A RECOMBINANT ADENOVIRAL VECTOR EXPRESSING A SOLUBLE FORM OF VCAM-1 INHIBITS VCAM-1 VLA-4 ADHESION IN TRANSDUCED SYNOVIOCYTES/

Intra-articular injection of recombinant adenovirus has been shown to be a feasible approach to the introduction of genetic reagents into sy novial tissues in vivo. Rheumatoid arthritis (RA) is an autoimmune dis order characterized by the infiltration of lymphocytes and monocytes i nto inflamed synovium. It has been hypothesized that the recruitment o f T lymphocytes/monocytes into sites of chronic inflammation is mediat ed by enhanced binding of very late antigen-4 (VLA-4) to vascular cell adhesion molecule-1 (VCAM-1) expressed on microvascular endothelial c ells. Additional evidence suggests that VLA-4 binding continues to be important within the inflamed synovial membrane, where it appears to p lay 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 m olecule to block VLA-4 binding. In order to test this concept, a recom binant serotype Ad5 human adenovirus encoding a secreted form of VCAM- 1 (Ad.CBsVCAM) was constructed. Human synoviocytes were readily infect ed in vitro with Ad.CBsVCAM, and sVCAM-1 expression and processing wer e analyzed by immunoprecipitation studies. Secretion of transgenic sVC AM was identified by ELISA of tissue culture supernatants, and biologi cal activity was demonstrated with cell adhesion assays. In vivo, tran sgenic sVCAM-1 expression was determined by immunohistochemical analys is and in situ hybridization of synovial tissue, and secretion of tran sgenic sVCAM-1 was demonstrated by ELISA of tidal knee lavage fluid. T he results showed that recombinant adenovirus can mediate the expressi on of a biologically active sVCAM-1 by synoviocytes in vivo and sugges t that this strategy may be useful for inhibiting T lymphocyte retenti on and activation within rheumatoid synovium.