VESICULAR INTERACTIONS OF THE CHLAMYDIA-TRACHOMATIS INCLUSION ARE DETERMINED BY CHLAMYDIAL EARLY PROTEIN-SYNTHESIS RATHER THAN ROUTE OF ENTRY

Chlamydiae replicate intracellularly within a vacuole that has recentl y been characterized as intersecting an exocytic pathway, One of the i nitial events during chlamydial infection is the expression of a chlam ydial early gene product(s) that effectively isolates the inclusion fr om the endocytic-lysosomal pathway and makes it fusogenic with sphingo mgelin-containing exocytic vesicles. Associated with this change in ve sicular interaction is the delivery of the vacuole to the peri-Golgi r egion of the host cell, Inhibition of chlamydial early transcription o r translation causes Chlamydia trachomatis-containing vesicles to rema in dispersed throughout the cytoplasm, where they eventually fuse with lysosomes. Chlamydiae that have been internalized by Fc-mediated endo cytosis also avoid lysosomal digestion by a mechanism that requires ch lamydial protein synthesis. These results suggest that the vesicular i nteractions of the chlamydial inclusion are defined by parasite-direct ed modification of the endocytic vesicle rather than by the route of i nternalization.