Identification of insertion mutations in HIV-1 reverse transcriptase causing multiple drug resistance to nucleoside analogue reverse transcriptase inhibitors

Objective: A navel 2-amino acid insertion between codons 69 and 70 of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) which con fers multiple drug resistance has recently been reported. Independently, ar e have identified similar insertion mutations in Japanese hemophiliacs and attempted to analyze their emergence In conjunction with therapy regimens a nd their contribution to drug resistance using recombinant technology. Methods: The plasma and peripheral blood mononuclear cells (PBMCs) of 348 H IV-1-infected hemophiliacs were screened for HIV-1 RT mutations relevant to nucleoside analogue inhibitors and isolating viruses. Contribution of each insertion to drug resistance was studied by introducing the mutations into a T-cell line-tropic NL4-3 infectious clone and testing the drug susceptib ilities of die recovered virus. Results: Insertion of the 2-amino acid residue was found in 4 of the 348 ca ses and was strongly associated with prolonged chemotherapy with zidovudine (AZT) and didanosine (ddI). The virus isolated from 1 of the 4 cases posse ssed the same insertion. Characterization of these virus and the recombinan t: NL4-3 with the insertion strongly suggested chat the insertion caused re sistance not only to AZT and ddI but also to lamivudine (3TC) and zalcitabi ne (ddC). Conclusion: A 2-amino acid insertion between codons 69 and 70 of RT was det ected in 4 of 348 (1.1%) Japanese hemophiliacs and was found to be associat ed with multiple drug resistance to nucleoside analogue RT inhibitors.