PubMed Health⌕ Search

Biomedical subjects

Bluma Brenner

Publications and source records attributed to Bluma Brenner.

17 recordsLinked to original sources
PubMed2006

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.

We analyzed the reverse transcriptase genotypes of human immunodeficiency virus type 1 subtype C viruses isolated from 23 patients in Botswana treated with didanosine-based regimens. The K65R mutation was selected either alone or together with the Q151M, S68G, or F116Y substitution in viruses from seven such individuals. The results of in vitro passage experiments were consistent with an apparent increased propensity of subtype C viruses to develop the K65R substitution.

Anti-HIV Agents↗
PubMed2006

Impact of human immunodeficiency virus type 1 subtype C on drug resistance mutations in patients from Botswana failing a nelfinavir-containing regimen.

Among 16 human immunodeficiency virus-infected (subtype C) Batswana patients who failed nelfinavir (NFV)-containing regimens, the most prevalent mutation observed was D30N (54%), followed by L90M (31%). L89I, K20T/I, and E35D polymorphic changes were also identified. These findings suggest that subtype C viruses in Botswana may develop resistance to NFV via subtype-specific pathways.

Amino Acid Substitution↗
PubMed2005

Substitutions in the reverse transcriptase and protease genes of HIV-1 subtype B in untreated individuals and patients treated with antiretroviral drugs.

The nucleotide transition G-->A is known as a hypermutation due to its high prevalence in HIV-1 and other pathogens. However, the contribution of the G-->A transition in the generation of drug resistance mutations is unknown . Our objective was to ascertain the rate of nucleotide substitutions in protease (PR) and reverse transcriptase (RT) in both untreated and treated HIV-1 patients. Genotypic analysis was performed on viruses from both treated and untreated patients with subtype B infections. Nucleotide genomic diversity was compared with a consensus subtype B reference virus. Then, the prevalence of resistance-associated mutations in different subgroups of treated patients was evaluated in relation to the patterns of nucleotide transitions. In untreated patients (n = 50) G-->A was most prevalent, followed by A-->G, C-->T, and T-->C transitions. In treated patients (n = 51), the prevalence of A-->G was similar to that of G-->A. Among mutations that confer resistance to antiretroviral drugs, M184V was present in 76% of treated patients and K70R in 31% (A-->G transitions). Other frequent mutations in RT included T215Y (C-->A and A-->T substitutions), which was prevalent in 31% of treated patients. In PR, a L90M (T-->A substitution) was prevalent in 47% of protease inhibitor (PI)-treated patients. In conclusion, the G-->A transition was most prevalent in RT and PR among untreated patients. In contrast, A-->G was the most prevalent transition in patients treated with antiretroviral drugs.

Adenine↗
PubMed2004

Diminished representation of HIV-1 variants containing select drug resistance-conferring mutations in primary HIV-1 infection.

This study compared the incidence of HIV-1 variants harboring mutations conferring resistance to thymidine analogues, ie, thymidine analogue mutations (TAMs), nonnucleoside reverse transcriptase (RT) inhibitors (NNMs), lamivudine (3TC) (ie, M184V), and protease inhibitors (PIs) acquired in primary HIV infection (PHI) (n = 59) to their observed prevalence in a corresponding potential transmitter (PT) population of persons harboring resistant infections (n = 380). Both of these populations in the context of this cohort analysis possessed similar demographics. Whereas the frequencies of observed TAMs, NNMs, M184V, and protease-associated mutations (PRAMs) were similar in the PT groups, the prevalence of M184V and major PI mutations were significantly lower in the PHI group (PHI/PT ratios of 0.14 and 0.39, respectively). There was a decreased prevalence in the PHI population of resistant viruses co-expressing NNMs or TAMs with M184V compared with viruses that harbored NNMs or TAMs in the absence of M184V (P < 0.0001). It was also observed that individuals in the PT subgroups who harbored RT mutations or PRAMs with M184V had lower levels of plasma viremia than individuals who lacked M184V (P < 0.05). These findings suggest that both decreased viremia and viral fitness in the case of M184V-containing HIV-1 variants may impact on viral transmissibility.

