Genotoxicity assessed by the comet and GPA assays following in vitro exposure of human lymphoblastoid cells (H9) or perinatal exposure of mother-child pairs to AZT or AZT-3TC

Environ Mol Mutagen. 2007 Apr-May;48(3-4):330-43. doi: 10.1002/em.20285.


The genotoxicity of zidovudine (AZT) based treatments was investigated in human H9 lymphoblastoid cells in an in vitro study and in red blood cells (RBCs) from perinatally exposed HIV-1-infected mothers and their infants in an observational cohort study. Exposure of H9 cells for 24 hr to AZT produced dose-dependent increases in Comet assay tail moment (TM) when electrophoresed at pH 13.0, but not at pH 12.1 or pH 8.0, suggesting that DNA damage was via alkali-labile lesions and not double-stranded DNA strand breaks. The TM dose response at pH 13.0 correlated directly with AZT-DNA incorporation determined by AZT-radioimmunoassay. Levels of DNA damage in utero, measured by Comet assay TM, were similar in cord blood mononuclear cells of nucleoside analog-exposed newborns (n = 43) and unexposed controls (n = 40). In contrast, the glycophorin A (GPA) somatic cell mutation assay (which screens for large-scale DNA damage in RBCs) showed clear evidence that GPA N/N variants, arising from chromosome loss and duplication, somatic recombination, and gene conversion, were significantly elevated in mother-child pairs receiving prepartum AZT plus lamivudine (3TC). Cord blood from newborns exposed to AZT-3TC had GPA N/N variant frequencies of 4.7 +/- 0.7 (mean +/- SE) x 10(-6) RBCs (n = 26 infants) compared with 2.2 +/- 0.3 x 10(-6) RBCs for unexposed controls (n = 30 infants; P < 0.001). Elevations in GPA N/N variants generally persisted through 1 year of age in nucleoside analog-exposed children. Overall, the mutagenic effects found in mother-child pairs receiving AZT-based treatments justify their surveillance for long-term genotoxic consequences.

Publication types

  • Clinical Trial
  • Research Support, N.I.H., Extramural

MeSH terms

  • Anti-HIV Agents / administration & dosage
  • Anti-HIV Agents / therapeutic use
  • Anti-HIV Agents / toxicity*
  • Cell Line
  • Comet Assay
  • Drug Combinations
  • Erythrocytes / drug effects
  • Female
  • Glycophorins / genetics
  • Humans
  • Infant
  • Infant, Newborn
  • Lamivudine / administration & dosage
  • Lamivudine / therapeutic use
  • Lamivudine / toxicity*
  • Leukocytes / drug effects
  • Maternal-Fetal Exchange
  • Mutagenicity Tests
  • Mutation
  • Pregnancy
  • Reverse Transcriptase Inhibitors / administration & dosage
  • Reverse Transcriptase Inhibitors / therapeutic use
  • Reverse Transcriptase Inhibitors / toxicity*
  • Zidovudine / administration & dosage
  • Zidovudine / therapeutic use
  • Zidovudine / toxicity*


  • Anti-HIV Agents
  • Drug Combinations
  • Glycophorins
  • Reverse Transcriptase Inhibitors
  • Lamivudine
  • Zidovudine