title: Alteration of viral lipid composition by expression of the phospholipid floppase ABCB4 reduces HIV vector infectivity.
abstract: BACKGROUND
  The presence of cholesterol in the Human Immunodeficiency Virus (HIV) lipid envelop is important for viral function as cholesterol depleted viral particles show reduced infectivity. However, it is less well established whether other viral membrane lipids are also important for HIV infection. The ABCB4 protein is a phosphatidyl choline (PC) floppase that mediates transport of PC from the inner to the outer membrane leaflet. This property enabled us to modulate the lipid composition of HIV vectors and study the effects on membrane composition and infection efficiency.
  
  
  RESULTS
  Virus generated in the presence of ABCB4 was enriched in PC and cholesterol but contained less sphingomyelin (SM). Viral titers were reduced 5.9 fold. These effects were not observed with an inactive ABCB4 mutant. The presence of the ABC transport inhibitor verapamil abolished the effect of ABCB4 expression on viral titers. The ABCB4 mediated reduction in infectivity was caused by changes in the viral particles and not by components co purified with the virus because virus made in the presence of ABCB4 did not inhibit virus made without ABCB4 in a competition assay. Incorporation of the envelope protein was not affected by the expression of ABCB4. The inhibitory effect of ABCB4 was independent of the viral envelope as the effect was observed with two different envelope proteins.
  
  
  CONCLUSIONS
  Our data indicate that increasing the PC content of HIV particles reduces infectivity.
authors.affiliation: AMC Liver Center, Meibergdreef 69, 1105 BK, Amsterdam, the Netherlands. n.vantil@erasmusmc.nl
authors.forename: Niek P
authors.initials: NP
authors.lastname: van Til
authors.forename: Kirstin M
authors.initials: KM
authors.lastname: Heutinck
authors.forename: Roos
authors.initials: R
authors.lastname: van der Rijt
authors.forename: Coen C
authors.initials: CC
authors.lastname: Paulusma
authors.forename: Michel
authors.initials: M
authors.lastname: van Wijland
authors.forename: David M
authors.initials: DM
authors.lastname: Markusic
authors.forename: Ronald P J Oude
authors.initials: RP
authors.lastname: Elferink
authors.forename: Jurgen
authors.initials: J
authors.lastname: Seppen
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000378:metabolism*; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism*; D002460:Cell Line; D002784:Cholesterol / Q000378:metabolism; D005822:Genetic Vectors / Q000502:physiology*; D006678:HIV / Q000502:physiology*; D006801:Humans; D010713:Phosphatidylcholines / Q000378:metabolism*; D013109:Sphingomyelins / Q000378:metabolism
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D018528:ATP-Binding Cassette Transporters; D010713:Phosphatidylcholines; D013109:Sphingomyelins; D002784:Cholesterol; C095122:multidrug resistance protein 3