Publications (10)85.76 Total impact
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Article: HIV Control through a Single Nucleotide on the HLA-B Locus.
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ABSTRACT: Genetic variation within the HLA-B locus has the strongest impact on HIV disease progression of any polymorphisms within the human genome. However, identifying the exact mechanism involved is complicated by several factors. HLA-Bw4 alleles provide ligands for NK cells and for CD8 T cells, and strong linkage disequilibrium between HLA class I alleles complicates the discrimination of individual HLA allelic effects from those of other HLA and non-HLA alleles on the same haplotype. Here, we exploit an experiment of nature involving two recently diverged HLA alleles, HLA-B*42:01 and HLA-B*42:02, which differ by only a single amino acid. Crucially, they occur primarily on identical HLA class I haplotypes and, as Bw6 alleles, do not act as NK cell ligands and are therefore largely unconfounded by other genetic factors. We show that in an outbred cohort (n = 2,093) of HIV C-clade-infected individuals, a single amino acid change at position 9 of the HLA-B molecule critically affects peptide binding and significantly alters the cytotoxic T lymphocyte (CTL) epitopes targeted, measured directly ex vivo by gamma interferon (IFN-γ) enzyme-linked immunospot (ELISPOT) assay (P = 2 × 10(-10)) and functionally through CTL escape mutation (P = 2 × 10(-8)). HLA-B*42:01, which presents multiple Gag epitopes, is associated with a 0.52 log(10) lower viral-load set point than HLA-B*42:02 (P = 0.02), which presents no p24 Gag epitopes. The magnitude of this effect from a single amino acid difference in the HLA-A*30:01/B*42/Cw*17:01 haplotype is equivalent to 75% of that of HLA-B*57:03, the most protective HLA class I allele in this population. This naturally controlled experiment represents perhaps the clearest demonstration of the direct impact of a particular HIV-specific CTL on disease control.Journal of Virology 08/2012; 86(21):11493-500. · 5.40 Impact Factor -
Article: Task shifting of antiretroviral treatment from doctors to primary-care nurses in South Africa (STRETCH): a pragmatic, parallel, cluster-randomised trial.
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ABSTRACT: Robust evidence of the effectiveness of task shifting of antiretroviral therapy (ART) from doctors to other health workers is scarce. We aimed to assess the effects on mortality, viral suppression, and other health outcomes and quality indicators of the Streamlining Tasks and Roles to Expand Treatment and Care for HIV (STRETCH) programme, which provides educational outreach training of nurses to initiate and represcribe ART, and to decentralise care. We undertook a pragmatic, parallel, cluster-randomised trial in South Africa between Jan 28, 2008, and June 30, 2010. We randomly assigned 31 primary-care ART clinics to implement the STRETCH programme (intervention group) or to continue with standard care (control group). The ratio of randomisation depended on how many clinics were in each of nine strata. Two cohorts were enrolled: eligible patients in cohort 1 were adults (aged ≥16 years) with CD4 counts of 350 cells per μL or less who were not receiving ART; those in cohort 2 were adults who had already received ART for at least 6 months and were being treated at enrolment. The primary outcome in cohort 1 was time to death (superiority analysis). The primary outcome in cohort 2 was the proportion with undetectable viral loads (<400 copies per mL) 12 months after enrolment (equivalence analysis, prespecified difference <6%). Patients and clinicians could not be masked to group assignment. The interim analysis was blind, but data analysts were not masked after the database was locked for final analysis. Analyses were done by intention to treat. This trial is registered, number ISRCTN46836853. 5390 patients in cohort 1 and 3029 in cohort 2 were in the intervention group, and 3862 in cohort 1 and 3202 in cohort 2 were in the control group. Median follow-up was 16·3 months (IQR 12·2-18·0) in cohort 1 and 18·0 months (18·0-18·0) in cohort 2. In cohort 1, 997 (20%) of 4943 patients analysed in the intervention group and 747 (19%) of 3862 in the control group with known vital status at the end of the trial had died. Time to death did not differ (hazard ratio [HR] 0·94, 95% CI 0·76-1·15). In a preplanned subgroup analysis of patients with baseline CD4 counts of 201-350 cells per μL, mortality was slightly lower in the intervention group than in the control group (0·73, 0·54-1.00; p=0·052), but it did not differ between groups in patients with baseline CD4 of 200 cells per μL or less (0·94, 0·76-1·15; p=0·577). In cohort 2, viral load suppression 12 months after enrolment was equivalent in intervention (2156 [71%] of 3029 patients) and control groups (2230 [70%] of 3202; risk difference 1·1%, 95% CI -2·4 to 4·6). Expansion of primary-care nurses' roles to include ART initiation and represcription can be done safely, and improve health outcomes and quality of care, but might not reduce time to ART or mortality. UK Medical Research Council, Development Cooperation Ireland, and Canadian International Development Agency.The Lancet 08/2012; 380(9845):889-98. · 38.28 Impact Factor -
