Gregory D. Hussey

Safety and efficacy of MVA85A, a new tuberculosis vaccine, in infants previously vaccinated with BCG: a randomised, placebo-controlled phase 2b trial

Summary Background BCG vaccination provides incomplete protection against tuberculosis in infants. A new vaccine, modified Vaccinia Ankara virus expressing antigen 85A (MVA85A), was designed to enhance the protective efficacy of BCG. We aimed to assess safety, immunogenicity, and efficacy of MVA85A against tuberculosis and Mycobacterium tuberculosis infection in infants. Methods In our double-blind, randomised, placebo-controlled phase 2b trial, we enrolled healthy infants (aged 4–6 months) without HIV infection who had previously received BCG vaccination. We randomly allocated infants (1:1), according to an independently generated sequence with block sizes of four, to receive one intradermal dose of MVA85A or an equal volume of Candida skin test antigen as placebo at a clinical facility in a rural region near Cape Town, South Africa. We actively followed up infants every 3 months for up to 37 months. The primary study outcome was safety (incidence of adverse and serious adverse events) in all vaccinated participants, but we also assessed efficacy in a protocol-defined group of participants who received at least one dose of allocated vaccine. The primary efficacy endpoint was incident tuberculosis incorporating microbiological, radiological, and clinical criteria, and the secondary efficacy endpoint was M tuberculosis infection according to QuantiFERON TB Gold In-tube conversion (Cellestis, Australia). This trial was registered with the South African National Clinical Trials Register (DOH-27-0109-2654) and with ClinicalTrials.gov on July 31, 2009, number NCT00953927 Findings Between July 15, 2009, and May 4, 2011, we enrolled 2797 infants (1399 allocated MVA85A and 1398 allocated placebo). Median follow-up in the per-protocol population was 24·6 months (IQR 19·2–28·1), and did not differ between groups. More infants who received MVA85A than controls had at least one local adverse event (1251 [89%] of 1399 MVA85A recipients and 628 [45%] of 1396 controls who received the allocated intervention) but the numbers of infants with systemic adverse events (1120 [80%] and 1059 [76%]) or serious adverse events (257 [18%] and 258 (18%) did not differ between groups. None of the 648 serious adverse events in these 515 infants was related to MVA85A. 32 (2%) of 1399 MVA85A recipients met the primary efficacy endpoint (tuberculosis incidence of 1·15 per 100 person-years [95% CI 0·79 to 1·62]; with conversion in 178 [13%] of 1398 infants [95% CI 11·0 to 14·6]) as did 39 (3%) of 1395 controls (1·39 per 100 person-years [1·00 to 1·91]; with conversion in 171 [12%] of 1394 infants [10·6 to 14·1]). Efficacy against tuberculosis was 17·3% (95% CI −31·9 to 48·2) and against M tuberculosis infection was −3·8% (–28·1 to 15·9). Interpretation MVA85A was well tolerated and induced modest cell-mediated immune responses. Reasons for the absence of MVA85A efficacy against tuberculosis or M tuberculosis infection in infants need exploration. Funding Aeras, Wellcome Trust, and Oxford-Emergent Tuberculosis Consortium (OETC).

A randomized, controlled trial of vitamin A in children with severe measles.

Abstract Background. Measles kills about 2 million children annually, and there is no specific therapy for the disease. It has been suggested that vitamin A may be of benefit in the treatment of measles. Methods. We conducted a randomized, double-blind trial involving 189 children who were hospitalized at a regional center in South Africa because of measles complicated by pneumonia, diarrhea, or croup. The children (median age, 10 months) were assigned to receive either vitamin A (total dose, 400,000 IU of retinyl palmitate, given orally; n = 92) or placebo (n = 97), beginning within five days of the onset of the rash. At base line, the characteristics of the two groups were similar. Results. Although clinically apparent vitamin A deficiency is rare in this population, the childrens serum retinol levels were markedly depressed (mean [±SEM], 0.405±0.021 μmol per liter [11.6±0.6 /μg per deciliter]), and 92 percent of them had hyporetinemia (serum retinol level <0.7 μmol per liter [20 μg per deciliter]). Se...

