Biochemical Studies on a Virus Associated with Egg Drop Syndrome 1976

Abstract

SUMMARY A number of hitherto undescribed, serologically identical viruses have been isolated from a syndrome of depressed egg production in broiler breeder flocks (Egg Drop Syndrome 1976). One of these, 127 virus, was purified after growth in chick embryo liver cells. Three particle types B1, B2 and B3 with densities of 1.32, 1.30 and 1.28 g/ml, respectively, were separated in CsCl equilibrium density gradients. B1 and B2 particles possessed infectivity and were labelled with 3H-thymidine. However, they differed morphologically and B2 particles agglutinated chicken erythrocytes whereas B1 particles did not. B3 particles were not infectious, were not labelled with 3H-thymidine but agglutinated chicken erythrocytes. They were penetrated by stain when examined by electron microscopy and probably correspond to empty particles. B1, B2 and B3 particles differed in their polypeptide compositions; seven of the polypeptides in B1 and B2 particles had counterparts in purified fowl adenovirus type 1. The soluble haemagglutinin from 127 virus, which did not sediment under centrifugation conditions sufficient to pellet virus particles, was purified using DEAE cellulose chromatography and gel filtration. Purified soluble haemagglutinin contained two polypeptides (mol. wt. 67000 and 65000), which co-migrated in polyacrylamide gels with two of those present in purified 127 virus particles. The soluble haemagglutinin sedimented heterogeneously (20 to 50S) in sucrose density gradients and had a density of 1.24 g/ml in CsCl. It was inactivated by trypsin, urea and pyridine. Electron microscopy of purified soluble haemagglutinin showed rod-like structures with lengths of 25 to 30 nm, which radiated from a central area measuring approx. 10 nm in diam. It is suggested that 127 virus is an adenovirus.