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The morphology of gnotobiotic and germfree mouse lungs and their response to parainfluenza type 1 virus

Robinson, David Paul (1983) The morphology of gnotobiotic and germfree mouse lungs and their response to parainfluenza type 1 virus. Masters by Research thesis, Murdoch University.

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Detailed morphological studies, at light and electron microscopic level, have been previously made of viral respiratory disease. These studies have not only encompassed the mode of reproduction and maturation of the virus in tissue cultures, but also of the pathological effect in conventional animals. However, at the ultrastructural level, the contribution of the immune system to the progress of a viral respiratory disease in an immunocompetent animal is not clear.

The present study was designed to provide morphological evidence of the development of disease caused by a respiratory virus, parainfluenza type 1, in lung mucosal cells of germfree mice. Epithelial cells from the lungs of germfree and gnotobiotic mice were used to establish ultrastructural criteria. Gnotobiotic mice infected with the virus were used as a control host.

The study has shown that the ultrastructure of similar cell types, in both germfree and gnotobiotic mice, was remarkably similar. The smooth endoplasmic reticulum of respiratory epithelial cells, in both germfree and gnotobiotic mice, was ordered and unvacuolated, whereas in conventional mice and in the infected mice it was vacuolated, prominent and disarrayed. Virus grew randomly throughout the epithelium of the respiratory tract of the infected germfree mice, and was prolific in alveolar type II cells.

Unusual floccular and myelinoid inclusion bodies were seen in cells of infected germfree mice. In the infected gnotobiotic mice, viral growth appeared to be less. Bacteria were not seen to be directly involved in the destruction of cells in the gnotobiotic mice. The ultimate effect of the virus on the respiratory epithelium of both classes of mice was very similar, resulting in the death and destruction of epithelial cells. The widespread and prolific distribution of virus in the germfree mice was assumed to reflect the lower immune status of these mice. The more limited distribution and growth of virus in the gnotobiotic mice was probably controlled by the immunologically enhanced experience of these mice. The cellular response of the gnotobiotic mice to the infection was much greater than that of the immunologically inexperienced germfree mice. This study has shown that microbiologically defined mice, reared and housed under gnotobiotic conditions, can be used to provide a better understanding of the role of the immune system in the pathogenesis of a viral infection in respiratory epithelia.

Item Type: Thesis (Masters by Research)
Murdoch Affiliation(s): School of Veterinary Studies
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Supervisor(s): Cook, Robert
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