Infectivity, disease patterns, and serologic profiles of reovirus serotypes 1, 2, and 3 in infant and weanling mice

The oronasal median infectious doses of reovirus serotypes 1, 2, and 3 were established in infant and weanling Sencar mice on the basis of disease expression and seroconversion. Infant mice were susceptible to infection with low doses of all three serotypes, whereas weanling mice were comparatively resistant to infection. Uniform transmission of virus to cagemates or mothers of infants did not occur, indicating low contagiousness of all three virus serotypes. The comparative susceptibility of 2-day-old Sencar mice to disease was examined following oronasal inoculation with reovirus 1, 2, or 3. Tissues were collected on days 3, 5, 7, 9, 14, 16, and 21 after inoculation for virus isolation, histologic examination, and serologic analysis. Disease patterns in infant mice were distinctly different among reovirus serotypes. Reovirus 3 induced severe disease, with focal myocarditis, hepatitis, diffuse encephalitis, and generalized lymphoid depletion, whereas reovirus 1 induced a similar pattern, but much milder disease. In contrast, reovirus 2 induced mild transient enteritis without lesions in other organs. Sera from experimentally infected mice were tested in virus serotype-specific enzyme immunoassays. Cross reactivity of antibody among the three virus serotypes was found, but antibody titers were always highest with the homologous antigen. These studies confirm that infant laboratory mice are susceptible to infection with all three serotypes of virus; weanling mice are comparatively resistant to infection and disease; the viruses induce different patterns of disease in infant mice; and infecting virus serotypes can be distinguished serologically by enzyme immunoassay.