Morphologic appearance of inclusion bodies and their association with the antigenic composition of naturally occurring rabies viruses.

A total of 112 rabies virus-infected skunk brain samples from naturally occurring cases (64 from Missouri, 48 from Kentucky) were code labeled and grouped into two morphologic categories according to the appearance and size of the discrete particles observed by immunofluorescent-antibody staining. The reactivity of the blind-labeled samples was then determined using a panel of 23 antinucleocapsid monoclonal antibodies to test whether morphologic appearance was associated with antigenicity. Two categories were defined and designated; they were morphologic type I (MO-I) and morphologic type II (MO-II). MO-I viruses produced granular-type fluorescing aggregates with no evidence of inclusions compatible in appearance with Negri bodies. MO-II viruses produced at least one and usually many large, round, or oval fluorescing inclusion bodies. No viruses categorized as MO-I reacted with antinucleocapsid monoclonal antibodies 103-7, 239-10, and 120-2; all MO-II viruses reacted positively to these three antibodies, with one exception involving antinucleocapsid monoclonal antibody 239-10. The results indicate a strong association between the reactivity of these antibodies and the morphologic appearance of the aggregates of antigen.