Genetic Divergence of Human Immunodeficiency Virus Type 1 Ethiopian Clade C Reverse Transcriptase (RT) and Rapid Development of Resistance against Nonnucleoside Inhibitors of RT

Abstract

We sequenced and phylogenetically analyzed the reverse transcriptase (RT) region of five human immunodeficiency virus type 1 isolates from treatment-naive Ethiopian émigrés to Israel. Heteroduplex mobility assays were performed to confirm the clade C status of env genomic regions. The RT sequences showed that the strains clustered phylogenetically with clade C viruses, and a KVEQ-specific motif of silent mutations (amino acids 65, 106, 138, and 161, respectively) at resistance sites was present in the polymerase region of all studied Ethiopian isolates and subtype C reference strains. In addition, many other silent mutations were observed in the clade C viruses at various resistance sites. In general, the Ethiopian isolates were more closely related genotypically to a clade C reference strain from Botswana (southern Africa) than to previously sequenced Ethiopian reference strains. Genotypic analysis showed that two Ethiopian isolates naturally harbored the mutations K70R and G190A associated with resistance to ZDV and nonnucleoside reverse transcriptase inhibitors, respectively. Phenotypic assays revealed that the K70R substitution in this context did not reduce susceptibility to ZDV, whereas the G190A substitution resulted in high-level resistance to nevirapine (NVP). Moreover, variants resistant to NVP, delavirdine (DLV), and efavirenz (EFV) were more rapidly selected at lower drug doses culture with clade C than with clade B wild-type isolates. In the case of subtype C, selection with NVP and/or EFV led to the appearance of several previously unseen mutations in RT, i.e., V106M and S98I, as well as other mutations that have been previously reported (e.g., K103N, V106A, V108I, and Y181C). After selection with DLV, a polymorphism, A62A, initially observed in the Ethiopian isolate 4762, mutated to A62V; the latter is a secondary substitution associated with multidrug resistance against nucleoside RT inhibitors. Phenotypic analysis of clade C mutants selected against NVP, DLV, and EFV revealed broad cross-resistance, particularly in regard to NVP and DLV. These findings suggest that RT genotypic diversity may influence the emergence of drug resistance.

Mutation D30N Is Not Preferentially Selected by Human Immunodeficiency Virus Type 1 Subtype C in the Development of Resistance to Nelfinavir

“…This mutation appears frequently in subtype-C-infected patients treated with efavirenz and rarely in subtype-B-infected patients or in subtype-C-infected patients treated with nevirapine (4,9,20). Moreover, in vitro studies of this group showed that the final drug concentration required for the development of resistance mutations conferring nonnucleoside reverse transferase inhibitors resistance was significantly lower for subtype C than for subtype B viruses and that resistant variants were fully selected more rapidly with the subtype C isolates than with the subtype B control (15,16). All these studies highlight the importance of further characterization of the development of resistance in non-subtype B viruses.…”

“…Primary and major mutations are indicated. In order to strengthen the comparison, Israeli subtype C data (Is) were compared also to subtype B data available from the public Stanford (St) database (16,27). tients.…”

“…Although none of the primary mutations occur as polymorphisms in wild-type HIV-1, several secondary mutations contributing to reduced susceptibility (i.e., M36I and I93L) are found in nearly 100% of subtype C virus from drug-naive patients (5,10). Upon antiretroviral treatment, such differences in baseline polymorphisms among subtypes may result in the evolution of drug resistance along distinct mutational pathways, or in differences in the incidence of these specific pathways (1,4,9,12,16,25,28,29). These genetic differences may be clinically relevant when considering long-term treatment strategies for patients infected with different subtypes.…”

Résistance du VIH aux antirétroviraux

“…En effet, des différences génotypiques de résistances aux ARV ont été trouvées dans différents groupes, types et sous-types du VIH-1. C'est ainsi que les virus appartenant au groupe O ainsi que le VIH-2 sont porteurs de mutations sur la TI qui induisent une résistance naturelle aux INNTI [22,23]. Une étude brési-lienne a également montré que les patients sous HAART infectés par des souches virales de sous-type non B devenaient plus rapidement résistants aux médicaments antiviraux [24].…”

Lack of Effect of Recombinant Human Growth Hormone on the In Vitro Activities of Antiretroviral Drugs against Human Immunodeficiency Virus Type 1

“…IC 50 s were determined by growing wt or drug-resistant variants of HIV in cultured PBMCs in the presence of various concentrations of the different ARVs, ranging from 0.001 to 10 M, as described previously (3,18). Viral p24 concentrations in culture fluids were measured (Abbott Laboratories Inc., North Chicago, Ill.) to generate IC 50 s (8). The effects of r-hGH on viral replication and antiretroviral activity were assessed by adding the hormone to cultures at a concentration of 10 or 50 ng/ml; these represent the midrange and maximum concentrations, respectively, expected in plasma after subcutaneous injection of a standard daily dose of 6 mg of r-hGH.…”