The lower doses of Ad5GFP (103 and 105 PFU/animal) used to induce adenovirus-specific pre-existing antibodies generated significantly higher levels of antigen-specific CD8+ T cell lysis than animals pre-immunized with the highest dose of Ad5GFP (107 PFU/animal) independently of the route of infection (i.n. or i.m.). This evidence concerns the gene CD8A and infection.