Abstract 20640: Human Parvovirus B19 Induces Apoptosis Through the Nonstructural Proteins NS1 and 11kDa in Circulating Cells With Endothelial Regenerative Potential
The vasculotropic human Parvovirus B19 (B19V) induces endothelial cell (EC) apoptosis and is associated with endothelial dysfunction and cardiac ischaemia. Infection with B19V modulates numbers of bone marrow-derived circulating angiogenic cells (CAC) involved in vascular repair. B19V replicates in erythroid progenitors (EP) of the bone marrow. We therefore hypothesised that B19V contributes to endothelial injury through direct damage of CAC. The receptor and coreceptor status for B19V infection of CAC in FACS analysis was comparable to the semi-permissive EP cell line UT7-Epo-S1 (P-Antigen 74%/ β1 integrin 98%/ Ku80 5%): cultured EPC, or EC-like cells, (63%/59%/17%), CFU-Hill (43%/91%/5%), ECFC (64%/81%/13%) and CD34+KDR+ progenitor cells (61%/68%/50%). In vitro infection of CAC demonstrated virus binding and DNA uptake by qPCR analysis. Virus uptake was confirmed by confocal microscopy, demonstrating intracellular viral capsid proteins, and by electron microscopy. Furthermore, in situ hybridization demonstrated B19V in CAC (ECFC 23%, EC-like cells 37% (both p<0.0001) and CFU-Hill 11% infected cells; p=0.985). CAC were transfected with expression plasmids for the viral nonstructural proteins NS1 and 11kDa (transfection efficiency in ECFC: 22%). Expression of NS1 in ECFC increased apoptosis 3-fold compared to controls, whereas 11kDa resulted in a 4,5-fold increase of apoptosis measured by FACS analysis. We are currently analyzing the signaling pathways. To assess the pathophysiological relevance of B19V infection in vivo, a functional assay for CAC was performed. Indeed, in patients with chronic B19V infection, numbers of EC-like cells were significantly reduced (B19V patients (n=17) 183/mm2 [137–278] vs. control (n=10) 310/mm2 [230–450]; p=0.04), pointing to reduced regeneration. We show for the first time, that CAC with the necessary receptors represent a novel target for B19V infection, thus being a causal agent for ongoing endothelial regenerative dysfunction and consequent cardiac ischaemia. Induction of apoptosis through B19V in CAC may lead to a higher turnover of CAC and promote senescence. This might promote exhaustion of a probably finite pool of CAC as trigger for systemic endothelial dysfunction.
- © 2010 by American Heart Association, Inc.