Potential xenozoonosis is a concern for the clinical application of xenotransplantation. Human cytomegalovirus (HCMV) is one of the most important pathogens in allotransplantation, but the consequences of HCMV cross-species infection of porcine xenografts are unknown. Therefore, we investigated the effects of HCMV infection of porcine endothelial cells (pEC) on cell surface molecule expression and human leukocyte recruitment.Methods.
Infection of pEC inoculated with untreated, UV-inactivated, or heparin-treated HCMV at a multiplicity of infection (MOI) of 1 was analyzed by immediate early (IE) antigen expression. Cell surface receptor expression was studied by flow cytometry on pEC bulk cultures and differentially on IE-positive and -negative pEC. Adhesion of human leukocytes was tested on pEC monolayers. pEC supernatants were analyzed for cytokine content, chemotactic activity, and stimulatory effect on resting secondary pEC cultures.Results.
At day 2 postinfection, IE staining was evident in 10% to 20% of HCMV-infected cells. Cell-surface expression of E-selectin and vascular cell adhesion molecule-1 (VCAM-1) was upregulated in both IE-negative and -positive fractions of HCMV-infected pEC. In contrast, porcine major histocompatibility complex class I expression was upregulated in IE-negative cells, but reduced in IE-positive cells. The receptor alterations in the IE-negative fraction were mediated by pEC-derived soluble factors. The increased adhesion receptor expression was paralleled by enhanced human leukocyte chemotaxis and adhesion to infected pEC cultures. Pretreatment of HCMV with heparin, but not UV-inactivation, prevented adhesion-receptor modulation and reversed the increased adhesion and chemotaxis.Conclusions.
After pig-to-human solid organ transplantation HCMV may infect and activate the porcine endothelium, rendering the xenograft more susceptible to human leukocyte recruitment and rejection.