TUMOR-NECROSIS-FACTOR-ALPHA PLAYS A CENTRAL ROLE IN IMMUNE-MEDIATED CLEARANCE OF ADENOVIRAL VECTORS

Adenovirus (Ad) gene transfer vectors are rapidly cleared from infecte d hepatocytes in mice, To determine which effector mechanisms are resp onsible for elimination of the Ad vectors, we infected mice that were genetically compromised in immune effector pathways [perforin, Fas, or tumor necrosis factor alpha (TNF-alpha)] with the Ad vector, Ad5-chlo ramphenicol acetyl transferase (CAT), Mice were sacrificed at 7-60 day s postinfection, and the levels of CAT expression in the liver determi ned by a quantitative enzymatic assay, When the livers of infected mic e were harvested 28 days postinfection, the levels of CAT expression r evealed that the effecters most important for the elimination of the A d vector were TNF-alpha > Fas > perforin, TNF-alpha did not have a cur ative effect on infected hepatocytes, as the administration of TNF-alp ha to infected severe combined immunodeficient mice or to infected cul tures in vitro had no specific effect on virus persistence, However, T NF-alpha-deficient mice demonstrated a striking reduction in the leuko cytic infiltration early on in the infection, suggesting that TNF-alph a deficiency resulted in impaired recruitment of inflammatory cells to the site of inflammation, In addition, the TNF-deficient mice had a s ignificantly reduced humoral immune response to virus infection, These results demonstrate a dominant role of TNF-alpha in elimination of Ad gene transfer vectors, This result is particularly important because viral proteins that disable TNF-alpha function have been removed from most Ad vectors, rendering them highly susceptible to TNF-alpha-mediat ed elimination.