title: Experimental depletion of CD8+ cells in acutely SIVagm-infected African Green Monkeys results in increased viral replication.
abstract: BACKGROUND
  In vivo CD8+ cell depletions in pathogenic SIV infections identified a key role for cellular immunity in controlling viral load (VL) and disease progression. However, similar studies gave discordant results in chronically-infected SMs, leading some authors to propose that in natural hosts, SIV replication is independent of cellular immunity. To assess the role of cellular immune responses in the control of SIV replication in natural hosts, we investigated the impact of CD8+ cell depletion during acute SIV infection in AGMs.
  
  
  RESULTS
  Nine AGMs were infected with SIVagm.sab and were followed up to day 225 p.i. Four were intravenously infused with the cM-T807 antibody on days 0 (50 mg/kg), 6, and 13 (10 mg/kg, respectively) post infection (p.i.). CD8+ cells were depleted for up to 28 days p.i. in peripheral blood and LNs in all treated AGMs. Partial CD8+ T cell depletion occurred in the intestine. SIVagm VLs peaked at similar levels in both groups (107-108 RNA copies/ml). However, while VLs were controlled in undepleted AGMs, reaching set-point levels (104-105 RNA copies/ml) by day 28 p.i., high VLs (>106 RNA copies/ml) were maintained by day 21 p.i. in CD8-depleted AGMs. By day 42 p.i., VLs were comparable between the two groups. The levels of immune activation and proliferation remained elevated up to day 72 p.i. in CD8-depleted AGMs and returned to preinfection levels in controls by day 28 p.i. None of the CD8-depleted animals progressed to AIDS.
  
  
  CONCLUSIONS
  CD8+ cells are responsible for a partial control of postacute viral replication in SIVagm.sab-infected AGMs. In contrast to macaques, the SIVagm-infected AGMs are able to control viral replication after recovery of the CD8+ T cells and avoid disease progression.
authors.affiliation: Division of Microbiology, Tulane National Primate Research Center, Covington, LA 70433, USA.
authors.forename: Thaidra
authors.initials: T
authors.lastname: Gaufin
authors.forename: Ruy M
authors.initials: RM
authors.lastname: Ribeiro
authors.forename: Rajeev
authors.initials: R
authors.lastname: Gautam
authors.forename: Jason
authors.initials: J
authors.lastname: Dufour
authors.forename: Daniel
authors.initials: D
authors.lastname: Mandell
authors.forename: Cristian
authors.initials: C
authors.lastname: Apetrei
authors.forename: Ivona
authors.initials: I
authors.lastname: Pandrea
mesh_terms: D000818:Animals; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D002522:Chlorocebus aethiops; D005500:Follow-Up Studies; D008212:Lymphocyte Depletion; D016097:Simian Acquired Immunodeficiency Syndrome / Q000276:immunology* / Q000821:virology*; D015302:Simian Immunodeficiency Virus / Q000276:immunology*; D019562:Viral Load; D014779:Virus Replication
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