Chapter: HIV Drug Resistance in Sub-Saharan Africa � Implications for Testing and Treatment
01/2012; , ISBN: 978-953-307-871-7 -
Article: Co-Operative Additive Effects between HLA Alleles in Control of HIV-1.
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ABSTRACT: HLA class I genotype is a major determinant of the outcome of HIV infection, and the impact of certain alleles on HIV disease outcome is well studied. Recent studies have demonstrated that certain HLA class I alleles that are in linkage disequilibrium, such as HLA-A*74 and HLA-B*57, appear to function co-operatively to result in greater immune control of HIV than mediated by either single allele alone. We here investigate the extent to which HLA alleles - irrespective of linkage disequilibrium - function co-operatively. We here refined a computational approach to the analysis of >2000 subjects infected with C-clade HIV first to discern the individual effect of each allele on disease control, and second to identify pairs of alleles that mediate 'co-operative additive' effects, either to improve disease suppression or to contribute to immunological failure. We identified six pairs of HLA class I alleles that have a co-operative additive effect in mediating HIV disease control and four hazardous pairs of alleles that, occurring together, are predictive of worse disease outcomes (q<0.05 in each case). We developed a novel 'sharing score' to quantify the breadth of CD8+ T cell responses made by pairs of HLA alleles across the HIV proteome, and used this to demonstrate that successful viraemic suppression correlates with breadth of unique CD8+ T cell responses (p = 0.03). These results identify co-operative effects between HLA Class I alleles in the control of HIV-1 in an extended Southern African cohort, and underline complementarity and breadth of the CD8+ T cell targeting as one potential mechanism for this effect.PLoS ONE 01/2012; 7(10):e47799. · 4.09 Impact Factor -
Article: HLA-A*7401-mediated control of HIV viremia is independent of its linkage disequilibrium with HLA-B*5703.
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ABSTRACT: The potential contribution of HLA-A alleles to viremic control in chronic HIV type 1 (HIV-1) infection has been relatively understudied compared with HLA-B. In these studies, we show that HLA-A*7401 is associated with favorable viremic control in extended southern African cohorts of >2100 C-clade-infected subjects. We present evidence that HLA-A*7401 operates an effect that is independent of HLA-B*5703, with which it is in linkage disequilibrium in some populations, to mediate lowered viremia. We describe a novel statistical approach to detecting additive effects between class I alleles in control of HIV-1 disease, highlighting improved viremic control in subjects with HLA-A*7401 combined with HLA-B*57. In common with HLA-B alleles that are associated with effective control of viremia, HLA-A*7401 presents highly targeted epitopes in several proteins, including Gag, Pol, Rev, and Nef, of which the Gag epitopes appear immunodominant. We identify eight novel putative HLA-A*7401-restricted epitopes, of which three have been defined to the optimal epitope. In common with HLA-B alleles linked with slow progression, viremic control through an HLA-A*7401-restricted response appears to be associated with the selection of escape mutants within Gag epitopes that reduce viral replicative capacity. These studies highlight the potentially important contribution of an HLA-A allele to immune control of HIV infection, which may have been concealed by a stronger effect mediated by an HLA-B allele with which it is in linkage disequilibrium. In addition, these studies identify a factor contributing to different HIV disease outcomes in individuals expressing HLA-B*5703.The Journal of Immunology 05/2011; 186(10):5675-86. · 5.79 Impact Factor -
Article: Progression to AIDS in South Africa is associated with both reverting and compensatory viral mutations.
