Most 1st and 2nd generation Ad vectors have the transforming genes of Ad, E1A, and E1B intentionally deleted. In addition to their transformation functions, these genes play a major role in the complex co-evolution of the host immune response to adenovirus (Ad) infection and the adenovirus response to the host defense mechanisms. Moreover, most Ad vectors lack E3 genes that encode the 10.4 and 14.5K proteins (RID) that facilitate Fas degradation and a number of proteins that antagonize TNF function. In the absence of these genes, the most important viral immunosuppression pathways may have been eliminated. Based on our previous studies identifying TNF-alpha and, to a lesser, Fas as central functional elements in both the cellular and humoral systemic immune response to viral infection, and studies demonstrating that Ad E3 expression prolongs transgene expression and therapeutic effect, we propose the following: (1) To determine whether neutralization of TNF-alpha, Fas, interferons or combinations of these host defense pathways prolong Ad transgene expression in the lung and other sites and to determine the mechanisms whereby this occurs; (2) distinguish between the immune response to Ad alone, versus Ad expressing either self or foreign transgenes; (3) To identify other cytokines/chemokines that are part of the innate immune response to Ad transgenes; and (4) To achieve high expression of transgene product repetitively and in the face of an already existing immune response. If successful, these strategies should prove useful for gene therapy for cystic fibrosis in the future.