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.

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.

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.

T-cell activation is an immune correlate of risk in BCG vaccinated infants

Vaccines to protect against tuberculosis (TB) are urgently needed. We performed a case-control analysis to identify immune correlates of TB disease risk in Bacille Calmette-Guerin (BCG) immunized infants from the MVA85A efficacy trial. Among 53 TB case infants and 205 matched controls, the frequency of activated HLA-DR(+) CD4(+) T cells associates with increased TB disease risk (OR=1.828, 95% CI=1.25-2.68, P=0.002, FDR=0.04, conditional logistic regression). In an independent study of Mycobacterium tuberculosis-infected adolescents, activated HLA-DR(+) CD4(+) T cells also associate with increased TB disease risk (OR=1.387, 95% CI=1.068-1.801, P=0.014, conditional logistic regression). In infants, BCG-specific T cells secreting IFN-γ associate with reduced risk of TB (OR=0.502, 95% CI=0.29-0.86, P=0.013, FDR=0.14). The causes and impact of T-cell activation on disease risk should be considered when designing and testing TB vaccine candidates for these populations.

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 > or =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.

Sputum induction for the diagnosis of pulmonary tuberculosis in infants and young children in an urban setting in South Africa

BACKGROUND

Bacteriological confirmation of pulmonary tuberculosis is difficult in infants and young children. In adults and older children, sputum induction has been successfully used; this technique has not been tested in younger children.

AIMS

To investigate whether sputum induction can be successfully performed in infants and young children and to determine the utility of induced sputum compared to gastric lavage (GL) for the diagnosis of pulmonary tuberculosis in HIV infected and uninfected children.

SUBJECTS AND METHODS

149 children (median age 9 months) admitted to hospital with acute pneumonia who were known to be HIV infected, suspected to have HIV infection, or required intensive care unit support. Sputum induction was performed on enrollment. Early morning GL was performed after a minimum four hour fast. Induced sputum and stomach contents were stained for acid fast bacilli and cultured for Mycobacterium tuberculosis.

RESULTS

Sputum induction was successfully performed in 142 of 149 children. M tuberculosis, cultured in 16 children, grew from induced sputum in 15. GL, performed in 142 children, was positive in nine; in eight of these M tuberculosis also grew from induced sputum. The difference between yields from induced sputum compared to GL was 4.3% (p = 0.08). M tuberculosis was cultured in 10 of 100 HIV infected children compared to six of 42 HIV uninfected children (p = 0.46).

CONCLUSION

Sputum induction can be safely and effectively performed in infants and young children. Induced sputum provides a satisfactory and more convenient specimen for bacteriological confirmation of pulmonary tuberculosis in HIV infected and uninfected children.

Pneumocystis carinii pneumonia in South African children infected with human immunodeficiency virus

BACKGROUND

Pneumocystis carinii pneumonia (PCP) has been regarded as uncommon in HIV-infected patients in Africa, but diagnostic difficulties and geographic variability may partly account for this. There is little information on the incidence of PCP in HIV-infected children in Africa.

AIM

To investigate (1) the incidence and associated features of PCP in African HIV-infected children and (2) the usefulness of sputum induction and nasopharyngeal aspirates (NPAs) for diagnosis of PCP.

METHODS

HIV-infected children hospitalized with pneumonia were prospectively enrolled in a 1-year study in South Africa. History, examination, chest radiology and blood tests (including HIV testing) were performed. Sputum induction (5% NaCl nebulization) or nondirected bronchoalveolar lavage in intubated patients was performed for P. carinii identification using immunofluorescence and silver stain; immunofluorescence was also done on nasopharyngeal aspirates (NPAs).

