Recombinant tuberculosis vaccine AEC/BC02 induces antigen-specific cellular responses in mice and protects guinea pigs in a model of latent infection

PurposeTo preliminarily evaluate the immunogenicity and efficacy of the recombinant tuberculosis vaccine AEC/BC02 in which Ag85b and fusion protein ESAT6-CFP10 were combined with bacillus Calmette-Guérin CpG and an aluminum salt-based adjuvant system.MethodsGroups of BALB/c mice were immunized intramuscularly three times at 10-day intervals with AEC/BC02 or the adjuvant alone and the vaccine-induced cell-mediated immune responses were evaluated. The efficacy of AEC/BC02 was evaluated in two guinea pig models, one a model of prevention and the other a model of latent infection.ResultsThe AEC/BC02 vaccine induced strong cellular immune responses characterized by a high frequency of antigen-specific interferon-γ-secreting T cells in mice at different time points after the last vaccination. In the preventive model of guinea pig, AEC/BC02 did not protect against Mycobacterium tuberculosis as a pre-exposure vaccine. However, in a latent infection model of guinea pig, it effectively controlled the reactivation of M. tuberculosis and lowered the bacterial load in the lung and spleen.ConclusionThese results indicate AEC/BC02 can protect against reactivation of latent infection and may function as a therapeutic vaccine.