BCG and HIV reconsidered: moving the research agenda forward

Immunopathogenesis in HIV-associated pediatric tuberculosis

Tuberculosis (TB) is an increasing global emergency in human immunodeficiency virus/acquired immune deficiency syndrome (HIV/AIDS) patients, in which host immunity is dysregulated and compromised. However, the pathogenesis and efficacy of therapeutic strategies in HIV-associated TB in developing infants are essentially lacking. Bacillus Calmette-Guerin vaccine, an attenuated live strain of Mycobacterium bovis, is not adequately effective, which confers partial protection against Mycobacterium tuberculosis (Mtb) in infants when administered at birth. However, pediatric HIV infection is most devastating in the disease progression of TB. It remains challenging whether early antiretroviral therapy (ART) could maintain immune development and function, and restore Mtb-specific immune function in HIV-associated TB in children. A better understanding of the immunopathogenesis in HIV-associated pediatric Mtb infection is essential to provide more effective interventions, reducing the risk of morbidity and mortality in HIV-associated Mtb infection in infants. IMPACT: Children living with HIV are more likely prone to opportunistic infection, predisposing high risk of TB diseases. HIV and Mtb coinfection in infants may synergistically accelerate disease progression. Early ART may probably induce immune reconstitution inflammatory syndrome and TB pathology in HIV/Mtb coinfected infants.

Nonpathologic Infection of Macaques by an Attenuated Mycobacterial Vaccine Is Not Reactivated in the Setting of HIV Co-Infection

Failure to replace Bacille Calmette-Guerin vaccines with efficacious anti-tuberculosis (TB) vaccines have prompted outside-the-box thinking, including pulmonary vaccination to elicit local immunity. Inhalational MtbΔsigH, a stress-response-attenuated strain, protected against lethal TB in macaques. While live mycobacterial vaccines show promising efficacy, HIV co-infection and the resulting immunodeficiency prompts safety concerns about their use. We assessed the persistence and safety of MtbΔsigH, delivered directly to the lungs, in the setting of HIV co-infection. Macaques were aerosol-vaccinated with ΔsigH and subsequently challenged with SIVmac₂₃₉. Bronchoalveolar lavage and tissues were sampled for mycobacterial persistence, pathology, and immune correlates. Only 35% and 3.5% of lung samples were positive for live bacilli and granulomas, respectively. Our results therefore suggest that the nonpathologic infection of macaque lungs by ΔsigH was not reactivated by simian immunodeficiency virus, despite high viral levels and massive ablation of pulmonary CD4⁺ T cells. Protective pulmonary responses were retained, including vaccine-induced bronchus-associated lymphoid tissue and CD8⁺ effector memory T cells. Despite acute simian immunodeficiency virus infection, all animals remained asymptomatic of pulmonary TB. These findings highlight the efficacy of mucosal vaccination via this attenuated strain and will guide its further development to potentially combat TB in HIV-endemic areas. Our results also suggest that a lack of pulmonary pathology is a key correlate of the safety of live mycobacterial vaccines.

Investments in tuberculosis research - what are the gaps?

Through decades of research, numerous studies have generated robust evidence about effective interventions for tuberculosis control. Yet, the global annual decline in incidence of approximately 1 % is evidence that current approaches and investment strategies are not sufficient. In this article, we assess recent tuberculosis research funding and discuss two critical gaps in funding and in scientific evidence from topics that have been left off the research priority agenda.We first examine research and development funding goals in the 2011-2015 Global Plan to Stop Tuberculosis and analyze disbursements to different research areas by funders worldwide in 2014. We then summarize, through a compilation of published literature and consultation with 35 researchers across multiple disciplines in the London School of Hygiene and Tropical Medicine TB Centre, priorities identified by the tuberculosis research community. Finally, we compare researchers' priority areas to the global funding agendas and activities.Our analysis shows that, among the five key research areas defined in the 2011-2015 Global Plan - namely drugs, basic science, vaccines, diagnostics and operational research - drug discovery and basic science on Mycobacterium tuberculosis accounted for 60 % of the $2 billion annual funding target. None of the research areas received the recommended level of funding. Operational research, which had the lowest target, received 66 % of its target funding, whereas new diagnostics received only 19 %. Although many of the priority research questions identified by researchers fell within the Global Plan categories, our analysis highlights important areas that are not explicitly mentioned in the current plan. These priority research areas included improved understanding of tuberculosis transmission dynamics, the role of social protection and social determinants, and health systems and policy research.While research priorities are increasingly important in light of the limited funding for tuberculosis, there is a risk that we neglect important research areas and encourage the formation of research silos. To ensure that funding priorities, researchers' agendas and national tuberculosis control policies are better coordinated, there should be more, and wider, dialogue between stakeholders in high tuberculosis burden countries, researchers, international policymakers and funders.