RESULTS

Of 151 HIV-infected children [47% female; median age, 9 (range, 3 to 23) months], 87 had been previously diagnosed with HIV whereas 64 (42.4%) were found to be HIV-positive at the time of admission. PCP occurred in 15 children (9.9%; 95% confidence interval, 5.9 to 15.5) and was the AIDS-defining infection in 13 of 64 (20.3%; 95% confidence interval, 11.8 to 31.5). Only 1 of 59 children receiving prophylaxis (1.7%) developed PCP compared with 14 of 92 (15.2%) not taking prophylaxis [relative risk, 0.11 (0.02 to 0.82), P = 0.007]. PCP-infected children were younger [3 (range, 3 to 4) vs. 10 (range, 4 to 24) months, P < 0.001] and presented with more severe pulmonary disease as indicated by a higher respiratory rate [63 (range, 60 to 73) vs. 50, (range, 40 to 60) P < 0.001], heart rate [160 (range, 136-180) vs. 140 (range, 120-152) P = 0.025] and a greater incidence of cyanosis (53% vs. 26%, P = 0.025). Clinical signs of HIV infection, occurring in 96% of children, were equally prevalent in both groups. High serum lactate dehydrogenase was the only laboratory investigation that distinguished PCP-infected from uninfected children [626 (range, 450 to 1098) vs. 307 (range, 243 to 465) units/l], P < 0.001. No radiologic features were found to be diagnostic of PCP. P. carinii was identified in 9 sputa and 6 bronchoalveolar lavage specimens, but all corresponding NPAs were negative. Seven of 15 (47%) children with PCP died while hospitalized compared with 24 of 136 (18%) without PCP [relative risk, 1.21 (range, 0.99 to 1.47), P = 0.008].

CONCLUSION

PCP is an important pathogen in HIV-infected infants in South Africa and is associated with a high mortality. Induced sputum is effective for obtaining lower respiratory tract secretions for diagnosis of PCP but an NPA is not useful.

Association of human TLR1 and TLR6 deficiency with altered immune responses to BCG vaccination in South African infants

The development of effective immunoprophylaxis against tuberculosis (TB) remains a global priority, but is hampered by a partially protective Bacillus Calmette-Guérin (BCG) vaccine and an incomplete understanding of the mechanisms of immunity to Mycobacterium tuberculosis. Although host genetic factors may be a primary reason for BCG's variable and inadequate efficacy, this possibility has not been intensively examined. We hypothesized that Toll-like receptor (TLR) variation is associated with altered in vivo immune responses to BCG. We examined whether functionally defined TLR pathway polymorphisms were associated with T cell cytokine responses in whole blood stimulated ex vivo with BCG 10 weeks after newborn BCG vaccination of South African infants. In the primary analysis, polymorphism TLR6_C745T (P249S) was associated with increased BCG-induced IFN-γ in both discovery (n = 240) and validation (n = 240) cohorts. In secondary analyses of the combined cohort, TLR1_T1805G (I602S) and TLR6_G1083C (synonymous) were associated with increased IFN-γ, TLR6_G1083C and TLR6_C745T were associated with increased IL-2, and TLR1_A1188T was associated with increased IFN-γ and IL-2. For each of these polymorphisms, the hypo-responsive allele, as defined by innate immunity signaling assays, was associated with increased production of TH1-type T cell cytokines (IFN-γ or IL-2). After stimulation with TLR1/6 lipopeptide ligands, PBMCs from TLR1/6-deficient individuals (stratified by TLR1_T1805G and TLR6_C745T hyporesponsive genotypes) secreted lower amounts of IL-6 and IL-10 compared to those with responsive TLR1/6 genotypes. In contrast, no IL-12p70 was secreted by PBMCs or monocytes. These data support a mechanism where TLR1/6 polymorphisms modulate TH1 T-cell polarization through genetic regulation of monocyte IL-10 secretion in the absence of IL-12. These studies provide evidence that functionally defined innate immune gene variants are associated with the development of adaptive immune responses after in vivo vaccination against a bacterial pathogen in humans. These findings could potentially guide novel adjuvant vaccine strategies as well as have implications for IFN-γ-based diagnostic testing for TB.

Tuberculosis (TB) is one of the leading infectious causes of death worldwide. The current vaccine for TB, BCG, is widely used but it is not highly effective in preventing disease. We investigated the role of host genetics in the immune response to BCG vaccination. We found that variants of innate immunity genes (TLR1 and TLR6) were associated with BCG-induced immune responses after vaccination. These findings may guide new strategies for vaccine development as well as diagnosis of TB.

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 > or =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.

Induced sputum or gastric lavage for community-based diagnosis of childhood pulmonary tuberculosis?

OBJECTIVES

To compare the diagnostic yield of Mycobacterium tuberculosis from induced sputum (IS) and gastric lavage (GL) among children in a community setting.

