DETERMINATION OF HUMAN-IMMUNODEFICIENCY-VIRUS RNA IN PLASMA AND CELLULAR VIRAL-DNA GENOTYPIC ZIDOVUDINE RESISTANCE AND VIRAL LOAD DURING ZIDOVUDINE-DIDANOSINE COMBINATION THERAPY

Eleven human immunodeficiency virus (HIV)-infected subjects on long-te rm zidovudine (ZDV) therapy had didanosine (ddI) added to their antire troviral regimen. HIV RNA in plasma was quantitated by branched-DNA si gnal amplification assay, Peripheral blood mononuclear cell (PBMC) HN viral DNA was quantitated by PCR. The relative amounts of wild-type (W T) sequence, ddI resistance-associated codon changes (reverse transcri ptase [RT] gene codon 65 K-->R [RT K65R], RT 174V, RT I135K/T/V, and R T M184I/V), and ZDV resistance-associated codon change (RT TZ15Y/F) fr om HIV RNA in plasma and RT T215Y/F from PBMC viral DNA were determine d by differential hybridization of PCR products from 10 of 11 subjects . All subjects had evidence of RT T215Y/F mutation in both RNA in plas ma and PBMC DNA at baseline, Subjects with a mixture of WT and RT T215 Y/F HIV RNA in plasma at baseline demonstrated a decline in RNA levels in plasma after the addition of ddI, However, after 6 months of ZDV-d dI therapy, WT HIV RNA in plasma was undetectable in all subjects who had demonstrated a mixture at baseline. Subjects with only RT T215Y/F RNA present in plasma at baseline remained so and demonstrated no decl ine in RNA levels in plasma. In all subjects, no significant changes i n PBMC DNA viral load and RT T215Y/F or WT levels were seen, HIV RNA i n plasma demonstrated a significantly higher RT T215Y/F mutant/WT rati o than that of PBMC viral DNA, both at baseline and after ZDV-ddI comb ination therapy in all subjects, No subjects developed mutations assoc iated with ddI resistance at codons 65, 74, 135, and 184 during this s tudy. This study suggests that determination of relative amounts of RT T215Y/F and WT species from HIV RNA in plasma at baseline may be pred ictive of virologic response during ZDV-ddI combination therapy.