PATHOGENESIS OF PNEUMOVIRUS INFECTIONS IN MICE - DETECTION OF PNEUMONIA VIRUS OF MICE AND HUMAN RESPIRATORY SYNCYTIAL VIRUS MESSENGER-RNA IN LUNGS OF INFECTED MICE BY IN-SITU HYBRIDIZATION

The pathogenesis of pneumonia virus of mice (PVM) and human respirator y syncytial virus (HRSV) in BALB/c mice were investigated by using in situ hybridization to detect virus mRNA in fixed lung sections. Follow ing intranasal inoculation with 120 p.f.u. PVM the pattern of hybridiz ation showed that virus mRNA was initially detected within 2 days in a lveolar cells. As the infection progressed the number of hybridizing a lveolar cells increased and signal was also detected in cells lining t he terminal bronchioles. By days 4 to 5 post-infection areas of morpho logical abnormality could be seen, particularly in the strongly hybrid izing regions of the lung, and this correlated with the appearance of clinical signs of infection. In animals which survived the infection v irus-specific mRNA could not be detected 10 days post-infection. Mice infected with 1500 p.f.u. HRSV showed significant differences in the d istribution of virus-specific mRNA when compared to the pattern seen w ith PVM. HRSV mRNA was detected over large areas, but predominantly in peribronchiolar and perivascular regions of the lungs 5 days post-inf ection. The yield of PVM from infected mouse lungs was considerably hi gher than that of HRSV. The possible implications of these results for the use of the mouse model for pneumo-virus infections are discussed.