Immunofluorescence Studies of T and Virus Capsid Antigens Induced by Chick Embryo Lethal Orphan Virus

SUMMARY Chick embryo lethal orphan virus induced both T and virus capsid antigens during cytolytic infection of chick kidney cells. The T antigen was produced relatively early, 8 or 9 hr after infection, while virus capsid antigen was first detected after 15 to 16 hr. The T antigen appeared as a fine granular fluorescence and also as small blobs confined to the cell nucleus. T antigen was detected in virus-infected hamster, mouse and human cells, but was present in very few cells compared with chick kidney monolayers, where almost all cells contained antigen. The virus capsid antigen had a more complex morphology, with fluorescing spots and blobs in the nucleus; it was also detected as a diffuse fluorescence in the cytoplasm later in infection. The production of virus capsid antigen in chick kidney cells was partially inhibited by cytosine arabinoside (100 µg./ml.) or 5-fluoro-2′-deoxyuridine (30 µg./ml.). These inhibitors of DNA viruses had no effect on the production of virus-induced T antigen in chick kidney cells. No antigenic relationship was detected by immunofluorescence or complement-fixation tests between chick embryo lethal orphan virus and T antigens of adenovirus type 12. In addition, the adenovirus group hexon antigen was not detected in preparations of chick embryo lethal orphan virus by complement-fixation or immunofluorescence tests.