The accumulation of mononuclear leukocytes is an early and persistent finding in atherosclerotic plaques. These mononuclear leukocytes are mostly monocyte-derived, but up to 20% are lymphocytes, predominantly CD4+ CD45RO+ (memory) T cells. To evaluate the potential of adenovirus vectors for studies of mononuclear leukocyte recruitment in vitro, we studied the effects of adenovirus vectors per se on human umbilical vein endothelial cells (HUVECs), a well-characterized in vitro model of vascular endothelium. A recombinant adenovirus containing the seven-domain isoform of rabbit vascular cell adhesion molecule-1 (rVCAM-1) was constructed and used to study lymphocyte adhesion under defined laminar flow conditions in transduced HUVEC monolayers. No increase in basal HUVEC surface expression of the inducible endothelial adhesion molecules and markers of activation, E-selectin and VCAM-1, was noted across a broad range of multiplicity of infection. A modest dose-dependent increase in surface intercellular adhesion molecule-1 expression was detectable by flow cytometry at an MOI of > 30 plaque-forming units per cell. Under defined laminar flow from 1.5 to 0.5 dyne/cm2, the adenovirus vector carrying rVCAM-1 mediated stable adhesion of both a Jurkat T-cell line and primary human CD4+ CD45RO+ (memory) T cells. Monoclonal antibodies to alpha 4-integrin or rVCAM-1 abolished adhesion, whereas monoclonal antibodies to CD18 or P-selectin had no effect. We conclude that adenoviral gene transfer in useful for studies of VCAM-1-dependent leukocyte adhesion in vitro and that endothelial expression of VCAM-1 alone, in the absence of over endothelial cell activation, is sufficient under simulated physiological flow conditions to support adhesion of memory T cells, the predominant lymphocyte subset in atherosclerotic plaque.
Adenoviridae Animals