The African Vaccine-Preventable Diseases Network: a vaccine advocacy initiative

Achieving high and equitable childhood immunisation coverage in Africa will not only protect children from disability and premature death, it will also boost productivity, reduce poverty and support the economic growth of the continent. Thus, Africa needs innovative and sustainable vaccine advocacy initiatives. One such initiative is the African Vaccine-Preventable Diseases Network, formed in 2009. This association of immunisation practitioners, vaccinologists, paediatricians, and infectious disease experts provides a platform to advocate for the introduction of newly available vaccines (e.g. 10-valent and 13-valent pneumococcal conjugate and rotavirus vaccines) into the Expanded Programme on Immunisation (EPI) as well as increased and equitable coverage for established EPI vaccines.

Predictive factors for latent tuberculosis infection among adolescents in a high-burden area in South Africa

SETTING

A high tuberculosis (TB) burden area in South Africa (notification rate for all TB cases 1400 per 100 000 population).

OBJECTIVE

To determine the prevalence of and predictive factors associated with latent TB infection in adolescents.

DESIGN

Adolescents aged 12-18 years were recruited from high schools, clinical and demographic data were collected, and a tuberculin skin test (TST) and a QuantiFERON®-TB Gold In-Tube (QFT) assay performed.

RESULTS

A total of 6363 (58.2%) of 10 942 adolescents at the schools were enrolled. After exclusions, of 5244 participants, 55.2% (95%CI 53.8-56.5) had TST ≥ 5 mm, while 50.9% (49.5-52.2) were QFT-positive. On multivariate analysis, Black/mixed race racial groups, male sex, older age, household TB contact, low income and low education level were predictive factors for both TST- and QFT-positive results.

CONCLUSION

About half of the adolescents were found to be latently infected with TB in a high TB burden area with demographic and poverty-related socio-economic factors predicting the risk of TB infection. Adolescents from deprived communities should be considered an important target group for educational interventions by TB control programmes in high-burden settings.

Higher human CD4 T cell response to novel Mycobacterium tuberculosis latency associated antigens Rv2660 and Rv2659 in latent infection compared with tuberculosis disease

One third of the world's population is infected with Mycobacterium tuberculosis (M.tb). A vaccine that would prevent progression to TB disease will have a dramatic impact on the global TB burden. We propose that antigens of M.tb that are preferentially expressed during latent infection will be excellent candidates for post-exposure vaccination. We therefore assessed human T cell recognition of two such antigens, Rv2660 and Rv2659. Expression of these was shown to be associated with non-replicating persistence in vitro. After six days incubation of PBMC from persons with latent tuberculosis infection (LTBI) and tuberculosis (TB) disease, Rv2660 and Rv2659 induced IFN-γ production in a greater proportion of persons with LTBI, compared with TB diseased patients. Persons with LTBI also had increased numbers of viable T cells, and greater specific CD4(+) T cell proliferation and cytokine expression capacity. Persons with LTBI preferentially recognize Rv2659 and Rv2660, compared with patients with TB disease. These results suggest promise of these antigens for incorporation into post-exposure TB vaccines.

Review of rotavirus studies in Africa: 1976-2006

BACKGROUND

Rotavirus is a common cause of severe diarrheal disease in children worldwide. Ninety percent of the associated deaths occur in sub-Saharan Africa and South East Asia. Our aim was to review the prevalence of rotavirus infection in Africa over the past 30 years.

METHODS

Eligible studies were identified from 3 Medline searches. Only studies including children <5 years of age that included >50 children and had an observational period >3 months were included. The data were analyzed during 3 periods (1976-1985, 1986-1995, and 1996-2006), as a summary (1976-2006), and by different study settings (ie, hospital, outpatient department, and combined).

RESULTS

The initial search identified 206 studies from 27 countries during 1976-2006. The refined search yielded 101 studies, of which 58 (57%) were hospital based, 25 (25%) were outpatient studies, and 18 (18%) were combined. Rotavirus was detected in 25% (interquartile range, 16%-32%) of stool samples. Rotavirus was the most common agent identified in 73% of studies in which multiple diarrheal agents were determined.

