Endothelium; Transplantation; Cytomegalovirus; Coagulation; Inflammation; xenotransplantation; herpesvirus; infection; indirect effects; enodthelium
Millard Anne-Laure, Häberli Lea, Sinzger Christian, Ghielmetti Maddalena, Schneider Mårten K J, Bossart Walter, Seebach Jörg D, Mueller Nicolas J (2010), Efficiency of porcine endothelial cell infection with human cytomegalovirus depends on both virus tropism and endothelial cell vascular origin., in Xenotransplantation
, 17(4), 274-87.
Millard Anne Laure, Mueller Nicolas J (2010), Can human viruses infect porcine xenografts?, in Xenotransplantation
, 17(1), 6-10.
Millard Anne-Laure, Mueller Nicolas J (2010), Critical issues related to porcine xenograft exposure to human viruses: lessons from allotransplantation., in Current opinion in organ transplantation
, 15(2), 230-5.
The recent success with reversal of diabetes using porcine islets cells in a nonhuman primate model has demonstrated the great potential of xenotransplantation. The limitless supply of cells or organs remains an important goal in transplantation. For solid organs, progress has been slower, despite the availability of genetically altered pigs. Besides immunological and physiological barriers, coagulation has emerged as a main obstacle and has prompted great efforts in deciphering the cross-species incompatibilities and in finding strategies to overcome them. The potential for xenogeneic infections has been a major concern. Much attention has been given to donor-derived infections, neglecting host-derived infection with potentially dire consequences for the graft.Infections represent a major cause of morbidity and mortality in transplantation. Not only do infections cause direct damage, but increasing evidence points to indirect effects such as vasculopathy and graft rejection. Together with ischemia/reperfusion injury and immunosuppressive drug toxicity, infections may lead to accelerated graft loss. Human cytomegalovirus (HCMV) is the most important pathogen posttransplant. After establishing life-long latent infection in immunocompetent hosts, it frequently reactivates in immunosuppressed transplant recipients and potentially triggers graft rejection. In pig-to-baboon preclinical xenotransplantation, porcine CMV was found to cause a consumptive coagulopathy in the recipient animal.The endothelium has emerged as a major compartment of immune regulation, coagulation control and inflammation. The resting endothelium maintains an anti-inflammatory and anti-coagulant state. Activation will result in inflammation and a pro-coagulant state. Being a necessary process in the context of infection or damage, this can be detrimental for a transplanted organ. The graft endothelium is in close contact with the circulating blood of the recipient, exposing it to various immune responses as well as to host-derived CMV infection.Our findings generated in a cross-species model illustrate the potential of CMV to profoundly disturb the delicate hemostasis maintained by the endothelium. We were able to convincingly demonstrate productive infection of HCMV in porcine endothelial cells. Long believed to be a very species-restricted infection, CMV was able to cross the species barrier despite its close evolution with the host. However, we did recognize differences in infectivity and cellular control of infection by apoptosis. Infected porcine endothelial cells (EC) showed an activated phenotype with upregulation of adhesion molecules and strongly increased adhesion of human leukocytes and release of porcine pro-inflammatory cytokines. We established the tools to study the role of suppressor of cytokine signaling proteins in the counter-regulation of pro-inflammatory cellular responses.Based on these findings, the goal of the present proposal is to deepen our understanding of the mechanisms to develop strategies to prevent graft injury mediated by pro-inflammatory and pro-coagulant responses to CMV infection. The following specific aims will be addressed:Aim #1:Study the molecular basis of HCMV entry and replication into porcine endothelial cellsAim #2: Examine immunological consequences of CMV-infected endothelial cellsAim #3: Investigate the interplay between coagulation and CMV infectionThe outlined experiments will improve our understanding of the CMV-induced mechanisms resulting in EC alterations, particularly HCMV infection in porcine EC, and will provide evidence for the potential of different interventional approaches. This knowledge may then help us to design better prophylactic or preemptive therapies in both the human allotransplantation setting, and in xenotransplantation. If xenotransplantation proceeds to the clinical stage, understanding the potential role of cross-species CMV infection will be crucial to guide clinical trials.