In vitro growth profiles of respiratory syncytial virus in the presence ofinfluenza virus

To elucidate epidemiological interference between respiratory syncytial(RSV ) and influenza viruses? the influence of influenza A (H1N1) virus on the g rowth of RSV was examined. Although RSV grew in MDCK cells, coinfection wit h influenza A virus led to a reduction of progeny RSV. The degree of growth interference depended on the time of infection with influenza A virus post infection (p.i.) with RSV. In fact, infection with influenza A virus 12 hr s p.i, with RSV did not influence growth of the latter virus. On the contra ry, growth suppression of influenza A virus by RSV was observed when the co infection began at the later stages of RSV infection. Suppression of the gr owth of RSV by influenza A infection was further demonstrated at the level of viral protein synthesis. An indirect immunofluorescence (IF) test reveal ed that a large proportion of infected cells synthesized both RSV and influ enza A virus antigens. Scanning electron microscopic (SEM) examination demo nstrated that influenza A and RSV virions possessing surface antigens speci fic For each virus were selectively released from dually infected cells. In the present study, we proved for the first time that the growth of RSV is blocked by competitive infection with influenza A virus in a susceptible ce ll population, competitive protein synthesis and selective budding of RSV a nd influenza viruses from the same infected cells.