Patterns of resistance mutations selected by treatment of human immunodeficiency virus type 1 infection with zidovudine, didanosine, and nevirapine

Resistance mutations selected in reverse transcriptase (RT) by incompletely suppressive therapy with combination zidovudine and didanosine with or wit hout nevirapine were identified in 141 human immunodeficiency virus type 1 isolates from peripheral blood mononuclear cells of 57 individuals in the A IDS Clinical Trials Group protocol 241. After prolonged treatment (16-48 we eks), the most common nevirapine-selected mutations were RT 181C (15/30 iso lates [50%]), 190A (15/30 [50%]), and 101E (9/30 [30%]), RT 103N and 188L, which individually confer cross-resistance to all nonnucleoside RT inhibito rs, were seen in a minority of viruses (6/30 [20%] and 4/30 [13%], respecti vely). Didanosine-resistance mutations arose rarely A newly recognized muta tion, RT 44D, was selected by the nucleosides, Two distinct zidovudine-resi stance mutational patterns were noted. Mutations selected during treatment with zidovudine, didanosine, and nevirapine differed among individuals and changed over time. Resistance testing is necessary to identify which mutati ons are selected by nevirapine-containing combinations.