THE ROLE OF KUPFFER CELL ACTIVATION AND VIRAL GENE-EXPRESSION IN EARLY LIVER TOXICITY AFTER INFUSION OF RECOMBINANT ADENOVIRUS VECTORS

Systemic application of first-generation adenovirus induces pathogenic effects in the liver. To begin unraveling the mechanisms underlying e arly liver toxicity after adenovirus infusion, particularly the role o f macrophage activation and expression of viral genes in transduced ta rget cells, first-generation adenovirus or adenovirus vectors that lac ked most early and late gene expression were administered to C3H/HeJ m ice after transient depletion of Kupffer cells by gadolinium chloride treatment. Activation of NF-kappa B, and the serum levels of the proin flammatory cytokines tumor necrosis factor (TNF) and interleukin-6 (IL -6) were studied in correlation with liver damage, apoptosis, and hepa tocellular DNA synthesis. While Kupffer cell depletion nearly eliminat ed adenovirus-induced TNF release, it resulted in a more robust IL-6 r elease, These responses were greatly reduced in animals receiving the deleted adenovirus. Although there were quantitative differences, NF-k appa B activation was observed within minutes of first-generation or d eleted adenovirus vector administration regardless of the status of th e Kupffer cells, suggesting that the induction is related to a direct effect of the virus particle on the hepatocyte. Early liver toxicity a s determined by serum glutamic-pyruvic transaminase elevation and infl ammatory cell infiltrates appeared to be dependent on adenovirus-media ted early gene expression and intact Kupffer cell function, Kupffer ce ll depletion had little effect on adenovirus-mediated hepatocyte apopt osis but did increase hepatocellular DNA synthesis. Finally, Kupffer c ell depletion decreased the persistence of transgene (human alpha 1-an titrypsin [hAAT]) expression that was associated with a more pronounce d humoral immune response against hAAT. The elucidation of these event s occurring after intravenous adenovirus injection will be important i n developing new vectors and transfer techniques with reduced toxicity .