Pre-existing immunity reduces, but does not prevent secondary expansion of transgene-specific CD8 T cells.

<p><b>A.</b> Mice were vaccinated with Ad5-IiGP, followed by a second vaccination with the same vector on day 40. The GP-specific CD8 T cell response was measured on days 5, 8 and 11 after the second vaccination; mice given a single vaccination with Ad5-IiGP 11 days earlier served as positive controls. <b>B.</b> Mice were primed using an Ad35-IiGP vector and about two month later given Ad5-IiGP. The GP-specific CD8 T cell response was measured on days 5, 8 and 11 after the second vaccination; mice given a single vaccination with Ad5-IiGP 11 days earlier served as positive controls. <b>C.</b> B-cell deficient mice were primed using Ad5-IiGP, followed by a second vaccination with the same vector about two months later. The GP-specific CD8 T cell response was measured on days 8 and 11 after the second vaccination; mice given a single vaccination with Ad5-IiGP 11 days earlier served as positive controls.