METHODS

Specimen-collection methods for bacteriological confirmation of pulmonary tuberculosis (PTB) were compared during a tuberculosis vaccine trial near Cape Town, South Africa (2001-2006). Children with a tuberculosis contact or compatible symptoms were investigated for suspected PTB. Diagnostic yields from 764 paired IS and GL specimens were compared in 191 culture-confirmed cases.

MEASUREMENTS AND MAIN RESULTS

The crude yield of M tuberculosis was 10.4%, n = 108 by IS (5.8%) and n = 127 by GL (6.8%), from a total of 194 cases, of which three had incomplete IS/GL specimen pairs. Agreement between IS and GL was poor (kappa = 0.31). The comparative yield of a single IS sample (38%) was equivalent to a single GL sample (42%), with a difference in yield of -4% (95% CI -15% to +7%). The combined yield of same-day IS and GL specimens (67%) was equivalent to two consecutive GL specimens (66%), with a difference in yield of 1% (95% CI -9% to 11%), but significantly greater than two consecutive IS specimens (55%), with a difference in yield of 12% (95% CI 2% to 21%). The adjusted odds of a M tuberculosis culture were increased by a positive tuberculin skin test or chest radiograph compatible with PTB.

CONCLUSIONS

In this community setting, the diagnostic yield of a single IS sample was equivalent to that of a single GL sample. The optimal diagnostic yield may be obtained from paired IS and GL specimens taken on a single day or two GL specimens taken on consecutive days.

Sputum induction as a diagnostic tool for community-acquired pneumonia in infants and young children from a high HIV prevalence area

Sputum induction is a standard diagnostic procedure to identify pathogens in lower respiratory tract secretions in adults with pneumonia, but has rarely been studied or used in infants and young children. Our aim was to determine the usefulness of induced sputum (IS) as a diagnostic method for infants and children hospitalized with community-acquired pneumonia (CAP) in a high HIV prevalence area. Children hospitalized for CAP were prospectively enrolled over a year. IS was obtained by nebulization with hypertonic (5%) saline, physiotherapy, and suctioning. Sputum was submitted for bacterial and mycobacterial culture and P. carinii detection. Gastric lavages (GLs) were done for M. tuberculosis culture; a nasopharyngeal aspirate (NPA) was obtained for bacterial culture and P. carinii detection. IS was obtained in 210 children (median age, 7 (25th to 75th percentile, 3-18) months); 138 (66%) were HIV-infected; 148 (70%) were receiving supplemental oxygen. Bacteria were isolated from 101 (50%) IS and 141 (70%) NPA paired specimens (P < 0.001). A significantly higher rate of S. aureus, H. influenzae, M. catarrhalis, and S. pneumoniae was found in NPAs compared to IS; this pattern was particularly evident in HIV-infected children. M. tuberculosis was cultured from sputum in 19 patients (9%); GLs performed in 142 children were positive in only 9 (6%). The difference (95% confidence interval) between yields for M. tuberculosis from culture of IS compared to GL was 4.3% (95% CI, 0-5.6%; P = 0.08). P. carinii was identified from IS in 12 (5.7%) children; all corresponding NPAs were negative. Seven (3%) children could not tolerate sputum induction. Side effects included increased coughing in 4%, epistaxis in 3%, and wheezing responsive to bronchodilators in 1%. In conclusion, induced sputum is a useful and safe diagnostic procedure in infants and children with CAP from a high HIV prevalence area.

Miliary tuberculosis in children: a review of 94 cases

This is a retrospective review of the clinical, radiologic and laboratory features of 94 cases of childhood miliary tuberculosis seen during a 5-year period, 1985 to 1989. A history of Bacillus Calmette-Guérin vaccination was documented in 88% of children. The median age at presentation was 10.5 months, 52% of cases occurring in those younger than 1 year. The presenting symptoms were nonspecific: cough (72%); fever (61%); loss of appetite and weight (40%); and diarrhea and vomiting (33%). The main presenting signs were hepatomegaly (82%), splenomegaly (54%), lymphadenopathy (46%) and pyrexia (39%). Most of the patients were malnourished and anergic. Meningitis occurred in 19% of patients and this was the only significant risk factor identified for mortality, the overall case fatality rate being 14%. The diagnosis in the vast majority was made on the clinical presentation supported by a classic miliary pattern on chest roentgenogram (91% of cases). Mycobacterium tuberculosis was cultured in 33% of cases. In addition a review of hospital admissions from 1981 to 1989 revealed that annually miliary tuberculosis in children and adults accounted for 8.3 and 1.3%, respectively, of all tuberculosis admissions. This study confirms that miliary tuberculosis is a relatively common complication of tuberculosis in young children.

