CCL2 and Treponema infectious disease: In particular, since the MCP-1/CCR2 axis has also been recently found to be involved in cell-mediated clearance of treponemal infection [37, 38], we speculate that CMV-mediated altered recruitment and function of monocytes/macrophages via the MCP-1/CCR2 axis may in turn affect the early immune response to Treponema pallidum and therefore increase the probability of acquisition of this pathogen.