Cellular immune responses to four doses of percutaneous bacille Calmette-Guérin in healthy adults

Bacille Calmette-Guérin Vaccine Strain Modulates the Ontogeny of Both Mycobacterial-Specific and Heterologous T Cell Immunity to Vaccination in Infants

Differences in Bacille Calmette-Guérin (BCG) immunogenicity and efficacy have been reported, but various strains of BCG are administered worldwide. Since BCG immunization may also provide protection against off-target antigens, we sought to identify the impact of different BCG strains on the ontogeny of vaccine-specific and heterologous vaccine immunogenicity in the first 9 months of life, utilizing two African birth cohorts. A total of 270 infants were studied: 84 from Jos, Nigeria (vaccinated with BCG-Bulgaria) and 187 from Cape Town, South Africa (154 vaccinated with BCG-Denmark and 33 with BCG-Russia). Infant whole blood was taken at birth, 7, 15, and 36 weeks and short-term stimulated (12 h) in vitro with BCG, Tetanus and Pertussis antigens. Using multiparameter flow cytometry, CD4+ T cell memory subset polyfunctionality was measured by analyzing permutations of TNF-α, IL-2, and IFN-γ expression at each time point. Data was analyzed using FlowJo, SPICE, R, and COMPASS. We found that infants vaccinated with BCG-Denmark mounted significantly higher frequencies of BCG-stimulated CD4+ T cell responses, peaking at week 7 after immunization, and possessed durable polyfunctional CD4+ T cells that were in a more early differentiated memory stage when compared with either BCG-Bulgaria and BCG-Russia strains. The latter responses had lower polyfunctional scores and tended to accumulate in a CD4+ T cell naïve-like state (CD45RA+CD27+). Notably, BCG-Denmark immunization resulted in higher magnitudes and polyfunctional cytokine responses to heterologous vaccine antigens (Tetanus and Pertussis). Collectively, our data show that BCG strain was the strongest determinant of both BCG-stimulated and heterologous vaccine stimulated T cell magnitude and polyfunctionality. These findings have implications for vaccine policy makers, manufacturers and programs worldwide and also suggest that BCG-Denmark, the first vaccine received in many African infants, has both specific and off-target effects in the first few months of life, which may provide an immune priming benefit to other EPI vaccines.

Mycobacterium bovis BCG and New Vaccines for the Prevention of Tuberculosis

Tuberculosis infects millions of people worldwide and remains a leading global killer despite widespread neonatal administration of the tuberculosis vaccine, bacillus Calmette-Guérin (BCG). BCG has clear and sustained efficacy, but after 10 years, its efficacy appears to wane, at least in some populations. Fortunately, there are many new tuberculosis vaccines in development today, some in advanced stages of clinical trial testing. Here we review the epidemiological need for tuberculosis vaccination, including evolving standards for administration to at risk individuals in developing countries. We also examine proven sources of immune protection from tuberculosis, which to date have exclusively involved natural or vaccine exposure to whole cell mycobacteria. After summarizing evidence for the use and efficacy of BCG, we detail the most promising new candidate vaccines against tuberculosis. The global need for a new tuberculosis vaccine is acute and huge, but clinical trials to be completed in the coming few years are likely either to identify a new tuberculosis vaccine or to substantially reframe how we understand immune protection from this historical scourge.

Interferon γ responses to mycobacterial antigens protect against subsequent HIV-associated tuberculosis

BACKGROUND

The cellular immune responses that protect against tuberculosis have not been identified.

METHODS

We assessed baseline interferon γ (IFN‐γ) and lymphocyte proliferation assay (LPA) responses to antigen 85 (Ag85), early secretory antigenic target 6 (ESAT‐6), and Mycobacterium tuberculosis whole cell lysate (WCL) in human immunodeficiency virus (HIV)-infected and bacille Calmette‐Guérin (BCG)-immunized adults with CD4 cell counts of >or= 200 cells/μL who received placebo in the DarDar tuberculosis vaccine trial in Tanzania. Subjects were followed prospectively to diagnose definite or probable tuberculosis.