CONCLUSION

Rotavirus is an important cause of severe diarrheal disease in children <5 years of age in Africa. Clinical trials in South Africa and Malawi have shown that severe rotavirus disease is a vaccine-preventable entity in Africa.

The novel tuberculosis vaccine, AERAS-402, induces robust and polyfunctional CD4+ and CD8+ T cells in adults

RATIONALE

AERAS-402 is a novel tuberculosis vaccine designed to boost immunity primed by bacillus Calmette-Guérin (BCG), the only licensed vaccine.

OBJECTIVES

We investigated the safety and immunogenicity of AERAS-402 in healthy Mycobacterium tuberculosis-uninfected BCG-vaccinated adults from a tuberculosis-endemic region of South Africa.

METHODS

Escalating doses of AERAS-402 vaccine were administered intramuscularly to each of three groups of healthy South African BCG-vaccinated adults, and a fourth group received two injections of the maximal dose. Participants were monitored for 6 months, with all adverse effects documented. Vaccine-induced CD4(+) and CD8(+) T-cell immunity was characterized by an intracellular cytokine staining assay of whole blood and peripheral blood mononuclear cells.

MEASUREMENTS AND MAIN RESULTS

AERAS-402 was well tolerated, and no vaccine-related serious adverse events were recorded. The vaccine induced a robust CD4(+) T-cell response dominated by cells coexpressing IFN-gamma, tumor necrosis factor-alpha, and IL-2 ("polyfunctional" cells). AERAS-402 also induced a potent CD8(+) T-cell response, characterized by cells expressing IFN-gamma and/or tumor necrosis factor-alpha, which persisted for the duration of the study.

CONCLUSIONS

Vaccination with AERAS-402 is safe and immunogenic in healthy adults. The immunity induced by the vaccine appears promising: polyfunctional T cells are thought to be important for protection against intracellular pathogens such as Mycobacterium tuberculosis, and evidence is accumulating that CD8(+) T cells are also important. AERAS-402 induced a robust and durable CD8(+) T-cell response, which appears extremely promising. Clinical trial registered with www.sanctr.gov.za (NHREC no. 1381).

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-gamma 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-gamma, TNF-alpha, IL-2, IL-17 and GM-CSF, were induced. Polyfunctional CD4+ T cells co-expressing IFN-gamma, TNF-alpha 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.

Delaying BCG vaccination from birth to 10 weeks of age may result in an enhanced memory CD4 T cell response

BACKGROUND

In most tuberculosis (TB) endemic countries, bacillus Calmette-Guérin (BCG) is usually given around birth to prevent severe TB in infants. The neonatal immune system is immature. Our hypothesis was that delaying BCG vaccination from birth to 10 weeks of age would enhance the vaccine-induced immune response.

METHODS

In a randomized clinical trial, BCG was administered intradermally either at birth (n=25) or at 10 weeks of age (n=21). Ten weeks after vaccination, and at 1 year of age, vaccine-specific CD4 and CD8 T cell responses were measured with a whole blood intracellular cytokine assay.

RESULTS

Infants who received delayed BCG vaccination demonstrated higher frequencies of BCG-specific CD4 T cells, particularly polyfunctional T cells co-expressing IFN-gamma, TNF-alpha and IL-2, and most strikingly at 1 year of age.

CONCLUSIONS

Delaying BCG vaccination from birth to 10 weeks of age enhances the quantitative and qualitative BCG-specific T cell response, when measured at 1 year of age.

HIV-1 infection in infants severely impairs the immune response induced by Bacille Calmette-Guérin vaccine

BACKGROUND

Worldwide, most infants born to mothers infected with human immunodeficiency virus (HIV) receive bacille Calmette-Guérin (BCG) vaccine. Tuberculosis is a major cause of death among infants infected with HIV in sub-Saharan Africa, and it should be prevented. However, BCG may itself cause disease (known as "BCGosis") in these infants. Information regarding the immunogenicity of BCG is imperative for the risk/benefit assessment of BCG vaccination in HIV-infected infants; however, no such data exist.

METHODS

We compared BCG-induced CD4 and CD8 T cell responses, as assessed by flow cytometry, in HIV-infected (n=20), HIV-exposed but uninfected (n=25), and HIV-unexposed (n=23) infants, during their first year of life.

