Robust γδ+ T cell expansion in infants immunized at birth with BCG vaccine

doi:10.1016/j.vaccine.2007.06.039

Vaccine

Volume 25, Issue 34, 21 August 2007, Pages 6313-6320

https://doi.org/10.1016/j.vaccine.2007.06.039 Get rights and content

Abstract

Cell-mediated immune responses to BCG vaccine were evaluated in 7-month-old infants vaccinated with intradermal combined BCG and Hepatitis B or intradermal BCG and intramuscular Hepatitis B at birth. Peripheral blood mononuclear cell cultures from both groups showed CD4⁺, CD8⁺ and remarkable γδ⁺ T cell BCG-specific proliferation, without significant differences. Also, IL-10, IL-12, IFN-γ and TNF-α concentrations in culture supernatants, measured by ELISA, were similar. The results suggested that the combined BCG and Hepatitis B vaccine was as immunogenic as BCG separated from Hepatitis B vaccine.

Introduction

With the increasing number of recommended children's vaccines it is often required that an infant receive multiple injections, which is disconcerting to parents and health care providers [1], [2], [3]. The value of combined vaccines relies on obtaining high levels of age-appropriate immunization, the possibility of reducing the number of underimmunized children, and in simplifying immunization schedules. There is a need, therefore, to demonstrate the safety and efficacy of combined vaccines by clinical trials [4], [5], [6].

Despite the controversy concerning its efficacy against adult pulmonary tuberculosis, intradermal Mycobacterium bovis Bacillus Calmette-Guérin (BCG) vaccine can, at least, protect against severe forms of systemic tuberculosis (TB) in children, particularly meningitis and miliary disease, and so World Health Organization has encouraged vaccination [7]. Moreover, there is no known standardization of protective immunity; neither the post-vaccination scar nor the tuberculin tests are recognized as protection markers [8]. A new vaccine against Mycobacterium tuberculosis is needed but it is still necessary to find out which immune response can lead to protection and thus reach this goal [7].

Regarding the evaluation of BCG immunogenicity, Coursaget et al. [9] used tuberculin reactivity as a surrogate marker, and Ota et al. [10] evaluated BCG immunogenicity with a radioactive proliferation assay using PPD as antigen. In our study, BCG immunogenicity was measured with a flow cytometry-based proliferation technique that allows the determination of expanding lymphocyte subsets, and the incubation with viable bacilli allows for a more detailed exploration of the complexity of antigen presentation and processing.

In children, there is no experience of an intradermal BCG combined vaccine. Since young children are very susceptible to systemic tuberculosis and there are only a few studies of BCG-responses in childhood [11], in this article cellular immune responses to BCG in vitro from 7-month-old infants immunized at birth with a single dose of combined BCG with recombinant Hepatitis B surface antigen (HBsAg) vaccine are described.

Section snippets

Study participants and vaccination

This cross-secctional study was conducted between October 2004 and December 2005. Study subjects were selected as a sample from a population of 498 children who took part in a phase III randomized controlled trial. Infants were immunized at birth either with combined intradermal BCG and Hepatitis B or intradermal BCG and intramuscular Hepatitis B vaccine into the antero-lateral area of the thigh. All vaccines were provided by Instituto Butantan, São Paulo, SP, Brazil. A total of 85 healthy

Study participants

Forty-seven infants (24 male and 23 female) in the combined vaccine group and 38 (17 male and 21 female) in the separate vaccine group were studied for BCG immune response. The combined vaccine group median age was 7.34 months (range 6.3–8.1) and 7.38 months in separate vaccine group (range 7.0–8.7). There were no differences in terms of gender (χ² = 0.337, d.f. = 1, p = 0.562) nor age (Mann–Whitney U = 872.5, p = 0.856) between the two vaccination groups. No local or systemic adverse reactions were

Discussion

Our main goal in this study was to examine whether a BCG and Hepatitis B combined vaccine could prime similar cell-mediated responses that BCG vaccine injected alone does. Comparable post-BCG vaccination cytokine and cell proliferation responses in 7-month-old vaccines were found. We also observed similar responses to Hepatitis B vaccine (data not shown). Given the requirement of a Th-1 type immune response in protective immunity against mycobacteria, we reasoned that vaccine efficacy would be

Acknowledgements

We thank all the parents which consented their children participation in this clinical trial. We also are grateful to Dr. Katherine Luzuriaga for critically reading this manuscript and offering useful suggestions. This project was supported by grant number 2002/05666-2 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), São Paulo, Brazil.

