Restriction of cell surface expression of Sendai virus hemagglutinin-neuraminidase glycoprotein correlates with its higher instability in persistently and standard plus defective interfering virus infected BHK-21 cells.

To gain an understanding of the mechanism(s) by which Sendai virus generates a persistent infection, the expression of the hemagglutinin-neuraminidase (HN) and fusion (Fo) glycoproteins at the surfaces of BHK-21 cells infected with standard virus, a mixture of standard and defective interfering (DI) particles (mixed virus infection), and during persistent infection was investigated. The expression of HN and Fo was measured on the surfaces of infected cells by the binding of anti-HN and anti-Fo monoclonal antibodies. The results show that HN expression was restricted relative to Fo during mixed virus and persistent infections. The decreased levels of HN were investigated further by pulse-chase experiments which revealed that HN has an increased turnover rate in persistently infected cells and, to a lesser extent, in mixed virus infected cells. In analyzing the [35S]methionine-labeled protein composition of virus particles produced during the pulse-chase experiments, the increased turnover of newly synthesized HN was found to correlate with its decreased incorporation into virus particles. Interestingly, the poor HN incorporation also correlates with less efficient incorporation of the matrix M protein into virus particles.