RESULTS

BCG vaccination of the 2 HIV-uninfected groups induced a robust response, which was characterized by CD4 T cells expressing interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha, and/or interleukin (IL)-2. In contrast, HIV-infected infants demonstrated a markedly lower response throughout the first year of life. These infants also had significantly reduced numbers of polyfunctional CD4 T cells coexpressing IFN-gamma, TNF-alpha, and IL-2, a finding that is thought to indicate T cell quality.

CONCLUSIONS

Infection with HIV severely impairs the BCG-specific T cell response during the first year of life. BCG may therefore provide little, if any, vaccine-induced benefit in HIV-infected infants. Considering the significant risk of BCGosis, these data strongly support not giving BCG to HIV-infected infants.

Rifampin pharmacokinetics in children, with and without human immunodeficiency virus infection, hospitalized for the management of severe forms of tuberculosis

BACKGROUND

Rifampin is a key drug in antituberculosis chemotherapy because it rapidly kills the majority of bacilli in tuberculosis lesions, prevents relapse and thus enables 6-month short-course chemotherapy. Little is known about the pharmacokinetics of rifampin in children. The objective of this study was to evaluate the pharmacokinetics of rifampin in children with tuberculosis, both human immunodeficiency virus type-1-infected and human immunodeficiency virus-uninfected.

METHODS

Fifty-four children, 21 human immunodeficiency virus-infected and 33 human immunodeficiency virus-uninfected, mean ages 3.73 and 4.05 years (P = 0.68), respectively, admitted to a tuberculosis hospital in Cape Town, South Africa with severe forms of tuberculosis were studied approximately 1 month and 4 months after commencing antituberculosis treatment. Blood specimens for analysis were drawn in the morning, 45 minutes, 1.5, 3.0, 4.0 and 6.0 hours after dosing. Rifampin concentrations were determined by liquid chromatography tandem mass spectrometry. For two sample comparisons of means, the Welch version of the t-test was used; associations between variables were examined by Pearson correlation and by multiple linear regression.

RESULTS

The children received a mean rifampin dosage of 9.61 mg/kg (6.47 to 15.58) body weight at 1 month and 9.63 mg/kg (4.63 to 17.8) at 4 months after commencing treatment administered as part of a fixed-dose formulation designed for paediatric use. The mean rifampin area under the curve 0 to 6 hours after dosing was 14.9 and 18.1 microg/hour/ml (P = 0.25) 1 month after starting treatment in human immunodeficiency virus-infected and human immunodeficiency virus-uninfected children, respectively, and 16.52 and 17.94 microg/hour/ml (P = 0.59) after 4 months of treatment. The mean calculated 2-hour rifampin concentrations in these human immunodeficiency virus-infected and human immunodeficiency virus-uninfected children were 3.9 and 4.8 microg/ml (P = 0.20) at 1 month after the start of treatment and 4.0 and 4.6 microg/ml (P = 0.33) after 4 months of treatment. These values are considerably less than the suggested lower limit for 2-hour rifampin concentrations in adults of 8.0 microg/ml and even 4 microg/ml

CONCLUSION

Both human immunodeficiency virus-infected and human immunodeficiency virus-uninfected children with tuberculosis have very low rifampin serum concentrations after receiving standard rifampin dosages similar to those used in adults. Pharmacokinetic studies of higher dosages of rifampin are urgently needed in children to assist in placing the dosage of rifampin used in childhood on a more scientific foundation.

Consensus statement on the revised World Health Organization recommendations for BCG vaccination in HIV-infected infants

This document outlines the consensus agreement from the Union's BCG Working Group regarding BCG vaccination in HIV-infected infants, in response to recently revised World Health Organization (WHO) guidelines, which make HIV infection in infants a full contraindication to bacille Calmette-Guérin (BCG) vaccination. BCG is one of the most widely given vaccines globally and is safe in immunocompetent individuals. Recent evidence shows that HIV-infected infants who were routinely vaccinated with BCG at birth, when asymptomatic, and who later developed AIDS, are at high risk of developing disseminated BCG disease (estimated incidence 407-1300 per 100 000). The document outlines requirements to implement selective BCG vaccination strategies in infants born to HIV-infected women and strategies to reduce the risk of vertical HIV transmission and disseminated BCG disease in infants.

