Isolation and characterization of an antigenically distinct 68-kd protein from nonviral intracytoplasmic inclusions in boa constrictors chronically infected with the inclusion body disease virus (IBDV: Retroviridae). Vet. Pathol

Abstract. The relationship between a retroviral infection and the development of nonviral intracytoplasmic inclusion bodies was studied in a Boa constrictor model. Twelve juvenile age- and size-matched inclusion body disease (IBD)-negative boas were randomly divided into three groups. Each group was inoculated intraperito-neally with 1 ml of an IBD virus (IBDV)-infected liver homogenate or 1 ml of normal boa liver homogenate (sham-inoculated control) or was left untreated. All boas were monitored for development of IBD by daily examination and serial liver biopsy over 1 year. The 4 IBDV-inoculated boas became IBDV and inclusion positive by 10 weeks postinoculation. The average size and density of inclusion bodies increased with the duration of infection. Ultrastructurally, inclusion bodies,2 mm in diameter consisted of intracytoplasmic ag-gregates of granular electron-dense material that were not membrane limited. Larger inclusions (3–6 mm in diameter) were characterized as membrane-bound aggregates of amorphous to granular electron-dense material admixed with membranelike fragments. The sham-inoculated and untreated control snakes did not become inclusion or IBDV positive. Direct comparison of the protein electrophoretograms of IBDV-infected and normal boa tissues demonstrated a prominent 68-kd protein band unique to infected inclusion-positive tissues. Mono-clonal antibodies directed against the 68-kd protein band specifically labeled inclusion bodies. The results of this study demonstrate that IBD inclusions represent an intracytoplasmic accumulation of an antigenically dis