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ABSTRACT: We lack the understanding of why HIV-infected individuals in South Africa progress to AIDS. We hypothesised that in end-stage disease there is a shifting dynamic between T cell imposed immunity and viral immune escape, which, through both compensatory and reverting viral mutations, results in increased viral fitness, elevated plasma viral loads and disease progression. We explored how T cell responses, viral adaptation and viral fitness inter-relate in South African cohorts recruited from Bloemfontein, the Free State (n = 278) and Durban, KwaZulu-Natal (n = 775). Immune responses were measured by γ-interferon ELISPOT assays. HLA-associated viral polymorphisms were determined using phylogenetically corrected techniques, and viral replication capacity (VRC) was measured by comparing the growth rate of gag-protease recombinant viruses against recombinant NL4-3 viruses. We report that in advanced disease (CD4 counts <100 cells/µl), T cell responses narrow, with a relative decline in Gag-directed responses (p<0.0001). This is associated with preserved selection pressure at specific viral amino acids (e.g., the T242N polymorphism within the HLA-B*57/5801 restricted TW10 epitope), but with reversion at other sites (e.g., the T186S polymorphism within the HLA-B*8101 restricted TL9 epitope), most notably in Gag and suggestive of "immune relaxation". The median VRC from patients with CD4 counts <100 cells/µl was higher than from patients with CD4 counts ≥ 500 cells/µl (91.15% versus 85.19%, p = 0.0004), potentially explaining the rise in viral load associated with disease progression. Mutations at HIV Gag T186S and T242N reduced VRC, however, in advanced disease only the T242N mutants demonstrated increasing VRC, and were associated with compensatory mutations (p = 0.013). These data provide novel insights into the mechanisms of HIV disease progression in South Africa. Restoration of fitness correlates with loss of viral control in late disease, with evidence for both preserved and relaxed selection pressure across the HIV genome. Interventions that maintain viral fitness costs could potentially slow progression.PLoS ONE 01/2011; 6(4):e19018. · 4.09 Impact Factor -
Article: Prevalence of HIV type-1 drug-associated mutations in pre-therapy patients in the Free State, South Africa.
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ABSTRACT: We aimed to characterize the molecular epidemiology of HIV type-1 (HIV-1) and the prevalence of drug-associated mutations prior to initiating highly active antiretroviral therapy (HAART) in the Free State province, South Africa. The Free State has a population of 3 million, an antenatal HIV prevalence of approximately 34% and a well established infrastucture for antiretroviral (ARV) provision. HIV-1 polymerase genes were sequenced from 425 HAART-naive HIV-1-positive patients at voluntary primary healthcare HIV testing centres, who were subsequently attending district centres for assessment for commencing ARVs. Patients (>18 years) were sampled randomly with no exclusion for gender or clinical criteria. Sequences were analysed according to phylogeny and drug resistance. Phylogenetic clustering within the cohort was suggestive of multiple introductions of subtype C virus into the region. Drug resistance mutations (according to the International AIDS Society-USA classification) were distributed randomly across the cohort phylogeny with an overall prevalence of 2.3% in the sampled patients. When stratified according to CD4(+) T-cell count, the prevalence of resistance was 3.6%, 0.9% and 1.2% for CD4(+) T-cell counts <100, 200-350 and >500 cells/microl, respectively, and was most common for non-nucleoside reverse transcriptase inhibitor resistance (3.1% in patients with CD4(+) T-cell count <100 cells/microl). We surveyed all drug-selected mutations and found further significant clustering among patients with low CD4(+) T-cell counts (P=0.003), suggesting unrecognized exposure to ARVs. In the Free State population, there was a statistical association between low CD4(+) T-cell counts and drug-associated viral polymorphisms. Our data advocate the benefit of detailed history taking from patients starting HAART at low CD4(+) T-cell counts with close follow-up of the virological response.Antiviral therapy 01/2009; 14(7):975-84. · 3.16 Impact Factor -
Article: Effectiveness of antiretroviral treatment in a South African program: a cohort study.