Safety and immunogenicity of a new tuberculosis vaccine, MVA85A, in healthy adults in South Africa

BACKGROUND

The efficacy of bacille Calmette-Guérin (BCG) may be enhanced by heterologous vaccination strategies that boost the BCG-primed immune response. One leading booster vaccine, MVA85A (where "MVA" denotes "modified vaccinia virus Ankara"), has shown promising safety and immunogenicity in human trials performed in the United Kingdom. We investigated the safety and immunogenicity of MVA85A in mycobacteria-exposed--but Mycobacterium tuberculosis-uninfected--healthy adults from a region of South Africa where TB is endemic.

METHODS

Twenty-four adults were vaccinated with MVA85A. All subjects were monitored for 1 year for adverse events and for immunological assessment.

RESULTS

MVA85A vaccination was well tolerated and induced potent T cell responses, as measured by interferon (IFN)-gamma enzyme-linked immunospot assay, which exceeded prevaccination responses up to 364 days after vaccination. BCG-specific CD4+ T cells boosted by MVA85A were comprised of multiple populations expressing combinations of IFN-gamma, tumor necrosis factor (TNF)-alpha, interleukin (IL)-2, and IL-17, as measured by polychromatic flow cytometry. IFN-gamma-expressing and polyfunctional IFN-gamma+TNF-gamma+IL-2+ CD4+ T cells were boosted during the peak BCG-specific response, which occurred 7 days after vaccination.

CONCLUSION

The excellent safety profile and quantitative and qualitative immunogenicity data strongly support further trials assessing the efficacy of MVA85A as a boosting vaccine in countries where TB is endemic.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT00460590.

Significantly skewed memory CD8+ T cell subsets in HIV-1 infected infants during the first year of life

HIV-1 infection causes a severe T cell compromise; however, little is known about changes in naive, memory, effector and senescent T cell subsets during the first year of life. T cell subsets were studied over the first year of life in blood from 3 infant cohorts: untreated HIV-infected, HIV-exposed but uninfected, and HIV-unexposed. In HIV-infected infants, the frequency of CCR7(+)CD45RA(+) naive CD8(+) T cells was significantly decreased, while the frequency of CCR7(-)CD45RA(-) effector memory CD8(+) T cells was increased, compared with the control cohorts. A larger population of CD8(+) T cells in HIV-infected infants displayed a phenotype consistent with senescence. Differences in CD4(+) T cell subset frequencies were less pronounced, and no significant differences were observed between exposed and unexposed HIV-uninfected infants. We concluded that the proportion of naive, memory, effector and senescent CD8(+) T cells during the first year of life is significantly altered by HIV-1 infection.

Bacillus Calmette-Guérin (BCG) vaccine-induced complications in children treated with highly active antiretroviral therapy

OBJECTIVE

To describe the frequency, risk factors, and clinical features of bacillus Calmette-Guérin (BCG) complications in HIV-infected children treated with highly active antiretroviral therapy (HAART).

METHODS

A retrospective study of children started on HAART between August 2002 and November 2004 was completed.

RESULTS

Six percent (21/352; 95% CI 3.7-8.0%) developed BCG complications. All developed ipsilateral axillary lymphadenitis; one child had suspected disseminated BCG infection. There were 14 females; median age at start of HAART was 5 months. BCG disease developed a median of 34 days after starting HAART. At baseline and 6 months into HAART, the median CD4 percentage and log(10) viral load were 12.3/6.1 and 23.9/4.5, respectively. Seventeen (81%) of the patients were treated with either zidovudine or stavudine combined with lamivudine and ritonavir. Young age and high baseline viral load were independent risk factors for development of BCG complications. Mycobacterium bovis BCG was isolated in 70% of patients who underwent incision and drainage of abscesses at the vaccination site or regional lymph nodes.

CONCLUSIONS

This study identified a high prevalence of BCG complications in children on HAART. A clinical case definition of BCG immune reconstitution syndrome independent of laboratory parameters for use in resource-limited settings should be developed.

