 This multi-nuclear formation, derived from several dozens of cells, survives for several days and subsequently releases functional viral particles.It has been demonstrated that the ability of a virus to destroy tumor cells increases along with an increase in the ability of the virus to form large multi-nuclear structures.The transfer of genes that are responsible for the formation of syncytium from the representative of Paramyxoviridae to the representatives of Rhabdoviridae or Herpesviridae makes the recipient viruses more oncolytic.