Heterogeneity of pseudorabies virus studied by isoelectric separation

Heterogeneity of four lines derived from a single strain of pseudorabies virus (PRV) was studied by isoelectric separation. The individual lines differed in the distribution pattern of infectious fractions separated in the pH range from 3.5 to 10.0. All virus fractions of the virulent and attenuated lines were infectious, but some fractions of the highly attenuated avirulent line were devoid of infectivity. Infectivity of the fractions isolated from the individual PVR lines depended on the degree of attenuation; the higher degree of attenuation, the greater the differences in infectivity of the isolated fractions. The possible causes of the different distribution of infectious fractions obtained by isoelectric separation from virus lines differing in biological properties are discussed. The relationship between physico-chemical and biological properties of PRV is stressed along with the possibilities of applying isoelectric separation in narrow pH gradients.