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Use of elution marker for the intratypic characterization of poliovirus strains.

Elution marker was used for intratypic characterization of poliovirus strains with Al(OH)3 gel as adsorbent. The virion suspensions to be tested were partially purified by chromatography and labelled with 32P. In the labelled preparations of wild virus strains practically all radioactivity was found in virus-specific bond, whereas in those of the vaccine strains and isolates of vaccine origin a considerable, but variable, proportion of the activity was bound to residual cell components. For this reason, the EC50 value (i.e. the phosphate molarity corresponding to the 50% adsorption equilibrium of virions), for the vaccine and vaccine-like strains showed a wide scattering. The activity bound to cell components was removable from the gel with 0.005 M phosphate buffer, whereas the elution maxima for all the poliovirus strains examined so far were over 0.02 M. The elution marker was calculated for 25 type-2 and 30 type-3 strains, all isolated during or soon after vaccination periods from cases suspect of poliomyelitis, both with and without taking into account the cell-bound activity. In the latter case, the EC50 values agreed with that for the corresponding reference vaccine strain much better than in the former; furthermore, the type-2 reference vaccine strain and the type-2 isolates, indistinguishable from the wild reference strain by the original method, could easily be differentiated on the basis of the corrected EC50 value. The possibility that the lack of an appreciable proportion of cell-bound radioactivity may reflect the pathogenicity of poliovirus strains is discussed.