ABSTRACT
BACKGROUND: Antiretroviral therapy that targets HIV type-1 (HIV-1) reverse transcriptase (RT) can be linked to mutations in the thumb-connection (amino acids [AA] 241-426) and RNase H (AA 427-560) domains, which could affect drug resistance. METHODS: Genotypical and statistical analyses were performed on HIV-1 RT from 100 antiretroviral treatment-naive and 248 antiretroviral treatment-experienced patients, the majority of whom were infected with HIV-1 subtype B. The RT region was analysed in three parts: the polymerase (AA 1-240), thumb-connection (AA 241-426) and RNase H (AA 427-560) domains. RESULTS: The polymerase domain had statistically significant changes between the two groups at 24 AA positions that are known resistance sites. Within the thumb-connection domain, R284 and N348 had statistically significant changes between the groups (P=0.007 and P< or =0.001, respectively). In treatment-experienced patients, 17.3% had R284K, whereas 24.5% had N348I substitutions. Both R284 and N348 were 100% conserved in treatment-naive patients. Within the RNase H domain, only K451 showed a statistically significant change (P=0.001), with K451R present in 11% of treatment-experienced patients but remaining 100% conserved among treatment-naive patients. CONCLUSIONS: RT mutations at three positions outside of the polymerase region were associated with antiretroviral therapy: R284K, N348I and K451R. Both R284K and K451R interact with the phosphate backbone of the template or primer in HIV-1 RT crystal structures and could potentially influence the positioning of the primer strand, thus affecting polymerization, the efficiency of nucleoside reverse transcriptase inhibitor excision and/or RNase H activity.
Subject(s)
HIV Reverse Transcriptase/genetics , HIV-1 , Mutation/drug effects , Reverse Transcriptase Inhibitors/therapeutic use , Adenine/analogs & derivatives , Adenine/therapeutic use , Alkynes , Amino Acid Substitution/drug effects , Benzoxazines/therapeutic use , Cyclopropanes , Drug Resistance, Multiple, Viral , Genetic Variation/drug effects , HIV Infections/drug therapy , HIV Infections/virology , HIV Reverse Transcriptase/chemistry , HIV-1/drug effects , HIV-1/genetics , Humans , Lamivudine/therapeutic use , Organophosphonates/therapeutic use , Protein Structure, Tertiary/genetics , Ribonuclease H, Human Immunodeficiency Virus/genetics , Stavudine/therapeutic use , TenofovirABSTRACT
BACKGROUND: Prior abacavir (ABC) or didanosine (ddI) therapy can result in the L74V/I or K65R mutation in HIV-1 reverse transcriptase. Preexisting K65R may have an impact on the treatment response to tenofovir disoproxil fumarate (TDF). METHODS: An allele-specific polymerase chain reaction (AS-PCR) assay was developed to detect K65R with a lower limit of quantitation of 0.5%. RESULTS: Among baseline plasma samples from 63 treatment-naive patients, no K65R was detected by AS-PCR. Among baseline samples from 154 treatment-experienced patients, 8 had K65R and 44 had L74V/I by population sequencing. Low-level K65R was detected in an additional 11 patients by AS-PCR, 3 of whom subsequently developed full K65R. Baseline K65R correlated with absence of thymidine analog mutations (TAMs; P = 0.003) and use of ABC or ddI (P = 0.004). Patients with full or low-level K65R at baseline or with L74V/I showed a diminished TDF response. Multivariate analyses confirmed that multiple TAMs, K65R, and L74V/I were independent predictors of diminished TDF response. CONCLUSIONS: Prior therapy with ABC or ddI can result in a population genotype that shows K65R or L74V/I but does not reveal low-level K65R present in some patients. Subsequent treatment intensification with TDF resulted in a poor virologic response and may result in expansion of the preexisting K65R mutant.
Subject(s)
Didanosine/therapeutic use , Dideoxynucleosides/therapeutic use , HIV Infections/drug therapy , HIV Reverse Transcriptase/genetics , HIV-1/genetics , Adenine/analogs & derivatives , Adenine/therapeutic use , Alleles , Didanosine/administration & dosage , Dideoxynucleosides/administration & dosage , Double-Blind Method , Drug Resistance, Viral , HIV Infections/virology , Humans , Mutation , Organophosphonates/therapeutic use , Polymerase Chain Reaction/methods , Reverse Transcriptase Inhibitors , Tenofovir , Treatment OutcomeABSTRACT
The presence of drug-associated mutations among ART-naive, HIV-1(+) patients may compromise the response to antiviral therapy. We evaluated the effect of preexisting drug-associated resistance mutations to the response in treatment-naive patients to therapy with emtricitabine (FTC) or stavudine (d4T) in combination with didanosine (ddI) and efavirenz (EFV). Study FTC-301A compared emtricitabine once daily (QD) with stavudine twice daily in combination with didanosine and efavirenz in ART-naive patients. Genotypic analysis was performed on baseline plasma HIV-1 RNA for all available samples and at time of virologic failure (VF). Drug resistance mutations present at baseline were evaluated as predictors of VF using logistic regression. VF rates were compared between subgroups using a two-sided exact test. Baseline drug resistance mutations were observed in 90/546 (16.5%) patients: 56/90 (62.2%) with nonnucleoside analogue (NNRTI) mutations and 42/90 (46.6%) with nucleoside analogue mutations. In a stepwise, multiple regression analysis, the presence of the K103N mutation at initiation of therapy was associated with VF in both arms (p = 0.001), however, there was a higher incidence of VF in the stavudine arm compared to the emtricitabine arm regardless of the presence or absence of mutations at baseline (p = 0.001). In this study, the presence of drug-associated resistance mutations in ART-naive patients was significantly correlated with subsequent development of virologic failure underscoring the utility of testing for resistance in addition to the use of potent and well-tolerated first line regimens in treatment-naive patients.