Induced sputum versus gastric lavage for microbiological confirmation of pulmonary tuberculosis in infants and young children: a prospective study

BACKGROUND For microbiological confirmation of diagnosis of pulmonary tuberculosis in young children, sequential gastric lavages are recommended; sputum induction has not been regarded as feasible or useful. We aimed to compare the yield of Mycobacterium tuberculosis from repeated induced sputum with that from gastric lavage in young children from an area with a high rate of HIV and tuberculosis. METHODS We studied 250 children aged 1 month to 5 years who were admitted for suspected pulmonary tuberculosis in Cape Town, South Africa. Sputum induction and gastric lavage were done on three consecutive days according to a standard procedure. Specimens were stained for acid-fast bacilli; each sample was cultured singly for M tuberculosis. FINDINGS Median age of children was 13 months (IQR 6-24). A positive smear or culture for M tuberculosis was obtained from 62 (25%) children; of these, 58 (94%) were positive by culture, whereas almost half (29 [47%]) were smear positive. Samples from induced sputum and gastric lavage were positive in 54 (87%) and 40 (65%) children, respectively (difference in yield 5.6% [1.4-9.8%], p=0.018). The yield from one sample from induced sputum was similar to that from three gastric lavages (p=1.0). Microbiological yield did not differ between HIV-infected and HIV-uninfected children (p=0.17, odds ratio 0.7 [95% CI 0.3-1.3]). All sputum induction procedures were well tolerated; minor side-effects were increased coughing, epistaxis, vomiting, or wheezing. INTERPRETATION Sputum induction is safe and useful for microbiological confirmation of tuberculosis in young children. This technique is preferable to gastric lavage for diagnosis of pulmonary tuberculosis in both HIV-infected and HIV-uninfected infants and children.

Specific T Cell Frequency and Cytokine Expression Profile Do Not Correlate with Protection against Tuberculosis after Bacillus Calmette-Guérin Vaccination of Newborns

RATIONALE Immunogenicity of new tuberculosis (TB) vaccines is commonly assessed by measuring the frequency and cytokine expression profile of T cells. OBJECTIVES We tested whether this outcome correlates with protection against childhood TB disease after newborn vaccination with bacillus Calmette-Guérin (BCG). METHODS Whole blood from 10-week-old infants, routinely vaccinated with BCG at birth, was incubated with BCG for 12 hours, followed by cryopreservation for intracellular cytokine analysis. Infants were followed for 2 years to identify those who developed culture-positive TB-these infants were regarded as not protected against TB. Infants who did not develop TB disease despite exposure to TB in the household, and another group of randomly selected infants who were never evaluated for TB, were also identified-these groups were regarded as protected against TB. Cells from these groups were thawed, and CD4, CD8, and γδ T cell-specific expression of IFN-γ, TNF-α, IL-2, and IL-17 measured by flow cytometry. MEASUREMENTS AND MAIN RESULTS A total of 5,662 infants were enrolled; 29 unprotected and two groups of 55 protected infants were identified. There was no difference in frequencies of BCG-specific CD4, CD8, and γδ T cells between the three groups of infants. Although BCG induced complex patterns of intracellular cytokine expression, there were no differences between protected and unprotected infants. CONCLUSIONS The frequency and cytokine profile of mycobacteria-specific T cells did not correlate with protection against TB. Critical components of immunity against Mycobacterium tuberculosis, such as CD4 T cell IFN-γ production, may not necessarily translate into immune correlates of protection against TB disease.

New vaccines for tuberculosis

New vaccines are urgently needed if we want to reach the goal of substantially reducing the incidence of tuberculosis by 2050. Despite a steady increase in funding over the past decade, there is still a striking financial shortfall for vaccine research and development for tuberculosis. Yet, around ten vaccine candidates have left the laboratory stage and entered clinical trials. These vaccines are either aimed at replacing the present vaccine, BCG, or at enhancing immunity induced by BCG. However, these pre-exposure candidates are designed for prevention of disease and will therefore neither eradicate the pathogen, nor prevent stable infection. Long-term vaccination strategies need to target these more ambitious goals. Even though vaccine development will have a price, the return of investment will greatly exceed original costs.

Bacillus Calmette-Guérin Vaccination of Human Newborns Induces T Cells with Complex Cytokine and Phenotypic Profiles

The immune response to vaccination with bacillus Calmette-Guérin (BCG), the only tuberculosis vaccine available, has not been fully characterized. We used multiparameter flow cytometry to examine specific T cell cytokine production and phenotypic profiles in blood from 10-wk-old infants routinely vaccinated with BCG at birth. Ex vivo stimulation of whole blood with BCG for 12 h induced expression of predominantly IFN-γ, IL-2, and TNF-α in CD4+ T cells in seven distinct cytokine combinations. IL-4 and IL-10 expression was detected in CD4+ T cells at low frequencies and only in cells that did not coexpress type 1 cytokines. Specific CD8+ T cells were less frequent than CD4+ T cells and produced mainly IFN-γ and/or IL-2 and less TNF-α, IL-4, and IL-10. Importantly, many mycobacteria-specific CD4+ and CD8+ T cells did not produce IFN-γ. The predominant phenotype of BCG-specific type 1 T cells was that of effector cells, i.e., CD45RA−CCR7−CD27+, which may reflect persistence of Mycobacterium bovis BCG in infants until 10 wk of age. Among five phenotypic patterns of CD4+ T cells, central memory cells were more likely to be IL-2+ and effector cells were more likely to be IFN-γ+. We concluded that neonatal vaccination with BCG induces T cells with a complex pattern of cytokine expression and phenotypes. Measuring IFN-γ production alone underestimates the magnitude and complexity of the host cytokine response to BCG vaccination and may not be an optimal readout in studies of BCG and novel tuberculosis vaccination.

