Infection of human endothelial cells with Chlamydia pneumoniae stimulates transendothelial migration of neutrophils and monocytes

We have previously shown that different isolates of Chlamydia pneumoniae display heterogeneity in the in vitro stimulation of chemokines and adhesion molecules from infected human endothelial cells. In the present study, we examined the ability of different isolates of C. pneumoniae to promote transendothelial migration of neutrophils and monocytes. Human umbilical vein endothelial cells (HUVEC) were infected with low (<15)passage C. pneumoniae isolates A-03, PS-32, and BR-393 and high (>40)-passage isolates BAL-16, TW-183, and T-2634, and levels of neutrophil and monocyte transendothelial migration were determined following 24 h of infection. Compared to mock-infected controls, significant increases in neutrophil migration were observed in response to most C. pneumoniae isolates examined (P < 0.001). Levels of monocyte migration were significantly increased in response to TW-183 and T-2634 (P < 0.001), Serial passage (>40 times) of the three low-passage isolates in HEp-2 cell cultures prior to infection of HUVEC generally resulted in the promotion of higher levels of neutrophil and monocyte transendothelial migration. These findings were compatible with differences observed in the extent of interleukin-8 (IL-8) and monocyte chemotactic protein-1 (MCP-1) stimulation between low- and high-passage A-03, PS-32, and BR-393. As opposed to C. pneumoniae, infection with C. trachomatis L2 caused only a slight increase in neutrophil transendothelial migration, which correlated with the lack of measurable IL-8 levels by this species. However, significant levels of monocyte migration were induced in response to C. trachomatis L2 despite a lack of measurable MCP-1 stimulation. C. trachomatis serovars A and E also failed to induce IL-8 and MCP-1 production in HUVEC. Results from this study indicate that the passage history of C. pneumoniae may play a role in the divergence of stimulatory activities observed among isolates in human endothelial cells. In addition, the differences observed between this organism and C. trachomatis suggest that the upregulation of IL-8 and MCP-1 in endothelial cells may be unique to C. pneumoniae.