The suitability of the 'emergency' foot-and-mouth disease antigens held by the International Vaccine Bank within a global context.

The International Vaccine Bank (IVB) based at the Institute of Animal Health (IAH) in Pirbright, United Kingdom (UK), routinely monitors the suitability of the currently held strains of foot-and-mouth disease (FMD) vaccine virus, in anticipation that vaccine may be required to control FMD outbreaks that pose a threat to member countries. Using primarily the two-dimensional micro-neutralisation test (VNT), bovine polyclonal sera raised against each of the seven current 'emergency' antigens were utilised to measure the relationship of IVB stocks to selected field isolates. The 'O' serotypes, Manisa and Lausanne, exhibited adequate levels of cross-protection against most of the type 'O' field isolates examined. A(22) Iraq 24/64 showed the broadest spectrum of reactivity against the type 'A' field isolates examined and was supplemented by A(15) Thailand 1/60. Some type 'Asia1' field isolates, particularly those from South East Asia, showed antigenic difference to the Asia1 India 8/79 vaccine strain by VNT, but in-vivo testing in the guinea pig model indicated this to be insignificant. The only 'C' serotype representative, C(1) Oberbayern, may be one of the least antigenically diverse of the current portfolio of bank antigens. Comparison of the serological and sequence data shows that despite significant genetic variation between the field isolates examined the antigens held by the IVB should still prove efficacious in the field.