Acute Disease↗
PubMed2004

Persistence of multidrug-resistant HIV-1 in primary infection leading to superinfection.

OBJECTIVE: The authors previous studies documented persistence of multidrug resistance (MDR) acquired in five primary HIV-1 infection (PHI) cases for 1-2 years in the absence of antiretroviral treatment. This study characterizes the evolution of transmitted wild-type (WT) (n = 15), resistant (n = 10), and MDR (n = 6) infections. Long-term persistence of MDR infections (2-7 years), leading to one observed MDR superinfection is documented. METHODS: Genotypic changes in circulating viral quasi-species were evaluated over 1.5-7 years in patients (n = 31) enrolled in the PHI study. Sequencing of reverse transcriptase and protease regions identified nucleotide substitutions in the viral quasi-species and mutations at sites implicated in resistance to antiretroviral drugs. Phylogenetic and clonal analysis were performed to confirm one observed superinfection. RESULTS: Patients acquiring WT, drug-resistant and MDR infections showed little quasi-species evolution (> 99.6% homology) for more than 1.5 years, regardless of route of transmission. Transmitted resistance mutations (other than 184V) persisted for 2-7 years. MDR persistence in two PHI cases contrasted with the corresponding rapid reversion of MDR infections to WT in their partners following treatment interruption. One MDR transmission eliciting low-level viremia resulted in clearance of the original MDR infection followed by re-infection with a second heterologous MDR strain from a different partner. Phylogenetic and clonal analysis of source and index partner confirmed the superinfection. Both MDR species showed approximately 13-fold reductions in replication capacity relative to the homologous WT strain isolated from the source partner. CONCLUSIONS: Genotypic analysis in PHI may identify superinfection and MDR infections that represent important determinants of virological and treatment outcome.

AIDS-Related Opportunistic Infections↗
PubMed2004

[HIV drug resistance and optimization of antiviral treatment in resource-poor countries].

HIV drug resistance has been associated with treatment failure in Western countries but the lessons learned can be useful in optimization of highly active antiretroviral treatment (HAART) in resource-poor settings. There is a need to improve access to HAART in such regions, but appropriate strategies must be rapidly implemented, such as adapted programs to facilitate adherence to therapy, rational use of genotypic drug resistance monitoring in specific situations, and use of alternative treatment regimens. The implications of HIV genetic diversity must also be considered in management of drug resistance.

Acquired Immunodeficiency Syndrome↗
PubMed2004

Nucleotide and amino acid polymorphisms at drug resistance sites in non-B-subtype variants of human immunodeficiency virus type 1.

We have compared nucleotide substitutions and polymorphisms at codons known to confer drug resistance in subtype B strains of human immunodeficiency virus type 1 (HIV-1) with similar substitutions in viruses of other subtypes. Genotypic analysis was performed on viruses from untreated individuals. Nucleotide and amino acid diversity at resistance sites was compared with a consensus subtype B reference virus. Among patients with non-subtype B infections, polymorphisms relative to subtype B were observed at codon 10 in protease (PR). These included silent substitutions (CTC-->CTT, CTA, TTA) and an amino acid mutation, L10I. Subtype A viruses possessed a V179I substitution in reverse transcriptase (RT). Subtype G viruses were identified by silent substitutions at codon 181 in RT (TAT-->TAC). Similarly, subtype A/G viruses were identified by a substitution at position 67 in RT (GAC-->GAT). Subtype C was distinguished by silent substitutions at codons 106 (GTA-->GTG) and 219 (AAA-->AAG) in RT and codon 48 (GGG-->GGA) in PR. Variations relative to subtype B were seen at RT position 215 (ACC-->ACT) for subtypes A and A/E. These substitutions and polymorphisms reflect different patterns of codon usage among viruses of different subtypes. However, the existence of different subtypes may only rarely affect patterns of drug resistance-associated mutations.

Amino Acid Substitution↗
PubMed2004

Variability in the PR and RT genes of HIV-1 isolated from recently infected subjects.

