Human Cytomegalovirus Secretome Contains Factors That Induce Angiogenesis and Wound Healing

Abstract

Human cytomegalovirus (HCMV) is implicated in the acceleration of a number of vascular diseases including transplant vascular sclerosis (TVS), the lesion associated with chronic rejection (CR) of solid organ transplants. Although the virus persists in the allograft throughout the course of disease, few cells are directly infected by CMV. This observation is in contrast to the global effects that CMV has on the acceleration of TVS/CR, suggesting that CMV infection indirectly promotes the vascular disease process. Recent transcriptome analysis of CMV-infected heart allografts indicates that the virus induces cytokines and growth factors associated with angiogenesis (AG) and wound healing (WH), suggesting that CMV may accelerate TVS/CR through the induction and secretion of AG/WH factors from infected cells. We analyzed virus-free supernatants from HCMV-infected cells (HCMV secretomes) for growth factors, by mass spectrometry and immunoassays, and found that the HCMV secretome contains over 1,000 cellular proteins, many of which are involved in AG/WH. Importantly, functional assays demonstrated that CMV but not herpes simplex virus secretomes not only induce AG/WH but also promote neovessel stabilization and endothelial cell survival for 2 weeks. These findings suggest that CMV acceleration of TVS occurs through virus-induced growth factors and cytokines in the CMV secretome.Numerous epidemiological and animal studies link human cytomegalovirus (HCMV) to the acceleration of vascular diseases including arterial restenosis, atherosclerosis, and transplant vascular sclerosis (TVS) (23,24,37). Recent advances in transplantation have significantly impacted short-term allograft and patient survival; however, long-term graft survival has not improved, due largely to chronic rejection (CR). The prevalence of CR is a concern, since retransplantation is the sole effective therapy. TVS represents the hallmark of CR in vascularized solid organ transplants, and HCMV infection nearly doubles the 5-year rate of cardiac graft failure due to accelerated TVS (11). In heart transplant recipients, ganciclovir, a potent inhibitor of CMV replication, delays the time to allograft rejection (25, 44). A higher incidence of viral DNA in the explant vascular intima from patients with cardiac allograft TVS than in explants without vasculopathy further underscores the influence of HCMV on CR development (47). In kidney transplant patients, the presence of HCMV infection, whether asymptomatic or displaying overt symptoms, negatively impacts allograft survival (9). The role of HCMV in TVS/CR development is clear; however, the mechanisms involved in this process remain illusive for the following reasons: HCMV disease etiology is multifactorial; HCMV is ubiquitous throughout the human population; HCMV infection is lifelong and infects all of the cell types involved in TVS, including smooth muscle cells (SMC), endothelial cells (EC), and macrophages; and HCMV evades the immune system by remaining latent, and clinically silent reactivation is diffic...

The Cell Biology of Cytomegalovirus: Implications for Transplantation

“…Consequently, IE84-mediated inhibition of p53 function may enhance proliferation of SMCs and contribute to coronary restenosis (129). HCMV-infected fibroblasts and ECs secrete PDGF, a mitogen and chemoattractant for mesenchymal cells, and TGF-b, which may produce changes in myofibroblasts and pericytes to promote stabilization of new vessels (120,133). Because SMC migration into the neointimal space is the hallmark of vascular disease, these observations provide a molecular link between HCMV and graft arterial vascular disease (134).…”

“…This includes laminins and >41 cytokines, chemokines and chemokine receptors that affect angiogenesis and wound healing (chemokines IL-6, osteoprotegerin, growth-regulated oncogene, C-C motif chemokine ligand [CCL] 3, CCL5, CCL7, CCL20, CXCL5, and CXCL16; receptors TNF receptors I and II and ICAM1; growth factors TGF-b1, hepatocyte growth factor and granulocyte macrophage (122) and VCAM1, which, in the early phase of infection, enhance transendothelial cell migration of inflammatory cells including monocytes, promoting angiogenesis by secretion of VEGF (120,123). Vascular proliferation is facilitated by degradation of basal membranes by matrix metalloproteinases and tissue inhibitors of matrix metalloproteinase released by HCMV-infected fibroblast and epithelial cells (120).…”

The immunology of human cytomegalovirus latency: could latent infection be cleared by novel immunotherapeutic strategies?

“…69,71,72 Manipulation of the cellular microenvironment by changes in the cell secretome HCMV lytic infection is also known to induce profound alterations in levels of secreted cellular proteins (secretome) and this includes a number of chemokines and cytokines with immune functions. 73,74 However, until recently, little was known about latency-associated changes in the cell secretome. The possibility that viral manipulation of secreted cellular proteins would likely be an effective mechanism to modify the microenvironment around latently infected cells to help maintain life-long carriage of latent virus in the face of constant immune surveillance has been investigated by us and others.…”

Human cytomegalovirus latency alters the cellular secretome, inducing cluster of differentiation (CD)4+T-cell migration and suppression of effector function

“…HCMV is known to regulate the secretion of numerous cellular chemokines, cytokines, and growth factors during lytic infection (7,8). Little is known, however, about the changes that occur in the secretome during latent infection, and yet this is likely to be of great importance for carriage of latently infected cells in vivo.…”