Purification and properties of chick embryo lethal orphan virus (an avian adenovirus)

Abstract

Chick embryo lethal orphan (CELO) virus, an oncogenic avian adenovirus, and one of its antigens (the hexon) were purified from infected allantoic fluid and some of their properties were studied. Particles of CELO virus contained 80.7% protein and 17.3% DNA and had a buoyant density of 1.35 g cm −3 in CsCl. CELO virus DNA was a linear double-stranded molecule with a molecular weight of 30 × 10 6 daltons (greater than that of human adenovirus DNA) and a G + C content of 54%. Particles of CELO virus had typical adenovirus morphology and the hexons appeared to be similar to those of adenovirus type 2. CELO virus pentons, however, differed remarkably from those of other adenoviruses. Pentons isolated from the soluble antigen fraction of infected allantoic fluid, or dissociated by dialysis from particles of CELO virus possessed a base which carried two knobbed fibres, one long (425 Å) and the other short (85 Å). Besides the hexon and penton antigens, CELO virus particles possessed another antigen which was probably one of the internal proteins. The amino acid composition of CELO virus hexon was similar to that of adenovirus type 2 hexon but these two hexons were completely unrelated immunologically. SDS-polyacrylamide gel electrophoresis showed that CELO virus particles contained fewer internal proteins than particles of adenovirus type 2. CELO virus particles, disrupted in various ways, did not show hexons arranged in groups of nine characteristic of adenovirus types 2 and 5.