Browsing by Author "Hanekom, Willem"

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    Open Access
    Comparison of mantoux and tine tuberculin skin tests in BCG-vaccinated children investigated for tuberculosis
    (Public Library of Science, 2009) Pan, Wenli; Matizirofa, Lyness; Workman, Lesley; Hawkridge, Tony; Hanekom, Willem; Mahomed, Hassan; Hussey, Gregory; Hatherill, Mark
    Background: Tuberculin skin tests (TSTs) are long-established screening methods for tuberculosis (TB). We aimed to compare agreement between the intradermal Mantoux and multipuncture percutaneous Tine methods and to quantify risk factors for a positive test result. Methodology/Principal Findings: 1512 South African children younger than 5 years of age who were investigated for tuberculosis (TB) during a Bacille Calmette Guerin (BCG) trial were included in this analysis. Children underwent both Mantoux and Tine tests. A positive test was defined as Mantoux ≥15 mm or Tine ≥ Grade 3 for the binary comparison. Agreement was evaluated using kappa (binary) and weighted kappa (hierarchical). Multivariate regression models identified independent risk factors for TST positivity. The Mantoux test was positive in 430 children (28.4%) and the Tine test in 496 children (32.8%, p<0.0001), with observed binary agreement 87.3% (kappa 0.70) and hierarchical agreement 85.0% (weighted kappa 0.66). Among 173 children culture-positive for Mycobacterium tuberculosis, Mantoux was positive in 49.1% and Tine in 54.9%, p<0.0001 (kappa 0.70). Evidence of digit preference was noted for Mantoux readings at 5 mm threshold intervals. After adjustment for confounders, a positive culture, suggestive chest radiograph, and proximity of TB contact were risk factors for a positive test using both TST methods. There were no independent associations between ethnicity, gender, age, or over-crowding, and TST result. Conclusions/Significance: The Tine test demonstrated a higher positive test rate than the Mantoux, with substantial agreement between TST methods among young BCG-vaccinated children. TB disease and exposure factors, but not demographic variables, were independent risk factors for a positive result using either test method. These findings suggest that the Tine might be a useful screening tool for childhood TB in resource-limited countries.
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    Evaluation of the quality of informed consent in a vaccine field trial in a developing country setting
    (BioMed Central Ltd, 2008) Minnies, Deon; Hawkridge, Tony; Hanekom, Willem; Ehrlich, Rodney; London, Leslie; Hussey, Greg
    BACKGROUND:Informed consent is an ethical and legal requirement for research involving human participants. However, few studies have evaluated the process, particularly in Africa.Participants in a case control study designed to identify correlates of immune protection against tuberculosis (TB) in South Africa. This study was in turn nested in a large TB vaccine efficacy trial.The aim of the study was to evaluate the quality of consent in the case control study, and to identify factors that may influence the quality of consent.Cross-sectional study conducted over a 4 month period. METHODS: Consent was obtained from parents of trial participants. These parents were asked to complete a questionnaire that contained questions about the key elements of informed consent (voluntary participation, confidentiality, the main risks and benefits, etc.). The recall (success in selecting the correct answers) and understanding (correctness of interpretation of statements presented) were measured. RESULTS: The majority of the 192 subjects interviewed obtained scores greater than 75% for both the recall and understanding sections. The median score for recall was 66%; interquartile range (IQR) = 55%-77% and for understanding 75% (IQR = 50%-87%). Most (79%) were aware of the risks and 64% knew that they participated voluntarily. Participants who had completed Grade 7 at school and higher were more likely (OR = 4.94; 95% CI = 1.57 - 15.55) to obtain scores greater than 75% for recall than those who did not. Participants who were consented by professional nurses who had worked for more than two years in research were also more likely (OR = 2.62; 95% CI = 1.35-5.07) to obtain such scores for recall than those who were not. CONCLUSION: Notwithstanding the constraints in a developing country, in a population with low levels of literacy and education, the quality of informed consent found in this study could be considered as building blocks for establishing acceptable standards for public health research. Education level of respondents and experience of research staff taking the consent were associated with good quality informed consent.
