Establishing Intracellular Infection: Escape From The Phagosome And Intracellular Colonization (Rickettsiaceae)

Much progress has been made in one's understanding of the mechanism of rickettsial actin-based motility, although the process of cell-to-cell spread remains poorly understood. This chapter examines historical and recent developments in our understanding of how rickettsiae establish intracellular infection. The focus is on the three major stages that include: (i) escape from the phagosome, (ii) intracellular growth, and (iii) actinbased motility. Several bacterial activities that may function in membrane disruption have since been discovered, including phospholipase A2 (PLA2), phospholipase D (PLD), and hemolysins (TlyA and TlyC). Each of these activities and its potential role in phagosome escape is discussed in the chapter. Interestingly, the growth kinetics for the spotted fever group rickettsiae (SFGR) species R. rickettsii did not follow the simple kinetics observed for the typhus group rickettsiae (TGR) species R.prowazekii. The function of intracellular movement is to promote cell-to-cell spread, a process that is discussed in the chapter.