The relation of poly(A) length to specific infectivity of viral RNA: a comparison of different types of foot-and-mouth disease virus.

The specific infectivities (PFU/μg) of oligo(dT)-cellulose bound and unbound fractions of viral RNAs (vRNA) isolated from representative strains of types O and C foot-and-mouth disease virus (FMDV) were determined and compared to previously reported results using vRNA from type A FMDV. The results show little or no difference in the specific infectivities of bound and unbound fractions from types A or O. In contrast, however, the bound fractions of vRNA from type C FMDV had specific infectivities from 5- to 16-fold greater than the unbound fractions from this type, a result similar to that found with vRNAs from polio, EMC, and Sindbis virus. The data suggest that a long length of 3′ terminal poly(A) is not essential for infectivity of viral RNA from all positive stranded viruses.