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-gamma, IL-2, and TNF-alpha 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-gamma and/or IL-2 and less TNF-alpha, IL-4, and IL-10. Importantly, many mycobacteria-specific CD4+ and CD8+ T cells did not produce IFN-gamma. 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-gamma+. We concluded that neonatal vaccination with BCG induces T cells with a complex pattern of cytokine expression and phenotypes. Measuring IFN-gamma 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.

Distinct, specific IL-17- and IL-22-producing CD4+ T cell subsets contribute to the human anti-mycobacterial immune response

We investigated whether the proinflammatory T cell cytokines IL-17 and IL-22 are induced by human mycobacterial infection. Remarkably, >20% of specific cytokine-producing CD4(+) T cells in peripheral blood of healthy, mycobacteria-exposed adults expressed IL-17 or IL-22. Specific IL-17- and IL-22-producing CD4(+) T cells were distinct from each other and from Th1 cytokine-producing cells. These cells had phenotypic characteristics of long-lived central memory cells. In patients with tuberculosis disease, peripheral blood frequencies of these cells were reduced, whereas bronchoalveolar lavage fluid contained higher levels of IL-22 protein compared with healthy controls. IL-17 was not detected in this fluid, which may be due to suppression by Th1 cytokines, as PBMC IL-17 production was inhibited by IFN-gamma in vitro. However, Th1 cytokines had no effect on IL-22 production in vitro. Our results imply that the magnitude and complexity of the anti-mycobacterial immune response have historically been underestimated. IL-17- and IL-22-producing CD4(+) T cells may play important roles in the human immune response to mycobacteria.

Culture-confirmed childhood tuberculosis in Cape Town, South Africa: a review of 596 cases

BACKGROUND

The clinical, radiological and microbiological features of culture-confirmed childhood tuberculosis diagnosed at two referral hospitals are described.

METHODS

Cultures of Mycobacterium tuberculosis from children less than 13 years of age at Tygerberg and Red Cross Children's Hospitals, Cape Town, South Africa, were collected from March 2003 through February 2005. Folder review and chest radiography were performed and drug susceptibility tests done.

RESULTS

Of 596 children (median age 31 months), 330 (55.4%) were males. Of all children, 281 (47.1%) were HIV-uninfected, 133 (22.3%) HIV-infected and 182 (30.5%) not tested. Contact with infectious tuberculosis adults was recorded in 295 (49.5%) children. Missed opportunities for chemoprophylaxis were present in 117/182 (64.3%) children less than 5 years of age. Extrathoracic TB was less common in HIV-infected than in HIV-uninfected children (49/133 vs. 156/281; odds ratio 0.50, 95% confidence interval 0.32-0.78). Alveolar opacification (84/126 vs. 128/274; OR 1.85, 95%CI 1.08-3.19) and cavitation (33/126 vs. 44/274; OR 2.28, 95%CI 1.44-3.63) were more common in HIV-infected than in HIV-uninfected children. Microscopy for acid-fast bacilli on gastric aspirates and sputum was positive in 29/142 (20.4%) and 40/125 (32.0%) children, respectively. Sixty-seven of 592 (11.3%) children's isolates showed resistance to isoniazid and/or rifampicin; 43 (7.3%) were isoniazid-monoresistant, 2 (0.3%) rifampicin-monoresistant and 22 (3.7%) multidrug-resistant. Death in 41 children (6.9%) was more common in HIV-infected children and very young infants.

CONCLUSION

HIV infection and missed opportunities for chemoprophylaxis were common in children with culture-confirmed TB. With cavitating disease and sputum or gastric aspirates positive for acid-fast bacilli, children may be infectious. Transmission of drug-resistant TB is high in this setting.

Determining causes of mortality in children enrolled in a vaccine field trial in a rural area in the Western Cape Province of South Africa

AIM

A mortality surveillance system was developed to identify and document causes of death among children enrolled in a tuberculosis vaccine field trial in South Africa. The aims of this study were to describe causes of mortality in children enrolled in a phase IV trial comparing intradermal with percutaneous administration of Bacille Calmette Guerin, and to compare causes of mortality recorded on death certificates with those obtained by clinical record review combined with verbal autopsies (CR/VA).

METHODS

For children who died, certified causes of death were compared with those determined by CR/VA.