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ABSTRACT: The effectiveness of the South African government's expanding antiretroviral treatment program is unknown. Observational studies of treatment effectiveness are prone to selection bias, rarely compare patients receiving antiretroviral treatment with similar patients not receiving antiretroviral treatment, and underestimate mortality rates unless patients are actively followed up. We followed up 14 267 patients in the Public Sector Anti-Retroviral Treatment project in Free State, South Africa, for up to 20 months after enrollment. A total of 3619 patients received highly active triple antiretroviral treatment (HAART) for up to 19 months (median, 6 months; interquartile range, 3-9 months) after enrollment. Patients' clinical data were linked with the national mortality register. Marginal structural regression models adjusted for baseline and time-varying covariates. Of 4570 patients followed up for at least 1 year, 53.2% died. Eighty-seven percent of patients who died had not received HAART. HAART was associated with lower mortality (hazard ratio, 0.14; 95% confidence interval [CI], 0.11-0.18) and with the presence of tuberculosis (hazard ratio, 0.61; 95% CI, 0.46-0.81) after adjusting for age, sex, weight, clinic, district, CD4 cell count, cotrimoxazole therapy, tuberculosis at baseline, and previous antiretroviral therapy. Cotrimoxazole therapy was associated with lower mortality (hazard ratio, 0.37; 95% CI, 0.32-0.42). Each month of HAART was associated with an increase in CD4 cell count of 15.1 cells/microL (95% CI, 14.7-15.5 cells/microL) and with an increase in body weight of 602 g (95% CI, 548-658 g). HAART provided through these South African government health services seems as effective as that provided in high-income countries. Delays starting HAART contributed to high mortality rates. Faster expansion and timely commencement of HAART are needed.Archives of Internal Medicine 02/2008; 168(1):86-93. · 11.46 Impact Factor -
Article: Streamlining tasks and roles to expand treatment and care for HIV: randomised controlled trial protocol.
