Saponin TQL1055 adjuvant-containing vaccine confers protection upon <i>Mycobacterium tuberculosis</i> challenge in mice

Tuberculosis (TB), caused by the intracellular pathogen <i>Mycobacterium tuberculosis</i> (<i>Mtb</i>), affects the lungs of infected individuals (pulmonary TB) but can also affect other sites (extrapulmonary TB). The only licensed vaccine <i>Mycobacterium bovis</i> bacillus <i>Calmette-Guerin</i> (BCG) protects infants and young children but exhibits variable efficacy in protecting against adult pulmonary TB. Poor compliance and prolonged treatment regimens associated with the use of chemotherapy has contributed to the development of multidrug-resistant (MDR) and extensively drug-resistant (XDR) <i>Mtb</i>. Thus, there is an urgent need for the design of more effective vaccines against TB. The development of safe and novel adjuvants for human use is critical. In this study, we demonstrate that saponin-based TQL1055 adjuvant when formulated with a TLR4 agonist (PHAD) and <i>Mtb</i> specific immunodominant antigens (ESAT-6 and Ag85B) and delivered intramuscularly in mice, the SA-TB vaccine induced potent lung immune responses. Additionally, the SA-TB vaccine conferred significant protection against <i>Mtb</i> infection, comparable with levels induced by BCG. These findings support the development of a SA-TB vaccine comprising TQL1055, as a novel, safe and effective TB vaccine for potential use in humans.