title: HIV-1 Tat-induced microgliosis and synaptic damage via interactions between peripheral and central myeloid cells.
abstract: Despite the ability of combination antiretroviral treatment (cART) to reduce viral burden to nearly undetectable levels in cerebrospinal fluid and serum, HIV-1 associated neurocognitive disorders (HAND) continue to persist in as many as half the patients living with this disease. There is growing consensus that the actual substrate for HAND is destruction of normal synaptic architecture but the sequence of cellular events that leads to this outcome has never been resolved. To address whether central vs. peripheral myeloid lineage cells contribute to synaptic damage during acute neuroinflammation we injected a single dose of the HIV-1 transactivator of transcription protein (Tat) or control vehicle into hippocampus of wild-type or chimeric C57Bl/6 mice genetically marked to distinguish infiltrating and resident immune cells. Between 8-24 hr after injection of Tat, invading CD11b(+) and/or myeloperoxidase-positive leukocytes with granulocyte characteristics were found to engulf both microglia and synaptic structures, and microglia reciprocally engulfed invading leukocytes. By 24 hr, microglial processes were also seen ensheathing dendrites, followed by inclusion of synaptic elements in microglia 7 d after Tat injection, with a durable microgliosis lasting at least 28 d. Thus, central nervous system (CNS) exposure to Tat induces early activation of peripheral myeloid lineage cells with phagocytosis of synaptic elements and reciprocal microglial engulfment of peripheral leukocytes, and enduring microgliosis. Our data suggest that a single exposure to a foreign antigen such as HIV-1 Tat can lead to long-lasting disruption of normal neuroimmune homeostasis with deleterious consequences for synaptic architecture, and further suggest a possible mechanism for enduring neuroinflammation in the absence of productive viral replication in the CNS.
authors.affiliation: Center for Neural Development and Disease, University of Rochester School of Medicine and Dentistry, Rochester, New York, United States of America. pat_lu@urmc.rochester.edu
authors.forename: Shao-Ming
authors.initials: SM
authors.lastname: Lu
authors.forename: Marie-Ève
authors.initials: MÈ
authors.lastname: Tremblay
authors.forename: Irah L
authors.initials: IL
authors.lastname: King
authors.forename: Jin
authors.initials: J
authors.lastname: Qi
authors.forename: Holly M
authors.initials: HM
authors.lastname: Reynolds
authors.forename: Daniel F
authors.initials: DF
authors.lastname: Marker
authors.forename: John J P
authors.initials: JJ
authors.lastname: Varrone
authors.forename: Ania K
authors.initials: AK
authors.lastname: Majewska
authors.forename: Stephen
authors.initials: S
authors.lastname: Dewhurst
authors.forename: Harris A
authors.initials: HA
authors.lastname: Gelbard
mesh_terms: D000818:Animals; D000073883:CX3C Chemokine Receptor 1; D002450:Cell Communication / Q000187:drug effects*; D006098:Granulocytes / Q000166:cytology / Q000187:drug effects / Q000276:immunology / Q000821:virology; D015497:HIV-1 / Q000502:physiology*; D007249:Inflammation / Q000276:immunology / Q000378:metabolism / Q000473:pathology / Q000821:virology; D007267:Injections; D051379:Mice; D017628:Microglia / Q000187:drug effects* / Q000276:immunology / Q000473:pathology / Q000821:virology; D022423:Myeloid Cells / Q000166:cytology / Q000187:drug effects* / Q000276:immunology / Q000821:virology; D009474:Neurons / Q000187:drug effects / Q000473:pathology; D020556:Neutrophil Infiltration / Q000187:drug effects; D019707:Receptors, Chemokine / Q000235:genetics; D013569:Synapses / Q000187:drug effects* / Q000276:immunology / Q000473:pathology / Q000821:virology; D013997:Time Factors; D054322:tat Gene Products, Human Immunodeficiency Virus / Q000494:pharmacology*
chemical_list: D000073883:CX3C Chemokine Receptor 1; C471885:Cx3cr1 protein, mouse; D019707:Receptors, Chemokine; D054322:tat Gene Products, Human Immunodeficiency Virus