title: Porphyromonas gingivalis evasion of autophagy and intracellular killing by human myeloid dendritic cells involves DC-SIGN-TLR2 crosstalk.
abstract: Signaling via pattern recognition receptors (PRRs) expressed on professional antigen presenting cells, such as dendritic cells (DCs), is crucial to the fate of engulfed microbes. Among the many PRRs expressed by DCs are Toll-like receptors (TLRs) and C-type lectins such as DC-SIGN. DC-SIGN is targeted by several major human pathogens for immune-evasion, although its role in intracellular routing of pathogens to autophagosomes is poorly understood. Here we examined the role of DC-SIGN and TLRs in evasion of autophagy and survival of Porphyromonas gingivalis in human monocyte-derived DCs (MoDCs). We employed a panel of P. gingivalis isogenic fimbriae deficient strains with defined defects in Mfa-1 fimbriae, a DC-SIGN ligand, and FimA fimbriae, a TLR2 agonist. Our results show that DC-SIGN dependent uptake of Mfa1+P. gingivalis strains by MoDCs resulted in lower intracellular killing and higher intracellular content of P. gingivalis. Moreover, Mfa1+P. gingivalis was mostly contained within single membrane vesicles, where it survived intracellularly. Survival was decreased by activation of TLR2 and/or autophagy. Mfa1+P. gingivalis strain did not induce significant levels of Rab5, LC3-II, and LAMP1. In contrast, P. gingivalis uptake through a DC-SIGN independent manner was associated with early endosomal routing through Rab5, increased LC3-II and LAMP-1, as well as the formation of double membrane intracellular phagophores, a characteristic feature of autophagy. These results suggest that selective engagement of DC-SIGN by Mfa-1+P. gingivalis promotes evasion of antibacterial autophagy and lysosome fusion, resulting in intracellular persistence in myeloid DCs; however TLR2 activation can overcome autophagy evasion and pathogen persistence in DCs.
authors: Department of Periodontics, Georgia Regents University, Augusta, Georgia, United States of America.
authors: Ahmed R
authors: AR
authors: El-Awady
authors: Department of Medicine, University of Colorado, Aurora, Colorado, United States of America.
authors: Brodie
authors: B
authors: Miles
authors: School of Dental Medicine, Stony Brook University, Stony Brook, New York, United States of America.
authors: Elizabeth
authors: E
authors: Scisci
authors: Department of Oral Health and Diagnostic Sciences, Georgia Regents University, Augusta, Georgia, United States of America.
authors: Zoya B
authors: ZB
authors: Kurago
authors: Department of Oral Health and Diagnostic Sciences, Georgia Regents University, Augusta, Georgia, United States of America.
authors: Chithra D
authors: CD
authors: Palani
authors: Department of Periodontics, Georgia Regents University, Augusta, Georgia, United States of America.
authors: Roger M
authors: RM
authors: Arce
authors: Department of Biostatistics and Epidemiology, Georgia Regents University, Augusta, Georgia, United States of America.
authors: Jennifer L
authors: JL
authors: Waller
authors: Department of Medicine, Section of Infectious Diseases, Boston University School of Medicine, Boston, Massachusetts, United States of America; Department of Microbiology, Boston University School of Medicine, Boston, Massachusetts, United States of America.
authors: Caroline A
authors: CA
authors: Genco
authors: Department of Microbiology, Boston University School of Medicine, Boston, Massachusetts, United States of America.
authors: Connie
authors: C
authors: Slocum
authors: Department of Cellular Biology and Anatomy, Georgia Regents University, Augusta, Georgia, United States of America.
authors: Matthew
authors: M
authors: Manning
authors: Department of Cellular Biology and Anatomy, Georgia Regents University, Augusta, Georgia, United States of America.
authors: Patricia V
authors: PV
authors: Schoenlein
authors: Department of Periodontics, Georgia Regents University, Augusta, Georgia, United States of America.
authors: Christopher W
authors: CW
authors: Cutler
mesh_terms: D001343:Autophagy / Q000276:immunology*; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D003712:Dendrites / Q000648:ultrastructure; D003713:Dendritic Cells / Q000276:immunology / Q000378:metabolism* / Q000648:ultrastructure; D010861:Fimbriae, Bacterial; D006801:Humans; D042541:Intracellular Space / Q000276:immunology / Q000378:metabolism; D037181:Lectins, C-Type / Q000378:metabolism*; D009000:Monocytes / Q000276:immunology / Q000648:ultrastructure; D022423:Myeloid Cells / Q000276:immunology / Q000378:metabolism*; D016966:Porphyromonas gingivalis / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D051195:Toll-Like Receptor 2 / Q000276:immunology / Q000378:metabolism*; D000099215:DC-Specific ICAM-3 Grabbing Nonintegrin
chemical_list: D015815:Cell Adhesion Molecules; D037181:Lectins, C-Type; D011956:Receptors, Cell Surface; D051195:Toll-Like Receptor 2; D000099215:DC-Specific ICAM-3 Grabbing Nonintegrin; C495342:TLR2 protein, human