RESULTS

Tuberculosis was diagnosed in 92 of 979 subjects during a mean follow‐up of 3.2 years. The relative risk of tuberculosis among subjects with positive IFN‐γ responses to Ag85 was 0.51 (95% confidence interval [CI], 0.26-0.99; P = .049), to ESAT‐6 was 0.44 (95% CI, 0.23-0.85; P = .004), and to WCL was 0.67 (95% CI, 0.49-0.88; P = .002). The relative risk of tuberculosis was not significantly associated with baseline LPA responses. In a multivariate Cox regression model, subjects with IFN‐γ responses to ESAT‐6 and WCL had a lower hazard of developing tuberculosis, with a hazard ratio for ESAT‐6 of 0.35 (95% CI, 0.16–0.77; P = .009) and a hazard ratio for WCL of 0.30 (95% CI, 0.16-0.56; P < .001).

CONCLUSIONS

Baseline IFN‐γ responses to ESAT-6 and WCL were associated with protection from subsequent tuberculosis among HIV-infected subjects with childhood BCG immunization in a region of high tuberculosis prevalence. Trial registration. ClinicalTrials.gov identifier: NCT00052195.

Inoculation route-dependent and allergen-specific suppressive effects of bacille Calmette-Guérin vaccination on asthmatic reactions in BALB/c mice

Intranasal bacille Calmette-Guérin (BCG) vaccination causes greater suppression of ovalbumin-induced airway eosinophilia in mice than does subcutaneous vaccination. Coadministration of ovalbumin with interleukin (IL)-18 induces an ovalbumin-specific Th1 immune reaction. The purpose of this study was to examine whether the suppressive effect of BCG is dependent on the inoculation method, using various murine asthma models. Female BALB/c mice (n = 7 per group) were immunized with BCG subcutaneously or intranasally, then sensitized with ovalbumin or Dermatophagoides farinae either immediately or one week later. After provocation with one of the allergens, the mice were tested by methacholine bronchial challenge, and analyses of the inflammatory cell numbers in the airways and cytokine levels in the supernatant of concanavalin A-stimulated splenocytes were conducted. Overall, the airway responses to the allergens were significantly lower and the interferon (IFN)-gamma level was significantly higher in BCG-treated mice than in untreated mice, and the number of airway eosinophils was significantly related to the IFN-gamma/IL-5 ratio (r = -0.444, p < 0.001). Subcutaneous BCG inoculation tended to have a greater suppressive effect on the development of airway hyperresponsiveness and eosinophilia than did intranasal inoculation. Concurrent BCG vaccination and D. farinae sensitization one week before ovalbumin sensitization tended to have a greater suppressive effect on airway responsiveness to methacholine induced by D. farinae aerosols than did that induced by ovalbumin aerosols. Subcutaneous BCG inoculation suppressed asthmatic reactions more remarkably than did intranasal inoculation, and concurrent BCG vaccination and allergen sensitization induced allergen-specific suppression of asthmatic reactions.

Dose-dependent immune response to Mycobacterium bovis BCG vaccination in neonates

In 10-week-old infants vaccinated at birth with Japanese Mycobacterium bovis BCG, the number of dermal needle penetrations correlated positively with frequency of proliferating CD4(+) T cells in whole blood following BCG stimulation for 6 days but did not correlate with secreted cytokine levels after 7 h or interferon CD4(+) T-cell frequency after 12 h of BCG stimulation.

BCG immunization at birth and atopic diseases in a homogeneous population of Spanish schoolchildren

BACKGROUND

The role of immunization with bacillus Calmette-Guérin (BCG) in the prevalence of asthma, hay fever and atopic dermatitis is not definitely established and seems to be influenced by ethnic background. The aim of this study was to analyze the relationship between this immunization and the prevalence of those diseases in a homogeneous population of Spanish schoolchildren.

