Peripheral Blood Endothelial Progenitors as Potential Reservoirs of Kaposi's Sarcoma-Associated Herpesvirus

Abstract

BackgroundThe cellular reservoirs of Kaposi's sarcoma-associated herpesvirus (KSHV) and the exact nature of the putative KSHV-infected circulating precursor of spindle cells of Kaposi's sarcoma (KS) still remain poorly defined. Because KS spindle cells are thought to be of endothelial origin, and because mature endothelial cells do not sustain persistent KSHV-infection, our attention was focalized on circulating hematopoietic precursors able to differentiate into endothelial lineage.Methods and FindingsLate endothelial progenitor cells (late-EPCs) were cultured from the peripheral blood mononuclear cells of 16 patients with classic KS. The presence and load of KSHV genomes were analyzed by real-time polymerase chain reaction in DNA extracted from cells and supernatants of late-EPC cultures obtained from 7 patients. Endothelial colonies cultured from the peripheral blood of KS patients were found to satisfy all requisites to be defined late-EPCs: they appeared from the CD14-negative fraction of adherent cells after 11–26 days of culture, could be serially expanded in vitro, expressed high levels of endothelial antigens but lacked leukocyte markers. Late-EPC cultures were found to harbor KSHV-DNA at variable levels and to retain the virus after multiple passages in cells as well as in supernatants, suggesting that a quote of KSHV lytic infection may spontaneously occur. Lytic phase induction or hypoxia could amplify virus release in supernatants.ConclusionOur results suggest that circulating endothelial progenitors from KS patients are KSHV-infected and support viral productive replication and may therefore represent potential virus reservoirs and putative precursors of KS spindle cells.

Productively Infected Murine Kaposi's Sarcoma-Like Tumors Define New Animal Models for Studying and Targeting KSHV Oncogenesis and Replication

“…Prominin-1/CD133 is a marker of EPCs [44], [53], [54], putative KS spindle-cell precursors [13], [14], [22], and has been shown by Liu et al to be upregulated upon KSHV infection of lymphatic endothelial cells [9], [45]. Our results displaying variable tumor formation from the mECK null .rK cells suggested the possibility of the existence of a limited number of true oncogenic cells.…”

The phosphatase Shp2 is required for signaling by the Kaposi's sarcoma-associated herpesvirus viral GPCR in primary endothelial cells

“…We therefore extended our studies into BOEC cells. BOEC are derived from circulating endothelial cell progenitors, display a micro-vascular phenotype, and as noted above have recently been found to harbor KSHV infection in vivo (Della Bella et al, 2008; Lin et al, 2002; Lin et al, 2000). To introduce exogenous DNA into these primary cells, we used lentiviral transduction.…”

“…It is clear that HIV infection or other non-HIV immunomodulatory co-factors must be present. It has been hypothesized that at least in its early stages, KS is a cytokine driven process (Della Bella et al, 2008; Monini et al, 1999). How the cytokine milieu in the tumor microenvironment is established and maintained and how it in turn supports viral propagation and tumor progression is still being defined.…”

“…(Jiang et al, 2007; Lin et al, 2000). Furthermore, BOEC have recently been shown to be infected with KSHV in vivo and are able to support the production of new virions; they are therefore a very suitable cell type for KSHV molecular pathogenesis studies (Della Bella et al, 2008). …”

Cancer Angiogenesis Induced by Kaposi Sarcoma–Associated Herpesvirus Is Mediated by EZH2

“…BOEC cells are derived from blood circulating precursor cells and have typical endothelial cobblestone morphology and features (28). BOEC cells harbor KSHV in KS patients and support KSHV infection (30). Almost all cells in the KSHV-infected BOEC cultures were LANA-positive 5 days after infection (Fig.…”