A Novel Human Immunodeficiency Virus Type 1 Reverse Transcriptase Mutational Pattern Confers Phenotypic Lamivudine Resistance in the Absence of Mutation 184V

Abstract

We describe a new human immunodeficiency virus type 1 (HIV-1) mutational pattern associated with phenotypic resistance to lamivudine (3TC) in the absence of the characteristic replacement of methionine by valine at position 184 (M184V) of reverse transcriptase. Combined genotypic and phenotypic analyses of clinical isolates revealed the presence of moderate levels of phenotypic resistance (between 4-and 50-fold) to 3TC in a subset of isolates that did not harbor the M184V mutation. Mutational cluster analysis and comparison with the phenotypic data revealed a significant correlation between moderate phenotypic 3TC resistance and an increased incidence of replacement of glutamic acid by aspartic acid or alanine and of valine by isoleucine at residues 44 and 118 of reverse transcriptase, respectively. This occurred predominantly in those isolates harboring zidovudine resistance-associated mutations (41L, 215Y). The requirement of the combination of mutations 41L and 215Y with mutations 44D and 44A and/or 118I for phenotypic 3TC resistance was confirmed by site-directed mutagenesis experiments. These data support the assumption that HIV-1 may have access to several different genetic pathways to escape drug pressure or that the increase in the frequency of particular mutations may affect susceptibility to drugs that have never been part of a particular regimen.The emergence of drug-resistant human immunodeficiency virus type 1 (HIV-1) variants is almost always observed during the course of treatment of patients with antiretroviral drugs (3, 10, 14-16, 18, 21, 27 Strategies, abstr. 19, p. 15, 1998). The mutational profile of the resistant viruses generally is characteristic for the particular drug(s) taken. For example, mutations at codons 41, 67, 70, 210, 215, and 219 of reverse transcriptase (RT) typically confer resistance to zidovudine (ZDV) (6,12,13,27). Similarly, mutation M184V in RT has been shown to be specifically associated with high-level (Ն50-fold) phenotypic resistance to lamivudine (3TC) (1,22,28). No "specific" mutation(s) associated with moderate levels of phenotypic resistance (4-to Ͻ50-fold) to 3TC has been described before. Those mutations that confer moderate (4-to Ͻ50-fold) levels of phenotypic resistance to 3TC reported previously always appeared in the context of a constellation of mutations that confer resistance to multiple nucleoside analogues or as a cross-resistance phenomenon that appears with the emergence of resistance to another nucleoside analogue. This has been the case for the nucleoside multidrug resistance complex of mutations Q151M, F77L, F116Y, A62V, and V75I, although the increase in the level of phenotypic resistance to 3TC in viruses that harbor those mutations is slight (9,20,24,25). In the case of the insertion mutations near position 69 of RT, a notable increase in the frequency of 3TC resistance has been reported together with an increased frequency of phenotypic resistance to other nucleosides (2, 17, 29). The K65R mutation appears infrequently during the course of tr...

Comparing the Accumulation of Active- and Nonactive-Site Mutations in the HIV-1 Protease

“…The V6 54/84 variant contains three mutations in the active site, V32I, V82A, and I84V, and occupies the S2/S2′ (32) and S1/S1′ (82 and 84) pockets. These pockets interact with the core of the inhibitor.…”

“…at residues 20,32,33,36,63,71,82, and 90 ( Figure 1 and Table 1). Mutated residues in variant V6 compared to LAI (wild type) are shown in Table 1.…”

Diversity and complexity of HIV-1 drug resistance: A bioinformatics approach to predicting phenotype from genotype

“…Nevertheless, some results are unexpected. For example, RT positions 44 and 118 show high peaks in the profiles for ZDV and d4T, but in clinical samples and mutagenesis experiments they have been associated only with resistance to 3TC (30). On the other hand, some positions previously associated with drug resistance (e.g., protease position 30 for NFV, RT position 151 for NRTI multidrug resistance) do not show up in the mutual information profiles; this may be because they are too rare in the data set or because their appearance is associated with different resistance levels than the chosen cutoffs specify.…”

“…Drug resistance can either be directly assessed by phenotypic assays or can be deduced from genotypic assays, which are based on sequencing of the relevant parts of the viral genome (4). Most phenotypic assays use recombinant virus techniques directly measuring viral replication in the presence of increasing drug concentrations (5,6). The results can be interpreted easily, but the assays are time-and labor-consuming, and are therefore restricted to specialized laboratories.…”

Rate of Virological Treatment Failure and Frequencies of Drug Resistance Genotypes among Human Immunodeficiency Virus-Positive Subjects on Antiretroviral Therapy in Spain

“…Table 2 summarizes the most prevalent resistance mutations affecting compounds of each of the three antiretroviral drug families. For the RT gene, mutations associated with resistance to zidovudine and lamivudine were the most frequently found, including the newly described lamivudine resistance genotypes 44D and 118I (6), which were present in 20% of the samples. It should be pointed out that 20% of patients harbored more than three classical zidovudine mutations, including 41L, 67N, 70R, 210W, 215Y/F, and 219Q/E.…”