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Title: Studies on Newcastle disease virus
Author: Alexander, Dennis John
Awarding Body: University of London
Current Institution: Imperial College London
Date of Award: 1971
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The object of this work was to investigate the cause of the differences of virulence between Newcastle disease virus (NDV) strains, with particular reference to the role of virus proteins. Methods for the purification of NDV using zonal rotors are described. Separation of purified virus by acrylamide gel discelectrophoresis after sodium dodecylsulphate (SDS) treatment revealed four structural polypeptides which were similar in migration and proportion for all strains. The molecular weights of the three major polypeptides were: 88,000, 58,000 and 42,000; haemagglutinin, ribonucleoprotein and neuraminidase were associated respectively with these polypeptides. The minor polypeptide, molecular weight> 200,000, was not associated with any known component or property of the virus. The four structural proteins and two other 'non-structural' proteins were detectable in infected chick cells. Strain Herts induced two other non-structural proteins but later than 10HR after infection. Virus induced proteins were detectable earliest after infection with virulent strains. Neither the biochemical properties of neuraminidase nor the amount per virion showed any relationship to virulence. The cell-associated titre of neuraminidase in chorioallantoic membranes 22 HR after infection was directly related to the virulence of the infecting strain. The extent of cell fusion and haemadaorption, and inhibition of cellular protein synthesis in infected chick embryo cells were related to the virulence of the infecting strain. All three required protein synthesis in the first four hours of infection. Congo red gave some protection of chick embryos against low but lethal, doses of virulent strains. Very high doses of avirulent virus showed greatly increased lethality to chick embryos in the presence of congo red. The cumulative production of RNA in infected cells treated with actinomycin D was directly related to the virulence of the infecting strain. It is concluded that the virulence of NDV strains is a result of the rate of production of one or more virus product in infected cells.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available