Natural evolution of oral vaccine poliovirus strains

摘要: The oral poliovirus vaccine, prepared with attenuated Sabin strains, is widely used to efficiently control poliomyelitis. One problem raised by its use is the occurrence of a certain, very few, number of vaccine-associated paralytic cases. This is due to the genetic instability of the three component viruses, mainly type 2 and type 3, upon multiplication in humans. Point mutations in critical nucleotide positions are generally accepted as one mechanism of reversion towards neurovirulence of Sabin strains. In this paper we present evidence that intermolecular recombi nation, possibly in combination with mutation, may also play a role in the loss of attenuation of vaccine polioviruses.