A suggested role of a host-parasite lipid complex in mycobacterial infection

On the basis of our previous observations and related literatures, was assumed tht cholesterol esters of host origin and phthiocerol dimycocerosate of bacterial origin are located as a lipid mixture around the periphery of pathogenic mycobacteria growing in vivo, probably within the phagocytic vacuole of macrophages. To examine the role of such a postulated lipid complex in mycobacterial infection, a model experiment was made in which tubercle bacilli grown in vitro were "coated" with both lipids and then suspended homogenously in water to serve as an inoculum to infect mice intravenously. Their fate in mouse tissue was compared with that of untreated control bacilli. The results indicated that the lipid "coating" had an infection-promoting effect as revealed by the longer persistence of the treated avirulent bacilli at higher levels of viable counts. When virulent tubercle bacilli were "coated" with the lipid mixture, they became less sensitive to the protective mechanism of BCG-immunized mice.