To study variability in reverse transcriptase (RT) and protease (PR) genes of HIV-1 isolated from recently infected patients identified between 1997 and 2003, sequences were obtained on the RT and PR genes of viruses harvested from plasma of 121 non-treated subjects who had undergone primary HIV infection. The degree of dissimilarity between the viruses studied and a reference HIV-1 subtype B strain (LAV-1) was calculated for each of RT and PR by counting all of the nucleotide substitutions that could be identified. Mutations associated with drug resistance were excluded from analysis. We observed a mean percentage of variation in the RT and PR genes of the viruses analysed of 0.42% between the years 1997--2003 (P<0.01). In PR, the mean variation was 0.71% (P<0.05), while that in RT was 0.3% (P<0.05). Increased diversity was also observed among nucleotides conferring amino-acid changes, although no significant differences in patterns of nucleotide substitutions were apparent over the period of analysis. In conclusion, variability in the RT and PR genes of viruses from recently infected patients has increased over time in a manner that is independent of variability attributable to HIV drug resistance.

Anti-HIV Agents↗
PubMed2003

Relationships among various nucleoside resistance-conferring mutations in the reverse transcriptase of HIV-1.

Highly active antiretroviral therapy has significantly improved HIV-related morbidity and mortality, and nucleoside reverse transcriptase inhibitors remain an essential component of treatment. However, the emergence of HIV-1 mutated strains that are resistant to one or more antiretroviral drugs is a leading cause of treatment failure among patients living with HIV/AIDS. These resistant strains may often suffer from a replication disadvantage in comparison with wild-type viruses when grown in the absence of drug pressure and a potential benefit in this regard has been shown for lamivudine-resistant viruses that contain a M184V mutation in reverse transcriptase, as well as for several other drug-resistant viral variants. Interactions between different mutations may complicate the understanding of HIV drug resistance with regard to the likelihood of therapeutic success.

Drug Resistance, Viral↗
PubMed2003

Didanosine, interferon-alfa and ribavirin: a highly synergistic combination with potential activity against HIV-1 and hepatitis C virus.

OBJECTIVE: To evaluate the antiviral triple combination didanosine (ddI), interferon-alfa (IFN-alpha), and ribavirin for potential synergy in inhibition of HIV-1 replication in vitro. METHODS: Phytohaemagglutinin-stimulated cord blood mononuclear cells were infected with HIV-1(IIIB) or the HXB2D molecular clone of HIV-1 then cultured with interleukin-2 with ddI, ribavirin or IFN-alpha, alone and in combination. Reverse transcriptase activity was measured after 7 days to determine the inhibitory concentration of 50% (IC(50)) for the various drugs in replicate assays. Analysis of combined effects was performed using both the median effect principle (CalcuSyn, Biosoft) and three-dimensional modelling (MacSynergy II). RESULTS: The triple combination was highly synergistic against HIV-1 in vitro with combination indices < 1. The mean IC(50) was reduced from 6.85 to 0.90 micromol/l (P < 0.001) for ddI and from 6.58 to 1.00 micromol/l (P < 0.001) for IFN-alpha. No increased cytotoxicity was observed. Results were similar with both viral strains and using both analyses. In the triple combination, increasing concentrations of IFN-alpha resulted only a slight enhancement of synergy: synergy volumes were 134 [95% confidence limit (CL), 77-191] with 5 U IFN-alpha and 214.92 (95% CL, 116-314) with 10 U. This supporting the observation that the majority of the synergistic activity was derived from the combination of ddI and ribavirin, with IFN-alpha providing additional additive suppression. CONCLUSIONS: This novel triple combination has the potential to provide simultaneous activity against both HIV and hepatitis C and deserves further study to determine if can be safely administered in the clinical setting.

Anti-HIV Agents↗
PubMed2003

A V106M mutation in HIV-1 clade C viruses exposed to efavirenz confers cross-resistance to non-nucleoside reverse transcriptase inhibitors.