RESULTS

Among 11677 children enrolled, 177 deaths were notified over 4 years. The incidence rate of death was 6.8/1000 person-years. Follow-up time ranged from 0.03 to 35.3 months (median 4 months; interquartile range 1.4-8.5). The infant mortality rate was 12.5/1000 live births and the neonatal mortality was 3/1000 live births. Pneumonia, gastroenteritis and septicaemia were among top causes of mortality by both methods. 'Sudden unexplained' and 'ill-defined' causes were among top causes of mortality based on CR/VA, while tuberculosis and 'natural causes' were among top causes based on death certificates. Important underlying causes of mortality by CR/VA include HIV/AIDS, prematurity/low birth weight and malnutrition. In 47% of deaths there was agreement on immediate causes of death. This increased to 54% when 'natural causes' and 'sudden unexplained deaths' were included.

CONCLUSION

In this cohort mortality was largely due to infectious diseases. While CR/VA provided additional information on most deaths, this was not always sufficient to assign specific causes of death.

Bacillus Calmette Guerin vaccination of human newborns induces a specific, functional CD8+ T cell response

Mounting evidence points to CD8+ T cells playing an important role in protective immunity against Mycobacterium tuberculosis. The only available vaccine against tuberculosis, bacillus Calmette Guérin (BCG), has traditionally been viewed not to induce these cells optimally. In this study, we show that vaccination of human newborns with BCG does indeed induce a specific CD8+ T cell response. These cells degranulated or secreted IFN-gamma, but not both, when infant blood was incubated with BCG. This stimulation also resulted in proliferation and up-regulation of cytotoxic molecules. Overall, the specific CD8+ T cell response was quantitatively smaller than the BCG-induced CD4+ T cell response. Incubation of whole blood with M. tuberculosis also caused CD8+ T cell IFN-gamma expression. We conclude that BCG induces a robust CD8+ T cell response, which may contribute to vaccination-induced protection against tuberculosis.

The impact of a change in bacille Calmette-Guérin vaccine policy on tuberculosis incidence in children in Cape Town, South Africa

BACKGROUND

A decision by the South African National Department of Health to change the route of administration and strain of bacille Calmette-Guérin (BCG) vaccine was implemented in Cape Town, South Africa, between July and December 2000. This provided an opportunity to compare the incidence of tuberculosis and proportion with disseminated disease in children less than 2 years old before and after the changeover from percutaneous (PC) Tokyo 172 BCG to intradermal (ID) 1331 Danish BCG immunization.

METHODS

Clinical records of all tuberculosis patients aged less than 2 years at diagnosis and born between January 1, 1999, and June 30, 2000 (PC cohort) and between January 1, 2001, and June 30, 2002 (ID cohort) were collected. All cases were reviewed for likelihood of TB, its severity and disease dissemination.

RESULTS

The number of reported patients with tuberculosis in the PC cohort was 1369 and in the ID cohort 1397, giving incidence rates of 866 (95% confidence interval [CI], 821-913) and 858 (95% CI, 814-904) per 100,000 person-years, respectively. The proportion who had disseminated disease (meningitis and/or miliary spread) was significantly lower in the ID cohort (4.7%) than in the PC cohort (8.6%) (relative risk, 0.54; 95% CI, 0.40-0.72). Those not vaccinated had a significantly higher proportion of disseminated disease cases (29.2%) than the PC and ID groups combined (6.6%) (relative risk, 4.4; 95% CI, 2.7-6.7).

CONCLUSION

A program using Danish 1331 BCG given intradermally did not prevent more tuberculosis cases in children overall as compared with a program using Tokyo 172 BCG given percutaneously but reduced the proportion with disseminated disease.

Comparison of mantoux skin test with three generations of a whole blood IFN-gamma assay for tuberculosis infection

SETTING

A rural town in South Africa.

OBJECTIVE

To compare the performance of Quanti-FERON assays with the tuberculin skin test (TST) for identifying latent tuberculosis infection (LTBI) in a high TB burden community.

DESIGN

In a cross-sectional study in healthy adults, we applied the TST and took blood for the three generations of QuantiFERON assays.