Single nucleotide polymorphisms in toll-like receptor 6 are associated with altered lipopeptide- and mycobacteria-induced interleukin-6 secretion

Toll-like receptors (TLRs) are critical mediators of the immune response to pathogens. The influence of human TLR6 polymorphisms on susceptibility to infection is only partially understood. Most microbes contain lipopeptides recognized by TLR2/1 or TLR2/6 heterodimers. Our aim was to determine whether single nucleotide polymorphisms (SNPs) in TLR6 are associated with altered immune responses to lipopeptides and whole mycobacteria.

We sequenced the TLR6 coding region in 100 healthy South African adults to assess genetic variation and determined associations between polymorphisms and lipopeptide- and mycobacteria-induced IL-6 production in whole blood. We found 2 polymorphisms, C745T and G1083C that were associated with altered IL-6 secretion. G1083C was associated with altered IL-6 levels in response to lipopeptides, Mycobacterium tuberculosis lysate (Mtb, P = 0.018) and BCG (P = 0.039). The 745T allele was also associated with lower NF-κB signaling in response to di-acylated lipopeptide, PAM2 (P = 0.019) or Mtb (P = 0.026) in a HEK293 cell line reconstitution assay, compared with the 745C allele.

We conclude that TLR6 polymorphisms may be associated with altered lipopeptide-induced cytokine responses and recognition of Mtb. These studies provide new insight into the role of TLR6 variation and the innate immune response to human infection.

Structured approaches for the screening and diagnosis of childhood tuberculosis in a high prevalence region of South Africa

OBJECTIVE

To measure agreement between nine structured approaches for diagnosing childhood tuberculosis; to quantify differences in the number of tuberculosis cases diagnosed with the different approaches, and to determine the distribution of cases in different categories of diagnostic certainty.

METHODS

We investigated 1445 children aged < 2 years during a vaccine trial (2001-2006) in a rural South African community. Clinical, radiological and microbiological data were collected prospectively. Tuberculosis case status was determined using each of the nine diagnostic approaches. We calculated differences in case frequency and categorical agreement for binary (tuberculosis/not tuberculosis) outcomes using McNemar's test (with 95% confidence intervals, CIs) and Cohen's kappa coefficient (Kappa).

FINDINGS

Tuberculosis case frequency ranged from 6.9% to 89.2% (median: 41.7). Significant differences in case frequency (P < 0.05) occurred in 34 of the 36 pair-wise comparisons between structured diagnostic approaches (range of absolute differences: 1.5-82.3%). Kappa ranged from 0.02 to 0.71 (median: 0.18). The two systems that yielded the highest case frequencies (89.2% and 70.0%) showed fair agreement (Kappa: 0.33); the two that yielded the lowest case frequencies (6.9% and 10.0%) showed slight agreement (Kappa: 0.18).

CONCLUSION

There is only slight agreement between structured approaches for the screening and diagnosis of childhood tuberculosis and high variability between them in terms of case yield. Diagnostic systems that yield similarly low case frequencies may be identifying different subpopulations of children. The study findings do not support the routine clinical use of structured approaches for the definitive diagnosis of childhood tuberculosis, although high-yielding systems may be useful screening tools.

Childhood tuberculosis: old and new vaccines

The world is witnessing an escalation of the tuberculosis (TB) epidemic, particularly in sub-Saharan Africa and South-East Asia. The problem has been compounded by the evolution of the human immunodeficiency virus pandemic, the increase in multidrug-resistant TB and the emergence of extensively drug-resistant TB. This has led to renewed interest in vaccines aimed at preventing tuberculosis. The current Bacille Calmette-Guérin (BCG) vaccine prevents the invasive complications of childhood tuberculosis, such as meningitis and miliary disease, but provides variable protection against adult pulmonary disease. This review discusses the history of the BCG vaccine, the reasons for its variable efficacy, protective immunity and TB, and the evolution of and obstacles to development of new candidate vaccines. Several new TB vaccines have demonstrated promising results in animal models; a number have gone into phase I clinical trials in humans, and it is anticipated that phase III trials will commence by 2009. Licensing of an effective new TB vaccine by 2015 is thus a possibility.