OBJECTIVE: We have shown that HIV-1 clade C variants contain a valine codon 106 polymorphism (GTG) that facilitates a V106M transition (GTG<--ATG) after selection with efavirenz (EFV). This study evaluates the prevalence of V106 (GTG) and 106M (ATG) codons in clinical isolates as well as the effects of V106M on resistance to non-nucleoside reverse transcriptase inhibitors (NNRTI). METHODS: Genotypic analysis ascertained sequence diversity at codon 106, including both valine polymorphisms (GTA and GTG) and the V106A (GCA) and V106M (ATG) resistance-conferring mutations in B (n = 440) and non-B (n = 84) clinical isolates. Cell-based phenotypic assays were performed to determine the effects of V106M and V106A on levels of resistance to EFV, nevirapine and delavirdine. RESULTS: Most subtype B isolates harbored GTA (valine) at codon 106 (97% of cases) while the GTG (valine) polymorphism was generally present in clade C viruses (94% of cases). Under conditions of EFV but not nevirapine or delavirdine pressure (n = 8) in tissue culture, clade C isolates developed the V106M mutation (GTG<--ATG), conferring high-level (100-1000-fold) cross-resistance to all NNRTI. Generation of V106M recombinant viruses by site-directed mutagenesis confirmed the ability of V106M to confer NNRTI cross-resistance. This mutation also developed in three of six EFV-treated patients harboring clade C infections. In current genotypic interpretative reports (including 15 algorithmic databases), V106A is listed as an nevirapine-specific mutation while V106M is not recognized. CONCLUSIONS: V106M may be a signature mutation in clade C patients treated with EFV and may have the potential to confer high-level multi-NNRTI resistance.

Alkynes↗
PubMed2003

The M184V substitution in human immunodeficiency virus type 1 reverse transcriptase delays the development of resistance to amprenavir and efavirenz in subtype B and C clinical isolates.

The M184V substitution in human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT), encoding high-level resistance to lamivudine (3TC), results in decreased HIV-1 replicative capacity, diminished RT processivity, and increased RT fidelity in biochemical assays. We assessed the effect of M184V on the development of resistance to the nonnucleoside RT inhibitors efavirenz (EFV) and nevirapine, and to the protease inhibitor amprenavir (APV) in tissue culture. Genotypic analysis revealed differences in EFV resistance-conferring mutations in subtype B (K103N) versus subtype C (V106 M), and the appearance of both was significantly delayed in the M184V-containing variants compared with the wild type (WT). Similarly, there was a marked delay in the emergence of mutations associated with APV resistance (I54 M/L/V) in subtype B viruses harboring M184V compared with paired WT viral isolates.

Alkynes↗
PubMed2002

Polymorphisms of cytotoxic T-lymphocyte (CTL) and T-helper epitopes within reverse transcriptase (RT) of HIV-1 subtype C from Ethiopia and Botswana following selection of antiretroviral drug resistance.

Drug resistance is the major limiting factor in the effective therapeutic management of HIV infection with antiretroviral drugs (ARVs). In developing countries, where access to ARVs may be limited, therapeutic vaccine protocols designed to restrict the advent of drug resistance may be of interest. Whereas the immunodominant regions of HIV-1 clade B RT peptides have been well characterized, little is known about potential divergence among RTs of other HIV-1 subtypes. In this study, RT sequence polymorphisms were ascertained in phylogenetically classified subtype C isolates from treatment-nai;ve Ethiopian (n = 5) and Botswanian persons (n = 9). There were clusters of variability in some RT epitopes associated with cytotoxic T lymphocyte (CTL) and helper T cell function within subtype C viruses, although other epitopes remained conserved among subtype C and B viruses. Subtype C mutations associated with drug resistance were identified in vitro, using increasing concentrations of non-nucleoside RT inhibitors (NNRTIs) and nucleoside RT inhibitors (NRTIs). Mutations within immunogenic regions of clade C RT were noted during drug selection of subtype C isolates with nevirapine (S98I, Y181C, V108I and K103N), delavirdine, (A62V, V75E, L100I, K103T, V108I, Y181C), efavirenz (K103E, V106M, V179D, Y188C/H, G190A), lamivudine (M184I, M184V), and zidovudine (K70R), respectively. Further characterization of predicted CTL and T-helper anchor motifs and ARV-induced mutations in HIV-1 non-B subtype RTs is warranted.