RESULTS

Of 358 participants whose results were analysed, 291 (81%) had a TST result of > or = 10 mm induration, and 187 (52%) > or = 15 mm. QuantiFERON-TB was positive in 215 (60%), QuantiFERON-TB Gold in 137 (38%), and QuantiFERON-TB Gold (In-Tube method) in 201 (56%). There was poor agreement between TST and QuantiFERON tests, and between the different generations of QuantiFERON tests (kappa = 0.12-0.50). Of the subset with TST indurations > or = 15 mm, 30-56% had negative QuantiFERON tests. However, positive Quanti-FERON tests were associated with males, who have a higher incidence of TB in this area.

CONCLUSION

We showed poor agreement between TST and the different QuantiFERON tests in diagnosing LTBI. The surprising discordance between the Quanti-FERON TB Gold and QuantiFERON TB Gold (In-Tube method) tests needs to be investigated further.

The effect of bacille Calmette-Guérin vaccine strain and route of administration on induced immune responses in vaccinated infants

Vaccination with Mycobacterium bovis bacille Calmette-Guerin (BCG) has variable efficacy in preventing tuberculosis. Both BCG strain and route of administration have been implicated in determining efficacy; however, these variables are not considered in current clinical recommendations for vaccine choice. We evaluated antigen-specific immunity after percutaneous or intradermal administration of Japanese BCG or intradermal administration of Danish BCG. Ten weeks after vaccination of neonates, percutaneous Japanese BCG had induced significantly higher frequencies of BCG-specific interferon- gamma -producing CD4(+) and CD8(+) T cells in BCG-stimulated whole blood than did intradermal Danish BCG. Similarly, percutaneous vaccination with Japanese BCG resulted in significantly greater secretion of the T helper 1-type cytokines interferon- gamma, tumor necrosis factor- alpha , and interleukin-2; significantly lower secretion of the T helper 2-type cytokine interleukin-4; and greater CD4(+) and CD8(+) T cell proliferation. Thus, BCG strain and route of neonatal vaccination confer different levels of immune activation, which may affect the efficacy of the vaccine.

Outcome of HIV infected children with culture confirmed tuberculosis

BACKGROUND

Tuberculosis (TB) is an important disease in human immunodeficiency virus (HIV) infected children living in regions where TB is endemic. There are limited data on the outcome of culture confirmed TB in HIV infected children.

AIMS AND METHODS

To describe the outcome on TB therapy and overall mortality in HIV infected children with culture confirmed TB through a retrospective cohort study.

RESULTS

Eighty seven children, median age 24 months, contributed to 93 TB episodes; six children had two confirmed episodes. Pulmonary disease (PTB) was present in 71 episodes (76.3%), extrapulmonary disease (EPTB) in 43 (46.2%), and of these, both PTB and EPTB were present in 21 (22.6%). There was cure based on bacteriological and/or radiological criteria in 54 episodes (58.1%). Eighteen children died during TB therapy and there were a total of 34 deaths (39.1%). In univariate analysis (n = 87 patients), severe malnutrition, age < or =1 year, and a negative tuberculin skin test were significant risk factors for death during TB therapy. In multivariate survival analysis (n = 87 patients), HIV disease category, severe malnutrition at diagnosis, and lack of cure at the end of TB therapy were significantly associated with overall mortality.

CONCLUSION

In the absence of antiretroviral therapy, HIV infected children with confirmed TB have poor outcomes on antituberculosis therapy and are at high risk of death during and after completion of antituberculosis therapy, especially due to non-TB related causes. There is an urgent need to optimise and monitor antituberculosis therapy in HIV infected children and to improve access to TB and other preventative therapy.

Novel application of a whole blood intracellular cytokine detection assay to quantitate specific T-cell frequency in field studies

We optimized a whole blood intracellular cytokine assay to quantitate the frequency of specific CD4+ and CD8+ T cells in small volumes of whole blood from infants from developing countries. The assay is performed in two steps. First, whole blood is stimulated in the presence of specific antigens for 6-18 h, ending with cryopreservation of fixed white cells. These stimulation steps were specifically adapted to be practical and reliable in a rural, developing country field setting. Later, in a more resourceful setting, interferon-gamma producing CD4+ or CD8+ T cells are detected by flow cytometry. The assay proved sensitive and specific for detecting mycobacteria-specific immunity 10 weeks after Bacillus Calmette-Guerin (BCG) vaccination of newborns from a rural field site.