Multiple Mutations in HIV-1 Reverse Transcriptase Confer High-Level Resistance to Zidovudine (AZT)

TLDR

The study aimed to identify the genetic mutations underlying zidovudine resistance in HIV isolates. The authors analyzed sequential patient isolates and engineered an infectious clone harboring the identified RT mutations to confirm their role in AZT resistance. Three core RT mutations (D67N, K70R, T215F/Y) and an additional K219Q mutation were consistently associated with high‑level AZT resistance, enabling the development of rapid PCR‑based resistance assays.

Abstract

Human immunodeficiency virus (HIV) isolates with reduced sensitivity to zidovudine (3′-azido-3′-deoxythymidine, AZT) from individuals with acquired immunodeficiency syndrome (AIDS) or AIDS-related complex were studied to determine the genetic basis of their resistance. Most were sequential isolates obtained at the initiation of and during therapy. Comparative nucleotide sequence analysis of the reverse transcriptase (RT) coding region from five pairs of sensitive and resistant isolates identified three predicted amino acid substitutions common to all the resistant strains (Asp 67 → Asn, Lys 70 → Arg, Thr 215 → Phe or Tyr) plus a fourth in three isolates (Lys 219 → Gln). Partially resistant isolates had combinations of these four changes. An infectious molecular clone constructed with these four mutations in RT yielded highly resistant HIV after transfection of T cells. The reproducible nature of these mutations should make it possible to develop rapid assays to predict zidovudine resistance by performing polymerase chain reaction amplification of nucleic acid from peripheral blood lymphocytes, thereby circumventing current lengthy HIV isolation and sensitivity testing.