Nucleoprotein (NP) generally binds to the viral RNA and is synthesized in large amounts during viral replication within the infected cells [26] . In the influenza A virus, NP is a comparatively conserved protein, and there is no recorded evolution in the viral strains of most birds over the past 60 years. [26] . Therefore, because of its high conservancy during the evolution of the virus, NP is an attractive target for inducing T-cell immunity [10, 26] . One of the promising approaches involves a direct DNA vaccination to stimulate T-cell immunity against NP. Some DNA vaccines and recombinant viral vaccines such as those constituting an adenovirus encoding the whole NP gene, are found effective in eliciting the T-cell immunity [6, 7, 14, 23] .