Low AZT activity against HIV-2 infection

Simon Collins, HIV i-Base

Although AZT is widely used to treat HIV-2 infection recent studies showing difference in response compared to patients with HIV-1. This prompted Garcia-Lerma and colleagues from CDC Atlanta USA to evaluate in vitro selection experiments with strains of each virus.

5/5 HIV-1 strains rapidly selected for resistance after 3-6 passages (in increasing AZT concentrations of four-32 fold). In contrast 0/5 HIV-2 virus acquired mutations after 10 passages (1024-fold increase in AZT concentration). In the presence of both AZT and ddI, HIV-1 viruses selected mutation for both drugs, while HIV-2 selected only for ddI (K65R and M184V).

All HIV-2 viruses replicated efficiently in concentration of AZT that was 2800-fold higher than the EC50 for HIV-1 and were 200-fold less sensitive. Sensitivity to ddI was similar for both HIV-1 and HIV-2.


Reid P, MacInnes H, Garcia-Lerma JG et al. Natural resistance of HIV-2 to zidovudine. XIII Intl HIV Drug Resistance Workshop, 2004. Abstract 32. Antiviral Therapy 2004; 9:S38.

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