Tuberculin skin test and QuantiFERON® assay in young children investigated for tuberculosis in South Africa

SETTING

Although the literature on interferon-gamma release assays on tuberculosis (TB) in children has increased, data pertaining to young children remain relatively limited.

OBJECTIVE

To compare results from the tuberculin skin test (TST) and the QuantiFERON®-TB Gold In-Tube assay (QFT) in children aged <3 years investigated for TB disease.

DESIGN

TB suspects were evaluated by medical history and examination, TST, QFT, chest radiography, induced sputum and gastric washings for smear and culture for Mycobacterium tuberculosis.

RESULTS

A total of 400 children were enrolled. Among 397 children with both test results, 68 (17%) were QFT-positive and 72 (18%) were TST-positive (≥10 mm). Agreement between the tests was excellent (94%, κ = 0.79, 95%CI 0.69-0.89). TB disease was diagnosed in 52/397 (13%) participants: 3 definite, 35 probable and 14 possible TB. QFT sensitivity and specificity for TB disease were respectively 38% and 81%. TST sensitivity and specificity were respectively 35% and 84%.

CONCLUSION

While TST and QFT had excellent concordance in this population, both tests had much lower sensitivity for TB disease than has been reported for other age groups. Our results suggested equivalent performance of QFT and TST in the diagnosis of TB disease in young children in a high-burden setting.

Lessons learnt from the first efficacy trial of a new infant tuberculosis vaccine since BCG

BACKGROUND

New tuberculosis (TB) vaccines are being developed to combat the global epidemic. A phase IIb trial of a candidate vaccine, MVA85A, was conducted in a high burden setting in South Africa to evaluate proof-of-concept efficacy for prevention of TB in infants.

OBJECTIVE

To describe the study design and implementation lessons from an infant TB vaccine efficacy trial.

METHODS

This was a randomised, controlled, double-blind clinical trial comparing the safety and efficacy of MVA85A to Candin control administered to 4-6-month-old, BCG-vaccinated, HIV-negative infants at a rural site in South Africa. Infants were followed up for 15-39 months for incident TB disease based on pre-specified endpoints.

RESULTS

2797 infants were enrolled over 22 months. Factors adversely affecting recruitment and the solutions that were implemented are discussed. Slow case accrual led to six months extension of trial follow up.

CONCLUSION

The clinical, regulatory and research environment for modern efficacy trials of new TB vaccines are substantially different to that when BCG vaccine was first evaluated in infants. Future infant TB vaccine trials will need to allocate sufficient resources and optimise operational efficiency. A stringent TB case definition is necessary to maximize specificity, and TB case accrual must be monitored closely.

Epidemiology of invasive Haemophilus influenzae infections in Cape Town, South Africa

The full spectrum of invasive Haemophilus influenzae disease has not been documented previously in Africa. This 1-year prospective study was designed to determine the epidemiology of invasive Haemophilus influenzae disease in Cape Town children. During this period, 142 children with invasive disease were hospitalized; 85 (59.9%) presented with meningitis, 35 (24.6%) with pneumonia and 22 (15.5%) with other diseases. No cases of epiglottitis were seen. Sixty per cent of cases were male and 40% female. The median age of the children was 9 months, with a range of 1-144 months, and 65.5% were aged < 12 months. Neurological dysfunction was noted in 40% and 18% of children with meningitis on admission and discharge, respectively. The overall case fatality rate (95% confidence intervals) was 9.2% (4.9-15.7), and for meningitis, pneumonia and septicaemia it was 4.7% (1.2-16.4), 14.3% (4.6-31.8) and 40% (8-78.1), respectively. Serotype b accounted for 86.5% of all cases, 97.3% of cases of meningitis, 71.4% of cases of pneumonia, 50% of cases of septicaemia, all cases of arthritis and cellulitis and none of mastoiditis. The incidence rates (95% confidence intervals) for all invasive type b infections were 169 (122-198) and 47 (39-57) per 100,000 population for children < 1 and < 5 years, respectively. For meningitis the rates were 112 (84-148) and 34 (25-40) per 100,000, respectively. Rates for mixed race and white children were similar, but those for black children were more than double those rates.(ABSTRACT TRUNCATED AT 250 WORDS)

