title: Dual effects of extracellular adherence protein from Staphylococcus aureus on peripheral blood mononuclear cells.
abstract: Extracellular adherence protein (Eap) has been suggested as an important virulence factor of Staphylococcus aureus because it enhances bacterial adherence and internalization into eukaryotic cells, interference with T cells, and neutrophil adherence to endothelial cells. We demonstrate that Eap has dual effects on peripheral blood mononuclear cells, depending on its concentration. At low concentrations (up to 9 microg/mL), Eap induces a proliferative response; at higher concentrations, it causes a significant inhibition of T cell proliferation induced by S. aureus supernatants toxic shock syndrome toxin-1 or phytohemagglutinin. A marked increase in apoptotic (i.e., Annexin V and propidium iodide positive) T and B cells could be demonstrated after exposure to the inhibitory concentration of Eap. Human anti-Eap antibodies prepared from polyspecific immunoglobulin G (IgG) blocked the immunomodulatory effects of Eap. Our results demonstrate novel immunomodulatory activities of Eap and identify potential mechanisms of action of intravenous IgG therapy in the treatment of S. aureus infections.
authors.affiliation: Department of Laboratory Medicine, Karolinska Institutet, Huddinge University Hospital, Stockholm, Sweden.
authors.forename: Axana
authors.initials: A
authors.lastname: Haggar
authors.forename: Oonagh
authors.initials: O
authors.lastname: Shannon
authors.forename: Anna
authors.initials: A
authors.lastname: Norrby-Teglund
authors.forename: Jan-Ingmar
authors.initials: JI
authors.lastname: Flock
mesh_terms: D001426:Bacterial Proteins / Q000494:pharmacology / Q000502:physiology*; D001427:Bacterial Toxins / Q000633:toxicity; D002455:Cell Division; D004768:Enterotoxins / Q000633:toxicity; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000166:cytology / Q000382:microbiology*; D008213:Lymphocyte Activation / Q000187:drug effects / Q000502:physiology; D010835:Phytohemagglutinins / Q000494:pharmacology; D016601:RNA-Binding Proteins / Q000494:pharmacology / Q000502:physiology*; D013211:Staphylococcus aureus / Q000276:immunology / Q000502:physiology*; D018089:Superantigens / Q000494:pharmacology / Q000633:toxicity; D013601:T-Lymphocytes / Q000276:immunology / Q000382:microbiology
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; C444739:Eap-N protein, Staphylococcus aureus; D004768:Enterotoxins; D010835:Phytohemagglutinins; D016601:RNA-Binding Proteins; D018089:Superantigens; C030107:enterotoxin F, Staphylococcal