Effect of isoniazid prophylaxis on mortality and incidence of tuberculosis in children with HIV: randomised controlled trial

Objectives To investigate the impact of isoniazid prophylaxis on mortality and incidence of tuberculosis in children with HIV. Design Two centre prospective double blind placebo controlled trial. Participants Children aged ≥8 weeks with HIV. Interventions Isoniazid or placebo given with co-trimoxazole either daily or three times a week. Setting Two tertiary healthcare centres in South Africa. Main outcome measures Mortality, incidence of tuberculosis, and adverse events. Results Data on 263 children (median age 24.7 months) were available when the data safety monitoring board recommended discontinuing the placebo arm; 132 (50%) were taking isoniazid. Median follow-up was 5.7 (interquartile range 2.0-9.7) months. Mortality was lower in the isoniazid group than in the placebo group (11 (8%) v 21 (16%), hazard ratio 0.46, 95% confidence interval 0.22 to 0.95, P=0.015) by intention to treat analysis. The benefit applied across Centers for Disease Control clinical categories and in all ages. The reduction in mortality was similar in children on three times a week or daily isoniazid. The incidence of tuberculosis was lower in the isoniazid group (5 cases, 3.8%) than in the placebo group (13 cases, 9.9%) (hazard ratio 0.28, 0.10 to 0.78, P=0.005). All cases of tuberculosis confirmed by culture were in children in the placebo group. Conclusions Prophylaxis with isoniazid has an early survival benefit and reduces incidence of tuberculosis in children with HIV. Prophylaxis may offer an effective public health intervention to reduce mortality in such children in settings with a high prevalence of tuberculosis. Trial registration. Clinical Trials NCT00330304

A blood RNA signature for tuberculosis disease risk: a prospective cohort study

BACKGROUND Identification of blood biomarkers that prospectively predict progression of Mycobacterium tuberculosis infection to tuberculosis disease might lead to interventions that combat the tuberculosis epidemic. We aimed to assess whether global gene expression measured in whole blood of healthy people allowed identification of prospective signatures of risk of active tuberculosis disease. METHODS In this prospective cohort study, we followed up healthy, South African adolescents aged 12-18 years from the adolescent cohort study (ACS) who were infected with M tuberculosis for 2 years. We collected blood samples from study participants every 6 months and monitored the adolescents for progression to tuberculosis disease. A prospective signature of risk was derived from whole blood RNA sequencing data by comparing participants who developed active tuberculosis disease (progressors) with those who remained healthy (matched controls). After adaptation to multiplex quantitative real-time PCR (qRT-PCR), the signature was used to predict tuberculosis disease in untouched adolescent samples and in samples from independent cohorts of South African and Gambian adult progressors and controls. Participants of the independent cohorts were household contacts of adults with active pulmonary tuberculosis disease. FINDINGS Between July 6, 2005, and April 23, 2007, we enrolled 6363 participants from the ACS study and 4466 from independent South African and Gambian cohorts. 46 progressors and 107 matched controls were identified in the ACS cohort. A 16 gene signature of risk was identified. The signature predicted tuberculosis progression with a sensitivity of 66·1% (95% CI 63·2-68·9) and a specificity of 80·6% (79·2-82·0) in the 12 months preceding tuberculosis diagnosis. The risk signature was validated in an untouched group of adolescents (p=0·018 for RNA sequencing and p=0·0095 for qRT-PCR) and in the independent South African and Gambian cohorts (p values <0·0001 by qRT-PCR) with a sensitivity of 53·7% (42·6-64·3) and a specificity of 82·8% (76·7-86) in the 12 months preceding tuberculosis. INTERPRETATION The whole blood tuberculosis risk signature prospectively identified people at risk of developing active tuberculosis, opening the possibility for targeted intervention to prevent the disease. FUNDING Bill & Melinda Gates Foundation, the National Institutes of Health, Aeras, the European Union, and the South African Medical Research Council.Background Identification of blood biomarkers that prospectively predict progression of Mycobacterium tuberculosis infection to tuberculosis disease may lead to interventions that impact the epidemic. Methods Healthy, M. tuberculosis infected South African adolescents were followed for 2 years; blood was collected every 6 months. A prospective signature of risk was derived from whole blood RNA-Sequencing data by comparing participants who ultimately developed active tuberculosis disease (progressors) with those who remained healthy (matched controls). After adaptation to multiplex qRT-PCR, the signature was used to predict tuberculosis disease in untouched adolescent samples and in samples from independent cohorts of South African and Gambian adult progressors and controls. The latter participants were household contacts of adults with active pulmonary tuberculosis disease. Findings Of 6,363 adolescents screened, 46 progressors and 107 matched controls were identified. A 16 gene signature of risk was identified. The signature predicted tuberculosis progression with a sensitivity of 66·1% (95% confidence interval, 63·2–68·9) and a specificity of 80·6% (79·2–82·0) in the 12 months preceding tuberculosis diagnosis. The risk signature was validated in an untouched group of adolescents (p=0·018 for RNA-Seq and p=0·0095 for qRT-PCR) and in the independent South African and Gambian cohorts (p values <0·0001 by qRT-PCR) with a sensitivity of 53·7% (42·6–64·3) and a specificity of 82·8% (76·7–86) in 12 months preceding tuberculosis. Interpretation The whole blood tuberculosis risk signature prospectively identified persons at risk of developing active tuberculosis, opening the possibility for targeted intervention to prevent the disease. Funding Bill and Melinda Gates Foundation, the National Institutes of Health, Aeras, the European Union and the South African Medical Research Council (detail at end of text).

