title: Tracking the Emergence of Host-Specific Simian Immunodeficiency Virus env and nef Populations Reveals nef Early Adaptation and Convergent Evolution in Brain of Naturally Progressing Rhesus Macaques.
abstract: While a clear understanding of the events leading to successful establishment of host-specific viral populations and productive infection in the central nervous system (CNS) has not yet been reached, the simian immunodeficiency virus (SIV)-infected rhesus macaque provides a powerful model for the study of human immunodeficiency virus (HIV) intrahost evolution and neuropathogenesis. The evolution of the gp120 and nef genes, which encode two key proteins required for the establishment and maintenance of infection, was assessed in macaques that were intravenously inoculated with the same viral swarm and allowed to naturally progress to simian AIDS and potential SIV-associated encephalitis (SIVE). Longitudinal plasma samples and immune markers were monitored until terminal illness. Single-genome sequencing was employed to amplify full-length env through nef transcripts from plasma over time and from brain tissues at necropsy. nef sequences diverged from the founder virus faster than gp120 diverged. Host-specific sequence populations were detected in nef (~92 days) before they were detected in gp120 (~182 days). At necropsy, similar brain nef sequences were found in different macaques, indicating convergent evolution, while gp120 brain sequences remained largely host specific. Molecular clock and selection analyses showed weaker clock-like behavior and stronger selection pressure in nef than in gp120, with the strongest nef selection in the macaque with SIVE. Rapid nef diversification, occurring prior to gp120 diversification, indicates that early adaptation of nef in the new host is essential for successful infection. Moreover, the convergent evolution of nef sequences in the CNS suggests a significant role for nef in establishing neurotropic strains.
  
  
  OBJECTIVE
  The SIV-infected rhesus macaque model closely resembles HIV-1 immunopathogenesis, neuropathogenesis, and disease progression in humans. Macaques were intravenously infected with identical viral swarms to investigate evolutionary patterns in the gp120 and nef genes leading to the emergence of host-specific viral populations and potentially linked to disease progression. Although each macaque exhibited unique immune profiles, macaque-specific nef sequences evolving under selection were consistently detected in plasma samples at 3 months postinfection, significantly earlier than in gp120 macaque-specific sequences. On the other hand, nef sequences in brain tissues, collected at necropsy of two animals with detectable infection in the central nervous system (CNS), revealed convergent evolution. The results not only indicate that early adaptation of nef in the new host may be essential for successful infection, but also suggest that specific nef variants may be required for SIV to efficiently invade CNS macrophages and/or enhance macrophage migration, resulting in HIV neuropathology.
authors.affiliation: Bioinfoexperts LLC, Thibodaux, Louisiana, USA.
authors.forename: Susanna L
authors.initials: SL
authors.lastname: Lamers
authors.affiliation: Department of Pathology, Immunology, and Laboratory Medicine, University of Florida, Gainesville, Florida, USA Emerging Pathogens Institute, University of Florida, Gainesville, Florida, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Nolan
authors.affiliation: Department of Pathology, Immunology, and Laboratory Medicine, University of Florida, Gainesville, Florida, USA Emerging Pathogens Institute, University of Florida, Gainesville, Florida, USA.
authors.forename: Brittany D
authors.initials: BD
authors.lastname: Rife
authors.affiliation: Natural Selection Inc., San Diego, California, USA.
authors.forename: Gary B
authors.initials: GB
authors.lastname: Fogel
authors.affiliation: Department of Medicine, University of California, San Francisco, San Francisco, California, USA.
authors.forename: Michael S
authors.initials: MS
authors.lastname: McGrath
authors.affiliation: Department of Biology, Boston College, Chestnut Hill, Massachusetts, USA.
authors.forename: Tricia H
authors.initials: TH
authors.lastname: Burdo
authors.affiliation: Department of Biology, Boston College, Chestnut Hill, Massachusetts, USA.
authors.forename: Patrick
authors.initials: P
authors.lastname: Autissier
authors.affiliation: Department of Biology, Boston College, Chestnut Hill, Massachusetts, USA.
authors.forename: Kenneth C
authors.initials: KC
authors.lastname: Williams
authors.affiliation: Department of Pathology, Immunology, and Laboratory Medicine, University of Florida, Gainesville, Florida, USA.
authors.forename: Maureen M
authors.initials: MM
authors.lastname: Goodenow
authors.affiliation: Department of Pathology, Immunology, and Laboratory Medicine, University of Florida, Gainesville, Florida, USA Emerging Pathogens Institute, University of Florida, Gainesville, Florida, USA salemi@pathology.ufl.edu.
authors.forename: Marco
authors.initials: M
authors.lastname: Salemi
mesh_terms: D000220:Adaptation, Biological / Q000235:genetics*; D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000378:metabolism*; D017931:DNA Primers / Q000235:genetics; D019143:Evolution, Molecular; D016013:Likelihood Functions; D008253:Macaca mulatta; D008562:Membrane Glycoproteins / Q000235:genetics*; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010802:Phylogeny; D012044:Regression Analysis; D012641:Selection, Genetic; D017422:Sequence Analysis, DNA; D015302:Simian Immunodeficiency Virus / Q000235:genetics* / Q000378:metabolism; D014759:Viral Envelope Proteins / Q000235:genetics*; D054334:Viral Regulatory and Accessory Proteins / Q000235:genetics*
chemical_list: D017931:DNA Primers; D008562:Membrane Glycoproteins; C429284:NEF protein, SIV; D014759:Viral Envelope Proteins; D054334:Viral Regulatory and Accessory Proteins; C069623:gp120 protein, Simian immunodeficiency virus