DRM: detergent resistant membrane; GM1: monosialotetrahexosylganglioside; GPI: glycosylphosphatidylinositol; GHOST: human osteosarcoma cells expressing CD4 and green fluorescent protein; CTxB: cholera toxin-b subunit. Two novel HLA-A*0201 T-cell epitopes in avian H5N1 viral nucleoprotein induced specific immune responses in HHD mice The influenza A nucleoprotein (NP) is an attractive target for avian flu vaccine development because of its high conversancy in the evolutionary chain of the virus. Here we identified two novel HLA-A*0201 restricted NP epitopes, named H5N1 NP373-381 AMDSNTLEL (NP373) and NP458-466 FQGRGVFEL (NP458), using computational bioinformatic analysis. The NP peptides showed a high binding affinity to HLA-A*0201 on T2 cells, and were able to induce the activation of the cytotoxic T cells in the human peripheral blood mononuclear cells. We examined the potential of using NP373 and NP458 peptide sequences supplemented with a single-chain trimer as potential DNA vaccine candidates in an HHD transgenic mouse model. A gene gun delivery system was used for administrating the vaccine candidates into the animals. The results from cytotoxicity and ELISPOT assays indicated that a significant amount of IFN-γ was secreted by the T cells of the vaccinated mice, and the T cells were able to eliminate the corresponding peptide-loaded T2 cells. The discovery of these novel immunogenic NP peptides provides valuable information for avian flu vaccine design and construction. The transmission of a pathogenic avian H5N1 virus from poultry to humans in Hong Kong and other Asian countries has caused a number of human deaths [13, 17, 19] . Confirmed cases of H5N1 transmission have also been reported in various African and European countries 1 and all incidences have caused an enormous economic loss in the poultry industries worldwide. The threat of an H5N1 pandemic is becoming a major problem not only in Asian countries but countries worldwide. The urgency of developing a strategy to combat the H5N1 virus is an imperative task for most health authorities, and one possible solution is to develop a human vaccine against the H5N1 virus.