Abstract
Peptidoglycan (PGN), a major component of bacterial cell walls, is a pathogen-associated molecular pattern (PAMP) that causes innate immune cells to produce inflammatory cytokines that escalate the host response during infection. In order to better understand the role of PGN in infection, we wanted to gain insight into the cellular receptor for PGN. Although the receptor was initially identified as Toll-like receptor 2 (TLR2), this receptor has remained controversial and other PGN receptors have been reported. We produced PGN from live cultures of Bacillus anthracis and Staphylococcus aureus and tested samples of PGN isolated during the purification process to determine at what point TLR2 activity was removed, if at all. Our results indicate that although live B. anthracis and S. aureus express abundant TLR2 ligands, highly-purified PGN from either bacterial source is not recognized by TLR2.
Highlights
During bacterial sepsis, the bacterial-produced pathogen-associated molecular patterns (PAMPs) are responsible for activation of the complement and coagulation systems, contributing to organ failure and death of the host [1, 2]
We have performed a series of experiments to determine whether the diaminopimelic acid (DAP)-type B. anthracis and/or Lys-type S. aureus PGNs are activating Toll-like receptor 2 (TLR2) ligands and/or to determine at what point in the purification process activating TLR ligands are removed
We found differences in the amount of TLR2 activity retained during purification of PGN from these bacteria
Summary
The bacterial-produced pathogen-associated molecular patterns (PAMPs) are responsible for activation of the complement and coagulation systems, contributing to organ failure and death of the host [1, 2]. Peptidoglycans (PGN), a disaccharide polymer with peptide cross-linkers and present in bacterial cell walls, have been established as important bacterial PAMPs: PGN has been shown to induce inflammatory mediators from human innate immune cells, to stimulate platelet aggregation and prothrombinase activity, and to stimulate complement consumption [3,4,5]. PGN is a large glycan polymer composed of alternating units of N-acetylglucosamine (GlcNac) and N-acetylmuramic acid (MurNac) residues joined by stem peptide units consisting of 4 or 5 L- and D-amino acids [7].
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