title: Resistance of Acanthamoeba species to complement lysis.
abstract: Acanthamoeba species were evaluated for susceptibility to complement lysis as determined by release of radiolabeled uridine. The 3 Acanthamoeba species tested, A. culbertsoni (ATCC 30171), A. castellanii (ATCC 30010), and A. polyphaga (ATCC 30461), depleted hemolytic complement activity from normal human serum (NHS), yet were resistant to its lytic effects. Examination of microtiter plates containing amoebae incubated in NHS demonstrated formation of a pellet in the wells. Pellet formation was not observed when amoebae were incubated in human cord serum, heat-inactivated serum, or C1q-deficient serum. Ultrastructural examination of serum-treated amoebae revealed the presence of a finely granular substance that surrounded the amoebae. Treatment of amoebae with enzymes or metabolic inhibitors prior to incubation in NHS was performed to investigate the mechanism of complement resistance. Cycloheximide or cytochalasin D pretreatment increased the susceptibility of A. culbertsoni and A. castellanii to complement lysis. Cytochalasin D treatment also increased the susceptibility of A. polyphaga to complement lysis. Inhibition of serine protease activity by phenylmethylsulfonylfluoride increased complement susceptibility of all 3 species of Acanthamoeba. Enzymatic removal of surface components from A. polyphaga or A. castellanii, with trypsin, neuraminidase, or phosphatidylinositol-specific phospholipase C (PIPLC), did not affect serum resistance. In contrast, PIPLC treatment of A. culbertsoni significantly increased lysis by complement. The ability of Acanthamoeba species to activate the alternative complement pathway yet resist complement-mediated cellular lysis can be attributed to both the release of a transport-dependent extracellular matrix as well as the presence of complement inhibitory surface proteins.
authors.affiliation: Department of Microbiology and Immunology, Medical College of Virginia, Virginia Commonwealth University, Richmond 23298-0678, USA.
authors.forename: D M
authors.initials: DM
authors.lastname: Toney
authors.forename: F
authors.initials: F
authors.lastname: Marciano-Cabral
mesh_terms: D000048:Acanthamoeba / Q000187:drug effects / Q000276:immunology* / Q000648:ultrastructure; D000818:Animals; D003170:Complement Pathway, Alternative; D003165:Complement System Proteins / Q000276:immunology*; D003513:Cycloheximide / Q000494:pharmacology; D015638:Cytochalasin D / Q000494:pharmacology; D006801:Humans; D008854:Microscopy, Electron; D009439:Neuraminidase / Q000494:pharmacology; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D010436:Pepstatins / Q000494:pharmacology; D010664:Phenylmethylsulfonyl Fluoride / Q000494:pharmacology; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D054801:Phosphoinositide Phospholipase C; D011480:Protease Inhibitors / Q000494:pharmacology; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D014357:Trypsin / Q000494:pharmacology; D010738:Type C Phospholipases / Q000494:pharmacology
chemical_list: D019384:Nucleic Acid Synthesis Inhibitors; D010436:Pepstatins; D011480:Protease Inhibitors; D011500:Protein Synthesis Inhibitors; C014195:Streptomyces pepsin inhibitor; D015638:Cytochalasin D; D010664:Phenylmethylsulfonyl Fluoride; D003165:Complement System Proteins; D003513:Cycloheximide; D010738:Type C Phospholipases; D054801:Phosphoinositide Phospholipase C; D009439:Neuraminidase; D014357:Trypsin; D043265:Phosphatidylinositol Diacylglycerol-Lyase; C031375:pepstatin