Factors contributing to protection against experimental tuberculosis have been studied with refined and well-characterized fractions from mycobacteria and with certain unrelated antigens. Mice were vaccinated intravenously with various combinations of materials presented on minute oil droplets in saline emulsion and were later challenged by aerosol. The minimal composition of an effective vaccine was P3 (a trehalose mycolate similar to cord factor) plus an antigen, which could be tuberculo-protein, or a low-molecular-weight tuberculin-active peptide, or unrelated antigen such as bovine serum albumin or bacterial endotoxin. Development of a hypersensitivity granuloma in the lungs appeared to be essential to protection in this laboratory model.
Ribi, E., Granger, D. L., Milner, K. C., Yamamoto, K., Strain, S. M., Parker, R., … Azuma, I. (1982). Induction of resistance to tuberculosis in mice with defined components of mycobacteria and with some unrelated materials. Zentralblatt Fur Bakteriologie Mikrobiologie Und Hygiene - Abt. 1 Orig. A, 251(3), 345–356. https://doi.org/10.1016/s0174-3031(82)80104-2