The global tuberculosis situation and the inexorable rise of drug-resistant disease

The highly cost-effective DOTS strategy helped to bring the global tuberculosis (TB) epidemic under control in many parts of the world; however, the emergence and spread of drug-resistant strains pose a major threat to these gains. Molecular epidemiology studies, together with recent genomic evidence, provide proof that some drug-resistant strains are highly transmissible with documented epidemic spread. The potential for epidemic replacement of drug-susceptible with drug-resistant strains provides strong motivation for renewed emphasis on TB drug and vaccine development. It also reflects the need for enhanced infection control measures in health care and congregate settings, especially in TB endemic areas. The exploration of preventive therapy options for close contacts of patients with infectious drug-resistant TB also warrants further exploration, in an attempt to break the transmission cycle. Increased population mobility and large scale cross-border migration imply that the inexorable rise of drug-resistant TB is not geographically confined; it is a global concern that poses a very real threat to TB endemic and non-endemic settings. Failure to find new solutions will compromise traditional TB control efforts and derail momentum toward future TB elimination.

Immunogenicity of BCG in HIV-exposed and non-exposed infants following routine birth or delayed vaccination

BACKGROUND

Human immunodeficiency virus (HIV) exposed infants are at high risk of Mycobacterium tuberculosis exposure, have high rates of progression to tuberculosis (TB) disease and are at significant risk of bacille Calmette-Guérin (BCG) induced adverse events.

OBJECTIVE

To evaluate a delayed BCG vaccination strategy in HIV-exposed infants.

DESIGN

A randomised trial of routine BCG vaccination given at birth compared to 14 weeks of age in HIV-exposed non-infected and non-HIV-exposed infants to investigate longitudinal BCG-induced immune responses using a 7-day whole blood interferon-gamma (IFN-γ) enzyme-linked immunosorbent assay.

RESULTS

A significantly higher proportion of infants had positive responses to M. tuberculosis purified protein derivative (PPD) and BCG at 14 weeks in the birth vs. delayed vaccination groups (P = 0.001 for both). This difference was no longer apparent at weeks 24 or 52. Among infants vaccinated at birth, the 14-week IFN-γ response to M. tuberculosis PPD was lower among HIV-exposed than non-exposed infants (276.5 pg/ml vs. 790.2, P = 0.048). Among all infants, there were significant correlations between the magnitude of IFN-γ responses to BCG, M. tuberculosis PPD, TB 10.4 and culture filtrate protein 10/early secreted antigenic target 6.

CONCLUSIONS

The timing of vaccination had limited effect on BCG-induced IFN-γ responses, which waned considerably over 1 year despite initial vigorous responses in both vaccination groups. The lower responses in HIV-exposed non-infected infants suggest potentially altered mycobacterial immunity early in life.

