Human immunodeficiency virus type 1 pol gene mutations which cause decreased susceptibility to 2',3'-dideoxycytidine

Abstract

To investigate whether human immunodeficiency virus type 1 pol gene mutations are selected during prolonged 2',3'-dideoxycytidine (ddC) therapy, we used the polymerase chain reaction to amplify a portion of the reverse transcriptase segment of the pol gene from the peripheral blood mononuclear cell DNA of a patient with AIDS before and after an 80-week course of ddC therapy. The consensus sequence from the second sample contained a unique double mutation (ACT to GAT) in the codon for reverse transcriptase amino acid 69, causing substitution of aspartic acid (Asp) for the wild-type threonine (Thr). A mutation (ACA to ATA) also occurred in the codon for position 165, causing substitution of isoleucine (Ile) for Thr. The GAT (Asp) codon was introduced into the pol gene of a molecular clone of human immunodeficiency virus via site-directed mutagenesis. Following transfection, mutant and wild-type viruses were tested for susceptibility to ddC by a plaque reduction assay. The mutant virus was fivefold less susceptible to ddC than the wild type; crossresistance to 3'-azido-3'-deoxythymidine or 2'3'-dideoxyinosine was not found. The lle-165 mutation did not confer additional ddC resistance. The Asp-69 substitution may have contributed to the generation of resistant virus in this patient.

Human immunodeficiency virus type 1: drug resistance in treated and untreated Brazilian children

“…The T69D was detected in 1 child. It causes resistance to ddC (Fitzgibbon et al 1992) and contributes to the NRTIs resistance when occurring together with NEMs (Winters et al 2001). The L74V, reported in 2 children, occurs commonly during ddI and ABC monotherapy (Miller et al 2000) and confers 2 to 5-fold resistance to ddI and ddC (Winters et al 1997) and 2 to 3-fold resistance to ABC (Tisdale et al 1997).…”

Mechanistic Studies to Understand the Progressive Development of Resistance in Human Immunodeficiency Virus Type 1 Reverse Transcriptase to Abacavir

“…AZT-resistant mutations occur in a pocket that is connected to the triphosphate binding region of the active site (Fig. 1, region I) (33,34,43). Reports have shown that AZTresistant mutations, in the absence of causing large changes in incorporation (25,35), may cause an increase in the rate of pyrophosphorolysis (36) and ATP-mediated removal (34,37).…”

Zidovudine treatment results in the selection of human immunodeficiency virus type 1 variants whose genotypes confer increasing levels of drug resistance

“…Human immunodeficiency virus (HIV) isolates resistant to many compounds targeted to the virus-encoded enzyme reverse transcriptase (RT) have been identified during drug therapy or by selection in vitro (Fitzgibbon et al, 1992;Larder, 1992;Nunberg et al, 199 l ;Richman et al, 1991a;St Clair et al, 1991). Variants of HIV highly resistant to zidovudine (AZT, Retrovir) have been isolated from AIDS patients receiving prolonged treatment (Boucher et al, 1990;Land et al, 1990;Richman et al, 1990;Rooke et al, 1989).…”