CROSS-RESISTANCE BETWEEN AZT, DDL AND OTHER ANTIRETROVIRAL DRUGS IN PRIMARY ISOLATES OF HIV-1

Primary isolates of human immunodeficiency virus type 1 (HIV-1) were t ested for sensitivity to 3'-azido-3'-deoxythymidine (AZT), 3'-fluoro-3 '-deoxythymidine (FLT), 2',3'-dideoxyinosine (ddl), 2',3'-dideoxycytid ine (ddC), and phosphonoformate (PFA) in peripheral blood mononuclear cells (PBMC). Forty-eight isolates from HIV-1-infected patients treate d with AZT for various lengths of time were investigated. More than ha lf of the patients harboured virus resistant to AZT after treatment. T here was no correlation between resistance and length of therapy. A si gnificant correlation between resistance to AZT and reduced susceptibi lity to ddl and ddC was apparent. These results indicate that developm ent of resistance to AZT is common in patients treated with AZT and ma y be associated with reduced sensitivity to ddl and ddC.