Stability and immunogenicity of empty particles of foot-and-mouth disease virus

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Abstract
Three strains of foot-and-mouth disease virus were shown to contain significant amounts of naturally occurring 75 S, empty particles as well as the infectious, 140 S full particles. One of these strains — A Pando (1970) — was studied in detail. The empty particles from this virus strain were shown to have an observed sedimentation coefficient of 67S in 0.04m phosphate buffer; they were labile in SDS, non-infectious and probably RNA-free and, on heating, they broke down to 12 S subunits as did the 140 S particles. The empty particles differed from the full particles in their polypeptide composition since they contained VP0, but there was no evidence for a diminished content of VP4. The 75 S particles were shown to be present in significant amounts and to be stable to AEI inactivation. At 4° C they were stable for at least two years. In guinea pigs they were as immunogenic as the 140 S particles. The antisera raised against the 75 S particles had the same serological specificity in neutralization tests as sera prepared against the 140 S particle. It was concluded that the 75 S particles from the A Pando (1970) strain of FMD virus may provide as important a contribution as 140 S particles to the immunogenicity of inactivated vaccines prepared from this virus strain.