title: Identification of unique reciprocal and non reciprocal cross packaging relationships between HIV-1, HIV-2 and SIV reveals an efficient SIV/HIV-2 lentiviral vector system with highly favourable features for in vivo testing and clinical usage.
abstract: BACKGROUND
  Lentiviral vectors have shown immense promise as vehicles for gene delivery to non-dividing cells particularly to cells of the central nervous system (CNS). Improvements in the biosafety of viral vectors are paramount as lentiviral vectors move into human clinical trials. This study investigates the packaging relationship between gene transfer (vector) and Gag-Pol expression constructs of HIV-1, HIV-2 and SIV. Cross-packaged vectors expressing GFP were assessed for RNA packaging, viral vector titre and their ability to transduce rat primary glial cell cultures and human neural stem cells.
  
  
  RESULTS
  HIV-1 Gag-Pol demonstrated the ability to cross package both HIV-2 and SIV gene transfer vectors. However both HIV-2 and SIV Gag-Pol showed a reduced ability to package HIV-1 vector RNA with no significant gene transfer to target cells. An unexpected packaging relationship was found to exist between HIV-2 and SIV with SIV Gag-Pol able to package HIV-2 vector RNA and transduce dividing SV2T cells and CNS cell cultures with an efficiency equivalent to the homologous HIV-1 vector however HIV-2 was unable to deliver SIV based vectors.
  
  
  CONCLUSIONS
  This new non-reciprocal cross packaging relationship between SIV and HIV-2 provides a novel way of significantly increasing bio-safety with a reduced sequence homology between the HIV-2 gene transfer vector and the SIV Gag-Pol construct thus ensuring that vector RNA packaging is unidirectional.
authors.affiliation: Department of Medicine, University of Cambridge, Addenbrooke's Hospital, Cambridge CB2 2QQ, UK. Padraig.Strappe@NUIGALWAY.IE
authors.forename: Padraig M
authors.initials: PM
authors.lastname: Strappe
authors.forename: David W
authors.initials: DW
authors.lastname: Hampton
authors.forename: Douglas
authors.initials: D
authors.lastname: Brown
authors.forename: Begona
authors.initials: B
authors.lastname: Cachon-Gonzalez
authors.forename: Maeve
authors.initials: M
authors.lastname: Caldwell
authors.forename: James W
authors.initials: JW
authors.lastname: Fawcett
authors.forename: Andrew M L
authors.initials: AM
authors.lastname: Lever
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000821:virology; D002460:Cell Line; D022761:Gene Transfer, Horizontal; D005822:Genetic Vectors / Q000502:physiology*; D015497:HIV-1 / Q000235:genetics / Q000502:physiology*; D015498:HIV-2 / Q000235:genetics / Q000502:physiology*; D006801:Humans; D012367:RNA, Viral / Q000502:physiology; D051381:Rats; D015302:Simian Immunodeficiency Virus / Q000235:genetics / Q000502:physiology*; D013234:Stem Cells / Q000821:virology; D014161:Transduction, Genetic; D019065:Virus Assembly
chemical_list: D012367:RNA, Viral