A recombinant adenoviral vector expressing a soluble form of VCAM-1 inhibits VCAM-1/VLA-4 adhesion in transduced...

Intra-articular injection of recombinant adenovirus has been shown to be a feasible approach to the introduction of genetic reagents into synovial tissues in vivo. Rheumatoid arthritis (RA) is an autoimmune disorder characterized by the infiltration of lymphocytes and monocytes into inflamed synovium. It has been hypothesized that the recruitment of T lymphocytes/monocytes into sites of chronic inflammation is mediated by enhanced binding of very late antigen-4 (VLA-4) to vascular cell adhesion molecule-1 (VCAM-1) expressed on microvascular endothelial cells. Additional evidence suggests that VLA-4 binding continues to be important within the inflamed synovial membrane, where it appears to play a role in T cell retention and activation. A feasible therapeutic strategy for RA could be to utilize a soluble congener of the VCAM-1 molecule to block VLA-4 binding. In order to test this concept, a recombinant serotype Ad5 human adenovirus encoding a secreted form of VCAM-1 (Ad.CBsVCAM) was constructed. Human synoviocytes were readily infected in vitro with Ad.CBsVCAM, and sVCAM-1 expression and processing were analyzed by immunoprecipitation studies. Secretion of transgenic sVCAM was identified by ELISA of tissue culture supernatants, and biological activity was demonstrated with cell adhesion assays. In vivo, transgenic sVCAM-1 expression was determined by immunohistochemical analysis and in situ hybridization of synovial tissue, and secretion of transgenic sVCAM-1 was demonstrated by ELISA of tidal knee lavage fluid. The results showed that recombinant adenovirus can mediate the expression of a biologically active sVCAM-1 by synoviocytes in vivo and suggest that this strategy may be useful for inhibiting T lymphocyte retention and activation within rheumatoid synovium.