Mycoplasma-virus interactions in mouse tracheal organ culture

The growth characteristics of Mycoplasma pulmonis and influenza A/PR-8 virus studies in a mouse tracheal organ culture system. M. pulmoins grew well in the tracheal organ culture producing inhibition of ciliary activity. The organism grew in close association with the epithelial cell membrane producing cytopathology as revealed by studies employing stained tissue sections, fluorescent antibody, and electron microscopy. The M. pulmoins did not grow in the culture fluid medium alone but grew when viable tracheal explants were present. However, cultures of heat treated explants with added cholesterol or horse serum supported growth of the mycoplasma. The M. pulmoins was shown to produce hydrogen peroxide. The addition of catalase to the mouse tracheal organ cultures infected with this organism appeared to protect the explants from the toxic effects produced by mycoplasma as indicated by inhibition of ciliary inactivation. This might indicate that the hydrogen peroxide production of the mycoplasma plays a role in the pathogenesis of this organism for the tracheal tissue. There was no ciliary inhibition in cultures that were maintained in medium in which M. pulmoins had grown but was removed by filtration and treatment with antibiotics. This indicated that the organisms must be present to produce ciliary inhibition and that stable toxic products produced by the organism were probably not responsible for this effect. Influenza A/PR-8 virus was also shown to grow and produce cytopathology in mouse tracheal organ cultures. Electron microscopy showed that the virions attached to and caused clumping of the cilia. The virus infection eventually resulted in complete desquamation of the epithelial surface of the tracheal tissue as revealed by stained histological sections. The addition of receptor destroying enzyme (RDE) to the medium was found to be significantly inhibit the growth of the virus in this system. When tracheal organ cultures were dually infected with both organisms, ciliary inactivation and tissue damage occurred earlier that when the organisms were cultured separately. The present of the virus appeared to have no effect on the growth of the mycoplasma, however the mycoplasma inhibited virus replication. The M. pulmoins may have inhibited the influenza virus growth by affecting the nucleic acid or amino acid metabolism of the tracheal epithelial cells. The mycoplasma could also have induced or caused a priming effect on an interferon response. The interferon could then have inhibited the viral replication. Data from this study suggests the possibility of mycoplasma-virus interactions occurring in respiratory infections of man.