Prolongation of adenoviral transgene expression in mouse liver by T lymphocyte subset depletion

Although first generation recombinant adenoviruses are efficient vehicles for gene transfer, their immunogenicity precludes long-term persistence. We show that adenoviral transgene expression in the liver of normal mice is prolonged from a baseline of less than 2 weeks to 7 weeks by depleting CD4+ T lymphocytes with thymectomy and a 3-day course of anti-CD4 monoclonal antibody or by nonselectively depleting T cells with a single dose of anti-thymocyte serum (ATS). Transgene expression persisted despite the development of an antiviral humoral immune response by 3 weeks after virus administration. In vitro assays of T lymphocyte function revealed an initial diminished capacity to proliferate in the presence of adenoviral antigens in animals depleted of CD4+ T cells or given anti-thymocyte serum. Eventual loss of recombinant gene expression coincided with the development of adenovirus-specific cytotoxic T lymphocyte activity in vitro. Immunosuppression provides a useful experimental tool to elucidate the immunobiology of recombinant adenoviruses and may have clinical application to adenovirus-mediated gene therapy.