to promote disease progression. In the complementary studies of Aim 2, we will use pharmacologic techniques and knockout mice to define those specific aspects of host innate immune defense that exert selective pressure on GAS M1T1 favoring the shift to invasive phenotype.
In Aim 3, we will determine the contribution of specific M1T1 GAS virulence genes and invasive phenotype shifting on GAS fitness during epithelial cell interactions and mucosal colonization. In this fashion, we will identify the competing selective pressures faced by this obligate human pathogen during the different stages of its overall ecology. Finally, we will assess the robustness of our experimental model (Nat Med 2007) that acquisition of a phage ?M1T1Z encoding the DNase Sda1 was a sentinel evident in the epidemic of invasive M1T1 infection, promoting resistance to phagocytic clearance through evasion of neutrophil extracellular traps. The last Aim will be achieved by exploring ?M1T1Z transduction mechanisms, phage distribution in diverse M serotype strains in the U.S. and an area of high endemic GAS disease (the Australian Northern Territory), and studying the contribution of the phage to disease switching and invasive disease in non-M1T1 strain backgrounds. Project Narrative Group A Streptococcus (GAS) is a bacteria that is a leading cause of infections in humans of all ages, from simple ?strep throat? to life-threatening ?flesh-eating? infections and shock. Serious disease is an unusual outcome, as most people can acquire the GAS bacterium in their throat or on their skin without developing symptoms. We are studying the ways in which the GAS bacteria shifts from an innocent member of our normal flora to an invasive pathogen, using molecular genetic techniques, assays of immune function, and mouse models of infection.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI077780-05
Application #
8310011
Study Section
Host Interactions with Bacterial Pathogens Study Section (HIBP)
Program Officer
GU, Xin-Xing
Project Start
2008-09-01
Project End
2014-08-31
Budget Start
2012-09-01
Budget End
2014-08-31
Support Year
5
Fiscal Year
2012
Total Cost
$408,056
Indirect Cost
$120,652
Name
University of California San Diego
Department
Pediatrics
Type
Schools of Medicine
DUNS #
804355790
City
La Jolla
State
CA
Country
United States
Zip Code
92093
Rivera-Hernandez, Tania; Pandey, Manisha; Henningham, Anna et al. (2016) Differing Efficacies of Lead Group A Streptococcal Vaccine Candidates and Full-Length M Protein in Cutaneous and Invasive Disease Models. MBio 7:
Stewart, Chelsea M; Buffalo, Cosmo Z; Valderrama, J Andrés et al. (2016) Coiled-coil destabilizing residues in the group A Streptococcus M1 protein are required for functional interaction. Proc Natl Acad Sci U S A 113:9515-20
Buffalo, Cosmo Z; Bahn-Suh, Adrian J; Hirakis, Sophia P et al. (2016) Conserved patterns hidden within group A Streptococcus M protein hypervariability recognize human C4b-binding protein. Nat Microbiol 1:16155
von Köckritz-Blickwede, Maren; Blodkamp, Stefanie; Nizet, Victor (2016) Interaction of Bacterial Exotoxins with Neutrophil Extracellular Traps: Impact for the Infected Host. Front Microbiol 7:402
Carey, Alison J; Weinberg, Jason B; Dawid, Suzanne R et al. (2016) Interleukin-17A Contributes to the Control of Streptococcus pyogenes Colonization and Inflammation of the Female Genital Tract. Sci Rep 6:26836
Döhrmann, Simon; Cole, Jason N; Nizet, Victor (2016) Conquering Neutrophils. PLoS Pathog 12:e1005682
Secundino, Ismael; Lizcano, Anel; Roupé, K Markus et al. (2016) Host and pathogen hyaluronan signal through human siglec-9 to suppress neutrophil activation. J Mol Med (Berl) 94:219-33
Cole, Jason N; Nizet, Victor (2016) Bacterial Evasion of Host Antimicrobial Peptide Defenses. Microbiol Spectr 4:
Henningham, Anna; Döhrmann, Simon; Nizet, Victor et al. (2015) Mechanisms of group A Streptococcus resistance to reactive oxygen species. FEMS Microbiol Rev 39:488-508
Lin, Ann E; Beasley, Federico C; Keller, Nadia et al. (2015) A group A Streptococcus ADP-ribosyltransferase toxin stimulates a protective interleukin 1β-dependent macrophage immune response. MBio 6:e00133

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