title: Zidovudine (AZT) monotherapy selects for the A360V mutation in the connection domain of HIV-1 reverse transcriptase.
abstract: BACKGROUND
  We previously demonstrated in vitro that zidovudine (AZT) selects for A371V in the connection domain and Q509L in ribonuclease H (RNase H) domain of HIV-1 reverse transcriptase (RT) which, together with the thymidine analog mutations D67N, K70R and T215F, confer greater than 100-fold AZT resistance. The goal of the current study was to determine whether AZT monotherapy in HIV-1 infected patients also selects the A371V, Q509L or other mutations in the C-terminal domains of HIV-1 RT.
  
  
  RESULTS
  Full-length RT sequences in plasma obtained pre- and post-therapy were compared in 23 participants who received AZT monotherapy from the AIDS Clinical Trials Group study 175. Five of the 23 participants reached a primary study endpoint. Mutations significantly associated with AZT monotherapy included K70R (p = 0.003) and T215Y (p = 0.013) in the polymerase domain of HIV-1 RT, and A360V (p = 0.041) in the connection domain of HIV-1 RT. HIV-1 drug susceptibility assays demonstrated that A360V, either alone or in combination with thymidine analog mutations, decreased AZT susceptibility in recombinant viruses containing participant-derived full-length RT sequences or site-directed mutant RT. Biochemical studies revealed that A360V enhances the AZT-monophosphate excision activity of purified RT by significantly decreasing the frequency of secondary RNase H cleavage events that reduce the RNA/DNA duplex length and promote template/primer dissociation.
  
  
  CONCLUSIONS
  The A360V mutation in the connection domain of RT was selected in HIV-infected individuals that received AZT monotherapy and contributed to AZT resistance.
authors.affiliation: Division of Infectious Diseases, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America.
authors.forename: Jessica H
authors.initials: JH
authors.lastname: Brehm
authors.forename: Yanille
authors.initials: Y
authors.lastname: Scott
authors.forename: Dianna L
authors.initials: DL
authors.lastname: Koontz
authors.forename: Steven
authors.initials: S
authors.lastname: Perry
authors.forename: Scott
authors.initials: S
authors.lastname: Hammer
authors.forename: David
authors.initials: D
authors.lastname: Katzenstein
authors.forename: John W
authors.initials: JW
authors.lastname: Mellors
authors.forename: Nicolas
authors.initials: N
authors.lastname: Sluis-Cremer
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D019943:Amino Acid Substitution / Q000235:genetics*; D019380:Anti-HIV Agents / Q000494:pharmacology / Q000627:therapeutic use; D024882:Drug Resistance, Viral / Q000187:drug effects / Q000235:genetics; D015658:HIV Infections / Q000097:blood / Q000188:drug therapy* / Q000821:virology; D054303:HIV Reverse Transcriptase / Q000737:chemistry* / Q000235:genetics*; D015497:HIV-1 / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D006801:Humans; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000378:metabolism; D009154:Mutation / Q000235:genetics*; D010641:Phenotype; D017434:Protein Structure, Tertiary; D012367:RNA, Viral / Q000097:blood; D011995:Recombination, Genetic / Q000235:genetics; D016914:Ribonuclease H / Q000378:metabolism; D015215:Zidovudine / Q000494:pharmacology / Q000627:therapeutic use*
chemical_list: D019380:Anti-HIV Agents; D050505:Mutant Proteins; D012367:RNA, Viral; D015215:Zidovudine; D000255:Adenosine Triphosphate; C514824:reverse transcriptase, Human immunodeficiency virus 1; D054303:HIV Reverse Transcriptase; D016914:Ribonuclease H