Unusual Features of the Oncogenicity of Chicken Embryo Lethal Orphan (CELO) Virus in Hamsters1

DNA-binding Proteins of Chick Embryo Lethal Orphan Virus: Lack of Complementation between Early Proteins of Avian and Human Adenoviruses

“…BHK cells werc found to express CELO virus DNA-binding proteins, and hamster cells also cxpress CELO virus T antigens (Asch et aL, 1979;Ishibashi et aL, 1980), but co-infection of BHK cells with CELO virus and Ad5 early gene mutants suggested that there was no complementation by CELO virus early proteins of Ad5 early functions carried out by Ad5 E 1A proteins, Ad5-encoded 140K DNA polymerase or Ad5 72K DNA-binding protein. Our data do not exclude complementation in the other direction; however, this seems unlikely due to the failure of CELO virus to produce DNA-binding protein in 293 cells.…”

“…To investigate further the possible functional links between human and avian adenoviruses, the ability of CELO virus early gene products to complement mutant human adenovirus early functions in BHK cells was tested. Hamster BHK cells are permissive to subgroup C human adenoviruses, and allow synthesis of CELO virus DNA-binding proteins: they also produce CELO virus tumour-specific (T) antigens (Asch et al, 1979: Ishibashi et al, 1980. Confluent BHK cells were mock-infected or infected with CELO virus at 50 i.u./cell, or infected with Ad5 at 25 i.u./cell, or co-infected with 50 i.u./cell of CELO virus and 25 i.u./cell of one of the following Ad5 early mutants: dl312, a deletion mutant that lacks the promoter and most of the coding sequence of the E 1A region ; d1314, a deletion mutant that lacks most of the 3' exon of E1A ; ts36, a temperature-sensitive mutant which carries lesion(s) in gene N in the E2B region of the Ad5 genome that encodes the 140K viral DNA polymerase (Williams et al, 1974;Galos et al, 1979: Stillman et al, 1982: and ts125, a temperature-sensitive mutant which carries a mutation in the gene coding for the 72K DBP (van der Vliet et al, 1975).…”

“…Yasue & Ishibashi (1977) reported eight chick embryo lethal orphan (CELO) virus-induced early polypeptides that could be detected in infected cells in the presence of cytosine arabinoside. Asch et al (1979) and Ishibashi et al (1980) described CELO virus tumour (T) antigens that reacted with sera from animals bearing CELO virus-induced tumours, and were also produced in infected cells in the presence of cytosine arabinoside. It is likely that CELO virus codes for one or more DNAbinding proteins (DBP), since CELO virus DNA replication shares general similarities with that of human adenovirus, and CELO virus DNA replication intermediates have extensive single-stranded regions (Bellett & Younghusband, 1972).…”

Chicken Embryo Lethal Orphan (CELO) Virus DNA Present in Hamster Cell Lines Derived from CELO-Induced Hepatomas

“…In this study we used the EcoRlproduced fragments to investigate whether cells originating from the CELO virus-induced hepatomas [2,3] also contained only a portion of the virus genome, analogous to the cell-culture-produced transformants. Of further interest was the fact that one of these hepatoma cell lines does not produce the CELO virus tumor (T) antigen [2,3]. CELO-induced hamster hepatoma cell lines, CILT-2 (T-antigen-negative) and CEHEP (T-antigen-positive), were grown, established and characterized…”

“…A sch [2,3]; both cell lines had been through at least 100 passages. Further more, fusion of these cells with permissive chicken embryo kidney cells has never released CELO virus [3].…”