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

Abstract

SUMMARYChick cells infected by chick embryo lethal orphan (CELO) virus (fowl adenovirus type 1) contained four prominent virus-specific, structurally related DNA-binding proteins with mol. wt. of 74K, 64K, 56K, 52K, and two minor forms. The CELO virus DNA-binding proteins were phosphorylated, delayed-early nuclear proteins. CELO virus early proteins were expressed in BHK cells, but did not complement human adenovirus type 5 mutants with lesions in E1A, E2A or E2B. Moreover, CELO virus DNA-binding proteins were not produced in 293 cells, which express human adenovirus E1 genes. These results suggest that activation of transcription by adenovirus E 1A genes involves specific interactions between the E 1A gene products and viral early promoters.

Replication-defective adenovirus type 5 as an in vitro and in vivo gene transfer vector in chickens

“…It can be anticipated that, in addition to the antibody response, intracellular synthesis of immunogenic proteins should be able to induce the development of a cytotoxic T cell response, as demonstrated for adenovirus-based vaccines in mammals (Jacobs, 1993). The safety requirements for these adenovirus-vectored vaccines should be met by (i) the deletion of the EIA gene (Oualikene et al, 1994), (ii) the lack of complementation of the E1A gene by its counterpart in avian adenovirus in the case of superinfection by a wild-type (wt) virus (Li et al, 1984), and (iii) the inability of Ad5 wt to develop a productive cycle in avian cells. The next step in our work will be to use new constructions harbouring an immunogenic protein of an avian pathogen in order to investigate the mucosal immunity induced by local routes of vaccination.…”

The Structural Proteins of Chick Embryo Lethal Orphan Virus (Fowl Adenovirus Type 1)

“…The polypeptides corresponding to the CELO virus penton base and the two fibres are identified and characterized in this paper. The CELO virus genome-linked terminal protein (Robinson et al, 1973;Robinson & Bellett, 1974;Li et al, 1983), core proteins, and single-stranded DNAbinding proteins have also been characterized (Li et al, 1984). Avian adenoviruses share with human adenoviruses basic structural similarities at the following levels: (i) the virion of both avian and human adenoviruses is an icosahedron of about 70 nm diam.…”

“…Apart from these structural similarities, avian and human adenoviruses also share similar basic DNA replication mechanisms (BeUett & Younghusband, 1972), similar early and late phases of gene expression and at least one similar non-structural protein, the single-stranded DNA-binding protein (Li et al, 1984).…”

Chick embryo lethal orphan virus can be polymer-coated and retargeted to infect mammalian cells

“…[37][38][39][40] Chicken embryo lethal orphan virus (CELO; fowl adenovirus type 1), characterized as an infectious agent in 1957, 41 is attractive as a gene delivery vector since it is simple and cheap to produce in bulk in chicken embryos and has a good safety profile being completely replication defective in human cells, even in the presence of wild-type human adenovirus. 42 CELO is structurally similar to mammalian adenoviruses possessing an icosahedral capsid of 70-80 nm composed of hexon and penton proteins. Unlike most adenoviruses that possess a single fibre, CELO viruses carry two fibres protruding from each vertex.…”

“…Fibre 1 is 42.5 nm in length and contains a sharp kink, while fibre 2 is 8.5 nm in length and straight. [42][43][44][45] Although recombinant CELO has been demonstrated to transduce a range of mammalian cell lines and primary cells, [37][38][39][40] in general, the level of transgene expression falls below that of adenovirus type 5 (Ad5) vectors when delivered at comparable multiplicity of infection.…”