[Integration of influenza A virus NSP gene into baculovirus genome and its expression in insect cells]

Segment NS in all human influenza A viruses and in the part of avian and animal ones was found to contain an additional (beside NS1 and NEP) long open reading frame (ORF) enabling to code a polypeptide of 18-26 kD in different strains. This ORF, in contrast to the NS1 and NEP, locates in positive sense orientation in the negative polarity genomic NS RNA segment and the encoded protein is referred NSP (Negative Strand Protein). Here, the NSP gene of human influenza A/WSN/33 (H1N1) virus was inserted into genomic DNA of baculovirus (insect nuclear polyhedrosis virus) and insect H5 cells (ovary cell line of Trichoplusia ni) were infected with the obtained chimeric virus. The NSP gene appeared to express 19 kD polypeptide which was intracellularly stable and accumulated predominantly in the cytoplasm of infected H5 cells. These data indicate that the NSP gene possesses sense sequence which is able to direct a physiological synthesis of stable protein in eukaryotic cells.