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Infection and Immunity, December 2009, p. 5551-5557, Vol. 77, No. 12
0019-9567/09/$08.00+0     doi:10.1128/IAI.00576-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Enterococcus faecalis Capsular Polysaccharide Serotypes C and D and Their Contributions to Host Innate Immune Evasion{triangledown}

Lance R. Thurlow, Vinai Chittezham Thomas, Sherry D. Fleming, and Lynn E. Hancock*

Division of Biology, Kansas State University, Manhattan, Kansas 66506

Received 22 May 2009/ Returned for modification 1 July 2009/ Accepted 23 September 2009

It has become increasingly difficult to treat infections caused by Enterococcus faecalis due to its high levels of intrinsic and acquired antibiotic resistance. However, few studies have explored the mechanisms that E. 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-producing E. 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 of E. 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 of E. 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 treat E. faecalis infections.

* Corresponding author. Mailing address: Division of Biology, Kansas State University, 116 Ackert Hall, Manhattan, KS 66506. Phone: (785) 532-6122. Fax: (785) 532-6653. E-mail: lynnh{at}ksu.edu

{triangledown} Published ahead of print on 5 October 2009.

Editor: B. A. McCormick

Infection and Immunity, December 2009, p. 5551-5557, Vol. 77, No. 12
0019-9567/09/$08.00+0     doi:10.1128/IAI.00576-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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