title: Peak SIV replication in resting memory CD4+ T cells depletes gut lamina propria CD4+ T cells.
abstract: In early simian immunodeficiency virus (SIV) and human immunodeficiency virus-1 (HIV-1) infections, gut-associated lymphatic tissue (GALT), the largest component of the lymphoid organ system, is a principal site of both virus production and depletion of primarily lamina propria memory CD4+ T cells; that is, CD4-expressing T cells that previously encountered antigens and microbes and homed to the lamina propria of GALT. Here, we show that peak virus production in gut tissues of SIV-infected rhesus macaques coincides with peak numbers of infected memory CD4+ T cells. Surprisingly, most of the initially infected memory cells were not, as expected, activated but were instead immunophenotypically 'resting' cells that, unlike truly resting cells, but like the first cells mainly infected at other mucosal sites and peripheral lymph nodes, are capable of supporting virus production. In addition to inducing immune activation and thereby providing activated CD4+ T-cell targets to sustain infection, virus production also triggered an immunopathologically limiting Fas-Fas-ligand-mediated apoptotic pathway in lamina propria CD4+ T cells, resulting in their preferential ablation. Thus, SIV exploits a large, resident population of resting memory CD4+ T cells in GALT to produce peak levels of virus that directly (through lytic infection) and indirectly (through apoptosis of infected and uninfected cells) deplete CD4+ T cells in the effector arm of GALT. The scale of this CD4+ T-cell depletion has adverse effects on the immune system of the host, underscoring the importance of developing countermeasures to SIV that are effective before infection of GALT.
authors.affiliation: Department of Microbiology, Medical School, University of Minnesota, MMC 196, 420 Delaware Street S.E, Minneapolis 55455, USA.
authors.forename: Qingsheng
authors.initials: Q
authors.lastname: Li
authors.forename: Lijie
authors.initials: L
authors.lastname: Duan
authors.forename: Jacob D
authors.initials: JD
authors.lastname: Estes
authors.forename: Zhong-Min
authors.initials: ZM
authors.lastname: Ma
authors.forename: Tracy
authors.initials: T
authors.lastname: Rourke
authors.forename: Yichuan
authors.initials: Y
authors.lastname: Wang
authors.forename: Cavan
authors.initials: C
authors.lastname: Reilly
authors.forename: John
authors.initials: J
authors.lastname: Carlis
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Miller
authors.forename: Ashley T
authors.initials: AT
authors.lastname: Haase
mesh_terms: D000818:Animals; D017209:Apoptosis; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology / Q000473:pathology* / Q000821:virology*; D003106:Colon / Q000276:immunology* / Q000473:pathology*; D053222:Fas Ligand Protein; D005260:Female; D007156:Immunologic Memory / Q000276:immunology*; D017403:In Situ Hybridization; D008253:Macaca mulatta / Q000276:immunology / Q000821:virology; D008562:Membrane Glycoproteins / Q000378:metabolism; D012367:RNA, Viral / Q000032:analysis; D015302:Simian Immunodeficiency Virus / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D014779:Virus Replication; D019014:fas Receptor / Q000378:metabolism
chemical_list: C505661:FASLG protein, human; D053222:Fas Ligand Protein; D008562:Membrane Glycoproteins; D012367:RNA, Viral; D019014:fas Receptor