Kenneth J. McCormick

An 18- to 20-nm virus particle was isolated from the Olson strain of quail bronchitis, an avian adenovirus. On density gradient separation the small virions were primarily found at densities of 1.39 and 1.42 g/cm(3). The majority of the infectious particles were at the heavier density. The virus had a hexagonal outline and contained single-stranded deoxyribonucleic acid. It was resistant to heating at 56 C for more than an hour and was not inactivated by treatment with chloroform or low pH. Purified virus did not agglutinate erythrocytes of various avian and mammalian species. Replication of the small particles occurred either in chicken embryos or in cultures of embryo kidney cells coinfected with an adenovirus helper. Antigenically the virus was distinct from the adeno-associated viruses types 1, 2, 3, and 4. The virus is the avian equivalent of the adeno-associated viruses of primates and lower animals.

A noninfectious hamster C-type oncornavirus (D9) associated with a spontaneous hamster lymphoma was characterized. The defective virions contained 70S RNA and the base composition was similar to that of a murine sarcoma-leukemia virus. With both endogenous and added templates, the virions were found to be deficient in DNA polymerase activity. These results suggest that DNA polymerase may be required for D9 infectivity.

Although biopsies of Burkitt's tumors contained no detectable complement-fixing (CF) antigen or antigens, tumor cell lines contained CF antigen or antigens related to the presence of a herpes-like virus particle.

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.

Human lymphoid cell lines which had been classified on the basis of studies on clonality and morphological, on the basis of studies on clonality and morphological, chromosomal and functional parameters as lymphoblastoid cell line (LCL) of presumed non-neoplastic origin and Burkitt lymphoma (BL) lines of proven malignant origin, were tested for susceptibility to natural killer (NK) cells obtained from the spleens of athymic nude mice. The 20 lines included normal diploid LCL and aneuploid BL lines. All cells carried the Epstein-Barr virus (EBV) genome. In addition, two EBV-negative BL lines were tested. The pronase-induced release of 14C-DNA from 14C-thymidine-labelled target cells was used to assess the sensitivity of the cell lines to NK activity. When attempts were made to correlate the growth of the EBV-positive LCL and the EBV-positive BL cell lines in the subcutaneous space of adult nude mice with their susceptibility to NK cells, no significant correlation was observed. The EBV-negative BL cell line, Ramos, however, could be transplanted subcutaneously in nude mice and was more resistant to NK activity than was the EBV-negative BL cell line, BJAB, which cannot be transplanted subcutaneously. Growth of heterotransplanted EBV-converted cell lines in the subcutaneous space of adult nude mice may be influenced by immune effectors other than NK cells.