Molecular mechanism of complex infection by bacteria and virus analyzed by a model using serratial protease and influenza virus in mice

T. Akaike, A. Molla, M. Ando, S. Araki, H. Maeda

Research output: Contribution to journalArticlepeer-review

47 Citations (Scopus)

Abstract

We examined the effect of a serratial exoprotease on the pathogenesis of influenza virus infection in mice as a model of complicated respiratory infection by bacteria and virus in humans. The 56-kilodalton (56-kDa) protease from Serratia marcescens was administered intranasally to mice at a dose of 10, 20, or 40 μg from day 0 to day 3 after inoculation of the influenza virus. Administration of the protease resulted in remarkable enhancement of the lethal effect of the virus and enhancement of pathological changes in the lungs. Influenza virus replication, determined by plaque-forming assay, was accelerated by the protease. Namely, we found a 100-fold increase in virus by day 2. The 56-kDa protease caused generation of plasmin activity in the lungs. In vitro experiments showed that plasmin greatly enhanced the yield of influenza virus, although the effect of the 56-kDa protease by itself was much lower than that of plasmin. Furthermore, the 56-kDa protease could induce plasmin production indirectly via activation of plasminogen by the Hageman factor-dependent cascade in the in vitro system. We conclude that this major serratial exoprotease has a deleterious effect on mice infected with influenza virus and that this effect seems to result from enhancement of viral growth by indirect acceleration of plasmin generation induced by the protease.

Original languageEnglish
Pages (from-to)2252-2259
Number of pages8
JournalJournal of virology
Volume63
Issue number5
DOIs
Publication statusPublished - 1989

ASJC Scopus subject areas

  • Microbiology
  • Immunology
  • Insect Science
  • Virology

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