title: Sabin type 2 polioviruses with intertypic vaccine/vaccine recombinant genomes.
abstract: Attenuated strains of the Sabin oral poliovirus vaccine replicate in the human gut and, in rare cases, cause vaccine-associated paralytic poliomyelitis. In the present study, 15 vaccine-derived strains isolated from patients with vaccine-associated paralytic poliomyelitis and from healthy vaccinees were examined. Four distant sequences of the poliovirus genome (5' NCR, VP3/VP1, VP1/2A, and 3DPol/3' NCR) were targeted, and the reverse-transcribed segments were amplified by polymerase chain reaction followed by restriction fragment length polymorphism analysis with four restriction enzymes. Among the 15 isolates (11 Sabin type 2, 3 Sabin type 1, and 1 Sabin type 3), four Sabin type 2 isolates (36%) were found to be intertypic vaccine/vaccine recombinant in the 3DPol/3' NCR region of the viral genome. The recombinant genotypes identified were S2/S2/S1 for two isolates and S2/S2/S2/S3 and S2/S2/S1/S2 for each of the other two isolates, respectively. Recombinant viruses with unmodified segments in the 5' NCR and the VP3/VP1 regions of the viral genome, a modified segment in the VPI/2A region only for one strain, and an often recombinant segment in the 3DPol/3' NCR parts of the genome were so identified. These findings provide strong evidence that recombination is a frequent phenomenon in type 2 poliovirus vaccine strains and suggest that recombination may be an important mechanism of the natural evolution of polioviruses of Sabin type 2 origin, perhaps even one of the mechanisms of reversion of attenuated vaccine strains toward neurovirulence.
authors.affiliation: Enterovirus Reference Center for South Greece, Department of Virology, Hellenic Pasteur Institute, Athens.
authors.forename: A
authors.initials: A
authors.lastname: Georgopoulou
authors.forename: P
authors.initials: P
authors.lastname: Markoulatos
mesh_terms: D001483:Base Sequence; D002648:Child; D002675:Child, Preschool; D016679:Genome, Viral; D006801:Humans; D007223:Infant; D008969:Molecular Sequence Data; D011051:Poliomyelitis / Q000517:prevention & control* / Q000821:virology*; D017955:Poliovirus / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity; D011055:Poliovirus Vaccine, Oral / Q000235:genetics*; D016133:Polymerase Chain Reaction; D011995:Recombination, Genetic; D012680:Sensitivity and Specificity; D014613:Vaccines, Attenuated / Q000235:genetics; D014774:Virulence
chemical_list: D011055:Poliovirus Vaccine, Oral; D014613:Vaccines, Attenuated