Although a strong antibody response is important for immediate and long-term protection against influenza viruses, the induction of early cellular immune responses following vaccination may enhance clearance of virus-infected cells following H5N1 influenza virus infection. T-cell responses were assayed using an enzymelinked immunosorbent spot (ELISPOT) assay to detect secretion of interferon gamma (IFNc) by activated lymphocytes. Splenocytes were obtained from mice vaccinated at days 8, 10, 14, and 21 with 10 10 vp/mouse of PAV3-HA or AdHu5-HA and the cells were restimulated with pools of overlapping peptides corresponding to the entire H05-HA protein. The peptide corresponding to the immunodominant H5N1-H05 HA (IYSTVASSL, conserved influenza A virus) epitope was evaluated alongside an unrelated control peptide (TYQRTRALV, A/PuertoRico/8/34 H1N1 nucleoprotein).