Amino Acid Sequence↗
PubMed2002

Genetic divergence of human immunodeficiency virus type 1 Ethiopian clade C reverse transcriptase (RT) and rapid development of resistance against nonnucleoside inhibitors of RT.

We sequenced and phylogenetically analyzed the reverse transcriptase (RT) region of five human immunodeficiency virus type 1 isolates from treatment-naive Ethiopian émigrés to Israel. Heteroduplex mobility assays were performed to confirm the clade C status of env genomic regions. The RT sequences showed that the strains clustered phylogenetically with clade C viruses, and a KVEQ-specific motif of silent mutations (amino acids 65, 106, 138, and 161, respectively) at resistance sites was present in the polymerase region of all studied Ethiopian isolates and subtype C reference strains. In addition, many other silent mutations were observed in the clade C viruses at various resistance sites. In general, the Ethiopian isolates were more closely related genotypically to a clade C reference strain from Botswana (southern Africa) than to previously sequenced Ethiopian reference strains. Genotypic analysis showed that two Ethiopian isolates naturally harbored the mutations K70R and G190A associated with resistance to ZDV and nonnucleoside reverse transcriptase inhibitors, respectively. Phenotypic assays revealed that the K70R substitution in this context did not reduce susceptibility to ZDV, whereas the G190A substitution resulted in high-level resistance to nevirapine (NVP). Moreover, variants resistant to NVP, delavirdine (DLV), and efavirenz (EFV) were more rapidly selected at lower drug doses culture with clade C than with clade B wild-type isolates. In the case of subtype C, selection with NVP and/or EFV led to the appearance of several previously unseen mutations in RT, i.e., V106M and S98I, as well as other mutations that have been previously reported (e.g., K103N, V106A, V108I, and Y181C). After selection with DLV, a polymorphism, A62A, initially observed in the Ethiopian isolate 4762, mutated to A62V; the latter is a secondary substitution associated with multidrug resistance against nucleoside RT inhibitors. Phenotypic analysis of clade C mutants selected against NVP, DLV, and EFV revealed broad cross-resistance, particularly in regard to NVP and DLV. These findings suggest that RT genotypic diversity may influence the emergence of drug resistance.

Alkynes↗
PubMed2002

Pressure of zidovudine accelerates the reversion of lamivudine resistance-conferring M184V mutation in the reverse transcriptase of human immunodeficiency virus type 1.

We cultured lamivudine-resistant human immunodeficiency virus type 1 (HIV-1) variants over an extended period of time in the presence of zidovudine and observed a premature reversion of the resistance-conferring M184V mutation. These data suggest that the presence of ZDV amplifies differences in replication capacity between wild-type HIV-1 and the mutant variant.

Anti-HIV Agents↗
PubMed2002

Co-receptor usage and HIV-1 intra-clade C polymorphisms in the protease and reverse transcriptase genes of HIV-1 isolates from Ethiopia and Botswana.

Knowledge of baseline amino acid substitutions arising at certain critical positions in the HIV-1 non-clade-B protease (PR) and reverse transcriptase (RT) enzymes may yield important information with regard to anticipation of responses to antiretroviral treatment and development of drug resistance. We have compared RT and PR sequences within HIV-1 clade C strains isolated from 14 treatment-naive patients originating from Ethiopia and Botswana with those of PR and RT consensus subtype B RT and PR sequences. Variations in the frequency of natural polymorphisms were observed in clade C isolates at drug-resistance sites. Intra-clade C divergence among mutations within PR was statistically significant while that within RT was not. Only a M361 substitution in PR was shared among almost all isolates from Ethiopia and Botswana. Analysis of the co-receptor usage of clade C isolates from Ethiopia and Botswana supports the known preferential usage of the CCR5 co-receptor by HIV-1 clade C strains. No Ethiopian or Botswanian isolates exclusively used the CXCR4 co-receptor, which is consistent with most data obtained with HIV-1 clade B isolates.

Amino Acid Substitution↗