title: Natural type 3/type 2 intertypic vaccine-related poliovirus recombinants with the first crossover sites within the VP1 capsid coding region.
abstract: BACKGROUND
  Ten uncommon natural type 3/type 2 intertypic poliovirus recombinants were isolated from stool specimens from nine acute flaccid paralysis case patients and one healthy vaccinee in China from 2001 to 2008.
  
  
  RESULTS
  Complete genomic sequences revealed their vaccine-related genomic features and showed that their first crossover sites were randomly distributed in the 3' end of the VP1 coding region. The length of donor Sabin 2 sequences ranged from 55 to 136 nucleotides, which is the longest donor sequence reported in the literature for this type of poliovirus recombination. The recombination resulted in the introduction of Sabin 2 neutralizing antigenic site 3a (NAg3a) into a Sabin 3 genomic background in the VP1 coding region, which may have been altered by some of the type 3-specific antigenic properties, but had not acquired any type 2-specific characterizations. NAg3a of the Sabin 3 strain seems atypical; other wild-type poliovirus isolates that have circulated in recent years have sequences of NAg3a more like the Sabin 2 strain.
  
  
  CONCLUSIONS
  10 natural type 3/type 2 intertypic VP1 capsid-recombinant polioviruses, in which the first crossover sites were found to be in the VP1 coding region, were isolated and characterized. In spite of the complete replacement of NAg3a by type 2-specific amino acids, the serotypes of the recombinants were not altered, and they were totally neutralized by polyclonal type 3 antisera but not at all by type 2 antisera. It is possible that recent type 3 wild poliovirus isolates may be a recombinant having NAg3a sequences derived from another strain during between 1967 and 1980, and the type 3/type 2 recombination events in the 3' end of the VP1 coding region may result in a higher fitness.
authors.affiliation: WHO WPRO Regional Polio Reference Laboratory and State Key Laboratory for Molecular Virology and Genetic Engineering, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, People's Republic of China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhang
authors.forename: Shuangli
authors.initials: S
authors.lastname: Zhu
authors.forename: Dongmei
authors.initials: D
authors.lastname: Yan
authors.forename: Guiyan
authors.initials: G
authors.lastname: Liu
authors.forename: Ruyin
authors.initials: R
authors.lastname: Bai
authors.forename: Dongyan
authors.initials: D
authors.lastname: Wang
authors.forename: Li
authors.initials: L
authors.lastname: Chen
authors.forename: Hui
authors.initials: H
authors.lastname: Zhu
authors.forename: Hongqiu
authors.initials: H
authors.lastname: An
authors.forename: Olen
authors.initials: O
authors.lastname: Kew
authors.forename: Wenbo
authors.initials: W
authors.lastname: Xu
mesh_terms: D000941:Antigens / Q000378:metabolism; D001483:Base Sequence; D036022:Capsid Proteins / Q000737:chemistry*; D002681:China; D016679:Genome, Viral; D005838:Genotype; D006801:Humans; D008969:Molecular Sequence Data; D009123:Muscle Hypotonia / Q000821:virology*; D009711:Nucleotides / Q000235:genetics; D010243:Paralysis / Q000821:virology*; D010641:Phenotype; D011055:Poliovirus Vaccine, Oral / Q000378:metabolism*; D012689:Sequence Homology, Nucleic Acid; D013696:Temperature
chemical_list: D000941:Antigens; D036022:Capsid Proteins; D009711:Nucleotides; D011055:Poliovirus Vaccine, Oral; C442540:VP1 protein, Poliovirus