title: Tim-3 is a Marker of Plasmacytoid Dendritic Cell Dysfunction during HIV Infection and Is Associated with the Recruitment of IRF7 and p85 into Lysosomes and with the Submembrane Displacement of TLR9.
abstract: In chronic diseases, such as HIV infection, plasmacytoid dendritic cells (pDCs) are rendered dysfunctional, as measured by their decreased capacity to produce IFN-α. In this study, we identified elevated levels of T cell Ig and mucin-domain containing molecule-3 (Tim-3)-expressing pDCs in the blood of HIV-infected donors. The frequency of Tim-3-expressing pDCs correlated inversely with CD4 T cell counts and positively with HIV viral loads. A lower frequency of pDCs expressing Tim-3 produced IFN-α or TNF-α in response to the TLR7 agonists imiquimod and Sendai virus and to the TLR9 agonist CpG. Thus, Tim-3 may serve as a biomarker of pDC dysfunction in HIV infection. The source and function of Tim-3 was investigated on enriched pDC populations from donors not infected with HIV. Tim-3 induction was achieved in response to viral and artificial stimuli, as well as exogenous IFN-α, and was PI3K dependent. Potent pDC-activating stimuli, such as CpG, imiquimod, and Sendai virus, induced the most Tim-3 expression and subsequent dysfunction. Small interfering RNA knockdown of Tim-3 increased IFN-α secretion in response to activation. Intracellular Tim-3, as measured by confocal microscopy, was dispersed throughout the cytoplasm prior to activation. Postactivation, Tim-3 accumulated at the plasma membrane and associated with disrupted TLR9 at the submembrane. Tim-3-expressing pDCs had reduced IRF7 levels. Furthermore, intracellular Tim-3 colocalized with p85 and IRF7 within LAMP1+lysosomes, suggestive of a role in degradation. We conclude that Tim-3 is a biomarker of dysfunctional pDCs and may negatively regulate IFN-α, possibly through interference with TLR signaling and recruitment of IRF7 and p85 into lysosomes, enhancing their degradation.
authors.affiliation: Department of Immunology, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Jordan Ari
authors.identifier: 0000-0001-9658-5282
authors.initials: JA
authors.lastname: Schwartz
authors.affiliation: Department of Immunology, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Kiera L
authors.initials: KL
authors.lastname: Clayton
authors.affiliation: Institute of Medical Sciences, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Shariq
authors.identifier: 0000-0002-6206-5622
authors.initials: S
authors.lastname: Mujib
authors.affiliation: Department of Immunology, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Hongliang
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Department of Immunology, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
authors.forename: A K M Nur-Ur
authors.initials: AK
authors.lastname: Rahman
authors.affiliation: Department of Immunology, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Immunology, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Feng Yun
authors.initials: FY
authors.lastname: Yue
authors.affiliation: Maple Leaf Clinic, Toronto, Ontario M5G 1K2, Canada.
authors.forename: Erika
authors.initials: E
authors.lastname: Benko
authors.affiliation: Maple Leaf Clinic, Toronto, Ontario M5G 1K2, Canada.
authors.forename: Colin
authors.initials: C
authors.lastname: Kovacs
authors.affiliation: Department of Immunology, University of Toronto, Toronto, Ontario M5S 1A8, Canada; mario.ostrowski@gmail.com.|Institute of Medical Sciences, University of Toronto, Toronto, Ontario M5S 1A8, Canada.|Clinical Science Division, University of Toronto, Toronto, Ontario M5S 1A8, Canada; and.|Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario M5B 1T8, Canada.
authors.forename: Mario A
authors.initials: MA
authors.lastname: Ostrowski
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000032:analysis*; D002469:Cell Separation; D003713:Dendritic Cells / Q000276:immunology* / Q000378:metabolism; D005260:Female; D015658:HIV Infections / Q000276:immunology* / Q000378:metabolism; D000072597:Hepatitis A Virus Cellular Receptor 2 / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D050839:Interferon Regulatory Factor-7 / Q000276:immunology / Q000378:metabolism; D008247:Lysosomes / Q000276:immunology / Q000378:metabolism; D008297:Male; D018613:Microscopy, Confocal; D008875:Middle Aged; D015398:Signal Transduction / Q000276:immunology*; D051217:Toll-Like Receptor 9 / Q000276:immunology / Q000378:metabolism; D055815:Young Adult
chemical_list: D015415:Biomarkers; C448908:HAVCR2 protein, human; D000072597:Hepatitis A Virus Cellular Receptor 2; C494234:IRF7 protein, human; D050839:Interferon Regulatory Factor-7; C495371:TLR9 protein, human; D051217:Toll-Like Receptor 9