In vitro infection of endothelial cells with R. conorii or R. rickettsii promotes the upregulation of pro-inflammatory cytokines, such as IL-6 and IL-18 (35), and chemokines, such as CX3CL1 and MCP-1, at both transcriptional and post-transcriptional levels (36, 37). This evidence concerns the gene CX3CL1 and infection.