Effect of dose and route of immunisation on the immune response induced in cattle by heterologous Bacille Calmette-Guerin priming and recombinant adenoviral vector boosting

sBCG is used experimentally as a vaccine against tuberculosis (TB), induced by Mycobacterium bovis, in cattle (bTB). However, the efficacy of BCG is variable in humans, cattle and guinea pigs. An adenoviral vector expressing Antigen 85A (Ad5Ag85A) has enhanced protection against TB in mice when used in combination with BCG for prime-boost experiments. However, the route of immunisation affects the degree of protection seen. This work examines the immunogenicity of a new vectored vaccine (Ad5-TBF) that expresses Ag85A, Rv0287, Rv0288 and Rv0251c to explore the effects of dose of adenoviral boost and route of inoculation on immunogenicity. We found that 2 × 109 infectious units (iu) delivered intradermally conferred the most consistent and strongest responses of the different regimes tested.