Interleukin 7 (IL-7) has an important function in the development and maintenance of IL-17A+ gamma delta T cells. We here constructed a recombinant Mycobacterium bovis bacillus Calmette-Guerin expressing antigen 85B (Ag85B)-IL-7 fusion protein (rBCG-Ag85B-IL-7). The Ag85B-IL-7 fusion protein and IL-7 were detected in the bacterial lysate of rBCG-Ag85B-IL-7. rBCG-Ag85B-IL-7 was the same in number as control rBCG expressing Ag85B (rBCG-Ag85B) in the lung at the early stage after intravenous inoculation, whereas the numbers of IL-17A+ gamma delta T cells and Ag-specific Th1 cells were significantly higher in the lungs of mice inoculated with rBCG-Ag85B-IL-7 than those inoculated with rBCG-Ag85B. The Ag-specific Thl cell response was impaired in mice lacking IL-17A+ gamma delta T cells after inoculation with rBCG-Ag85B-IL-7. Thus, rBCG-Ag85B-IL-7 increases the pool size of IL-17A+ gamma delta T cells, which subsequently augment the Thl response to mycobacterial infection. (C) 2016 Elsevier Ltd. All rights reserved.