Genotypic resistance profile of HIV-1 protease gene: a preliminary report from Vellore, south India

Drug resistance mutations in protease gene of HIV-1 subtype C infected patient population

Failure of antiretroviral therapy (ART) in HIV-1 infection is a critical issue for the physicians treating HIV patients. The major cause of drug failure is the development of resistance mutations in reverse transcriptase (RT) and/or protease (PR) genes. Mutations associated with drug resistance decrease drug effectiveness. This study was conducted to assess drug resistance profile of the entire PR gene in 90 HIV-1 patients consisting of 23 ART non-responsive, 32 ART responsive and 35 drug naive patients. It was observed that the majority of the sequences (94.4%) belonged to subtype C and (5.5%) to subtype A1. The ART non-responsive and responsive patients were treated with either first line of ART regimen (two NRTI and one NNRTI) or second line of ART regimen that included additional one protease inhibitor (PI). All the patients in each group except one responsive patient had various minor resistance mutations. Thus, drug failures in ART non-responsive patients may not always be due to drug resistance mutations instead other factors may also be responsible for drug failures such as non-compliance, suboptimal dose or drug interaction. The presence of minor drug resistance mutations in drug naive patients is suggestive of transmitted resistance mutations.

Mutations in the reverse transcriptase and protease genes of human immunodeficiency virus-1 from antiretroviral naïve and treated pediatric patients

The success of highly active antiretroviral therapy (HAART) is challenged by the emergence of resistance-associated mutations in human immunodeficiency virus-1 (HIV-1). In this study, resistance associated mutations in the reverse transcriptase (RT) and protease (PR) genes in antiretroviral therapy (ART) naïve and treated HIV-1 infected pediatric patients from North India were evaluated. Genotyping was successfully performed in 46 patients (30 ART naive and 16 treated) for the RT gene and in 53 patients (27 ART naive and 26 treated) for PR gene and mutations were identified using Stanford HIV Drug Resistance Database. A major drug resistant mutation in RT gene, L74I (NRTI), and two such mutations, K101E and G190A (NNRTI), were observed in two ART naïve patients, while M184V was detected in two ART treated patients. Overall, major resistance associated mutations in RT gene were observed in nine (30%) and seven (36%) of ART naïve and treated children respectively. Minor mutations were identified in PR gene in five children. Few non-clade C viral strains (≈30%) were detected, although subtype C was most predominant. The screening of ART naïve children for mutations in HIV-1 RT and protease genes, before and after initiation of ART is desirable for drug efficacy and good prognosis.

No clinically significant drug-resistance mutations in HIV-1 subtype C-infected women after discontinuation of NRTI-based or PI-based HAART for PMTCT in Botswana

Risk of developing drug resistance after stopping antiretroviral regimens to prevent mother-to-child HIV-1 transmission is unknown. The Mma Bana Study randomized treatment-naive pregnant women with CD4 ≥200 cells per cubic millimeter to receive either abacavir/zidovudine/lamivudine [triple nucleoside reverse transcriptase inhibitor (NRTI) arm] or lopinavir/ritonavir/zidovudine/lamivudine [protease inhibitor (PI) arm]. Drugs were discontinued after 6 months of breastfeeding. One month after discontinuation, 29 NRTI arm samples and 25 PI arm samples were successfully genotyped. No clinically significant antiretroviral resistance mutations were detected. Eight minor resistance mutations were found among 11 (20%) women (3 from NRTI arm and 8 from PI arm), occurring at similar frequencies to those reported in HIV-1 subtype C treatment-naive cohorts.

