Risk of Disease After Isoniazid Preventive Therapy for Mycobacterium tuberculosis Exposure in Young HIV-uninfected Children.

BACKGROUND: The risk of developing tuberculosis (TB) disease in HIV-uninfected children after isoniazid preventive therapy (IPT) for a positive QuantiFERON-TB Gold In-Tube test (QFT-GIT) is unknown. The aim of this study was to evaluate risk of TB disease after IPT in young HIV-uninfected children with a positive QFT-GIT result, or household TB contact. METHODS: HIV-uninfected South African infants aged 4-6 months were screened for enrolment in a TB vaccine trial. Baseline household TB contact and positive QFT-GIT result were exclusion criteria, and these infants were referred for IPT. Outcome data are reported for 36 months after IPT referral. RESULTS: Four thousand seven hundred forty-nine infants were screened. Household TB contact was reported in 131 (2.8%) infants; 279 (6.0%) were QFT-GIT positive, and 138 of these 410 infants (34.0%) started IPT. Forty-four cases of TB disease (11.0%) were recorded within 991 child years of observation. TB disease incidence was 4.8 versus 3.6 per 100 child years in household exposed versus QFT-GIT-positive children [incidence rate ratio: 1.35; 95% confidence interval (CI): 0.67-2.88] and 2.4 versus 5.5 per 100 child years in children who received versus did not receive IPT, respectively (incidence rate ratio: 0.44; 95% CI: 0.17-0.96). Adjusted hazard ratio (Cox regression) for TB disease was 0.48 (95% CI: 0.21-1.05) for those who received IPT. CONCLUSION: In young HIV-uninfected children, the effect of IPT on risk of TB disease is similar, whether TB exposure was defined by household contact history or by positive QFT-GIT result. International IPT guidelines for HIV-uninfected children with a positive QFT-GIT result should be updated.

The Role of Clinical Symptoms in the Diagnosis of Intrathoracic Tuberculosis in Young Children.

BACKGROUND: Childhood tuberculosis (TB) is usually Mycobacterium tuberculosis (MTB) culture negative. Furthermore, clinical presentation may be altered by active case finding, isoniazid prophylaxis and early treatment. We aimed to establish the value of presenting symptoms for intrathoracic TB case diagnosis among young children. METHODS: Healthy, HIV-uninfected, South African infants in an efficacy trial of a novel TB vaccine (MVA85A) were followed for 2 years for suspected TB. When suspected, investigation followed a standardized algorithm comprising symptom history, QuantiFERON Gold-in-Tube, chest radiography (CXR), MTB culture and Xpert MTB/RIF from paired gastric lavage and induced sputa. Adjusted odds ratios and 95% confidence intervals describe the associations between symptoms and positive MTB culture or Xpert MTB/RIF, and CXR compatible with intrathoracic TB. RESULTS: Persistent cough was present in 172/1017 (16.9%) of the children investigated for TB. MTB culture/Xpert MTB/RIF was positive in 38/1017 children (3.7%); and CXR was positive, that is, compatible with intrathoracic TB, in 131/1017 children (12.9%). Children with persistent cough had more than triple the odds of a positive MTB culture/Xpert MTB/RIF (adjusted odds ratios: 3.3, 95% confidence interval: 1.5-7.0) and positive CXR (adjusted odds ratios: 3.5, 95% confidence interval: 2.2-5.5). Persistent cough was the only symptom that differentiated children with severe (56.5%) from nonsevere intrathoracic TB disease (28.2%; P = 0.001). CONCLUSION: Persistent cough was the cardinal diagnostic symptom associated with microbiologic and radiologic evidence, and disease severity, of intrathoracic TB. Symptom-based definitions of TB disease for diagnostic, preventive and therapeutic studies should prioritize persistent cough above other symptoms compatible with childhood TB.

First-in-human trial of the post-exposure tuberculosis vaccine H56:IC31 in Mycobacterium tuberculosis infected and non-infected healthy adults.

BACKGROUND: H56:IC31 is a candidate tuberculosis vaccine comprising a fusion protein of Ag85B, ESAT-6 and Rv2660c, formulated in IC31 adjuvant. This first-in-human, open label phase I trial assessed the safety and immunogenicity of H56:IC31 in healthy adults without or with Mycobacterium tuberculosis (M.tb) infection. METHODS: Low dose (15 µg H56 protein in 500 nmol IC31) or high dose (50 µg H56, 500 nmol IC31) vaccine was administered intramuscularly thrice, at 56-day intervals. Antigen-specific T cell responses were measured by intracellular cytokine staining and antibody responses by ELISA. RESULTS: One hundred and twenty-six subjects were screened and 25 enrolled and vaccinated. No serious adverse events were reported. Nine subjects (36%) presented with transient cardiovascular adverse events. The H56:IC31 vaccine induced antigen-specific IgG responses and Th1 cytokine-expressing CD4(+) T cells. M.tb-infected vaccinees had higher frequencies of H56-induced CD4(+) T cells than uninfected vaccinees. Low dose vaccination induced more polyfunctional (IFN-γ(+)TNF-α(+)IL-2(+)) and higher frequencies of H56-specific CD4(+) T cells compared with high dose vaccination. A striking increase in IFN-γ-only-expressing CD4(+) T cells, displaying a CD45RA(-)CCR7(-) effector memory phenotype, emerged after the second high-dose vaccination in M.tb-infected vaccinees. TNF-α(+)IL-2(+) H56-specific memory CD4(+) T cells were detected mostly after low-dose H56 vaccination in M.tb-infected vaccinees, and predominantly expressed a CD45RA(-)CCR7(+) central memory phenotype. Our results support further clinical testing of H56:IC31.

