|Rieder, Aida - Elizabeth|
Submitted to: European Study Group on the Molecular Biology of Picornaviruses
Publication Type: Abstract only
Publication Acceptance Date: 3/5/2008
Publication Date: 5/26/2008
Citation: Blignault, B., Theron, J., Visser, N., Rieder, A.E., Maree, F. 2008. Sat type foot-and-mouth disease (fmd) chimeric vaccine elicits protection in pigs. European Study Group on the Molecular Biology of Picornaviruses. p. 133. Interpretive Summary:
Technical Abstract: The recent development of infectious cDNA clone technology for foot-and-mouth disease (FMD), Southern African Territories (SAT) viruses has provided a valuable tool for genetic and biological characterization of field and laboratory strains. Recombinant chimeric viruses, containing the capsid-coding region (1B-1D) of a field isolate, retain the replication machinery of the genetic backbone, while acquiring the antigenic properties, capsid biophysical stability and receptor recognition preference of the field virus. In this study, a genome-length construct was engineered by replacing the 1B-1D/2A region of SAT2/ZIM/7/83 with that of SAT1/KNP/196/91. In vitro-synthesized RNA was used to transfect BHK-21 cells and a viable chimeric virus, i.e. vKNP/SAT2 was recovered, indicative of the ability of viral proteases to functionally cleave the SAT1 polypeptide. The recovered vKNP/SAT2 chimera exhibited comparable growth kinetics, virion stability and antigenic profiles when compared to the SAT1/KNP/196/91 parental virus. The plaque morphologies of the respective viruses were similar in various cells, indicating that the phenotypic characteristics of the parental virus were maintained in the chimera and confirmed by similar genetic identities. Inactivated vaccines produced from intact 146S particles of both the chimera and parental viruses, induced an antibody response in guinea pigs that neutralised the homologous SAT1/KNP/196/91 virus in vitro. Inoculation of pigs with the chimeric vaccine elicited a protective immunity, also at < 1 µg per dose, although not as sterile as for the parental virus. The possibility of a bottleneck effect when immunising with a clone-derived vaccine compared to the complete quasispecies when using a normal population of the virus (parental vaccine) was investigated. The population genomics of the challenge virus, which had been derived from the parental SAT1/KNP/196/91 passaged and three times in pigs, was determined and compared to the vaccine.