Sputum induction for the diagnosis of pulmonary tuberculosis: a systematic review and meta-analysis

Sputum induction (SI) has been proposed as the optimal sample collection method for patients with paucibacillary tuberculosis (TB). Studies reporting the culture of Mycobacterium tuberculosis from SI were reviewed. A random-effects meta-analysis of diagnostic yield (numerator M. tuberculosis SI culture-positive cases; denominator all culture-positive cases) was conducted. Diagnostic yields (95% confidence intervals, CIs) were displayed as Forest plots. Heterogeneity was evaluated using Chi-squared and I-squared tests and meta-regression analysis. Ninety publications were screened, 28 full-text papers reviewed, and 17 analyzed. Collectively, n=627 SI culture-positive cases among n=975 culture-confirmed TB cases were reported. The diagnostic yield of SI ranged from 35 to 95%. The pooled diagnostic yield was 74% (CI 65-81%), with significant heterogeneity (p<0.0001, I2=86%). There were no statistically significant differences in the yield between sub-groups defined by human immunodeficiency virus (HIV) prevalence or age. Univariate analysis demonstrated that the use of fiberoptic bronchoscopy (FOB) as the comparator method was associated with a 22% reduction (CI 2-42%) in the diagnostic yield of SI. However, after adjustment for confounding, the meta-regression analysis showed that FOB usage (p=0.21) and saline concentration (p=0.31) were not independently associated with the diagnostic yield. SI will detect approximately three-quarters of M. tuberculosis culture-positive cases under study conditions. Significant heterogeneity in the diagnostic yield was not explained by HIV prevalence, age, or the use of FOB as the comparator method. The use of a particular nebulized saline concentration for SI cannot be recommended on the basis of this meta-regression analysis.

Conjugate vaccines for preventing Haemophilus influenzae type b infections

BACKGROUND

Haemophilus influenzae (H. influenzae) is an important cause of meningitis and pneumonia in children, causing an estimated three million cases of serious disease and hundreds of thousands of deaths annually worldwide. The introduction of H. influenzae type b (Hib) vaccines into routine immunisation schedules in developed countries has been followed by a rapid decline in disease occurrence, but vaccine cost is a significant barrier to use in developing countries. There is a need to determine the size of the effects of the vaccine, to enable cost-effectiveness comparisons with competing priorities in developing countries.

OBJECTIVES

1. To determine the effects of conjugate Hib vaccine in preventing Hib disease or death in children under five years.2. To determine any serious adverse outcomes.

SEARCH STRATEGY

Searches of the Cochrane Central Register of Controlled Trials (CENTRAL) (issue 1, 2003); MEDLINE (January 1966 to April 2003), EMBASE (1990 to April 2003); and scanning of reference lists and contacting of authors of trial reports. Reports in all languages were considered.

SELECTION CRITERIA

All randomised controlled trials or quasi-randomised trials of conjugate H. influenzae type b vaccines compared with placebo or no treatment in children who were followed until at least two years of age.

DATA COLLECTION AND ANALYSIS

Two investigators independently selected eligible studies and extracted data. Differences were resolved by discussion.

MAIN RESULTS

Five studies were included in the review, and four in meta-analyses. The overall quality of the trials was good. The relative risk for invasive Hib disease was 0.20 (95% confidence interval 0.07 to 0.54; random effects model), but there was statistically significant unexplained variation (heterogeneity) in the effects of the four trials in the meta-analysis (p = 0.002). The size of the effects found in the trials did not appear to differ consistently with different vaccine types, the number of vaccine doses, age at first vaccination or use in developed vs developing countries, but the confidence intervals for the effect estimates were wide.Hib-related mortality data showed a non-significant trend towards benefit (relative risk was 0.29; 95% confidence interval 0.07 to 1.20; random effects model). The relative risk for all cause mortality in the single trial from which data were available was 1.01 (95% confidence interval 0.38 to 2.67, random effects model). No serious adverse effects were reported in any of the trials, involving a total of 257,000 infants.

REVIEWER'S CONCLUSIONS

Hib vaccine is safe and effective. The size of the effect could plausibly be anywhere between a 46% and 93% reduction in Hib invasive disease, before the effect of herd immunity is taken into account. In resource-poor settings, decisions to use the vaccine will depend on its cost, the local burden of Hib disease and competing priorities. Insufficient evidence from randomised controlled trials was identified of the effects of Hib conjugate vaccine on either Hib-specific or on all-cause mortality.