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ABSTRACT: BACKGROUND: A major barrier to accessing free government-provided antiretroviral treatment (ART) in South Africa is the shortage of suitably skilled health professionals. Current South African guidelines recommend that only doctors should prescribe ART, even though most primary care is provided by nurses. We have developed an effective method of educational outreach to primary care nurses in South Africa. Evidence is needed as to whether primary care nurses, with suitable training and managerial support, can initiate and continue to prescribe and monitor ART in the majority of ART-eligible adults. METHODS/DESIGN: This is a protocol for a pragmatic cluster randomised trial to evaluate the effectiveness of a complex intervention based on and supporting nurse-led antiretroviral treatment (ART) for South African patients with HIV/AIDS, compared to current practice in which doctors are responsible for initiating ART and continuing prescribing. We will randomly allocate 31 primary care clinics in the Free State province to nurse-led or doctor-led ART. Two groups of patients aged 16 years and over will be included: a) 7400 registering with the programme with CD4 counts of </= 350 cells/mL (mainly to evaluate treatment initiation) and b) 4900 already receiving ART (to evaluate ongoing treatment and monitoring). The primary outcomes will be time to death (in the first group) and viral suppression (in the second group). Patients' survival, viral load and health status indicators will be measured at least 6-monthly for at least one year and up to 2 years, using an existing province-wide clinical database linked to the national death register. TRIAL REGISTRATION: Controlled Clinical Trials ISRCTN46836853.Trials 01/2008; 9:21. · 2.02 Impact Factor -
Article: Effectiveness of Antiretroviral Treatment in a South African ProgramA Cohort Study
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ABSTRACT: Background The effectiveness of the South African government's expanding antiretroviral treatment program is unknown. Observational studies of treatment effectiveness are prone to selection bias, rarely compare patients receiving antiretroviral treatment with similar patients not receiving antiretroviral treatment, and underestimate mortality rates unless patients are actively followed up.Methods We followed up 14 267 patients in the Public Sector Anti-Retroviral Treatment project in Free State, South Africa, for up to 20 months after enrollment. A total of 3619 patients received highly active triple antiretroviral treatment (HAART) for up to 19 months (median, 6 months; interquartile range, 3-9 months) after enrollment. Patients' clinical data were linked with the national mortality register. Marginal structural regression models adjusted for baseline and time-varying covariates.Results Of 4570 patients followed up for at least 1 year, 53.2% died. Eighty-seven percent of patients who died had not received HAART. HAART was associated with lower mortality (hazard ratio, 0.14; 95% confidence interval [CI], 0.11-0.18) and with the presence of tuberculosis (hazard ratio, 0.61; 95% CI, 0.46-0.81) after adjusting for age, sex, weight, clinic, district, CD4 cell count, cotrimoxazole therapy, tuberculosis at baseline, and previous antiretroviral therapy. Cotrimoxazole therapy was associated with lower mortality (hazard ratio, 0.37; 95% CI, 0.32-0.42). Each month of HAART was associated with an increase in CD4 cell count of 15.1 cells/μL (95% CI, 14.7-15.5 cells/μL) and with an increase in body weight of 602 g (95% CI, 548-658 g).Conclusions HAART provided through these South African government health services seems as effective as that provided in high-income countries. Delays starting HAART contributed to high mortality rates. Faster expansion and timely commencement of HAART are needed. Figures in this Article More than 5 million South Africans are infected with human immunodeficiency virus (HIV).1 In sub-Saharan Africa, antiretroviral treatment coverage was estimated to be 23% among those with advanced infection in 2006.2 Efforts to expand highly active triple antiretroviral treatment (HAART) provision in Africa may be slowed by concerns that HAART will be less effective because of inadequate health services and poor treatment adherence. It is unethical to estimate HAART effectiveness using randomized placebo-controlled trials, but cohort studies3- 4 can potentially provide valid estimates. Studies5- 10 in developing countries describe improved outcomes among patient cohorts receiving HAART. To our knowledge, no studies have compared patients receiving HAART with similar patients not receiving HAART, as performed in cohort studies11- 12 from Europe and the United States. Descriptions of changes in outcomes among patients receiving HAART probably underestimate HAART effectiveness because, without treatment, health outcomes tend to deteriorate. Concurrent or historical comparisons of treated and untreated patients are likely to be biased because treatments tend to be selected according to patients' health status. However, with successive observations of changes in individuals, it is possible to adjust for these selection biases, as has recently been performed for European and United States cohorts.9- 14 Following South African national policy,15 the Free State provincial health department established its Comprehensive Care, Management and Treatment of HIV and AIDS Program, which includes provision of HAART. This study estimates the effects of HAART on mortality, tuberculosis, CD4 cell counts, and body weight, in addition to the effects of cotrimoxazole prophylaxis on mortality in this program.Archives of Internal Medicine 168(1):86-93. · 11.46 Impact Factor
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Institutions
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2009
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University of Oxford
- Nuffield Department of Clinical Medicine
Oxford, ENG, United Kingdom
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