Open AccessLL-37 Triggers Formation of <b><i>Streptococcus pyogenes</i></b> Extracellular Vesicle-Like Structures with Immune Stimulatory Properties
Author(s) -
Julia Uhlmann,
Manfred Rohde,
Nikolai Siemens,
Bernd Kreikemeyer,
Peter Bergman,
Linda Johansson,
AnorrbyTeglund
Publication year - 2015
Publication title -
journal of innate immunity
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.078
H-Index - 64
eISSN - 1662-8128
pISSN - 1662-811X
DOI - 10.1159/000441896
Subject(s) - streptococcus pyogenes , microbiology and biotechnology , myeloperoxidase , biology , bacteria , virulence , extracellular , vesicle , immune system , virulence factor , inflammation , chemistry , immunology , biochemistry , staphylococcus aureus , gene , membrane , genetics
Reports have shown that the antimicrobial peptide LL-37 is abundantly expressed but has limited bactericidal effect in Streptococcus pyogenes infections. At sub-inhibitory concentrations, LL-37 has been reported to alter virulence gene expression. Here, we explored the interaction of S. pyogenes strains with LL-37, focusing on bacterial growth, cell surface alterations and pro-inflammatory responses. Bioscreen turbidity measurements of strain 5448 cultured in the presence or absence of LL-37 confirmed the poor antimicrobial effect, and revealed a significant increase in turbidity of bacterial cultures exposed to sub-inhibitory concentrations of LL-37. However, this was not linked to increased bacterial counts. Electron microscopy of LL-37-exposed bacteria revealed the presence of vesicle-like structures on the bacterial surface. The vesicles stained positive for LL-37 and were released from the bacterial surface. Concentrated supernatants enriched in these structures had a broader protein content, including several virulence factors, compared to supernatants from untreated bacteria. The supernatants from LL-37-exposed bacteria were pro-inflammatory and elicited resistin and myeloperoxidase release from neutrophils. This is the first report on S. pyogenes extracellular vesicle-like structures formed at the bacterial surface in response to LL-37. The associated increased pro-inflammatory activity further implicates LL-37 as a potential factor involved in S. pyogenes pathogenesis.