Open AccessEnterococcus faecalis Capsular Polysaccharide Serotypes C and D and Their Contributions to Host Innate Immune Evasion
Author(s) -
Lance Thurlow,
Vinai C. Thomas,
Sherry D. Fleming,
Lynn E. Hancock
Publication year - 2009
Publication title -
infection and immunity
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.508
H-Index - 220
eISSN - 1070-6313
pISSN - 0019-9567
DOI - 10.1128/iai.00576-09
Subject(s) - enterococcus faecalis , microbiology and biotechnology , innate immune system , biology , virulence factor , virulence , immune system , lipoteichoic acid , bacterial capsule , neisseria meningitidis , capsule , bacteria , immunology , staphylococcus aureus , gene , biochemistry , botany , genetics
It has become increasingly difficult to treat infections caused byEnterococcus faecalis due to its high levels of intrinsic and acquired antibiotic resistance. However, few studies have explored the mechanisms thatE. faecalis employs to circumvent the host innate immune response and establish infection. Capsular polysaccharides are important virulence factors that are associated with innate immune evasion. We demonstrate, using cultured macrophages (RAW 264.7), that capsule-producingE. faecalis strains of either serotype C or D are more resistant to complement-mediated opsonophagocytosis than unencapsulated strains. We show that differences in opsonophagocytosis are not due to variations in C3 deposition but are due to the ability of capsule to mask bound C3 from detection on the surface ofE. faecalis . Similarly,E. faecalis capsule masks lipoteichoic acid from detection, which correlates with decreased tumor necrosis factor alpha production by cultured macrophages in the presence of encapsulated strains compared to that in the presence of unencapsulated strains. Our studies confirm the important role of the capsule as a virulence factor ofE. faecalis and provide several mechanisms by which the presence of the capsule influences evasion of the innate immune response and suggest that the capsule could be a potential target for developing alternative therapies to treatE. faecalis infections.