EMERGENCE OF MULTI-DIDEOXYNUCLEOSIDE-RESISTANT HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 VARIANTS, VIRAL SEQUENCE VARIATION, AND DISEASE PROGRESSION IN PATIENTS RECEIVING ANTIRETROVIRAL CHEMOTHERAPY

A set of five reverse transcriptase mutations, which include Q151M, is known to confer multidideoxynucleoside resistance (MDR) in human immu nodeficiency virus type 1 (HIV-1). MDR mutations were found in 6 (17%) HIV-I isolates from 36 patients, most of whom were receiving long-ter m combination therapy. Q151M was among the first of the substitutions to appear. Additional substitutions were observed, although none were common among all 6 patients, Certain zidovudine-related mutations were not observed together with the MDR mutations, indicating possible enz ymatic constraint. During chemotherapy, the HIV-1 RNA levels in the 6 patients initially decreased and then rose. Initially, CD4 cell counts also responded favorably but were near or below baseline beyond 40 mo nths of therapy. Such loss of clinical benefits appeared to coincide w ith the appearance of the MDR mutations. A common background genotype was not observed among HIV-1 isolates with or without MDR.