Prevalence of primary resistance to zidovudine and lamivudine in drug-naive human immunodeficiency virus type-1 infected patients: High proportion ofreverse transcriptase codon 215 mutant in circulating lymphocytes and freevirus

The presence of primary zidovudine (AZT)resistance (mutation T215Y/F) or la mivudine (3TC)-resistance (mutation M184V) was evaluated in 90 drug-naive p atients infected with human immunodeficiency virus type-1 (HIV-1) between 1 987 and 1997. The proportion of mutant strains in proviral samples or plasm a viral samples was determined using a differential hybridization assay. Mu tation T215Y/F was found in five (5.6%) patients infected between 1994 and 1997, whereas none of these patients harbored the mutation M184V. The T215Y /F mutation was present in the virus and/or provirus and persisted for at l east two years. In one patient, the mutant provirus was associated with onl y wildtype free virus. Four of these patients were followed, and two were t reated subsequently to a regimen containing AZT but with low response. The persistence of primary resistance mutations might depend on the proportion of these mutations at the time of infection, although mutant provirus might not give rise to replicating variants. (C) 2000 Wiley-Liss, Inc.