METHODS

The International Study of Asthma and Allergies in Childhood (ISAAC) core and environmental questionnaires were used in four different centers of the Spanish North Atlantic coast. Bilbao, San Sebastián and Asturias have a universal BCG immunization policy during the first days of life, whereas La Coruña discontinued this practice in 1989. Except for this center, immunization coverage was above 90%. A random sample of schools of Asturias or all schools in the city district (rest of centers) with children 6 and 7 years old was surveyed.

RESULTS

The participation rate was above 70%. After excluding those children born outside Spain, the numbers were 6,762 immunized and 2,828 nonimmunized. After adjusting for gender, age, smoking habits of the father and mother, truck traffic near the household, older and younger siblings and having a cat or a dog during the first year of the child's life, the adjusted ORs of the BCG-immunized children suffering from asthma, hay fever and atopic dermatitis were respectively 0.87 (95% CI 0.76-1.00), 0.87 (0.75-1.01) and 0.89 (0.76-1.05).

CONCLUSIONS

BCG immunization offers a weak but significant protection against asthma and hay fever in Spanish schoolchildren.

Effect of Mycobacterium vaccae on cytokine responses in children with atopic dermatitis

The increasing prevalence of atopic diseases over the last few decades is thought to be due to reduced exposure to environmental microbes that normally down-regulate allergic responses (hygiene hypothesis). We have shown previously that administration of the environmental microbe Mycobacterium vaccae ameliorates atopic dermatitis in school-age children at 3 months post-treatment. The present study tested the hypothesis that M. vaccae suppresses Th2-type cytokine activity and increases transforming growth factor (TGF)-beta(1) immunomodulatory activity in these children. Interleukin (IL)-4, IL-5, TGF-beta(1) and interferon (IFN)-gamma activity were assessed in resting and stimulated peripheral blood mononuclear cells (PBMC) isolated from 12 of the children who received M. vaccae in our original clinical trial. A cDNA expression array was used to examine a broader range of cytokine pathway transcripts. There were no significant changes in either Th2-type or TGF-beta(1) activity. A 5- to 10-fold increase in Th1-type activity was found at 1 month post-M. vaccae administration (P < 0.05), but it had returned to baseline by 3 months. The results do not support the hypothesis that M. vaccae reduces Th2-type or increases TGF-beta(1) activity of PBMC isolated from children with atopic dermatitis. The transient surge in IFN-gamma at 1 month is unlikely to explain any improvement in eczema score at 3 months.

Intranasal bacille Calmette-Guerin (BCG) vaccine dosage needs balancing between protection and lung pathology

Intranasal vaccination may offer practical benefits and better protection against respiratory infections, including tuberculosis. In this paper, we investigated the persistence of the Mycobacterium bovis-strain bacille Calmette-Guerin (BCG) Pasteur, lung granuloma formation and protection against pathogenic tuberculous challenge in mice. A pronounced BCG dose-dependent granulomatous infiltration of the lungs was observed following intranasal, but not after subcutaneous, vaccination. Corresponding doses of BCG, over a 100-fold range, imparted similar protection against H37Rv challenge when comparing the intranasal and subcutaneous vaccination routes. Interestingly, a BCG dose-dependent reduction of the H37Rv challenge infection was observed in the lungs, but not in the spleens, following both intranasal and subcutaneous vaccination. In the light of the observed concurrence between the extent of granuloma formation and the level of protection of the lungs, we conclude that intranasal vaccination leading to best protective efficacy needs to be balanced with an acceptable safety margin avoiding undue pathology in the lungs.

Immunogenicity of an inactivated mycobacterial vaccine for the prevention of HIV-associated tuberculosis: a randomized, controlled trial

OBJECTIVE

Prior to the widespread use of Mycobacterium bovis, Bacille Calmette-Guerin (BCG), inactivated whole cell mycobacterial vaccines had been shown effective in the prevention of tuberculosis. The present study was conducted to determine the safety and immunogenicity of an inactivated whole cell mycobacterial vaccine in persons with HIV infection.DESIGN Randomized, controlled trial.

