Background: The purpose of this paper is to analyse the effects of local or systemic administration of adenovirus type 5 encoding the inducible costimulator fusion protein (AdICOSIg) on its influence on prolonging corneal allograft survival.
Methods: The ICOSIg chimeric molecule was generated by fusing the murine ICOS to a rat FcIgG portion and a recombinant adenovirus (Ad) was made thereof. A major histocompatibility complex (MHC) class I/II mismatched rat corneal transplant model was used. The recipients were randomly assigned to receive ex vivo gene-modified corneas expressing either ICOSIg or a single i.p. injection (1.0 x 10(9) infectious particles) of AdICOSIg two days after transplantation and graft survival was analysed. Moreover, the influence of ICOSIg fusion protein on anti-adenovirus immunity also was investigated.
Results: The ex vivo gene transfer of ICOSIg in cultured corneas resulted in high levels of ICOSIg protein in culture supernatants. However, neither ex vivo nor systemic gene therapy resulted in a significant prolongation of graft survival. Interestingly, the generation of anti-adenovirus antibodies could not be inhibited by systemic ICOSIg fusion protein expression.
Conclusions: Unlike CTLA4Ig, sole ICOSIg gene therapy is not a successful strategy for the prevention of allogeneic graft rejection in corneal transplantation.