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Effective combined antiretroviral therapy provides partial immune recovery to mycobacterial antigens in vertically infected, BCG-vaccinated youth living with HIV
2022, Tuberculosis
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An important feature of our study is that all individuals in both YLHIV and control groups received the BCG vaccine in their first month of life, as per Brazil's national immunization program [6]. We have previously shown that this vaccine induces potent Th1 and γδ T-cell responses [23]. BCG vaccine is well known to be less efficient for TB prevention in children and adolescents living with HIV [24].
We assessed the cytokine response by PBMC of youth living with HIV (YLHIV) under combined antiretroviral therapy (cART) to Mycobacterium tuberculosis (Mtb) and Mycobacterium bovis (BCG) antigens.
PBMC from 20 Brazilian YLHIV under cART with long-term (≥1 year) virological control, and 20 healthy controls were cultured for 24–96 h under stimulation with BCG, Mtb lysates, ESAT-6 and SEB. We measured TNF-α, IFN-γ, IL-2, IL-4, IL-5, IL-10 and IL-17 in culture supernatants using a cytometric bead array.
Controls had higher IFN-γ production at 24, 48, 72 and 96 h upon stimulation with BCG lysate, plateauing at 48 h (Median = 1991 vs. 733 pg/mL; p = 0.01), and after 48–72 h of stimulation with Mtb lysate, plateauing at 48 h (3838 vs. 2069 pg/mL; p = 0.049). YLHIV had higher TNF-α production at all time points upon stimulation with ESAT-6, with highest concentration at 36 h (388 vs. 145 pg/mL; p = 0.02). Within the YLHIV group, total CD4 T cell count and CD4/CD8 ratio were associated with IFN-γ response to Mtb lysate and ESAT-6, respectively.
Even under long-term cART, YLHIV seem to have a suboptimal T-helper-1 response to mycobacterial antigens. This can be explained by early immunodeficiency in vertical infection, with lasting damage.
Comparable CD4 and CD8 T cell responses and cytokine release after at-birth and delayed BCG immunisation in infants born in Australia
2016, Vaccine
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However, no influence on memory phenotypes was found in the two previous studies that investigated the influence of delayed BCG on this aspect of the mycobacteria-specific immune response [12,13]. We also did not determine non-conventional T cells, which have recently been recognised to play an important role in the immune response to BCG [20–22]. Another inevitable limitation of our study is that we were not able to compare clinical outcomes (i.e. protective efficacy) as a result of the low TB incidence in Australia.
More than 120 million doses of BCG vaccine are administered worldwide each year. Most infants are given BCG at birth in accordance with WHO recommendations. However, the effect of the maturing neonatal immune system on the immune response and protection conferred by BCG remains uncertain. Previous studies investigating the influence of age at immunisation on the immune response induced by BCG have reported conflicting results. This study compared BCG given at birth and at two months of age in infants in Australia.
Infants born in Melbourne were randomly allocated to immunisation with BCG-Denmark at birth or two months of age. Ten weeks after immunisation, anti-mycobacterial immune responses were measured in a whole blood assay using intracellular cytokine assays and xMAP multiplex cytokine analysis.
Result from 98 BCG-immunised infants were included in the final analysis. BCG immunisation at birth (n = 54) and at 2 months of age (n = 44) induced comparable proportions of mycobacteria-specific cytokine-producing CD4 and CD8 T cells, as well as comparable proportions of polyfunctional (TNF⁺ IL-2⁺ IFN-γ⁺) CD4 T cells. Concentrations of cytokines in supernatants were also similar in both groups.
Cellular immunity measured 10 weeks after BCG immunisation was similar in infants given BCG at birth and in those given BCG at 2 months of age. Although definitive correlates of protection against TB remain uncertain, these results suggest that delaying BCG immunisation does not confer any immunological advantage in cellular immunity.
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Recent studies demonstrated a significant increase in the number, and IFNγ secreting capacity, of WC1+ γδ T cells in the blood of cattle post-BCG vaccination [90]. Mazzola et al. [91] also described significant expansion of γδ T cells in response to BCG vaccination in human neonates. We demonstrated significant infiltration of WC1+ γδ T cells into tissues of the head and lungs following intranasal delivery of BCG to calves [92].
Bovine tuberculosis is a disease of increasing incidence in the UK causing major economic losses and with significant impact on bovine and, potentially human health: the causative agent Mycobacterium bovis is a zoonotic pathogen. Neonatal vaccination with the attenuated M. bovis Bacille Calmette Guerin (BCG) vaccine confers a significant degree of protection in cattle, and is a widely used control strategy for human TB. The adaptive immune system is relatively immature in neonates and increased numbers of innate effector cells present in young animals and human infants may compensate for this, enabling effective immune responses to vaccination. Natural killer cells and subsets of γδ TCR⁺ T lymphocytes secrete high levels of interferon gamma and can interact with antigen presenting cells to promote both innate and adaptive immune responses. These cell populations may be pivotal in determining immune bias following neonatal vaccination with BCG.
BCG vaccination induces innate immune memory in γδ T cells in humans
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IV BCG Vaccination and Aerosol BCG Revaccination Induce Mycobacteria-Responsive γδ T Cells Associated with Protective Efficacy against M. tb Challenge
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Training vs. Tolerance: The Yin/Yang of the Innate Immune System
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^☆: Preliminary results of these findings were presented at the New Approaches to Vaccine Development—From bench to the field, Berlin, Germany, 8–10 September 2005.

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Robust γδ+ T cell expansion in infants immunized at birth with BCG vaccine☆

Abstract

Introduction

Section snippets

Study participants and vaccination

Study participants

Discussion

Acknowledgements

Vaccine

J Pediatr Health Care

Ann Allergy Asthma Immunol

Vaccine

Lancet

Vaccine

J Immunol Methods

Microbes Infect

J Immunol Methods

Trends Immunol

Immunization safety: a global priority

Bull World Health Organ

Safety concerns regarding combination vaccines. Perspective of select European countries

Hum Vaccin

Influence of Mycobacterium bovis Bacillus Calmette-Guérin on antibody and cytokine responses to human neonatal vaccination

J Immunol

Robust γδ⁺ T cell expansion in infants immunized at birth with BCG vaccine☆