The frequency of HIV-I drug resistance mutations among treatment-naive individuals at a tertiary care centre in south India

Antiretroviral treatment (ART) use in India requires information on baseline drug resistance mutations and polymorphisms in the protease (Pr) and reverse transcriptase (RT) genes of HIV-1 strains from treatment-naïve individuals. We report resistance predictor mutations and polymorphisms in the Pr and the RT sequence of non-clade B HIV-1 strains from ART naïve individuals. The genotypic resistance assay was done on 93 treatment-naïve individuals. The sequences were analysed by Stanford HIV drug resistance data for genotypic drug resistance analysis and REGA HIV-1 subtyping tool. Phylogenetic tree was generated with MEGA 4 for quality control. Ninety-two strains belonged to clade C and one to clade A (A1). Amino acid substitutions were seen at positions associated with drug resistance in Pr gene--10, 24, 74 (each 3%) and position 82 (11%). Substitutions were seen at positions 41 (1%), 100 (1%), 101 (6%), 103 (2%), 179 (6%) and 181 (1%) of the RT sequence known to confer drug resistance in clade B. Polymorphisms in HIV-1 pol gene among treatment-naïve individuals were similar when compared with previous data. One strain each had Y181C substitution, T74S and E35G substitutions in the Pr and one had A98G, K101R and L210FL substitutions in RT.

Transmitted drug resistance in nonsubtype B HIV-1 infection

HIV-1 nonsubtype B variants account for the majority of HIV infections worldwide. Drug resistance in individuals who have never undergone antiretroviral therapy can lead to early failure and limited treatment options and, therefore, is an important concern. Evaluation of reported transmitted drug resistance (TDR) is challenging owing to varying definitions and study designs, and is further complicated by HIV-1 subtype diversity. In this article, we discuss the importance of various mutation lists for TDR definition, summarize TDR in nonsubtype B HIV-1 and highlight TDR reporting and interpreting challenges in the context of HIV-1 diversity. When examined carefully, TDR in HIV-1 non-B protease and reverse transcriptase is still relatively low in most regions. Whether it will increase with time and therapy access, as observed in subtype-B-predominant regions, remains to be determined.

Differences in resistance mutations among HIV-1 non-subtype B infections: a systematic review of evidence (1996-2008)

Ninety percent of HIV-1-infected people worldwide harbour non-subtype B variants of HIV-1. Yet knowledge of resistance mutations in non-B HIV-1 and their clinical relevance is limited. Although a few reviews, editorials and perspectives have been published alluding to this lack of data among non-B subtypes, no systematic review has been performed to date.With this in mind, we conducted a systematic review (1996-2008) of all published studies performed on the basis of non-subtype B HIV-1 infections treated with antiretroviral drugs that reported genotype resistance tests. Using an established search string, 50 studies were deemed relevant for this review.These studies reported genotyping data from non-B HIV-1 infections that had been treated with either reverse transcriptase inhibitors or protease inhibitors. While most major resistance mutations in subtype B were also found in non-B subtypes, a few novel mutations in non-B subtypes were recognized. The main differences are reflected in the discoveries that: (i) the non-nucleoside reverse transcriptase inhibitor resistance mutation, V106M, has been seen in subtype C and CRF01_AE, but not in subtype B, (ii) the protease inhibitor mutations L89I/V have been reported in C, F and G subtypes, but not in B, (iii) a nelfinavir selected non-D30N containing pathway predominated in CRF01_AE and CRF02_AG, while the emergence of D30N is favoured in subtypes B and D, (iv) studies on thymidine analog-treated subtype C infections from South Africa, Botswana and Malawi have reported a higher frequency of the K65R resistance mutation than that typically seen with subtype B.Additionally, some substitutions that seem to impact non-B viruses differentially are: reverse transcriptase mutations G196E, A98G/S, and V75M; and protease mutations M89I/V and I93L.Polymorphisms that were common in non-B subtypes and that may contribute to resistance tended to persist or become more frequent after drug exposure. Some, but not all, are recognized as minor resistance mutations in B subtypes. These observed differences in resistance pathways may impact cross-resistance and the selection of second-line regimens with protease inhibitors. Attention to newer drug combinations, as well as baseline genotyping of non-B isolates, in well-designed longitudinal studies with long duration of follow up are needed.