Partial RNA sequencing of eight supposed derivatives of type 3 poliovirus/USA/Saukett/50 reveals remarkable differences between three apparent substrains.

Eight supposed derivatives of type 3 poliovirus/USA/Saukett/50 could be divided in three subgroups differing from each other as much as from the independent P3/Sabin strain as judged by partial genomic sequences covering about 25% of the portion of RNA coding for the structural proteins. This suggests that strains designated as Saukett in different laboratories are derived from three separate but related American isolates of type 3 poliovirus. Deduced amino acid sequence of the "Saukett" strains revealed amino acid substitutions at all known major antigenic sites compared with P3/Sabin or P3/Finland/23127/84 strain, but also between individual Saukett strains. These substitutions may be responsible for the known antigenic differences between the studied strains.