Chemiluminescence: An early event in the interaction of sendai and influenza viruses with mouse spleen cells I. The role of the envelope glycoproteins in the stimulation of chemiluminescence

Abstract

On infection with Sendai virus, non-adherent mouse spleen cells emit a burst of chemiluminescence (CL) starting within a few seconds and peaking at 6–8 min postinfection. The biological reactions leading to CL are not known in mouse spleen cells, but in phagocytic cells are believed to be correlated with the generation of unstable oxygen species by the cells (e.g., H 20 2, 0 2 −, OH·, singlet oxygen). In this paper, we have investigated the mechanism of CL induction by the virus. Envelope particles, possessing the hemagglutinin-neuraminidase (HN) and fusion (F) glycoproteins stimulated CL, suggesting that the biochemical reactions leading to light emission are triggered by the interaction of the envelope “spike” glycoproteins with the cell surface. The individual contributions of HN and F to CL stimulation were investigated by removing F from egg-grown virus and by using Sendai virus (grown in MDBK cells) which possesses F 0, the biologically inactive precursor of F. Both viral preparations still induced CL. However, CL was reduced and the peak of light emission shifted from 6–8 to 2.5 min postinfection. In MDBK cell-grown Sendai virus, cleavage of F 0 into F resulted in the increase of CL and shift back of the peak CL to 6–8 min postinfection. These results suggest that the bulk of light emission by the spleen cells is correlated with the action of the F protein. In addition, HN correlates with CL in the initial period following the addition of the virus to the spleen cell suspension, while F is important for the subsequent further increase in light emission. The mechanism of CL induction by the F glycoprotein was investigated using egg-grown nonhemolytic “early harvest” and hemolytic “late harvest” Sendai virus, respectively. “Early harvest” virus, known to possess F and to have fusion activity, was less active in CL induction than “late harvest” Sendai virus which expresses both the fusion and hemolytic activities. This suggests that F stimulates CL by a mechanism related to hemolysis, rather than by envelope-cell membrane fusion. In addition, we show that influenza virus (strain A/RI/5-) also induces CL. The kinetics and extent of CL induction by this virus were similar to those induced by Sendai virus lacking the fusion protein and by nonhemolytic Sendai virus possessing F. As with Sendai virus, Pronase treatment resulted in the loss of CL stimulation while uv-inactivation of the virus did not affect its CL-inducing activity, suggesting that influenza virus also triggers CL by a mechanism involving the envelope glycoproteins.