Applying experiences from trials of bacille Calmette-Guérin vaccine

Immunological Characterization of Proteins Expressed by Genes Located in Mycobacterium tuberculosis-Specific Genomic Regions Encoding the ESAT6-like Proteins

The 6 kDa early secreted antigen target (ESAT6) is a low molecular weight and highly immunogenic protein of Mycobacterium tuberculosis with relevance in the diagnosis of tuberculosis and subunit vaccine development. The gene encoding the ESAT6 protein is located in the M. tuberculosis-specific genomic region known as the region of difference (RD)1. There are 11 M. tuberculosis-specific RDs absent in all of the vaccine strains of BCG, and three of them (RD1, RD7, and RD9) encode immunodominant proteins. Each of these RDs has genes for a pair of ESAT6-like proteins. The immunological characterizations of all the possible proteins encoded by genes in RD1, RD7 and RD9 have shown that, besides ESAT-6 like proteins, several other proteins are major antigens useful for the development of subunit vaccines to substitute or supplement BCG. Furthermore, some of these proteins may replace the purified protein derivative of M. tuberculosis in the specific diagnosis of tuberculosis by using interferon-gamma release assays and/or tuberculin-type skin tests. At least three subunit vaccine candidates containing ESAT6-like proteins as antigen components of multimeric proteins have shown efficacy in phase 1 and phase II clinical trials in humans.

Evidence for the Effect of Vaccination on Host-Pathogen Interactions in a Murine Model of Pulmonary Tuberculosis by Mycobacterium tuberculosis

The global control of Tuberculosis remains elusive, and Bacillus Calmette-Guérin (BCG) -the most widely used vaccine in history-has proven insufficient for reversing this epidemic. Several authors have suggested that the mass presence of vaccinated hosts might have affected the Mycobacterium tuberculosis (MTB) population structure, and this could in turn be reflected in a prevalence of strains with higher ability to circumvent BCG-induced immunity, such as the recent Beijing genotype. The effect of vaccination on vaccine-escape variants has been well-documented in several bacterial pathogens; however the effect of the interaction between MTB strains and vaccinated hosts has never been previously described. In this study we show for the first time the interaction between MTB Beijing-genotype strains and BCG-vaccinated hosts. Using a well-controlled murine model of progressive pulmonary tuberculosis, we vaccinated BALB/c mice with two different sub-strains of BCG (BCG-Phipps and BCG-Vietnam). Following vaccination, the mice were infected with either one of three selected MTB strains. Strains were selected based on lineage, and included two Beijing-family clinical isolates (strains 46 and 48) and a well-characterized laboratory strain (H37Rv). Two months after infection, mice were euthanized and the bacteria extracted from their lungs. We characterized the genomic composite of the bacteria before and after exposure to vaccinated hosts, and also characterized the local response to the bacteria by sequencing the lung transcriptome in animals during the infection. Results from this study show that the interaction within the lungs of the vaccinated hosts results in the selection of higher-virulence bacteria, specifically for the Beijing genotype strains 46 and 48. After exposure to the BCG-induced immune response, strains 46 and 48 acquire genomic mutations associated with several virulence factors. As a result, the bacteria collected from these vaccinated hosts have an increased ability for immune evasion, as shown in both the host transcriptome and the histopathology studies, and replicates far more efficiently compared to bacteria collected from unvaccinated hosts or to the original-stock strain. Further research is warranted to ascertain the pathways associated with the genomic alterations. However, our results highlight novel host-pathogen interactions induced by exposure of MTB to BCG vaccinated hosts.

Ancient Disease, Modern Epidemiology: A Century of Progress in Understanding and Fighting Tuberculosis

A century's worth of efforts to better understand the epidemiology of tuberculosis (TB) and to develop new vaccines, drugs, preventive interventions, and case-finding approaches have provided important insights and helped to advance the field of epidemiology as a whole. Wade Hampton Frost developed methods for cohort analysis that formed the early basis for adjustment of confounding variables. The streptomycin trial in the United Kingdom in the 1940s introduced random allocation for participants to either the treatment or control group, ensuring blinded treatment assignment and comparable treatment groups, which is now a key element in randomized clinical trials. Research into the bacille Calmette-Guérin vaccine demonstrated the importance of comparative analyses, potential difficulties in generalizability to populations not under study, and the role of meta-analysis for discrepant data-approaches now strongly recommended prior to implementing any novel public health intervention. George Comstock's work on preventive therapy for TB demonstrated the use of epidemiologic methods to evaluate interventions on a population level. Finally, studies from the Consortium to Respond Effectively to the AIDS/TB Epidemic focused on the evaluation of real-world effectiveness and of targeting of high-risk subpopulations. In this article, we discuss how TB research in each of these domains has helped to advance epidemiologic thinking and methodology over the past 100 years.

"Let there be light": the role of vitamin D in the immune response to vaccines

Vitamin D's non-skeletal actions, including immunomodulatory role, have been increasingly recognized. Of significance, many immune cells are able to synthesize a biologically active form of vitamin D from circulating 25-hydroxyvitamin D with subsequent intracrine actions, and the vitamin D receptor is broadly distributed. In this review, we discuss vitamin D's potent role in innate and adaptive immune responses and published studies evaluating the impact of serum vitamin D, vitamin D gene pathway polymorphisms or empiric vitamin D supplementation on vaccine immunogenicity. We highlight existing knowledge gaps and propose the steps needed to advance the science and answer the question of whether vitamin D may prove valuable as a vaccine adjuvant for certain vaccines against infectious diseases.

