The South African Territories (SAT) types of foot-and-mouth disease virus (FMDV) show marked genomic and antigenic variation throughout sub-Saharan Africa. This variation is geographically linked and requires the use of custom-made vaccines. Adaptation of field isolates as vaccine strains is cumbersome, time consuming, and expensive. As an alternative to the adaptation process, the construction of recombinant FMD viruses followed by the production of conventional, inactivated vaccines utilizing these viruses is proposed. The advantage of such a strategy would be the ability to manipulate the antigenicity of these viruses by substituting the antigenic coding regions (i.e., structural proteins) of a full-length cDNA clone of a suitable strain. A chimeric cDNA clone between types A and SAT 2 was constructed by inserting the external capsid-coding region of the vaccine strain ZIM/7/83/2 into the genetic backbone of the A12 cDNA clone. Preliminary evaluation of the recombinant FMD virus revealed a slower growth rate for the recombinant than the parental ZIM/7/83/2, although similar antigen yields could be obtained. The chimera was found to be thermally less stable than the parental strain, suggesting it to be an inferior strain for inactivated vaccine production.
The South African Territories (SAT) types of foot-and-mouth disease (FMD) virus show marked genomic and antigenic variation in sub-Saharan Africa that is to a large extent geographically determined. This has implications for selection of appropriate vaccine strains as well as the accuracy of laboratory diagnosis. However, adaptation of field isolates as vaccine strains is cumbersome, time consuming and expensive. We propose the construction of recombinant viruses in which specific antigenic determinants can be manipulated. To achieve this goal, the structural-protein-coding region of a SAT 2 vaccine strain, ZIM 7/83/2, was determined and compared with two other known SAT 2 P1 regions. Five hypervariable regions were identified of which four are situated within VP1. The cleavage sites for proteolytic processing differs from serotype A, while the junction between P1/2A is variable within the SAT 2 serotype. These differences could influence the construction of recombinant vaccines.
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