[HTML][HTML] Safety and immunogenicity of boosting BCG vaccinated subjects with BCG: comparison with boosting with a new TB vaccine, MVA85A

KT Whelan, AA Pathan, CR Sander, HA Fletcher… - PloS one, 2009 - journals.plos.org
KT Whelan, AA Pathan, CR Sander, HA Fletcher, I Poulton, NC Alder, AVS Hill, H McShane
PloS one, 2009journals.plos.org
Objectives To investigate the safety and immunogenicity of a booster BCG vaccination
delivered intradermally in healthy, BCG vaccinated subjects and to compare with a previous
clinical trial where BCG vaccinated subjects were boosted with a new TB vaccine, MVA85A.
Design Phase I open label observational trial, in the UK. Healthy, HIV-negative, BCG
vaccinated adults were recruited and vaccinated with BCG. The primary outcome was safety;
the secondary outcome was cellular immune responses to antigen 85, overlapping peptides …
Objectives
To investigate the safety and immunogenicity of a booster BCG vaccination delivered intradermally in healthy, BCG vaccinated subjects and to compare with a previous clinical trial where BCG vaccinated subjects were boosted with a new TB vaccine, MVA85A.
Design
Phase I open label observational trial, in the UK. Healthy, HIV-negative, BCG vaccinated adults were recruited and vaccinated with BCG. The primary outcome was safety; the secondary outcome was cellular immune responses to antigen 85, overlapping peptides of antigen 85A and tuberculin purified protein derivative (PPD) detected by ex vivo interferon-gamma (IFN-γ) ELISpot assay and flow cytometry.
Results and Conclusions
BCG revaccination (BCG-BCG) was well tolerated, and boosting of pre-existing PPD-specific T cell responses was observed. However, when these results were compared with data from a previous clinical trial, where BCG was boosted with MVA85A (BCG-MVA85A), MVA85A induced significantly higher levels (>2-fold) of antigen 85-specific CD4+ T cells (both antigen and peptide pool responses) than boosting with BCG, up to 52 weeks post-vaccination (p = 0.009). To identify antigen 85A-specific CD8+ T cells that were not detectable by ex vivo ELISpot and flow cytometry, dendritic cells (DC) were used to amplify CD8+ T cells from PBMC samples. We observed low, but detectable levels of antigen 85A-specific CD8+ T cells producing IFNγ (1.5% of total CD8 population) in the BCG primed subjects after BCG boosting in 1 (20%) of 5 subjects. In contrast, in BCG-MVA85A vaccinated subjects, high levels of antigen 85A-specific CD8+ T cells (up to 14% total CD8 population) were observed after boosting with MVA85A, in 4 (50%) of 8 subjects evaluated.
In conclusion, revaccination with BCG resulted in modest boosting of pre-existing immune responses to PPD and antigen 85, but vaccination with BCG-MVA85A induced a significantly higher response to antigen 85 and generated a higher frequency of antigen 85A-specific CD8+ T cells.
Trial Registration
ClinicalTrials.gov NCT00654316 NCT00427830
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