Formation of vegetations during infective endocarditis excludes binding of bacterial-specific host antibodies to Enterococcus faecalis.
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.
McCormick
John K
JK
Department of Microbiology, University of Minnesota Medical School, Minneapolis, Minnesota, USA. jmccormi@lri.sjhc.london.on.ca
Tripp
Timothy J
TJ
Dunny
Gary M
GM
Schlievert
Patrick M
PM
D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood / Q000276:immunology*; D000918:Antibody Specificity; D001426:Bacterial Proteins / Q000008:administration & dosage / Q000276:immunology*; D001428:Bacterial Vaccines / Q000008:administration & dosage / Q000276:immunology*; D001792:Blood Platelets / Q000382:microbiology; D004697:Endocarditis, Bacterial / Q000276:immunology* / Q000382:microbiology / Q000473:pathology / Q000517:prevention & control; D013293:Enterococcus faecalis / Q000276:immunology*; D005337:Fibrin; D016908:Gram-Positive Bacterial Infections / Q000276:immunology* / Q000382:microbiology / Q000473:pathology / Q000517:prevention & control; D007114:Immunization; D007150:Immunohistochemistry; D011817:Rabbits
D000907:Antibodies, Bacterial; D001426:Bacterial Proteins; D001428:Bacterial Vaccines; C065937:aggregation substance, Enterococcus faecalis; D005337:Fibrin