Modified vaccinia Ankara-expressing Ag85A, a novel tuberculosis vaccine, is safe in adolescents and children, and induces polyfunctional CD4+ T cells

Modified vaccinia Ankara‐expressing Ag85A (MVA85A) is a new tuberculosis (TB) vaccine aimed at enhancing immunity induced by BCG. We investigated the safety and immunogenicity of MVA85A in healthy adolescents and children from a TB endemic region, who received BCG at birth. Twelve adolescents and 24 children were vaccinated and followed up for 12 or 6 months, respectively. Adverse events were documented and vaccine‐induced immune responses assessed by IFN‐γ ELISpot and intracellular cytokine staining. The vaccine was well tolerated and there were no vaccine‐related serious adverse events. MVA85A induced potent and durable T‐cell responses. Multiple CD4+ T‐cell subsets, based on expression of IFN‐γ, TNF‐α, IL‐2, IL‐17 and GM‐CSF, were induced. Polyfunctional CD4+ T cells co‐expressing IFN‐γ, TNF‐α and IL‐2 dominated the response in both age groups. A novel CD4+ cell subset co‐expressing these three Th1 cytokines and IL‐17 was induced in adolescents, while a novel CD4+ T‐cell subset co‐expressing Th1 cytokines and GM‐CSF was induced in children. Ag‐specific CD8+ T cells were not detected. We conclude that in adolescents and children MVA85A safely induces the type of immunity thought to be important in protection against TB. This includes induction of novel Th1‐cell populations that have not been previously described in humans.

Comparison of T-SPOT.TB Assay and Tuberculin Skin Test for the Evaluation of Young Children at High Risk for Tuberculosis in a Community Setting

OBJECTIVE. We wished to compare the sensitivity of an enzyme-linked immunospot assay (T-SPOT.TB; Oxford Immunotec, Oxford, United Kingdom) and the tuberculin skin test for the detection of tuberculosis infection in very young children being evaluated for active tuberculosis in a rural community setting. METHODS. Children with a history of exposure to tuberculosis and children presenting to a local clinic or hospital with symptoms suggesting tuberculosis were admitted to a dedicated case verification ward. T-SPOT.TB testing was performed, and children were evaluated with a clinical examination, a tuberculin skin test, chest radiographs, and cultures of induced sputum and gastric lavage specimens. The diagnosis was determined by using a clinical algorithm. RESULTS. A total of 243 children (median age: 18 months) were recruited, of whom 214 (88%) had interpretable T-SPOT.TB results. Children ≥12 months of age were more likely than younger children to have positive T-SPOT.TB results, whereas tuberculin skin test results were unaffected by age. The sensitivity of the T-SPOT.TB was no better than that of the tuberculin skin test for culture-confirmed tuberculosis (50% and 80%, respectively) and was poorer for the combined group of culture-confirmed and clinically probable tuberculosis (40% and 52%, respectively). For the 50 children clinically categorized as not having tuberculosis, the specificity of both the T-SPOT.TB and the tuberculin skin test was 84%. CONCLUSIONS. For young children presenting in a community setting after exposure to tuberculosis or with symptoms suggesting tuberculosis, T-SPOT.TB cannot be used to exclude active disease. The sensitivity of this assay may be impaired for very young children.