Abstract 196: Effects of an Engineered Herpes Simplex Virus (HSV-1) on Vascular Cell Adhesion

Abstract

Introduction The genetically engineered HSV R7020 is known to block vascular smooth muscle cell (SMC) proliferation while allowing for re-endothelialization after balloon angioplasty. This HSV-1 anti-proliferative effect requires MEK activation. However, it is unknown what effect R7020 has on vascular inflammation and monocyte adhesion. We hypothesized that exposure of SMCs to HSV R7020 would not affect vascular adhesion molecules. Methods Human aortic SMCs were exposed to R7020 for 10 minutes in the absence and presence of TNF-α (10 ng/ml). After washing cells were cultured for 24 hours in the absence and presence of TNF-α. Vascular cell adhesion molecule 1 (VCAM-1) and intracellular adhesion molecue-1 (ICAM-1) levels were determined using immunocytochemistry and image J. The adhesion of calcein AM labeled PBMCs to these cells were also analyzed at 24 hours. VCAM-1 and ICAM-1 levels were measured in the carotids of New Zealand White Rabbits that underwent balloon injury and exposed to R7020 (n=4) or saline (n=4) for 10 minutes using microarray analysis. Results There was no significant difference in ICAM-1 levels in the R7020 treated and control SMCs (219±11 vs 223±1; p=0.758); there was an 8 fold increase in ICAM-1 in the TNF-α treated SMCs (219±11 vs 1587±68; p=1.2x10 -13 ). Results were similar for VCAM-1. R7020 caused an increase in the adhesion strength of SMCs to collagen coated glass slides at 24 hours. Microscopic experiments (n=3) showed PBMCs adhered similarly to SMCs treated with TNF-α in the absence and presence of the virus (4 times that of control cells as measured by PBMC adhesion assay). Interestingly, after adhesion, Calcein AM was frequently observed in virus infected SMCs in the presence and absence of TNF-α. In cells not exposed to R7020, this rarely occurred. Microarray analysis demonstrated a 2.3 fold reduction in VCAM-1 expression in the R7020 treated rabbits (p=2.8x10 -14 ) and no significant difference in expression in ICAM gene expression (p=0.3). Conclusions In contrast to TNF-α, R7020 does not increase ICAM-1 or VCAM-1. Both treatments domonstrate PBMC SMC adhesion with no additive or synergistic effect. However, R7020 results in intracellular transfer from PBMCs to SMCs suggesting the virus changes PBMC-SMC interplay.