Combinations of Mutations in the Connection Domain of Human Immunodeficiency Virus Type 1 Reverse Transcriptase: Assessing the Impact on Nucleoside and Nonnucleoside Reverse Transcriptase Inhibitor Resistance

Abstract

PLoS Med. 4:e335, 2007). In the present study, novel mutations in the connection domain of RT (T369I/V), first identified in patient-derived viruses, were characterized, and their effects on NNRTI and NNRTI susceptibility were determined. Furthermore, the effect of N348I on NRTI and NNRTI resistance was confirmed. HIV-1 with either N348I or T369I/V demonstrated reduced susceptibility to nevirapine (NVP), efavirenz (EFV), delaviridine (DLV), and zidovudine (ZDV) compared to wild-type HIV-1. However, HIV-1 with T369I and N348I demonstrated 10-to 60-fold resistance to these same drugs. In clinical samples, these two connection domain RT mutations were predominantly observed in viruses containing TAMs and NNRTI mutations and did not alter the susceptible-resistant classifications of these samples. Introduction of T369I, N348I, or T369I/N348I also reduced replication capacity (RC). These observations suggest that it may be of scientific interest to test these mutations against new NNRTI candidates.

The N348I Mutation at the Connection Subdomain of HIV-1 Reverse Transcriptase Decreases Binding to Nevirapine

“…However, our in-depth transient kinetics analysis clearly demonstrated a significantly (Ͼ3-fold) decreased catalytic efficiency for p66 N348I /p51 N348I . This reduction in catalytic efficiency is consistent with previous reports by us and others that HIV-1 N348I virus has a reduced replicative capacity (32,33). Hence, N348I imparts a fitness cost to the virus, placing it in the special category of "desirable" mutations that would weaken the virus once acquired.…”

“…These in vitro changes are smaller than those observed in cell-based assays for viruses harboring the same mutation (typically 7-8-fold and up to 27-fold) (31)(32)(33)(34). Such quantitative differences between enzymatic and cell-based estimates of drug resistance are not uncommon.…”

“…In cell culture experiments, HIV harboring N348I RT (HIV-1 N348I ) is resistant to NRTIs, including AZT and didanosine, and when in combination with excision-enhancing mutations enhances resistance to tenofovir (31,32,37). HIV-1 N348I is also resistant to NNRTIs, such as nevirapine (NVP), and to a lesser extent to delavirdine (31)(32)(33). When in combination with the NNRTI resistance mutation Y181C, N348I enhances resistance to the second generation NNRTI etravirine (37).…”

“…Lately, an increasing number of mutations at the connection subdomain and RNase H domain have been shown to enhance resistance to azidothymidine (AZT) (29,30). We and others have recently shown that N348I is the first clinically significant single amino acid mutation found to confer resistance to multiple members of both NRTI and NNRTI classes of inhibitors (31)(32)(33). N348I often emerges as a result of AZT-and/or didanosine-containing therapy and is found in combination with AZT excision-enhancing mutations (32,34).…”

Identification of Novel Resistance-Related Polymorphisms in HIV-1 Subtype C RT Connection and RNase H Domains from Patients Under Virological Failure in Brazil

“…However, recent studies have shown the importance of the Cterminal RT domains (CN and RNH) to drug resistance to NRTI and NNRTI. [23][24][25]30,34,[39][40][41] In this study, mutations in these portions were found in HIV-1B and C infecting patients under virological failure. Despite previous reports that have sporadically documented RT C-terminal mutations in non-B subtypes, 30,35,36 this is the first study specifically assessing differences of mutation occurrence in non-B subtype-specific contexts under the same therapeutic setting.…”