title: Mutations in the highly conserved SLQYLA motif of Vif in a simian-human immunodeficiency virus result in a less pathogenic virus and are associated with G-to-A mutations in the viral genome.
abstract: The simian-human immunodeficiency virus (SHIV)/macaque model for human immunodeficiency virus type 1 has become a useful tool to assess the role of accessory genes in lentiviral pathogenesis. In this study, we introduced two amino acid changes in the highly conserved SLQYLA domain (to AAQYLA) of the SIV Vif protein. The resulting virus, SHIV(VifAAQYLA), was used to infect three macaques, which were followed for over six months. Plasma viral loads and circulating CD4(+) T cell levels were assessed during the course of infection. The three macaques inoculated with SHIV(VifAAQYLA) did not develop significant CD4(+) T cell loss over the course of their infection, had plasma viral RNA loads that were over 100-fold lower than macaques inoculated with parental SHIV(KU-1bMC33), and developed no histological lesions in lymphoid tissues. DNA and RT-PCR analysis revealed that only a select number of tissues were infected with this virus. Sequence analysis indicates that the site-directed changes were stable during the first three weeks after inoculation but thereafter the S147A amino acid substitution changed to a threonine in two of three macaques. The L148A substitution remained stable in the vif amplified from the PBMC of all three macaques. Sequence analysis of vif, vpu, env and nef genes revealed G-to-A mutations in the genes amplified from macaques inoculated with SHIV(VifAAQYLA), which were higher than in a macaque inoculated with parental SHIV(KU-1bMC33). We found that the majority (>85%) of the G-to-A mutations were in the context of 5'-TC (minus strand) and not 5'-CC, suggestive that one or more of the rhesus APOBEC3 proteins may be responsible for the observed mutational patterns. The data also suggest that rhesus APOBEC3G probably accounted for a minority of the mutations since its GG-to-AG mutational pattern was infrequently detected. Finally, macaques inoculated with SHIV(VifAAQYLA) developed immunoprecipitating antibody responses against the virus. The results from this study provide the first in vivo evidence of the importance of the SLQYLA domain in viral pathogenesis and show that targeted mutations in vif can lead to a persistent infection with G-to-A changes accumulating in the viral genome.
authors.affiliation: Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, Kansas 66160, USA.
authors.forename: Kimberly
authors.initials: K
authors.lastname: Schmitt
authors.forename: M Sarah
authors.initials: MS
authors.lastname: Hill
authors.forename: Autumn
authors.initials: A
authors.lastname: Ruiz
authors.forename: Nathan
authors.initials: N
authors.lastname: Culley
authors.forename: David M
authors.initials: DM
authors.lastname: Pinson
authors.forename: Scott W
authors.initials: SW
authors.lastname: Wong
authors.forename: Edward B
authors.initials: EB
authors.lastname: Stephens
mesh_terms: D020816:Amino Acid Motifs; D019943:Amino Acid Substitution / Q000235:genetics; D000818:Animals; D018791:CD4 Lymphocyte Count; D017124:Conserved Sequence; D015497:HIV-1 / Q000235:genetics* / Q000472:pathogenicity*; D008221:Lymphoid Tissue / Q000473:pathology; D008251:Macaca; D016297:Mutagenesis, Site-Directed; D020125:Mutation, Missense; D017354:Point Mutation; D012367:RNA, Viral / Q000235:genetics; D017422:Sequence Analysis, DNA; D015302:Simian Immunodeficiency Virus / Q000235:genetics* / Q000472:pathogenicity*; D019562:Viral Load; D037521:Virulence Factors / Q000235:genetics* / Q000502:physiology*; D054320:vif Gene Products, Human Immunodeficiency Virus / Q000235:genetics* / Q000502:physiology*
chemical_list: D012367:RNA, Viral; D037521:Virulence Factors; D054320:vif Gene Products, Human Immunodeficiency Virus; C514847:vif protein, Human immunodeficiency virus 1