TLR4 and tuberculosis: Our novel first-generation vaccine candidate, ID93, a fusion of Rv2608, Rv3619, Rv3620, and Rv1813 Mtb antigens, combined with synthetic toll-like receptor 4 (TLR4) agonist glucopyranosyl lipid adjuvant (GLA) in a stable nano-emulsion (SE), is an effective prophylactic TB vaccine which has been tested in several preclinical animal models, demonstrating protection against lab-adapted and virulent clinical isolates of Mtb, as well as DS and DR Mtb strains, and is currently in phase 2 clinical trials [11,12,13,14,15,16,17,18,19,20] (trial identifiers: NCT01599897, NCT02508376).