Fas-Fas Ligand Interactions Play a Major Role in Effector Functions of Cytotoxic T Lymphocytes after Adenovirus Vector-Mediated Gene Transfer

Abstract

Adenovirus vectors transduce liver hepatocytes with extreme efficiency; however, transgene expression is eliminated within 2 weeks. Extinction of transgene expression has been attributed to infiltrating cytotoxic T lymphocytes (CTLs) in the liver in a process that resembles a number of human diseases, including viral and autoimmune hepatitis. In this study we investigated the role of Fas-Fas ligand interactions in killing of vector-transduced hepatocytes in vitro and in vivo. Intrahepatic lymphocytes (IHLs) isolated from livers of mice administered adenovirus vector demonstrated cytolytic activity against vector-infected primary hepatocytes. The in vitro CTL activity of the IHLs involving both CD4+ and CD8+ T cells was MHC class I restricted and could be blocked by soluble Fas-IgG. Adoptive transfer of IHLs from immune-competent mice immunized with Ad-lacZ into Ragl-deficient mice previously infused with Ad-lacZ resulted in rapid elimination of beta-galactosidase-transduced hepatocytes. Transfer of these cells into Fas-deficient mice (B6-lpr) failed to eliminate lacZ expression; likewise IHLs from immunized FasL-deficient mice (B6-gld) failed to eliminate lacZ expression in Rag1-deficient mice. Finally, in vivo administration of soluble Fas-IgG abrogated the ability of Ad-lacZ-primed IHLs to eliminate transgene expression. These studies establish an essential role for Fas-Fas ligand interactions in the mechanism of elimination of adenoviral vector-mediated transgene expression in the liver.

Apoptosis and Regeneration of Hepatocytes during Recovery from Transient Hepadnavirus Infections

“…Thus, even when CTLs could kill only once, an unproven assumption, the continuous expansion of CD8 ϩ T cells could account for the replacement of an entire liver over a relatively short period. The potential of CTLs to induce the turnover of a whole liver in a short time span has recently been demonstrated with adenovirus infections in mice (2). In this system, clearance of an infection involving nearly every hepatocyte occurs by CTLs in a Fas-dependent pathway.…”

“…The platelets and lymphocytes were transferred to a new centrifuge tube, and the cells were washed twice with Hank's balanced salt solution. Approximately 10 6 peripheral blood mononuclear cells (PBMC) were cultured in 2 ml of complete RPMI 1640 medium containing concanavalin A (5 U/ml) for 12 to 24 h at 37°C in a humidified incubator containing 5% CO 2 .…”

Critical roles of TRAIL in hepatic cell death and hepatic inflammation

“…Recent studies suggest that death ligands of the TNF family may play a crucial role. Thus, both FasL and TNF appear to be involved in mediating hepatic cell death in experimental models of hepatitis, and blocking FasL and/or TNF may ameliorate the disease to various degrees (1)(2)(3)(4). However, whether and to what degree other death ligands are involved in hepatic cell death are not clear.…”

Fas and TNFR1, but not cytolytic granule-dependent mechanisms, mediate clearance of murine liver adenoviral infection

“…In contrast, marked delay in hepatic adenoviral infection is noted in mice deficient in Fas, FasL, or TNF expression. 13,20,[23][24][25] However, mice with isolated defects in expression of TNFR1, the major mediator of TNF-induced apoptosis, clear hepatic adenoviral infection at rates similar to those in wild-type mice, whereas mice with defects in either TNF or tumor necrosis factor receptor 2 expression exhibit delays in adenoviral clearance that seem to be related to diminished activation of intrahepatic FasL-expressing CTL. 24 Thus, results of prior studies suggest that among the various CTL effector pathways, FasL/Fas-mediated cytotoxic effector mechanisms play the most prominent role in clearance of hepatic viral infections, 20,24 whereas the potential role of other cytotoxic effector mechanisms remains unclear.…”