The accumulation of mononuclear cells is an early event in the development of atherosclerotic lesions both in humans and in experimental models. These mononuclear cells are predominantly monocytes which give rise to foam cells. Lymphocytes comprise 5 to 20 percent of the mononuclear cell population and are predominantly of the memory (CD45RO+) T cell subset. The investigator's hypothesis is that the local expression of adhesion molecules and cytokines significantly modulates the adherence and infiltration of mononuclear leukocytes in the vessel wall, and that these leukocytes, in turn, influence atherogenesis. Expression of adhesion molecules such as vascular cell adhesion molecule-1 (VCAM-1) and chemokines such as monocyte chemoattractant protein-1 (MCP-1) has been identified preceding mononuclear infiltration in experimental models of atherosclerosis and in advanced lesions from human subjects. VCAM-1 supports adhesion of both monocytes and lymphocytes in vitro. MCP-1 is a powerful chemoattractant for monocytes and memory T cells in vitro. Therefore co-expression of VCAM-1 and MCP-1 may contribute to the local, specific recruitment of monocytes and memory T cells in atheromas. However this hypothesis and its impact on lesion formation remain largely untested. To more precisely define the role of VCAM-1 and MCP-1 in modulating leukocyte-endothelial cell interactions, leukocyte recruitment, and atherogenesis, recombinant adenoviral vectors will be used to create constitutive over-expression models in vitro and in vivo. cDNAs for VCAM-1, and wild-type or modified chemokines will be substituted for E1 into human Adenovirus type 5 (Ad5) genome under the transcriptional control of Rous Sarcoma Virus (RSV) LTR to provide efficient, high-level gene transfer to endothelial cells. In vitro, the hypothesis that co-expression of chemokine constructs can modulate the adhesion of specific leukocyte subsets will be tested. The possible roles of cell-associated chemokine or a soluble chemokine gradient will be addressed. The same adenoviral constructs will be used in vivo to transduce rabbit carotid arteries with the contralateral side transduced with null- mutant cDNAs and reporter constructs, serving as a control. These studies will determine whether local overexpression of VCAM-1 alone or in combination with chemokine constructs can promote recruitment of mononuclear leukocytes to the vessel wall, and whether this can modulate the formation of atherosclerotic lesions either in normo- or hypercholesterolemic rabbits.
