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

Abstract

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...

Impact of Drug Resistance-Associated Amino Acid Changes in HIV-1 Subtype C on Susceptibility to Newer Nonnucleoside Reverse Transcriptase Inhibitors

“…In the current study, only a single subtype C reference isolate was used, and the phenotypic responses observed could be isolate specific. Third, the variation in responses could be subtype specific, and several studies have shown differences between subtypes regarding both replication capacity and phenotypic susceptibility (44)(45)(46). The screening of additional subtype C isolates could validate the phenotypic differences that were observed between our subtype C mutants and the published subtype B mutants.…”

Evolutionary consequences of drug resistance: shared principles across diverse targets and organisms

“…For example, a dual-infection competition assay with sequence-tagged HIV 36 (BOX 1) measured replicative fitness costs caused by mutations leading to resistance to NNRTI drugs 37 . The relative magnitude of the fitness costs depended on the HIV subtype (subtype B or subtype C), suggesting epistatic effects on fitness 38 .…”

HIV-1 Resistance to Maraviroc Conferred by a CD4 Binding Site Mutation in the Envelope Glycoprotein gp120

“…However, drug resistance mutations conferring lower fitness costs are often found at higher frequencies in the untreated HIV-1 population or within the intrapatient population. For example, there is a low genetic and fitness barrier to nevirapine (NVP) resistance via the K103N mutation (61,62), which reflects (i) the slow reversion of this mutation following cessation of NVP treatment (63)(64)(65) and (ii) increasing circulation and transmission of the K103N virus within the human population where NVP-based treatment regimens are most prevalent (66). In this study, we have shown that the collection of E33bG, R117Q, Q290K, L/G396V, N425K, and D461E selected under MVC pressure resulted in virus of higher replicative fitness than the wildtype passage control virus.…”