Comparative Restriction Enzyme Analysis of the Genome in Variola Virus Strains from the Russian Collection

Comparative RFLP analysis was for the first time performed for 21 variola virus (VARV) strains of the Russian collection with 20 amplicons covering the total VARV genome. The amplicons were synthesized in the long polymerase chain reaction. A database useful as a reference for identifying VARV strains was generated. VARV strains isolated in different geographical regions were compared and proved to vary mostly in variable genome regions. Each of the dendrograms constructed included three clusters of African, Asian, and VARV-alastrim isolates. The VARV-alastrim isolates differed to the greatest extent from the other strains. VARV strains isolated during an ecdemic variola burst in Moscow (1960) grouped with Asian isolates. Polymorphism of VARV strains was for the first time observed for a single variola burst with a few affected patients.