Cytomegalovirus infection is a risk factor for tuberculosis disease in infants

Immune activation is associated with increased risk of tuberculosis (TB) disease in infants. We performed a case-control analysis to identify drivers of immune activation and disease risk. Among 49 infants who developed TB disease over the first 2 years of life, and 129 healthy matched controls, we found the cytomegalovirus-stimulated (CMV-stimulated) IFN-γ response to be associated with CD8+ T cell activation (Spearman's rho, P = 6 × 10-8). A CMV-specific IFN-γ response was also associated with increased risk of developing TB disease (conditional logistic regression; P = 0.043; OR, 2.2; 95% CI, 1.02-4.83) and shorter time to TB diagnosis (Log Rank Mantel-Cox, P = 0.037). CMV+ infants who developed TB disease had lower expression of NK cell-associated gene signatures and a lower frequency of CD3-CD4-CD8- lymphocytes. We identified transcriptional signatures predictive of TB disease risk among CMV ELISpot-positive (area under the receiver operating characteristic [AUROC], 0.98, accuracy, 92.57%) and -negative (AUROC, 0.9; accuracy, 79.3%) infants; the CMV- signature was validated in an independent infant study (AUROC, 0.71; accuracy, 63.9%). A 16-gene signature that previously identified adolescents at risk of developing TB disease did not accurately classify case and control infants in this study. Understanding the microbial drivers of T cell activation, such as CMV, could guide new strategies for prevention of TB disease in infants.

Integrating prevention of mother-to-child HIV transmission into antenatal care: learning from the experiences of women in South Africa

In 1999, for the first time in South Africa, a Mother-to-Child HIV Transmission (MTCT) prevention programme was implemented at the routine primary care level and not as part of a research protocol. A total of 264 women attending prenatal care in these clinics were interviewed in Xhosa using a standardized questionnaire. All had been offered HIV testing, and 95% had accepted. Women who had not been tested were four times more likely to believe that in the community families reject HIV-positive women (p<0.005). Of women who tested, 19% were HIV positive and 83% had told their partner that they had taken the test. HIV-positive women who had not disclosed testing to their partners were three times more likely to believe that, in the community, partners are violent towards HIV-positive women (p<0.005); 86% stated that they would have taken AZT if found to be HIV positive. Only 11% considered that the use of formula feeding indicated that a woman was HIV positive. In conclusion, routine prenatal HIV testing and interventions to reduce perinatal HIV transmission are acceptable to the majority of women in a South African urban township, despite an awareness of discrimination in the community towards HIV-positive women.

Pyridoxal-5-phosphate plasma concentrations in children receiving tuberculosis chemotherapy including isoniazid

AIM

Little is known about pyridoxine nutriture of children treated with isoniazid (INH) regimens. This study documents plasma pyridoxal 5'-phosphate (PLP) concentrations in children, HIV-infected and HIV-uninfected, receiving INH regimens.

METHODS

Children from the Western Cape of South Africa hospitalized for tuberculosis (TB) management were studied. Plasma PLP concentrations were determined on enrolment, 1-month after commencing TB treatment, and again after 4-month's treatment. The children received a supplement meeting pyridoxine requirements.

RESULTS

Nineteen HIV-infected and 33 HIV-uninfected children received INH (dosage range 4-20 mg/kg) daily. Mean PLP plasma concentrations on enrolment were 8.32 (SD 6.75) ng/mL and 11.28 (SD 3.02) ng/mL in HIV-infected and HIV-uninfected children, respectively (p = 0.11) and after 4-month's treatment 6.75 (SD 2.71) ng/mL and 14.76 (SD 7.96) ng/mL (p < 0.001). On enrolment 9 (50%) HIV-infected and 5 (15%) HIV-uninfected children (p = 0.016) had suboptimal PLP concentrations (<6 ng/mL); after 4-month's treatment 8 (42%) and 2 (6%) (p = 0.004).

CONCLUSION

Plasma PLP concentrations in children treated for TB were low on enrolment in HIV-infected and HIV-uninfected children; after 4-month's treatment low values were still common in HIV-infected children. Additional pyridoxine supplementation of malnourished children treated for tuberculosis is advisable, particularly those HIV-infected.