title: Inhibition of the complement membrane attack complex by the galactose-specific adhesion of Entamoeba histolytica.
abstract: The human complement system is an important early host defense against infection. Entamoeba histolytica activates the complement system but is resistant to killing by complement C5b-9 complexes deposited on the membrane surface. Our aim was to identify components of the amebic plasma membrane that mediate resistance to human complement C5b-9 by screening for neutralizing monoclonal antibodies. A monoclonal antibody was identified that abrogated amebic resistance to C5b-9, and the mAb was shown to recognize the parasite's galactose-specific adhesin. The purified adhesin bound to C8 and C9 and conferred C5b-9 resistance to sensitive ameba upon reconstitution; these activities of the adhesin were inhibited by the antiadhesin mAb. The E. histolytica adhesin shared sequence similarities and antigenic cross-reactivity with CD59, a membrane inhibitor of C5b-9 in human blood cells, suggesting both molecular mimicry and shared complement-inhibitory functions.
authors.affiliation: Department of Medicine, University of Virginia School of Medicine, Charlottesville 22908.
authors.forename: L L
authors.initials: LL
authors.lastname: Braga
authors.forename: H
authors.initials: H
authors.lastname: Ninomiya
authors.forename: J J
authors.initials: JJ
authors.lastname: McCoy
authors.forename: S
authors.initials: S
authors.lastname: Eacker
authors.forename: T
authors.initials: T
authors.lastname: Wiedmer
authors.forename: C
authors.initials: C
authors.lastname: Pham
authors.forename: S
authors.initials: S
authors.lastname: Wood
authors.forename: P J
authors.initials: PJ
authors.lastname: Sims
authors.forename: W A
authors.initials: WA
authors.lastname: Petri
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D015703:Antigens, CD / Q000502:physiology; D018957:CD59 Antigens; D003185:Complement C8 / Q000502:physiology; D003186:Complement C9 / Q000502:physiology; D015938:Complement Membrane Attack Complex / Q000037:antagonists & inhibitors*; D004748:Entamoeba histolytica / Q000276:immunology*; D000939:Epitopes / Q000032:analysis; D005690:Galactose / Q000494:pharmacology*; D006801:Humans; D037102:Lectins; D008562:Membrane Glycoproteins / Q000276:immunology / Q000494:pharmacology* / Q000502:physiology; D008565:Membrane Proteins / Q000276:immunology / Q000502:physiology*; D051379:Mice; D008969:Molecular Sequence Data; D015800:Protozoan Proteins / Q000276:immunology / Q000494:pharmacology*; D011817:Rabbits
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D018957:CD59 Antigens; D003185:Complement C8; D003186:Complement C9; D015938:Complement Membrane Attack Complex; D000939:Epitopes; D037102:Lectins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D015800:Protozoan Proteins; C052452:galactose inhibitable adherence protein, Entamoeba histolytica; D005690:Galactose