Insertion of two amino acids combined with changes in reverse transcriptase containing tyrosine-215 of HIV-1 resistant to multiple nucleoside analogs

Objective: To identify genotypic drug resistance patterns of HIV-1 in patie nts who were extensively pretreated with anti-HIV drugs and not responding to their current antiretroviral combination therapy. Methods: Drug susceptibility of the viruses was tested by a phenotypic reco mbinant virus assay. Genotypic analysis of HIV resistance was performed by sequencing of the amino-terminal part of the corresponding reverse transcri ptase (RT) gene (amino acids 1-280) for serum-derived and recombinant virus es. Results: Among Viruses from 92 patients studied, three (3%) Viruses contain ed a T215Y amino-acid change as well as a previously unseen combination of an aminoacid change at codon 67 (N-->E/S) and a two amino-acid insertion be tween codons 68 and 69 of the RT gene of HIV-1. Phenotypic resistance analy sis showed high levels of resistance to zidovudine, lamivudine and stavudin e tin all patients) and moderate levels of resistance to didanosine and zal citabine tin two patients), whereas neither serum-derived nor recombinant V iruses contained previously known amino-acid changes conferring resistance to didanosine, zalcitabine, lamivudine and stavudine. However, all recombin ant viruses contained an insertion of two amino acids between codons 68 and 69 of RT as well as an amino-acid change at codon 67, as was seen in the s erum-derived viruses. Conclusions: Antiretroviral therapy including zidovudine may yield replicat ing viruses with a two amino-acid insertion in RT in combination with amino -acid changes at codons 67 and 215, which are highly resistant to lamivudin e and stavudine on top of zidovudine and have unpredictable susceptibility to didanosine and zalcitabine despite lack of previously reported correspon ding resistance-associated amino-acid changes. It is currently unknown what regimens can induce the emergence of this type of multidrug-resistant viru ses. This will only be elucidated when resistance assays are capable of det ecting these mutants. (C) 1999 Lippincott Williams & Wilkins.