Abstract 15187: The Nonstructural Proteins Ns1 and 11kda of Human Parvovirus B19 Induce Apoptosis Through Caspases 8 and 10 Inducing Dysfunction of Circulating Cells with Endothelial Regenerative Potential
The vasculotropic Parvovirus B19 (B19V) is associated with endothelial dysfunction and cardiac ischaemia and has an impact on endothelial regenerating cells (CERP) and endothelial cell apoptosis in humans. In erythroid progenitor cells, NS1 and 11kDa proteins are potent inducers of apoptosis. We have previously shown that CERP carry the necessary receptor status for B19V infection. We, therefore tested the hypothesis, that is a causal agent for impaired endothelial regeneration. Concentrations of B19V DNA were found in high concentrations in CD34+KDR+-progenitor cells (PC) compared to endomyocardial (EMB) in 17 patients with B19V-cardiomyopathy (EMB: 847 ± 444; bone marrow PC: 5620 ± 12551; blood PC: 10455 ± 19845 copies B19V DNA /genomic DNA; Figure 1A). Strikingly, B19V mRNA, indicating B19V replication, was found in these 6 of these 17 patients in PC, but only in 2 EMB samples. Early outgrowth endothelial progenitor cells (EPC) were effectively infected with B19V, with higher concentrations of B19V after 72 h compared to 24h, indicating replication in EPC. Similarly, after infection of ECFC with B19V, mRNA expression of early (NS1, 7.5kDa protein) and late (11kDa protein) genes confirmed these CERP as at least semipermissive cells. Expression of NS1 in ECFC increased apoptosis threefold compared to controls whereas 11kDa resulted in a 4,5-fold increased number of Annexin V positive cells measured by FACS analysis, and were confirmed with the TUNEL assay. Hypoxia further increased apoptosis induction of ECFC.After infection of ECFC with B19V apoptosis as measured by caspase 3 (p<0.01) and Annexin V+/ PI- cells (p<0.01) in FACS analysis was significantly reduced an inhibition experiment pretreatment with caspase 8- and 10-inhibitors. Since B19V is pathogenetic for humans only, B19V-infected EPC were injected in SCID beige mice (B19V-mice) after denudation of the carotid artery. Compared to mice receiving uninfected EPC B19V-mice had a significant increase of murine ckit+flk+-cells in blood (p<0.05) and reduced reendothelialisation. Thus, we show for the first time that B19V infects and replicates in CPC with a causal impact on endothelial repair capacity, confirming the strong relation of haematopoiesis and endothelial cellular regeneration.
- © 2011 by American Heart Association, Inc.