Boosting with mycobacterial heparin-binding haemagglutinin enhances protection of Mycobacterium bovis BCG-vaccinated newborn mice against M. tuberculosis

Heterologous prime-boost regimens are a valuable strategy to improve the generation of effector-memory T cell responses against intracellular pathogens. In this study we show that newborn mice vaccinated with bacillus Calmette-Guérin (BCG) and boosted with heparin-binding haemagglutinin (HBHA) had enhanced protective immunity against intranasal or aerosol Mycobacterium tuberculosis challenge over non-boosted mice, as evidenced by a considerable reduction of mycobacterial load in spleen and lung. The route of HBHA delivery had a differential impact on cytokine and antibody production in BCG-primed mice. The prime-boost regimen induced not only HBHA-specific IFN-γ, but also other cytokines, such as IL-12 and TGF-β, which may be associated with the generation of lung Th1 effector-memory lymphocytes, responsible for the enhanced protection against M. tuberculosis challenge.