Mycolic acids from Mycobacterium tuberculosis: purification by countercurrent distribution and T-cell stimulation

Bacterial cell wall lipids are recognized as immunostimulatory molecules which make an important component of vaccines against bacterial diseases. Even mycolic acids, forming the waxy outer layer of the bacilli which cause tuberculosis, have been shown to stimulate human CD4/8 double negative T-cells. The role of these cells in resistance to tuberculosis is currently still debated. In this work, a method is described to purify mycolic acids from bacterial crude extracts in a single step using countercurrent distribution. Mycolic acids obtained in this way approach 100% purity and stimulate both double negative and CD4 positive T-cells in peripheral blood leucocytes obtained from healthy human donors. Stimulation of CD4 cells by mycolic acid antigens has not been reported before, emphasizing the potential importance of mycolic acids in the context of the fight against tuberculosis.