Priming with a recombinant pantothenate auxotroph of Mycobacterium bovis BCG and boosting with MVA elicits HIV-1 Gag specific CD8+ T cells

A safe and effective HIV vaccine is required to significantly reduce the number of people becoming infected with HIV each year. In this study wild type Mycobacterium bovis BCG Pasteur and an attenuated pantothenate auxotroph strain (BCGΔpanCD) that is safe in SCID mice, have been compared as vaccine vectors for HIV-1 subtype C Gag. Genetically stable vaccines BCG[pHS400] (BCG-Gag) and BCGΔpanCD[pHS400] (BCGpan-Gag) were generated using the Pasteur strain of BCG, and a panothenate auxotroph of Pasteur respectively. Stability was achieved by the use of a codon optimised gag gene and deletion of the hsp60-lysA promoter-gene cassette from the episomal vector pCB119. In this vector expression of gag is driven by the mtrA promoter and the Gag protein is fused to the Mycobacterium tuberculosis 19 kDa signal sequence. Both BCG-Gag and BCGpan-Gag primed the immune system of BALB/c mice for a boost with a recombinant modified vaccinia virus Ankara expressing Gag (MVA-Gag). After the boost high frequencies of predominantly Gag-specific CD8(+) T cells were detected when BCGpan-Gag was the prime in contrast to induction of predominantly Gag-specific CD4(+) T cells when priming with BCG-Gag. The differing Gag-specific T-cell phenotype elicited by the prime-boost regimens may be related to the reduced inflammation observed with the pantothenate auxotroph strain compared to the parent strain. These features make BCGpan-Gag a more desirable HIV vaccine candidate than BCG-Gag. Although no Gag-specific cells could be detected after vaccination of BALB/c mice with either recombinant BCG vaccine alone, BCGpan-Gag protected mice against a surrogate vaccinia virus challenge.

Future vaccination strategies against tuberculosis: thinking outside the box

With almost a dozen vaccine candidates in clinical trials, tuberculosis (TB) research and development is finally reaping the first fruits of its labors. Vaccine candidates in clinical trials may prevent TB disease reactivation by efficiently containing the pathogen Mycobacterium tuberculosis (Mtb). Future research should target vaccines that achieve sterile eradication of Mtb or even prevent stable infection. These are ambitious goals that can be reached only by highly cooperative engagement of basic immunologists, vaccinologists, and clinical researchers--or in other words, by translation from basic immunology to vaccine research and development, as well as reverse translation of insights from clinical trials back to hypothesis-driven research in the basic laboratory. Here, we review current and future strategies toward the rational design of novel vaccines against TB, as well as the progress made thus far, and the hurdles that need to be overcome in the near and distant future.

Priorities for tuberculosis research: a systematic review

Reliable and relevant research can help to improve tuberculosis control worldwide. In recent years, various organisations have assessed research needs and proposed priorities for tuberculosis. We summarise existing priority statements and assess the rigour of the methods used to generate them. We found 33 documents that specifically outline priorities in tuberculosis research. The top priority areas were drug development (28 articles), diagnosis and diagnostic tests (27), epidemiology (20), health services research (16), basic research (13), and vaccine development and use (13). The most focused questions were on the treatment and prevention of multidrug-resistant tuberculosis in people co-infected with HIV. Methods used to identify these priorities were varied. Improvements can be made to ensure the process is more rigorous and transparent, and to use existing research or systematic reviews more often. WHO, Stop TB Partnership, and other organisations could adopt an incremental process of priority development, building on the existing knowledge base.

Scale-up of services and research priorities for diagnosis, management, and control of tuberculosis: a call to action

The Millennium Development Goal target for tuberculosis control is to halt the spread of tuberculosis by 2015, and begin to reverse the worldwide incidence. After the introduction of standard control practices in 1995, 36 million people were cured and about 6 million deaths were averted. However, substantial scientific advances and innovative solutions are urgently needed together with creative new strategies. Strong international and national political commitment is essential. Urgent action is needed by national governments to fund their own programmes, and for the G8 countries and other donor governments and organisations to support governmental and non-governmental efforts. To foster the global need for urgent action to control the tuberculosis epidemic, The Lancet, in collaboration with the Stop TB Partnership, WHO, Global Fund to Fight AIDS, Tuberculosis and Malaria, and the experts participating in this Series, is launching The Lancet TB Observatory, which will assess and monitor progress in tuberculosis control and research, assess domestic and global financing, regularly disseminate information, and advocate for intensified efforts with stakeholders at all levels.

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.

