Trehalose 6,6'-dimycolate on the surface of Mycobacterium tuberculosis modulates surface marker expression for antigen presentation and costimulation in murine macrophages.

Trehalose 6,6'-dimycolate (TDM) is the most abundant lipid extracted from Mycobacterium tuberculosis (MTB). TDM promotes MTB survival by decreasing phagosomal acidification and phagolysosomal fusion in macrophages. Delipidation of MTB using petroleum ether removes TDM and decreases MTB survival within host cells. TDM reconstituted onto MTB restores its virulent wild-type characteristics. We investigated the role of TDM in regulating surface marker expression in MTB-infected macrophages. Macrophages were infected with wild-type, delipidated, and TDM-reconstituted MTB for 24h and measured for changes in surface marker expression. TDM on MTB was found to specifically target MHCII, CD1d, CD40, CD80 and CD86. Both wild-type and TDM-reconstituted MTB suppressed or induced no change in expression of these surface markers, whereas delipidated MTB increased expression of the same markers. MTB-infected macrophages were also overlaid with MHCII-restricted T cell hybridomas which recognize Antigen 85B. Macrophages infected by wild-type and TDM-reconstituted MTB did not present antigen as well as delipidated MTB-infected macrophages. The evidence shown furthers supports the notion that TDM present on MTB promotes its survival and persistence in host macrophages.