Mouse hepatitis virus strain--related patterns of tissue tropism in suckling mice

The pattern of tissue tropism for several prototype and uncharacterized strains of mouse hepatitis virus (MHV) was studied by intranasal inoculation of each virus strain into groups of neonatal Swiss mice under otherwise identical conditions. Mice were killed at intervals up to 18 days after inoculation, and their tissues were examined for the presence of MHV antigen by indirect immunofluorescence. Two patterns of infection were apparent. Prototype MHV strains 1, 3, A59, JHM, S and uncharacterized MHV strains Tettnang and wt-1 produced a respiratory pattern, in which nose and lung were consistently involved with dissemination to other organs in a vascular distribution. Pulmonary vascular endothelium and alveolar septal cells, but not airway epithelium, were infected. An enteric pattern was observed with MHV-Y and wt-2 in which MHV antigen was largely restricted to the nose and bowel, with limited dissemination to other abdominal organs but not lung. Intestinal lesions in these mice were severe compared to those manifesting the respiratory pattern of infection. These results indicate that, like coronaviruses of other species, different strains of MHV possess different primary and secondary organotropisms following a natural route of inoculation in a susceptible host.