Novel vaccine prime and selective BCG boost: a new tuberculosis vaccine strategy for infants of HIV-infected mothers

Novel tuberculosis vaccination strategies hinge on BCG priming, yet newborn BCG vaccination may cause BCG disease in HIV-infected infants. Viral-vectored or subunit prime vaccine, followed by delayed BCG boost only for HIV-uninfected infants, may be a safe alternative for all newborns, regardless of maternal HIV infection. This approach should be tested using new tuberculosis vaccine candidates. If safety and immunogenicity of a novel vaccine prime is established in infants of HIV-infected mothers, for whom newborn BCG carries unacceptable risk, this strategy might then be compared to conventional BCG prime and viral-vectored or subunit boost, and BCG alone, in HIV-unexposed infants.

Randomized trials to study the nonspecific effects of vaccines in children in low-income countries

The Expanded Program on Immunization (EPI) has led to large reductions in morbidity and mortality among children in low-income countries. However, the basic EPI schedule may no longer be optimal because of changes in vaccines, programs, and epidemiologic circumstances. In addition, evidence has accumulated that some EPI vaccines may have nonspecific effects that increase or decrease mortality from subsequent infections with other unrelated organisms. There is therefore a need for randomized trials to evaluate the effects of alternative EPI schedules on all-cause mortality, as well as vaccine efficacy against the target diseases. We have reviewed the available literature on the nonspecific effects of vaccines on mortality, and compiled a list of potential trials that might address this issue. We have then ranked the trials based on the potential importance of the results and the ethical and practical considerations. Trials of early BCG vaccination in low-birth-weight babies, early measles vaccination, and altered timing of DTP vaccination all have a high priority.

Reduced rate of adverse reactions to the BCG vaccine in children exposed to the vertical transmission of HIV infection and in HIV-infected children from an endemic setting in Brazil

We report on the adverse reactions to the Bacillus Calmette-Guérin (BCG) vaccine in BCG-vaccinated children. We examined children exposed to the vertical transmission of human immunodeficiency virus (HIV) (n = 141), who participated in a prevention program of vertical transmission, and HIV-infected children (n = 66) in a setting endemic for HIV and tuberculosis (TB) in Brazil from August 2000 to February 2008. No cases of disseminated BCG disease occurred in either group of children. While no cases of regional BCG disease were noted in exposed/uninfected children, the rate of regional BCG disease in HIV-infected children was 4.5% (3/66); the three events occurred in <1-year-old children (3/17; 17.6%). One case was associated with severe immunodepression before highly active antiretroviral therapy (HAART). Two cases were manifestations of immune reconstitution inflammatory syndrome (IRIS). Among the HIV-infected children, the accrued benefits of potentially preventing severe TB outweighed the risks associated with the use of the BCG vaccine.

Paediatric tuberculosis

Tuberculosis continues to cause an unacceptably high toll of disease and death among children worldwide, particularly in the wake of the HIV epidemic. Increased international travel and immigration have led to a rise in childhood tuberculosis rates even in traditionally low burden, industrialised settings, and threaten to promote the emergence and spread of multidrug-resistant strains. Whereas intense scientific and clinical research efforts into novel diagnostic, therapeutic, and preventive interventions have focused on tuberculosis in adults, childhood tuberculosis has been relatively neglected. However, children are particularly vulnerable to severe disease and death following infection, and those with latent infection become the reservoir for future transmission following disease reactivation in adulthood, fuelling future epidemics. Further research into the epidemiology, immune mechanisms, diagnosis, treatment, and prevention of childhood tuberculosis is urgently needed. Advances in our understanding of tuberculosis in children would provide insights and opportunities to enhance efforts to control this disease.

Tuberculosis in children

Tuberculosis (TB) control poses one of the major global health challenges in the new millennium. Children in TB-endemic areas suffer severe TB related morbidity and mortality, despite the availability of cheap and effective TB treatment. However, providing an accurate TB diagnosis together with access to supervised, child friendly treatment remains difficult in resource-limited settings. This review provides a broad overview of recent advances related to child TB, focusing on intra-thoracic disease manifestations. It summarizes current understanding of TB epidemiology, disease prevention, diagnosis and treatment, but also introduces novel concepts for further discussion and future evaluation.