Human newborn bacille Calmette–Guérin vaccination and risk of tuberculosis disease: a case-control study

Fletcher et al. BMC Medicine (2016) 14:76 DOI 10.1186/s12916-016-0617-3 World TB Day RESEARCH ARTICLE Open Access Human newborn bacille Calmette–Guérin vaccination and risk of tuberculosis disease: a case-control study Helen A. Fletcher1†, Ali Filali-Mouhim2†, Elisa Nemes3†, Anthony Hawkridge3, Alana Keyser3, Samuel Njikan3, Mark Hatherill3, Thomas J. Scriba3, Brian Abel3, Benjamin M. Kagina3, Ashley Veldsman3, Nancy Marín Agudelo4, Gilla Kaplan5, Gregory D. Hussey3, Rafick-Pierre Sekaly2, Willem A. Hanekom3* and the BCG study team Abstract Background: An incomplete understanding of the immunological mechanisms underlying protection against tuberculosis (TB) hampers the development of new vaccines against TB. We aimed to define host correlates of prospective risk of TB disease following bacille Calmette–Guérin (BCG) vaccination. Methods: In this study, 5,726 infants vaccinated with BCG at birth were enrolled. Host responses in blood collected at 10 weeks of age were compared between infants who developed pulmonary TB disease during 2 years of follow-up (cases) and those who remained healthy (controls). Results: Comprehensive gene expression and cellular and soluble marker analysis failed to identify a correlate of risk. We showed that distinct host responses after BCG vaccination may be the reason: two major clusters of gene expression, with different myeloid and lymphoid activation and inflammatory patterns, were evident when all infants were examined together. Cases from each cluster demonstrated distinct patterns of gene expression, which were confirmed by cellular assays. Conclusions: Distinct patterns of host responses to Mycobacterium bovis BCG suggest that novel TB vaccines may also elicit distinct patterns of host responses. This diversity should be considered in future TB vaccine development. Keywords: Tuberculosis, Vaccine, Correlates of risk, Systems biology Background Newborn vaccination with bacille Calmette–Guérin (BCG) protects infants and young children against disseminated forms of tuberculosis (TB), and to some extent, against pulmonary TB [1]. As BCG’s protective efficacy in other age groups is variable and mostly poor [1], new vaccines against TB are needed. An incomplete understanding of immunological mechanisms underlying protection against TB hampers vaccine discovery and development. Our aim was to define host correlates of prospective risk of TB disease following BCG vaccination. We proposed that this knowledge would lead to greater * Correspondence: † Equal contributors 3 South African Tuberculosis Vaccine Initiative (SATVI), Institute of Infectious Disease and Molecular Medicine, Division of Immunology, Department of Pathology, University of Cape Town, Cape Town, South Africa Full list of author information is available at the end of the article insight into protective mechanisms against the disease, which, in turn, would inform vaccine development. We applied a systems biology approach to analyze unique prospective samples, and showed that in healthy infants who displayed different patterns of immune responses to the BCG vaccine, distinct mechanisms may underlie susceptibility to future TB disease, suggesting that the same intervention may not benefit all. Methods Study participants, blood collection and follow-up We enrolled infants at the South African Tuberculosis Vaccine Initiative (SATVI) field site, near Cape Town, South Africa. This area has a high TB disease incidence in children < 2 years of age (>1,000/100,000/year). This study was nested within a randomized controlled trial (RCT) [2], which aimed to determine whether intradermal © 2016 Fletcher et al. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Fletcher et al. BMC Medicine (2016) 14:76 or percutaneous delivery of Japanese BCG at birth resulted in equivalent protection against TB. For our correlates of risk study, we enrolled 5,724 infants, randomly, from the 11,680 infants enrolled in the RCT, when they were 10 weeks of age, as previously described [3] (Fig. 1). The following were exclusion criteria: mothers known to be HIV-infected, BCG not received within 24 h of birth, significant perinatal complications, any acute or chronic disease in the infant, clinically apparent anemia in the infant, and household contact of the infant with any person with TB, or any person who was coughing. Page 2 of 13 At 10 weeks of age, blood was collected. Infants were then followed for 2 years. Community-wide surveillance systems, described for the parent study [2], identified all children exposed to adults with TB, or children with suspected TB disease. These children were admitted to a dedicated case verification ward for evaluation [2]. Investigations included clinical and epidemiologic evaluation, two induced sputa and gastric aspirates for mycobacterial culture, chest roentgenography and a tuberculin skin test [2]. Cases included in the current study were either culture positive for Mycobacterium tuberculosis (primary analysis), Fig. 1 Cohort of infants vaccinated with BCG at birth. At 10 weeks of age, blood was collected from HIV-negative, HIV-unexposed infants with no active or chronic illnesses (including suspected TB), and with no household exposure to an adult who was coughing, or who had TB disease. Infants were then followed for 2 years. Community-wide surveillance systems identified all children exposed to adults with TB, or children with suspected TB disease. Among these children, “definite” TB cases were defined by presence of clinical signs and symptoms of lung disease plus a sputum (induced, or early morning gastric aspirate) culture positive for M. tuberculosis, while “probable” TB cases were defined by absence of a positive culture in the presence of strong epidemiological, clinical and chest roentgenographic evidence of TB disease. Two groups of controls were identified: “household” controls were exposed to an adult in the household with TB but were found not to have TB, whereas “community” controls were infants who were either investigated for TB and found not to have disease, or infants chosen at random from the rest of the cohort. For functional assays, up to 29 definite cases and 110 controls (household controls, n = 55, and community controls, n = 55) were included in different analyses. Primary analysis of transcriptional profiling was restricted to those cases and controls included in functional assay analysis for whom PBM (...truncated)