Antigen-specific B-cell responses by neonatal calves after early vaccination

The objective of this research was to evaluate the effects of early vaccination on the phenotype (i.e., activation marker expression) and functional capacity of B cell populations in neonatal calves. In the first of 2 experiments, 6 calves were vaccinated with ovalbumin at 3 and 5 wk of age. Three of the 6 calves also were vaccinated with Mycobacterium bovis, strain bacillus Calmette-Guerin (BCG) at 3 wk of age. Mycobacterium bovis lipoarabinomannan-reactive IgG1 and IgG2 were detected in calf sera prior to vaccination, indicative of colostral transfer of maternal Ig cross-specific to BCG. Ovalbumin-specific IgG1 and IgG2 were not detected before vaccination. Vaccination of 3-wk-old calves with ovalbumin elicited antigen-specific IgG1 and IgG2 anti-body responses that were amplified by secondary vaccination. Vaccination with BCG did not elicit a measurable antibody response. In the second experiment, 6 calves were vaccinated with ovalbumin at 3 and 5 wk of age in addition to BCG at 3 wk of age. Lymph node cell populations stimulated with ovalbumin had decreased CD5, CD21, and CD40 expression and increased B-B2, CD25, and CD80 expression on IgM+ cells. Stimulation of the same population with purified-protein derivative increased CD25 and CD80 expression on IgM+ cells. Expression of activation molecules on ovalbumin- and purified protein derivative-stimulated CD5+ IgM+ cells was similar to expression on the larger IgM+ cell population. An increased expression of major histocompatibility class II on CD5+ IgM+ cells after stimulation was the only exception. Interestingly, IgM+ cells isolated from the superficial cervical lymph node draining the vaccination site, but not from the opposing cervical lymph node, responded to antigen stimulation in vitro. In conclusion, calves generated B cell responses to ovalbumin and BCG after vaccination. Additional studies are necessary to determine whether maternal immunologic experience transferred via colostral immunoglobulin inhibits production of mycobacteria-specific immunoglobulin production in the calf.

Vaccines for travel and international adoption

Vaccines have been one of the most important health advances of the 20th century. As more children emigrate from and travel to underdeveloped countries where they can be exposed to unusual endemic pathogens beyond their previous immunologic experience, it is critical to protect them against these potentially life-threatening infections.

Évaluation de la prise en charge en pneumologie: tuberculose

INTRODUCTION

The management of patients affected by tuberculosis raises issues including epidemiology, the identification and treatment of disease or infection, infection control measures, BCG vaccination and national and international strategies against the disease.

STATE OF THE ART

BCG vaccination is controversial because of its undesirable effects and the conflicting evidence from trials. It provides partial but undeniable protection; 50% against all forms and 80% against the most severe forms, particularly in children. Vaccination strategies (generalised, selective or not at all) provide different cost/benefits depending on the population involved and its prior vaccination history. This variation in response does not outweigh the ethical and pragmatic considerations underlying the current approach of universal vaccination. The directly observed therapy, short course (DOTS) strategy has been well evaluated notwithstanding the huge potential scope of its global implementation.

PERSPECTIVES

A more effective vaccine is one of the possible solutions for eliminating tuberculosis. DOTS could be usefully implemented in France as part of a strategy to eliminate the disease.

CONCLUSION

BCG vaccination and elements of DOTS are effective interventions for the management of TB.

Infection-induced apoptosis deletes bystander CD4+ T cells: a mechanism for suppression of autoimmunity during BCG infection

Infection with Mycobacterium bovis Bacille Calmette Guérin (BCG) induces high levels of apoptosis among activated CD4+ T cells. We have investigated the specificity of this pro-apoptotic response and its influence on CD4+ T cell mediated autoimmunity. Apoptosis induced by BCG-infection is unrelated to antigenic specificity, as demonstrated by the increased apoptosis of activated TCR transgenic CD4+ T cells of unrelated specificity. Moreover, infection-induced apoptosis promoted the deletion of CD4+ T cells activated either by peptide or anti-CD3/anti-CD28 stimulation. Infection-induced apoptosis required IFN-gamma production by the infected host, and expression of the IFN-gamma receptor on donor CD4+ T cells. We used an adoptive transfer model of experimental autoimmune encephalomyelitis (EAE) to assess the influence of infection-induced apoptosis on a CD4+ T cell-mediated response. A significantly higher level of apoptosis was seen among sorted encephalitogenic CD4+ T cells transferred to BCG-infected versus uninfected hosts. BCG-infected mice displayed a milder course of clinical disease than their uninfected counterparts and a decreased recovery of donor cells from the CNS. The data suggest that mycobacterial infection attenuates the severity of EAE, at least in part, by promoting the apoptotic elimination of autoreactive CD4+ T cells.

Travel-related vaccines

Travelers are at increased risk for several infections, including familiar infections such as measles that are widely distributed but more common in developing countries. Vaccines can markedly decrease the risk for many of these infections and are an important part of pretravel preparation. Travel provides an opportunity to review and update routine vaccines in adults and assess risk from unusual infections. Global travel is growing. Persons who are elderly, HIV-infected, and immunocompromised account for many of the travelers. Studies that assess the immunogenicity, efficacy, and adverse effects of some of the special vaccines used primarily in travelers generally have been done in young, healthy populations. Findings in young adults do not apply to other populations in whom immune response can be slower, less effective, and less durable. Recent reports of severe adverse events in elderly persons who have received yellow fever vaccine are a reminder that widely used, old vaccines can have unexpected side effects when used in a new population. It is biologically plausible that adverse effects might be more common in the elderly, and epidemiologically plausible that occasional instances of similar adverse events in the past could have been missed. Studies on special and travel vaccines in the elderly are needed urgently to define how these vaccines should be used in older populations and whether alternative means for protection are needed.