METHODS

A total of 39 HIV-positive patients with prior BCG immunization and CD4 cell counts >/= 200 x 10(6) cells/l were randomized to five doses of inactivated Mycobacterium vaccae (MV) vaccine or control vaccine (CV). Lymphocyte proliferation (LPA) and interferon gamma (IFN-gamma) responses to mycobacterial antigens were assayed at baseline, after three and five doses of vaccine and > 1 year later. Parallel studies were conducted in 10 HIV-negative subjects with prior BCG immunization.

RESULTS

Among HIV-positive patients, 19 MV recipients had higher LPA and IFN-gamma responses to MV sonicate than 20 CV recipients after three and five doses of vaccine and > 1 year later. LPA responses to Mycobacterium tuberculosis whole cell lysate increased over time in both groups consistent with prior BCG immunization and current antiretroviral therapy; after three doses, responses were boosted to higher levels in MV subjects than CV subjects. LPA responses to WCL were also boosted in HIV-negative MV recipients. Immunization was safe and had no adverse effects on HIV viral load or CD4 cell count.

CONCLUSIONS

In BCG-primed, HIV-positive and HIV-negative subjects, MV induces durable cellular immune responses to a new mycobacterial antigen and boosts pre-existing responses to WCL. MV is a candidate for clinical trials for the prevention of HIV-associated tuberculosis.

Differential effects of control and antigen-specific T cells on intracellular mycobacterial growth

We investigated the effects of peripheral blood mononuclear cells expanded with irrelevant control and mycobacterial antigens on the intracellular growth of Mycobacterium bovis bacillus Calmette-Guérin (BCG) in human macrophages. More than 90% of the cells present after 1 week of in vitro expansion were CD3(+). T cells were expanded from purified protein derivative-negative controls, persons with latent tuberculosis, and BCG-vaccinated individuals. T cells expanded with nonmycobacterial antigens enhanced the intracellular growth of BCG in suboptimal cultures of macrophages. T cells expanded with live BCG or lysates of Mycobacterium tuberculosis directly inhibited intracellular BCG. Recent intradermal BCG vaccination significantly enhanced the inhibitory activity of T cells expanded with mycobacterial antigens (P < 0.02), consistent with the induction of memory-immune inhibitory T-cell responses. Selected mycobacterial antigens (Mtb41 > lipoarabinomannan > 38kd > Ag85B > Mtb39) expanded inhibitory T cells, demonstrating the involvement of antigen-specific T cells in intracellular BCG inhibition. We studied the T-cell subsets and molecular mechanisms involved in the memory-immune inhibition of intracellular BCG. Mycobacteria-specific gammadelta T cells were the most potent inhibitors of intracellular BCG growth. Direct contact between T cells and macrophages was necessary for the BCG growth-enhancing and inhibitory activities mediated by control and mycobacteria-specific T cells, respectively. Increases in tumor necrosis factor alpha, interleukin-6, transforming growth factor beta, and vascular endothelial growth factor mRNA expression were associated with the enhancement of intracellular BCG growth. Increases in gamma interferon, FAS, FAS ligand, perforin, granzyme, and granulysin mRNA expression were associated with intracellular BCG inhibition. These culture systems provide in vitro models for studying the opposing T-cell mechanisms involved in mycobacterial survival and protective host immunity.