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    Investigations of mycobacteria-specific memoryy/effector T cell responses in HIV infected children receiving antiretroviral therapy
    (2011) Tena-Coki, Nontobeko Gwendoline; Hanekom, Willem; Scriba, Thomas; Kampmann, Beate
    Human immunodeficiency virus (HIV) infected children are at greater risk of developing tuberculosis disease, and might benefit from vaccination with novel TB vaccines. However, little is known about the effect of HIV-infection on function and phenotype of T cell responses to mycobacterial antigens in children. This study compares both CD4 and CD8 T cell cytokine expression and memory phenotype in children, following in vitro stimulation with mycobacterial antigens, also contained in novel anti-TB vaccines that are currently undergoing clinical trials.
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    Isolation of Non-Tuberculous Mycobacteria in Children Investigated for Pulmonary Tuberculosis
    (Public Library of Science, 2006) Hatherill, Mark; Hawkridge, Tony; Whitelaw, Andrew; Tameris, Michele; Mahomed, Hassan; Moyo, Sizulu; Hanekom, Willem; Hussey, Gregory
    Objective To evaluate the frequency and clinical significance of non-tuberculous mycobacteria (NTM) isolates among children investigated for pulmonary tuberculosis in a rural South African community. METHODS: Children were investigated for pulmonary tuberculosis as part of a tuberculosis vaccine surveillance program (2001-2005). The clinical features of children in whom NTM were isolated, from induced sputum or gastric lavage, were compared to those with culture-proven M. tuberculosis . RESULTS: Mycobacterial culture demonstrated 114 NTM isolates from 109 of the 1,732 children investigated, a crude yield of 6% (95% CI 5-7). The comparative yield of positive NTM cultures from gastric lavage was 40% (95% CI 31-50), compared to 67% (95% CI 58-76) from induced sputum. 95% of children with NTM isolates were symptomatic. Two children were HIV-infected. By contrast, M. tuberculosis was isolated in 187 children, a crude yield of 11% (95% CI 9-12). Compared to those with culture-proven M. tuberculosis , children with NTM isolates were less likely to demonstrate acid-fast bacilli on direct smear microscopy (OR 0.19; 95% 0.0-0.76). Children with NTM were older (p<0.0001), and more likely to demonstrate constitutional symptoms (p = 0.001), including fever (p = 0.003) and loss of weight or failure to gain weight (p = 0.04), but less likely to demonstrate a strongly positive tuberculin skin test (p<0.0001) or radiological features consistent with pulmonary tuberculosis (p = 0.04). DISCUSSION: NTM were isolated in 6% of all children investigated for pulmonary tuberculosis and in more than one third of those with a positive mycobacterial culture. NTM may complicate the diagnosis of PTB in regions that lack capacity for mycobacterial species identification. The association of NTM isolates with constitutional symptoms suggestive of host recognition requires further investigation.
