Studies on the synthesis of the influenza V virus NB glycoprotein

The synthesis of the influenza B virus glycoprotein NB has been demonstrated in cells infected with four different virus strains isolated from 1940 to 1983. Time-course studies have shown that the neuraminidase protein (NA) and NB appear simultaneously in infected cells, in agreement with the previous observation that both proteins are translated from a single, bicistronic mRNA. Pulse-chase experiments indicated that the NB protein disappears from infected cells within 3 hr after synthesis. The influenza B virus nonstructural protein NS2 was also observed to disappear rapidly from infected cells, with none detected 1 hr after synthesis. Immunoprecipitation of viral proteins from infected cells using hyperimmune mouse serum has demonstrated antigenic cross-reactivity among the NB proteins of the four virus strains studied. The finding of polypeptides smaller than NB that exhibit a labeling pattern with different amino acids which is characteristic of NB and which are precipitated by the mouse antiviral serum suggests that specific cleavage products of NB may be formed in infected cells.