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Antigenic characteristics of avian reoviruses

Enriquez, Carlos Enriquez (1987) Antigenic characteristics of avian reoviruses. Masters by Research thesis, Murdoch University.

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Abstract

The avian reovirus and mammalian reovirus groups and the unique Nelson Bay virus (NBV) are distinguishable viruses within the genus reovirus that share a number of common morphological and structural characteristics. The antigenic relationship between these three groups of animal reoviruses is uncertain and studies were undertaken to further investigate this relationship. By indirect fluorescent antibody and haemagglutination-inhibition tests, no antigenic relationship was detected. However, it was demonstrated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of radio-immunoprecipitated viral proteins in lysates of infected cells, that mammalian reovirus, avian reovirus and NBV encode viral proteins that are antigenically related. The results suggest that mammalian reovirus, avian reovirus and NBV had a common origin.

Studies were also conducted to investigate the extent of the antigenic cross-reactivity of individual viral polypeptides in three antigenic types of avian reovirus which were previously reported in Australia. It was shown by SDS-PAGE of radio-immunoprecipitated viral proteins in cell lysates of infected cells that there was extensive cross-reactivity in at least 5 viral polypeptides detected in the cell lysates. One type-specific protein which was precipitated only by homologous chicken antiserum was also detected.

After coinfection of chicken kidney cells with 2 strains of avian reovirus, 2 isolated clones were identified as reassortants by the comparison of their ds-RNA electropherotype with those of the parent avian reoviruses. The reasserted gene segments were M2 and M3, but as some genome segments in both parent avian reovirus displayed a similar migration pattern during SDS-PAGE, other undetected reasserted genes could also have been present in the reassortant viruses. The reassortant viruses were only partially related to the parent viruses as evaluated by reciprocal serum neutralisation tests, which demonstrated that genetic reassortment in avian reovirus could contribute to the extensive antigenic heterogeneity which has been detected in this group of viruses. Each reassortant virus also contained a type-specific protein derived from one or the other parent avian reoviruses. There was an association between this type-specific protein and replication of the viruses in Vero cells, suggesting that the type-specific protein may be the principal attachment protein.

The homologous immune response of 6-week-old chickens to inactivated or live avian reovirus strains 724 (grown in chicken kidney cells) or RAM-1 (grown in chicken kidney cells or Vero cells) was shown to be similar. However, the heterologous immune response was greater and appeared earlier in chickens inoculated with the avian reovirus strain RAM-1 than with avian reovirus strain 724. These results confirmed the broad antigenicity of the RAM-1 strain of avian reovirus which was reported previously. The broad antigenicity and growth of the RAM-1 strain in Vero cells suggest that this strain would be a suitable strain for use in any future avian reovirus vaccine used in Australia.

The administration of chicken anti-RAM-1 serum to one-day-old chickens was used to simulate the presence of passively-acquired antibodies to avian reovirus. These passively-aquired antibodies resulted in more prolonged virus replication and inhibition of the active immune response following virus infection of chickens at 2 days of age. However, an active immune response subsequently developed in the passively immune chickens as the titre of the passive antibodies declined.

Item Type: Thesis (Masters by Research)
Murdoch Affiliation: School of Veterinary Studies
Notes: Note to the author: If you would like to make your thesis openly available on Murdoch University Library's Research Repository, please contact: repository@murdoch.edu.au. Thank you.
Supervisor(s): Wilcox, Graham
URI: http://researchrepository.murdoch.edu.au/id/eprint/53034
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