Purpose: A non-randomised, open-label, Phase I safety and immunogenicity dose-finding study to assess the safety and immunogenicity of the candidate TB vaccine Modified Vaccinia virus Ankara expressing Antigen 85A (MVA85A) from Mycobacterium tuberculosis (MTB) in healthy adult volunteers previously vaccinated with BCG. Methods: Healthy BCG-vaccinated volunteers were vaccinated with either 1×107 or 1×108PFU of MVA85A. All adverse events were documented and antigen specific T cell responses were measured using an ex vivo IFN-γ ELISPOT assay. Safety and immunogenicity were compared between the 2 dose groups and with a previous trial in which a dose of 5×107PFU MVA85A had been administered. Results: There were no serious adverse events recorded following administration of either 1×107 or 1×108PFU of MVA85A. Systemic adverse events were more frequently reported following administration of 1×108PFU of MVA85A when compared to either 5×107 or 1×107PFU of MVA85A but were mild or moderate in severity and resolved completely within 7days of immunisation. Antigen specific T cell responses as measured by the IFN-γ ELISPOT were significantly higher following immunisation in adults receiving 1×108PFU compared to the 5×107 and 1×107 doses. Additionally, a broader range of Ag85A epitopes are detected following 1×108PFU of MVA85A. Conclusion: A higher dose of 1×108PFU of MVA85A is well-tolerated, increases the frequency of IFN-γ secreting T cells detected following immunisation and broadens the range of Ag85A epitopes detected. © 2012 Elsevier Ltd.
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