Construction of a chimeric foot-and-mouth disease virus between serotypes A and SAT 2: Comparison with wild type SAT 2 in terms of antigenicity, growth properties and thermal stabilityl

Effective vaccination in sub-Saharan Africa requires the use of custom-made vaccines for specific geographic localities, due to the genetic and antigenic variability of the SAT types of FMDV. Comparison of r-values (expression of antigenic relationships between viruses) determined for ZIMJ7/8312 (a west Zimbabwean strain) and KNP/19/89/2 (originating from the Kruger National Park, South Africa) in relation to isolates from the Kruger National Park, revealed much lower r-values for ZIMJ7/83/2 than the KNP strain (Esterhuysen, 1994). The serological data demonstrated therefore the closer relatedness of the KNP strains. A similar study investigating the antigenic relationships of isolates originating from northern and southern Zimbabwe, indicated these isolates to belong to antigenically different groups (Bauman & Esterhuysen, 2000). These results were confirmed genetically which clearly showed the closer gene relationships of isolates originating in the same geographical region (Vosloo et aI., 1995; Bastos et aI., 2001). Taken together, these results are indicative of the independent evolution of FMDV in different geographical regions and argue thus for the use of custom-made vaccines.