title: Nucleoproteins of animal influenza viruses, in contrast to those of human strains, are not cleaved in infected cells.
abstract: We previously reported that nucleoproteins (NPs) of human influenza viruses are cleaved in infected cells and, as a result, two forms of NP, uncleaved (mol. wt. 56000) and cleaved (mol. wt. 53000) were accumulated late in infection. Here, we report that NPs of animal influenza viruses of non-human origin (isolated from pigs, equids , seals, whales, birds) exhibited proteolytic resistance in infected cells and did not undergo a change in mol. wt. in the course of infection. The resistance of the animal virus NPs to proteolytic cleavage was shown to be a virus-specific property and not the consequence of a low level of proteolysis in infected cells. Influenza A/H3N2 viruses isolated from swine in Hong Kong in 1976 were found to have a cleavable NP like that of 'human' viruses, supporting the hypothesis concerning the 'human' origin of these strains. The NP of human influenza virus (A/Aichi/2/68) adapted to an animal host (mouse) retained susceptibility to limited intracellular proteolysis. Thus, NP resistance to cleavage seems to be a stable viral characteristic enabling the NP56 ---- NP53 modification to be used as an indication of the origin of influenza viruses.
mesh_terms: D000818:Animals; D002642:Chick Embryo; D006801:Humans; D009980:Influenza A virus / Q000378:metabolism*; D007251:Influenza, Human / Q000378:metabolism / Q000382:microbiology*; D009698:Nucleoproteins / Q000378:metabolism*; D009975:Orthomyxoviridae / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000378:metabolism; D010455:Peptides / Q000032:analysis / Q000378:metabolism; D014764:Viral Proteins / Q000378:metabolism*; D014776:Virus Cultivation
chemical_list: D009698:Nucleoproteins; D010455:Peptides; D014764:Viral Proteins; D010447:Peptide Hydrolases