CMV-induced CEACAM1 Up-regulation and Effects on the Oral Mucosa

Introduction: The N-terminal domain of CEACAM1 is the main target of several bacterial pathogens specialized to colonize the human mucosa. In CMV infection, CEACAM1 is up-regulated in response to CMV-induced hypoxia. Although not well studied, variations in soluble CEACAM1 (sCEACAM1) are associated with different pathologies.

Objective: (1) To evaluate CEACAM1 expression, (2) quantify the secreted form in infected human umbilical vein endothelial cells (HUVEC), and (3) study the functional effects of sCEACAM1.

Methods: CEACAM1 expression was examined by immunoflourescence and detected by immunoblot analysis of cell extracts. sCEACAM1 was measured in conditioned media from HUVEC infected with a pathogenic CMV strain (VR1814) and uninfected control cells at 3, 6, and 9 days postinfection. We quantified sCEACAM1 by ELISA to measure the protein in conditioned media. To assess the functions of sCEACAM1 on cell migration, wound healing assays were preformed on scratched HUVEC monolayers incubated with conditioned media from infected and control cells. Dose-response assays were performed using media supplemented with recombinant CEACAM1 (rCEACAM1).

Results: Immunoflourescence analysis showed that CMV-infected HUVEC increase CEACAM1 expression at late times. Immunoblotting revealed that the protein increased slightly at 3 days and to a greater extent after 9 days. In addition, sCEACAM1 increased dramatically at 9 days postinfection. In functional assays, cells incubated in 6-day and 9-day conditioned media (i.e., highest sCEACAM1 levels) were severely impaired in wound closure. Likewise, HUVEC incubated in media supplemented with 50 pg-100 ng of rCEACAM1 slowed initial wound repair as compared with untreated controls.

Conclusions: CMV-infected HUVEC increased expression of CEACAM1 and the soluble form that impairs cell migration in vitro. Similar processes can occur in cells of the human mucosa. Increased CEACAM1 expression in CMV-infection can alter microbe colonization. Increase in sCEACAM1 can inhibit cell migration and impair repair of oral lesions in AIDS patients.