Infectious endocarditis is a microbial infection of the endothelial lining of the heart that typically occurs on damaged or prosthetic heart valves. The characteristic lesion seen with infective endocarditis, termed "the vegetation," is composed of bacteria surrounded by a platelet/fibrin layer attached to the underlying endothelium. The vegetation has long been believed to exclude or hinder host defenses from clearing bacteria, although formal demonstration of mechanisms by which this occurs are lacking. This study investigated the ability of the vegetation to exclude host antibodies specific for the bacterial surface protein aggregation substance in vivo during experimental endocarditis caused by Enterococcus faecalis. The results demonstrate that, once the vegetation encloses bacteria, they are no longer accessible to high-titer bacterial-specific host antibodies, establishing a mechanism by which the vegetation functions to protect the bacteria from the humoral immune response.
Bibliographical noteFunding Information:
Received 13 August 2001; revised 27 November 2001; electronically published 11 March 2002. The University of Minnesota Institutional Animal Care and Use Committee approved all animal experiment protocols. Financial support: National Institutes of Health (HL-51987). a Present affiliation: The Lawson Health Research Institute, University of Western Ontario, London, Ontario, Canada. Reprints or correspondence: Dr. John K. McCormick, The Lawson Health Research Institute, Grosvenor Campus, University of Western Ontario, 268 Grosvenor St., London, Ontario, Canada N6A 4V2 (email@example.com .on.ca).