New vaccines for the prevention of tuberculosis

Mycobacterium bovis, bacille Calmette-Guérin (BCG) is administered widely to newborns throughout the world and has been shown to be effective in preventing childhood tuberculosis but not reactivation pulmonary disease or human immunodeficiency virus-associated tuberculosis. Development of a more effective, better standardized, affordable vaccine with durable activity and fewer side effects is a major priority. Contemporary molecular techniques have identified promising immunodominant antigens and novel immunization strategies. Vaccine development has also been informed by an improved understanding of the role of nontuberculous mycobacteria in the efficacy of BCG and in the prevention of tuberculosis. Vaccines under investigation include attenuated or enhanced whole-cell live, whole-cell inactivated, subunit, DNA, and prime-boost vaccines. Several candidate vaccines have demonstrated activity in animal models that is equal to or superior to that of BCG, and human trials are under way. Because there is no identified surrogate marker for protection, identification of an improved vaccine will require long-term efficacy trials in humans.

Therapeutic effects of BCG vaccination in adult asthmatic patients: a randomized, controlled trial

BACKGROUND

Bacille Calmette-Guérin (BCG) vaccination in humans induces Th1 immune responses. Th1 and Th2 cells are reciprocally regulated.

OBJECTIVE

To examine whether BCG vaccination of adult patients with asthma, a Th2-associated allergic disease, is clinically effective.

METHODS

Forty-three moderate-to-severe asthma patients were randomly assigned into groups that received percutaneous injection of 58.2 x 10(7) CFUs BCG (n = 22) or placebo (n = 21) in a double-blinded fashion, on the first day of a 12-week treatment period. Medications were adjusted every 4 weeks to maintain optimal asthma control. Spirometric measurements were performed before treatment and at weeks 4, 8, and 12 after vaccination. The daily peak expiratory flow rate values, asthma symptoms, and medications were also recorded. Tuberculin skin tests, and sputum inflammatory cell and cytokine analyses were carried out before treatment and 12 weeks after vaccination.

RESULTS

BCG vaccination significantly increased forced expiratory volume in 1 second and forced expiratory flow rate 25% to 75% at weeks 4, 8, and 12. Morning peak expiratory flow rate was significantly increased only during the first 4 weeks. Although the asthma symptom scores were not significantly changed, the weekly medication scores were significantly decreased. Tuberculin skin reactivities were significantly increased without significant alterations in induced sputum profiles. In contrast, medication scores and sputum eosinophils were significantly increased, and the interferon-gamma:interleukin-4 ratio in sputum was significantly decreased in the placebo group.

CONCLUSIONS

BCG vaccination improved lung function and reduced medication use in adults with moderate-to-severe asthma. This amelioration was accompanied by a suppressed Th2-type immune response, suggesting that BCG vaccination might be an effective therapeutic modality against asthma.

Neonatal mycobacterial specific cytotoxic T-lymphocyte and cytokine profiles in response to distinct BCG vaccination strategies

This study evaluated whether different bacillus Calmette-Guérin (BCG) strains, routes of administration, vaccination age and percutaneous tools influenced immune responses to BCG vaccination in infants. Proliferative responses, cytokine production and cell-mediated cytotoxicity obtained in post-vaccinated children were compared to baseline cord bloods and unvaccinated 10-week-old infants. BCG vaccination generally induced strong lymphoproliferative and T helper type 1 (Th1)-type cytokine responses. There was a trend for greater responsiveness following the intradermal route of vaccination, with Japanese-172 strain and with delaying vaccination until 10 weeks. Cord mononuclear cells differentially stimulated the Th2-type cytokines interleukin-5 (IL-5) and IL-10 selectively in response to BCG, as compared to H37Rv or purified protein derivative stimulation. We document for the first time the generation of mycobacterium-specific cytotoxic T lymphocytes in neonates, following BCG vaccination. Cytotoxic activity correlated with the ratio of interferon-gamma to IL-5, aside from a single instance where use of the Biovac tool resulted in a striking dissociation selectively against H37Rv targets. These data have implications for correlates of protective immunity in design of vaccine studies.

