Bacillus anthracis is the causative agent of anthrax, a zoonotic disease transmitted by spores that germinate in the infected host. The resulting vegetative forms of B. anthracis invade and replicate in all host organs, triggering a lethal outcome to infection and subsequently generating spores for dissemination. Formation of a poly-D-3-glutamic acid (PDGA) capsule represents a key virulence strategy of anthrax bacilli. Further, B. anthracis elaborates a protein surface (S)-layer that is composed of twenty-four S-layer proteins, which are required for this microbe's virulence. The functions of S-layer proteins include the adherence of bacilli to host tissues, the scavenging of heme-iron, and the control of B. anthracis chain length as an escape from phagocytic clearance. S-layer assembly is initiated via precursor transport across the bacterial plasma membrane by a specialized Sec machine. S-layer proteins subsequently associate via their S-layer homology (SLH) domains with pyruvylated / acetylated secondary cell wall polysaccharide (SCWP), a carbohydrate that is linked to peptidoglycan. S-layer proteins likely contribute to capsule assembly. In B. anthracis, linear PDGA strands are linked to peptidoglycan and threaded across the S-layer. Bacillus cereus G9241, which causes anthrax-like respiratory disease, elaborates a hyaluronic acid capsule;its genetic determinants are conserved in B. anthracis. We propose to use molecular genetic approaches and animal models of anthrax pathogenesis to identify key S-layer virulence factors of B. anthracis, to appreciate their molecular contribution to anthrax pathogenesis and to explore their potential for anthrax vaccine development. Our experimental plan entails studies on the chemical composition of the B. anthracis envelope, microscopic analysis of S-layer protein traffic and capsule synthesis, the structural biology of SLH domain association with SCWP, the characterization of the host receptor for B. anthracis and the development of conjugate capsule-S-layer protein vaccines to protect experimental animals against lethal anthrax challenge.

Public Health Relevance

Efforts at generating a human anthrax vaccine from purified subunits, for example protective antigen (PA), have failed. Importantly, PA is dispensable for anthrax pathogenesis. An important frontier is the identification of B. anthracis antigen(s) essential for virulence and that, when used as immunogens, elicit anthrax protective immunity. These questions are addressed in our proposal.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
2R01AI069227-06
Application #
8244303
Study Section
Bacterial Pathogenesis Study Section (BACP)
Program Officer
Breen, Joseph J
Project Start
2006-04-01
Project End
2016-12-31
Budget Start
2012-01-01
Budget End
2012-12-31
Support Year
6
Fiscal Year
2012
Total Cost
$384,624
Indirect Cost
$134,624
Name
University of Chicago
Department
Microbiology/Immun/Virology
Type
Schools of Medicine
DUNS #
005421136
City
Chicago
State
IL
Country
United States
Zip Code
60637
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Wang, Ya-Ting; Missiakas, Dominique; Schneewind, Olaf (2014) GneZ, a UDP-GlcNAc 2-epimerase, is required for S-layer assembly and vegetative growth of Bacillus anthracis. J Bacteriol 196:2969-78
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Wang, Ya-Ting; Oh, So-Young; Hendrickx, Antoni P A et al. (2013) Bacillus cereus G9241 S-layer assembly contributes to the pathogenesis of anthrax-like disease in mice. J Bacteriol 195:596-605
Schneewind, Olaf; Missiakas, Dominique M (2012) Protein secretion and surface display in Gram-positive bacteria. Philos Trans R Soc Lond B Biol Sci 367:1123-39
Garufi, Gabriella; Wang, Ya-Ting; Oh, So-Young et al. (2012) Sortase-conjugation generates a capsule vaccine that protects guinea pigs against Bacillus anthracis. Vaccine 30:3435-44
Hendrickx, Antoni P A; Budzik, Jonathan M; Oh, So-Young et al. (2011) Architects at the bacterial surface - sortases and the assembly of pili with isopeptide bonds. Nat Rev Microbiol 9:166-76
Kern, Justin; Wilton, Rosemarie; Zhang, Rongguang et al. (2011) Structure of surface layer homology (SLH) domains from Bacillus anthracis surface array protein. J Biol Chem 286:26042-9
Anderson, Valerie J; Kern, Justin W; McCool, Justin W et al. (2011) The SLH-domain protein BslO is a determinant of Bacillus anthracis chain length. Mol Microbiol 81:192-205

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