Significance of host cell kinesin in the development of Chlamydia psittaci

The influence of the microtubule-associated motor protein kinesin on Chlamy dia psittaci inclusion development in epithelial and fibroblast cell lines was addressed. Kinesin was blocked early after chlamydial internalization ( 4 h postinfection [p.i.]) and before the initiation of active chlamydial mu ltiplication (8 h p.i.). Chlamydia development was monitored by fluorescenc e and transmission electron microscopy at different times during the cycle. In both host cell lines, kinesin blockage restricted mitochondria from the chlamydial vacuole. The effects of kinesin blockage on the C. psittaci rep lication cycle included the presence of multiple inclusions up to late in t he cycle, the presence of enlarged pleomorphic reticulate bodies, and a del ayed reappearance of elementary bodies. The last effect seems to be greater when kinesin is blocked early after infection. Our results show that kines in activity is required for optimal development of these microorganisms, mo st probably acting through the apposition of mitochondria to the C. psittac i inclusions.