Evidence for the extracellular delivery of influenza NS1 protein

We constructed a reporter influenza A/Puerto Rico/8/1934 virus expressing truncated 124aa N-terminal NS1 protein fused to luciferase sequence (NanoLuc) without signal peptide. The reproduction activity of the vector correlated well with luminescent in lysates infected cell cultures or mouse respiratory organ suspensions. Surprisingly, we found that enzymatic was present not only intracellular compartments but also culture supernatants as sera bronchiolar lavages mice. This fact allowed us formulate working hypothesis about extracellular delivery mechanism protein. To test this idea, conducted co-transfection experiments Vero cells different combinations plasmids encoding genomic segments and chimeric NS1-NanoLuc plasmid. emergence compartment promoted by formation ribonucleoprotein complex (RNP) from PB1, PB2, PA, NP proteins. Therefore, may be delivered together nascent RNP complexes during maturation particles.