Factors influencing adenoviral gene transfer

Intra-articular injection of an adenoviral vector in nonhuman primates with arthritis results in effecient gene transfer of the synoviocyte like fibroblasts, whereas no gene transfer has been observed to cartilage cells (Goossens et al: Hum Gene Ther 1999). In humans a possible factor that may influence gene transfer are pre-existing antibodies to adenovirus. Now, we have demonstrated that 70% of the synovial fluid samples harvested from 53 different patients inhibited gene transfer of adenovirus.

In 10 samples this was studied in detail by fractionation of the synovial fluid samples. The fraction that inhibited gene transfer most strongly had a molecular mass of 150 kDa and could be purified by protein-A sepharose columns, strongly suggesting that this fraction consisted of antibodies. In order to avoid the influence of naturally occurring autoantibodies we tested if different types of adenoviruses (Ad5, Ad26, Ad34, Ad35 and Ad48) were inhibited as strongly as Ad5. Only 4% of the synovial fluid samples contained antibodies that inhibited Ad35-mediated gene transfer. Next we tested if a vector that contained a fiber from subgroupB (Ad11, 16 or 35) was as efficient in transducing synoviocytes as the original Ad5 vector. The Ad5-fib35 vector encoding luciferase was about 10 times as efficient than the wild-type fiber when similar particle concentration was used to infect synoviocytes.

In conclusion, the current data suggest that fib35 is efficient in the binding of an adenoviral vector to synoviocyte-like fribroblasts, and that very few RA patients have naturally occurring antibodies to the type 35 adenoviral vector.