title: Dual anti-HIV mechanism of clofarabine.
abstract: BACKGROUND
  HIV-1 replication kinetics inherently depends on the availability of cellular dNTPs for viral DNA synthesis. In activated CD4(+) T cells and other rapidly dividing cells, the concentrations of dNTPs are high and HIV-1 reverse transcription occurs in an efficient manner. In contrast, nondividing cells such as macrophages have lower dNTP pools, which restricts efficient reverse transcription. Clofarabine is an FDA approved ribonucleotide reductase inhibitor, which has shown potent antiretroviral activity in transformed cell lines. Here, we explore the potency, toxicity and mechanism of action of clofarabine in the human primary HIV-1 target cells: activated CD4(+) T cells and macrophages.
  
  
  RESULTS
  Clofarabine is a potent HIV-1 inhibitor in both activated CD4(+) T cells and macrophages. Due to its minimal toxicity in macrophages, clofarabine displays a selectivity index over 300 in this nondividing cell type. The anti-HIV-1 activity of clofarabine correlated with a significant decrease in both cellular dNTP levels and viral DNA synthesis. Additionally, we observed that clofarabine triphosphate was directly incorporated into DNA by HIV-1 reverse transcriptase and blocked processive DNA synthesis, particularly at the low dNTP levels found in macrophages.
  
  
  CONCLUSIONS
  Taken together, these data provide strong mechanistic evidence that clofarabine is a dual action inhibitor of HIV-1 replication that both limits dNTP substrates for viral DNA synthesis and directly inhibits the DNA polymerase activity of HIV-1 reverse transcriptase.
authors.affiliation: Center for Drug Discovery, Department of Pediatrics, Emory Center for AIDS Research, Emory University, Children's Healthcare of Atlanta, 1760 Haygood Dr., Atlanta, GA, 30322, USA.
authors.forename: Michele B
authors.initials: MB
authors.lastname: Daly
authors.affiliation: Institute for Molecular Virology, University of Minnesota, 18-242 Moos Tower, 515 Delaware St SE, Minneapolis, MN, 55455, USA.|Department of Diagnostic and Biological Sciences, School of Dentistry, University of Minnesota, Minneapolis, MN, 55455, USA.|Department of Microbiology and Immunology, University of Minnesota, Minneapolis, MN, 55455, USA.
authors.forename: Megan E
authors.initials: ME
authors.lastname: Roth
authors.affiliation: Center for Drug Design, Academic Health Center, University of Minnesota, Minneapolis, MN, 55455, USA.
authors.forename: Laurent
authors.initials: L
authors.lastname: Bonnac
authors.affiliation: Institute for Molecular Virology, University of Minnesota, 18-242 Moos Tower, 515 Delaware St SE, Minneapolis, MN, 55455, USA.|Department of Diagnostic and Biological Sciences, School of Dentistry, University of Minnesota, Minneapolis, MN, 55455, USA.|Department of Microbiology and Immunology, University of Minnesota, Minneapolis, MN, 55455, USA.
authors.forename: José O
authors.initials: JO
authors.lastname: Maldonado
authors.affiliation: Center for Drug Design, Academic Health Center, University of Minnesota, Minneapolis, MN, 55455, USA.
authors.forename: Jiashu
authors.initials: J
authors.lastname: Xie
authors.affiliation: Institute for Molecular Virology, University of Minnesota, 18-242 Moos Tower, 515 Delaware St SE, Minneapolis, MN, 55455, USA.
authors.forename: Christine L
authors.initials: CL
authors.lastname: Clouser
authors.affiliation: Center for Drug Design, Academic Health Center, University of Minnesota, Minneapolis, MN, 55455, USA.
authors.forename: Steven E
authors.initials: SE
authors.lastname: Patterson
authors.affiliation: Center for Drug Discovery, Department of Pediatrics, Emory Center for AIDS Research, Emory University, Children's Healthcare of Atlanta, 1760 Haygood Dr., Atlanta, GA, 30322, USA. baek.kim@emory.edu.
authors.forename: Baek
authors.initials: B
authors.lastname: Kim
authors.affiliation: Institute for Molecular Virology, University of Minnesota, 18-242 Moos Tower, 515 Delaware St SE, Minneapolis, MN, 55455, USA. mansky@umn.edu.|Department of Diagnostic and Biological Sciences, School of Dentistry, University of Minnesota, Minneapolis, MN, 55455, USA. mansky@umn.edu.|Department of Microbiology and Immunology, University of Minnesota, Minneapolis, MN, 55455, USA. mansky@umn.edu.|Center for Drug Design, Academic Health Center, University of Minnesota, Minneapolis, MN, 55455, USA. mansky@umn.edu.
authors.forename: Louis M
authors.initials: LM
authors.lastname: Mansky
mesh_terms: D000227:Adenine Nucleotides / Q000494:pharmacology* / Q000633:toxicity; D019380:Anti-HIV Agents / Q000494:pharmacology* / Q000633:toxicity; D000963:Antimetabolites / Q000494:pharmacology* / Q000633:toxicity; D001087:Arabinonucleosides / Q000494:pharmacology* / Q000633:toxicity; D015496:CD4-Positive T-Lymphocytes / Q000187:drug effects* / Q000821:virology; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D000077866:Clofarabine; D015497:HIV-1 / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D008264:Macrophages / Q000187:drug effects* / Q000821:virology; D014779:Virus Replication / Q000187:drug effects
chemical_list: D000227:Adenine Nucleotides; D019380:Anti-HIV Agents; D000963:Antimetabolites; D001087:Arabinonucleosides; D000077866:Clofarabine
keywords: Clofarabine; Human immunodeficiency virus (HIV); Nucleoside/nucleotide analogue; Reverse transcription; Ribonucleotide reductase