A randomized clinical trial in adults and newborns in South Africa to compare the safety and immunogenicity of bacille Calmette-Guérin (BCG) vaccine administration via a disposable-syringe jet injector to conventional technique with needle and syringe.

INTRODUCTION: Intradermal bacille Calmette-Guérin (BCG) vaccination by needle-free, disposable-syringe jet injectors (DSJI) is an alternative to the Mantoux method using needle and syringe (NS). We compared the safety and immunogenicity of BCG administration via the DSJI and NS techniques in adults and newborn infants at the South African Tuberculosis Vaccine Initiative (SATVI) research site in South Africa. METHOD: Thirty adults and 66 newborn infants were randomized 1:1 to receive intradermal BCG vaccine (0.1 mL in adults; 0.05 mL in infants) via DSJI or NS. Wheal diameter (mm) and skin fluid deposition at the site of injection (SOI) were measured immediately post-vaccination. Adverse events and SOI reactogenicity data were collected 30 min and 1, 2, 4, and 12 weeks after vaccination for adults and at 30 min and 4, 10, and 14 weeks for infants. Blood was collected in infants at 10 and 14 weeks to assess BCG-specific T-cell immune responses. RESULTS: More infant BCG vaccinations by DSJI deposited >5 µL fluid on the skin surface, compared to NS (49% versus 9%, p=0.001). However, all 12 infant vaccinations that did not produce any SOI wheal occurred in the NS group (36%, p<0.001). Median wheal diameter, in participants for which an SOI wheal formed, did not differ significantly between groups in infants (combined 3.0mm IQR 2.0 to 4.0, p=0.59) or in adults (combined 9.0mm IQR 7.0 to 10.0, p=0.13). Adverse events were similar between study arms. Proportion of participants with BCG scars after three months did not differ in adults (combined 97%, p=0.67) or infants (combined 62%, p=0.13). Frequencies of BCG-specific clusters of differentiation 4 (CD4) and clusters of differentiation 8 (CD8) T-cells co-expressing IFN-γ, TNF-α, IL-2, and/or IL-17 were not different in the DSJI and NS groups. CONCLUSION: BCG vaccination of newborn infants via DSJI was more likely to deliver an appropriate intradermal wheal at the SOI as compared to NS, despite leaving more fluid on the surface of the skin. Safety, reactogenicity, and antigen-specific T-cell immune responses did not differ between DSJI and NS techniques.

The novel tuberculosis vaccine, AERAS-402, is safe in healthy infants previously vaccinated with BCG, and induces dose-dependent CD4 and CD8T cell responses.

BACKGROUND: Efforts to reduce risk of tuberculosis disease in children include development of effective vaccines. Our aim was to test safety and immunogenicity of the new adenovirus 35-vectored tuberculosis vaccine candidate AERAS-402 in infants, administered as a boost following a prime with the Bacille Calmette-Guerin vaccine. METHODS: In a phase 1 randomised, double-blind, placebo-controlled, dose-escalation trial, BCG-vaccinated infants aged 6-9 months were sequentially assigned to four study groups, then randomized to receive an increasing dose-strength of AERAS-402, or placebo. The highest dose group received a second dose of vaccine or placebo 56 days after the first. The primary study outcome was safety. Whole blood intracellular cytokine staining assessed immunogenicity. RESULTS: Forty-two infants received AERAS-402 and 15 infants received placebo. During follow-up of 182 days, an acceptable safety profile was shown with no serious adverse events or discontinuations related to the vaccine. AERAS-402 induced a specific T cell response. A single dose of AERAS-402 induced CD4T cells predominantly expressing single IFN-γ whereas two doses induced CD4T cells predominantly expressing IFN-γ, TNF-α and IL-2 together. CD8T cells were induced and were more likely to be present after 2 doses of AERAS-402. CONCLUSIONS: AERAS-402 was safe and immunogenic in healthy infants previously vaccinated with BCG at birth. Administration of the highest dose twice may be the most optimal vaccination strategy, based on the induced immunity. Multiple differences in T cell responses when infants are compared with adults vaccinated with AERAS-402, in the same setting and using the same whole blood intracellular cytokine assay, suggest specific strategies may be important for vaccination for each population.

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

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 4­6 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 19·2­28·1), 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).