Association of interleukin-10 cytokine expression status with HLA non-DRB1*02 and Mycobacterium bovis BCG scar-negative status in south Indian pulmonary tuberculosis patients

HLA DRB1*02 and its subtypes predispose individuals for a far-advanced sputum-positive pulmonary tuberculosis transcending ethnic boundaries. Mycobacterium bovis BCG does not afford the desired protection against adult pulmonary tuberculosis, and a spectrum of immune reactivity exists in controls and hospital contacts. All of these findings have been identified and demonstrated in areas of endemicity. Skewing of immunity from protective to pathogenic may involve a shift in the Th1-Th2 paradigm. To elaborate these ideas, we studied gamma interferon (IFN-gamma), interleukin-4 (IL-4), and IL-10 cytokine expression in 71 adult pulmonary tuberculosis patients and 74 controls from areas of endemicity in south India by 48-h microculture and reverse transcription-PCR. Most of the patients and controls expressed IFN-gamma de novo, and in the presence of purified protein derivative (PPD), all of them expressed significantly higher levels of IFN-gamma, suggesting a PPD-specific recall memory. HLA DRB1* allele-dependent IFN-gamma expression was identified only in controls, suggesting a skewing of the immune response in patients. In contrast to the case for IFN-gamma, only some patients and controls expressed IL-4 or IL-10 (Th2 profile); thus, the Th1 profile was identifiable only by a nonexpression of IL-4 or IL-10 in this area of endemicity. The Th2 profile was associated with HLA non-DRB1*02 and BCG scar-negative status in patients, attributing a significant risk (odds ratio = 2.074; 95% confidence interval = 0.612 to 7.07). It is possible that Mycobacterium tuberculosis (PPD)-specific IL-10 is expressed preemptively in unvaccinated (BCG scar-negative) individuals with a non-DR2 genetic background by chronic exposure in this area of endemicity and leads to pulmonary tuberculosis of adults.

M. tuberculosis: immunology and vaccination

Tuberculosis is increasing. Current treatment regimens require at least 6 months, because latent or stationary phase organisms are difficult to kill. Such regimens do not achieve full compliance, and "directly observed therapy short course" (DOTS) is having less impact than expected. This worrying situation is aggravated by coinfection with human immunodeficiency virus (HIV), and by the increase in drug-resistant strains. We need new insights that lead to more rapid therapies and immunotherapies, and more reliable vaccines. Recent insights have come from: understanding of the relationship between Mycobacterium tuberculosis and macrophages; the multiple T cell types that recognise mycobacterial peptides, lipids and glycolipids; the critical role of interferon-gamma (IFNgamma) and interleukin-12 (IL-12) in human mycobacterial infection revealed by genetically defective children; quantitation of the presence and importance of Th2 lymphocyte activation in human tuberculosis; the role of local conversion of inactive cortisone to active cortisol in the lesions; the recognition that some effective prophylactic vaccines also work as immumotherapeutics whereas others do not. In the longer term the recent sequencing of the M. tuberculosis genome will lead to further advances. In the short term, effective immunotherapy remains the most accessible breakthrough in the management of tuberculosis. The types of practical advance that will result from sequencing the genome are discussed speculatively, but cannot yet be predicted with certainty.

Randomised trial of intradermal Mycobacterium vaccae or intradermal hepatitis B immunisation in children with HIV infection

This study assessed the safety of inactivated Mycobacterium vaccae as a candidate vaccine to prevent disseminated mycobacterial disease in children with HIV infection. 35 children ages 1-8 with CD4 counts > or =300/mm3 in New Hampshire, Boston and Chicago were randomised in a 2:1 schedule to receive a 3-dose series of intradermal M. vaccae vaccine (MV) or hepatitis B vaccine (HBV) at 2-month intervals. Immunisation was safe and well tolerated; 2-day median vaccine site in duration was 5 mm in MV recipients and 0 mm in HBV recipients (p < 0.001). There were no significantly different changes in viral load or CD4 count between the two vaccine groups. No PPD skin test conversions occurred after immunisation. MV is safe and well tolerated and deserves further evaluation as a vaccine to prevent mycobacterial disease in HIV-infected children.