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    Serum indoleamine 2,3-dioxygenase activity is associated with reduced immunogenicity following vaccination with MVA85A
    (2014-12-03) Tanner, Rachel; Kakalacheva, Kristina; Miller, Ellen; Pathan, Ansar A; Chalk, Rod; Sander, Clare R; Scriba, Tom; Tameris, Michelle; Hawkridge, Tony; Mahomed, Hassan; Hussey, Greg; Hanekom, Willem; Checkley, Anna; McShane, Helen; Fletcher, Helen A
    Abstract Background There is an urgent need for improved vaccines to protect against tuberculosis. The currently available vaccine Bacille Calmette-Guerin (BCG) has varying immunogenicity and efficacy across different populations for reasons not clearly understood. MVA85A is a modified vaccinia virus expressing antigen 85A from Mycobacterium tuberculosis which has been in clinical development since 2002 as a candidate vaccine to boost BCG-induced protection. A recent efficacy trial in South African infants failed to demonstrate enhancement of protection over BCG alone. The immunogenicity was lower than that seen in UK trials. The enzyme Indoleamine 2,3-dioxygenase (IDO) catalyses the first and rate-limiting step in the breakdown of the essential amino acid tryptophan. T cells are dependent on tryptophan and IDO activity suppresses T-cell proliferation and function. Methods Using samples collected during phase I trials with MVA85A across the UK and South Africa we have investigated the relationship between vaccine immunogenicity and IDO using IFN-γ ELISPOT, qPCR and liquid chromatography mass spectrometry. Results We demonstrate an IFN-γ dependent increase in IDO mRNA expression in peripheral blood mononuclear cells (PBMC) following MVA85A vaccination in UK subjects. IDO mRNA correlates positively with the IFN-γ ELISPOT response indicating that vaccine specific induction of IDO in PBMC is unlikely to limit the development of vaccine specific immunity. IDO activity in the serum of volunteers from the UK and South Africa was also assessed. There was no change in serum IDO activity following MVA85A vaccination. However, we observed higher baseline IDO activity in South African volunteers when compared to UK volunteers. In both UK and South African serum samples, baseline IDO activity negatively correlated with vaccine-specific IFN-γ responses, suggesting that IDO activity may impair the generation of a CD4+ T cell memory response. Conclusions Baseline IDO activity was higher in South African volunteers when compared to UK volunteers, which may represent a potential mechanism for the observed variation in vaccine immunogenicity in South African and UK populations and may have important implications for future vaccination strategies. Trial registration Trials are registered at ClinicalTrials.gov; UK cohort NCT00427830 , UK LTBI cohort NCT00456183 , South African cohort NCT00460590 , South African LTBI cohort NCT00480558 .
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    Transcriptional profiling of mycobacterial antigen-induced responses in infants vaccinated with BCG at birth
    (BioMed Central Ltd, 2009) Fletcher, Helen; Keyser, Alana; Bowmaker, Mark; Sayles, Peter; Kaplan, Gilla; Hussey, Greg; Hill, Adrian; Hanekom, Willem
    BACKGROUND:Novel tuberculosis (TB) vaccines recently tested in humans have been designed to boost immunity induced by the current vaccine, Mycobacterium bovis Bacille Calmette-Guerin (BCG). Because BCG vaccination is used extensively in infants, this population group is likely to be the first in which efficacy trials of new vaccines will be conducted. However, our understanding of the complexity of immunity to BCG in infants is inadequate, making interpretation of vaccine-induced immune responses difficult. METHODS: To better understand BCG-induced immunity, we performed gene expression profiling in five 10-week old infants routinely vaccinated with BCG at birth. RNA was extracted from 12 hour BCG-stimulated or purified protein derivative of tuberculin (PPD)-stimulated PBMC, isolated from neonatal blood collected 10 weeks after vaccination. RNA was hybridised to the Sentrix(R) HumanRef-8 Expression BeadChip (Illumina) to measure expression of >16,000 genes. RESULTS: We found that ex vivo stimulation of PBMC with PPD and BCG induced largely similar gene expression profiles, except that BCG induced greater macrophage activation. The peroxisome proliferator-activated receptor (PPAR) signaling pathway, including PPAR-gamma, involved in activation of the alternative, anti-inflammatory macrophage response was down-regulated following stimulation with both antigens. In contrast, up-regulation of genes associated with the classic, pro-inflammatory macrophage response was noted. Further analysis revealed a decrease in the expression of cell adhesion molecules (CAMs), including integrin alpha M (ITGAM), which is known to be important for entry of mycobacteria into the macrophage. Interestingly, more leukocyte genes were down-regulated than up-regulated. CONCLUSION: Our results suggest that a combination of suppressed and up-regulated genes may be key in determining development of protective immunity to TB induced by vaccination with BCG.