Induced Liver Allograft Immunological Tolerance in Rats by Intramuscular Injection of Recombinant Adeno-Associated Virus–Human Cytotoxic T-lymphocyte-associated Antigen-4 Immunoglobulin (rAAV-hCTLA4Ig)

Induction of liver allograft immunological tolerance was performed in rats by intramuscular injection of recombinant adeno-associated virus-human cytotoxic T-lymphocyte-associated antigen-4 immunoglobulin (rAAV-hCTLA4Ig). Dark Agouti and Lewis rats were liver allograft donors and recipients, respectively, in four groups: (A) syngeneic control, (B) blank control, (C) rAAV-enhanced green fluorescent protein negative control, (D) rAAV-hCTLA4Ig. Gene transfers occurred 6 weeks before transplantation. Group D had a significantly longer liver graft survival time (> 100 days) than groups B (11.9 ± 1.3 days) and C (11.6 ± 1.1 days). Groups B and C showed severe rejection responses and large amounts of CD4+ and CD8+ T-lymphocyte infiltration, while only a mild response and few T-lymphocytes were observed in group D. There were no significant differences in interleukin-2 and interferon-γ levels in liver grafts between groups D and C, but there were significant decreases in granzyme B and lymphotoxin β levels in group D compared with group C. It is concluded that immunological tolerance to liver allograft could be achieved by gene transfer of rAAV-hCTLA4Ig through intramuscular injection.