Induction of Tumors in the Liver of Hamsters by an Avian Adenovirus (CELO)2

Abstract

The oncogenic activity of CELO virus, an avian adenovirus, was tested in randombred or LSH/LAK inbred hamsters inoculated as newborns. Approximately 50% of the animals developed tumors, usually at the site of injection. The randombred hamsters appeared to be slightly more susceptible to tumor formation. Injection by the subcutaneous (sc) route el icited more tumors than did injection by the intraperitoneal (ip) or intracerebral (ic) routes. In approximately 4% of the animals, remote tumors of the liver were found. These liver tumors were classified as hepatocellular carcinomas or hepatomas (in 4 inbred hamsters; in 1 randombred),adenocarcinomas (in 5 randombred), and sarcomas (in 2 inbred). They developed in animals whether inoculated ip, sc, or ic. No local tumors were found in these animals. Electron microscopic examination revealed a preponderance of cytoplasmic type A virus particles, especially in the hepatocellular carcinomas of inbred animals, and sporadic occurrence of budding type C and "spoked" hamster virus particles. All liver tumors tested (except the 2 sarcomas) induced antibodies to CELO T antigen.