title: Clustering patterns of cytotoxic T-lymphocyte epitopes in human immunodeficiency virus type 1 (HIV-1) proteins reveal imprints of immune evasion on HIV-1 global variation.
abstract: The human cytotoxic T-lymphocyte (CTL) response to human immunodeficiency virus type 1 (HIV-1) has been intensely studied, and hundreds of CTL epitopes have been experimentally defined, published, and compiled in the HIV Molecular Immunology Database. Maps of CTL epitopes on HIV-1 protein sequences reveal that defined epitopes tend to cluster. Here we integrate the global sequence and immunology databases to systematically explore the relationship between HIV-1 amino acid sequences and CTL epitope distributions. CTL responses to five HIV-1 proteins, Gag p17, Gag p24, reverse transcriptase (RT), Env, and Nef, have been particularly well characterized in the literature to date. Through comparing CTL epitope distributions in these five proteins to global protein sequence alignments, we identified distinct characteristics of HIV amino acid sequences that correlate with CTL epitope localization. First, experimentally defined HIV CTL epitopes are concentrated in relatively conserved regions. Second, the highly variable regions that lack epitopes bear cumulative evidence of past immune escape that may make them relatively refractive to CTLs: a paucity of predicted proteasome processing sites and an enrichment for amino acids that do not serve as C-terminal anchor residues. Finally, CTL epitopes are more highly concentrated in alpha-helical regions of proteins. Based on amino acid sequence characteristics, in a blinded fashion, we predicted regions in HIV regulatory and accessory proteins that would be likely to contain CTL epitopes; these predictions were then validated by comparison to new sets of experimentally defined epitopes in HIV-1 Rev, Tat, Vif, and Vpr.
authors.affiliation: Los Alamos National Laboratory, Los Alamos, New Mexico 87545. Santa Fe Institute, Santa Fe, New Mexico 87501, USA.
authors.forename: Karina
authors.initials: K
authors.lastname: Yusim
authors.forename: Can
authors.initials: C
authors.lastname: Kesmir
authors.forename: Brian
authors.initials: B
authors.lastname: Gaschen
authors.forename: Marylyn M
authors.initials: MM
authors.lastname: Addo
authors.forename: Marcus
authors.initials: M
authors.lastname: Altfeld
authors.forename: Søren
authors.initials: S
authors.lastname: Brunak
authors.forename: Alexandre
authors.initials: A
authors.lastname: Chigaev
authors.forename: Vincent
authors.initials: V
authors.lastname: Detours
authors.forename: Bette T
authors.initials: BT
authors.lastname: Korber
mesh_terms: D000595:Amino Acid Sequence; D000940:Antigenic Variation; D003546:Cysteine Endopeptidases / Q000378:metabolism; D018604:Epitope Mapping; D018984:Epitopes, T-Lymphocyte / Q000737:chemistry / Q000276:immunology*; D014644:Genetic Variation; D015658:HIV Infections / Q000276:immunology* / Q000821:virology; D015497:HIV-1 / Q000145:classification / Q000235:genetics / Q000276:immunology* / Q000472:pathogenicity; D006801:Humans; D009097:Multienzyme Complexes / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex; D016415:Sequence Alignment; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D014764:Viral Proteins / Q000145:classification / Q000235:genetics* / Q000276:immunology
chemical_list: D018984:Epitopes, T-Lymphocyte; D009097:Multienzyme Complexes; D014764:Viral Proteins; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex