High Prevalence of the K65R Mutation in Human Immunodeficiency Virus Type 1 Subtype C Isolates from Infected Patients in Botswana Treated with Didanosine-Based Regimens

Single-dose nevirapine (NVP) is quite effective in preventing transmission of the human immunodeficiency virus (HIV) from mother to child; however, many women develop resistance to NVP in this setting. Comparing outcomes of clinical studies reveals an increased amount of resistance in subtype C relative to that in other subtypes. This study investigates how nonnucleoside reverse transcriptase inhibitor (NNRTI) drug resistance mutations of subtype C affect replication capacity. The 103N, 106A, 106M, 181C, 188C, 188L, and 190A drug resistance mutations were placed in a reverse transcriptase (RT) that matches the consensus subtype C sequence as well as the HXB2 RT, as a subtype B reference. The replicative fitness of each mutant was compared with that of the wild type in a head-to-head competition assay. The 106A mutant of subtype C would not grow in the competition assay, making it the weakest virus tested. The effect of the 106M mutation was weaker than those of the 181C and 188C mutations in the consensus C RT, but in subtype B, this difference was not seen. To see if the 106A mutation in a different subtype C background would have a different replicative profile, the same NNRTI resistance mutations were added to the MJ4 RT, a reference subtype C molecular clone. In the context of MJ4 RT, the 106A mutant was not the only mutant that showed poor replicative fitness; the 106M, 188C, and 190A mutants also failed to replicate. These results suggest that NNRTIs may be a cost-effective alternative for salvage therapy if deleterious mutations are present in a subtype C setting.The emergence of drug-resistant mutants is common among HIV-infected patients undergoing antiviral therapy. Clinically, the standard practice is to drop the antiviral to which the resistance has developed from the treatment regimen in such drug failure cases. However, a notable exception to this is the continuing use of lamivudine (3TC) as a salvage regimen because the 184V mutation linked to 3TC treatment has decreased replication ability relative to that of the wild type (WT) in subtype B (7). Mechanistically, Back et al. (2) found that the 184V mutant is less processive than wild-type RT under conditions of limiting deoxynucleoside triphosphates (dNTPs), and in primary lymphoid cells, the mutant is less fit than wildtype virus. These studies were extended further in vivo by Paredes et al. (35), who looked at multidrug-resistant virus from patients who were ending 3TC treatment. They used an allele-specific PCR assay to track the reversion of the M184V sequence and found that there was a fitness cost of 4 to 8% for the 184V mutation compared to that of the viral sequence that grew without 3TC drug pressure. Taken together, these studies illustrate how clinical management of HIV-infected patients can benefit from the study of the fitness cost of HIV drugresistant mutants.The use of antiretroviral drugs is increasing in the developing world. In particular, the use of single-dose nevirapine (NVP) has been shown to be an effective means of mitigat...

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confidence: 65%

Replicative Fitness Costs of Nonnucleoside Reverse Transcriptase Inhibitor Drug Resistance Mutations on HIV Subtype C

Armstrong

Lee

Essex

2011

“…An increasing number of reports now show that the occurrence of K65R is increasing worldwide, especially in subtype C-infected patients who have failed antiretroviral therapy (54)(55)(56). It was previously shown that K65R confers hypersusceptibility to compound A, while W153L confers hypersusceptibility to TFV (17).…”

Section: Discussionmentioning

confidence: 99%

Effects of the W153L Substitution in HIV Reverse Transcriptase on Viral Replication and Drug Resistance to Multiple Categories of Reverse Transcriptase Inhibitors

Colby-Germinario

Oliveira

et al. 2014

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A W153L substitution in HIV-1 reverse transcriptase (RT) was recently identified by selection with a novel nucleotide-competing RT inhibitor (NcRTI) termed compound A that is a member of the benzo[4,5]furo[3,2,d]pyrimidin-2-one NcRTI family of drugs.To investigate the impact of W153L, alone or in combination with the clinically relevant RT resistance substitutions K65R (change of Lys to Arg at position 65), M184I, K101E, K103N, E138K, and Y181C, on HIV-1 phenotypic susceptibility, viral replication, and RT enzymatic function, we generated recombinant RT enzymes and viruses containing each of these substitutions or various combinations of them. We found that W153L-containing viruses were impaired in viral replicative capacity and were hypersusceptible to tenofovir (TFV) while retaining susceptibility to most nonnucleoside RT inhibitors. The nucleoside 3TC retained potency against W153L-containing viruses but not when the M184I substitution was also present. W153L was also able to reverse the effects of the K65R substitution on resistance to TFV, and K65R conferred hypersusceptibility to compound A. Biochemical assays demonstrated that W153L alone or in combination with K65R, M184I, K101E, K103N, E138K, and Y181C impaired enzyme processivity and polymerization efficiency but did not diminish RNase H activity, providing mechanistic insights into the low replicative fitness associated with these substitutions. We show that the mechanism of the TFV hypersusceptibility conferred by W153L is mainly due to increased efficiency of TFV-diphosphate incorporation. These results demonstrate that compound A and/or derivatives thereof have the potential to be important antiretroviral agents that may be combined with tenofovir to achieve synergistic results. C urrent standard anti-HIV-1 therapy, termed highly active antiretroviral therapy (HAART), consists of three or more antiretroviral compounds from six distinct classes, including nucleoside reverse transcriptase (RT) inhibitors (NRTIs), nonnucleoside RT inhibitors (NNRTIs), protease inhibitors (PIs), fusion inhibitors, entry inhibitors, and integrase inhibitors (INIs) (for recent reviews, see references 1 and 2). HAART commonly includes two NRTIs in combination with either an NNRTI, a PI, or more recently, an INI (66). HAART has been effective at suppressing HIV-1 replication, partially reversing immunodeficiency, reducing HIV-1-associated complications, and prolonging life (3, 4). However, all antiretrovirals can be compromised by the development of drug resistance (5, 6) that arises from the rapid replication rate of HIV-1 and the error-prone nature of its RT (7, 8). In the absence of an effective vaccine against HIV-1 infection, it is important to develop novel effective antiretrovirals with superior resistance profiles.There are currently 8 approved NRTIs that all compete with natural deoxynucleoside triphosphate (dNTP) substrates to act as DNA chain terminators. In contrast, NNRTIs act allosterically and noncompetitively by inducing conformational changes in RT. The me...

“…For example, a V106M mutation (GTG 3 ATG) confers high-level resistance against multiple nonnucleoside reverse transcriptase inhibitors (NNRTIs), with the V106A substitution being more common in subtype B (1). Moreover, unique polymorphisms at reverse transcriptase (RT) codons 64 (AAG 3 AAA), 65 (AAA 3 AAG), and 66 (AAA 3 AAG) may cause the K65R nucleoside resistance mutation to be selected more rapidly by several members of the nucleoside RT inhibitor (NRTI) family of drugs in subtype C than by those in subtype B both in cell culture and in the clinic (2,5).…”

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confidence: 99%

Development of an Allele-Specific PCR for Detection of the K65R Resistance Mutation in Patients Infected with Subtype C Human Immunodeficiency Virus Type 1

Toni

Brenner

Asahchop

et al. 2010

Self Cite

The selection of drug-resistant variants of human immunodeficiency virus type 1 (HIV-1) is an impediment to the efficiency of antiretroviral (ARV) therapy. We have developed an allele-specific real-time PCR assay to explore the presence of K65R minority species among treated HIV-1 subtype B and C infections. Thirty HIV-1 subtype C-and 26 subtype B-infected patients lacking K65R as determined by conventional sequencing methods were studied, and viral minority species were found in four HIV-1 subtype C samples.