Characteristics of an environmentally monitored prolonged type 2 vaccine derived poliovirus shedding episode that stopped without intervention.
Vaccine derived poliovirus (VDPV) type 2 strains strongly divergent from the corresponding vaccine strain, Sabin 2, were repeatedly isolated from sewage in Slovakia over a period of 22 months in 2003-2005. Cell cultures of stool specimens from known immune deficient patients and from an identified putative source population of 500 people failed to identify the potential excretor(s) of the virus. The occurrence of VDPV in sewage stopped without any intervention. No paralytic cases were reported in Slovakia during the episode. According to a GenBank search and similarity plotting-analysis, the closest known relative of the first isolate PV2/03/SVK/E783 through all main sections of the genome was the type 2 poliovirus Sabin strain, with nucleotide identities in 5'UTR, P1, P2, P3, and 3'UTR parts of the genome of 88.6, 85.9, 87.3, 88.5, and 94.0 percent, respectively. Phenotypic properties of selected Slovakian aVDPV strains resembled those of VDPV strains isolated from immune deficient individuals with prolonged PV infection (iVDPV), including antigenic changes and moderate neurovirulence in the transgenic mouse model. One hundred and two unique VP1 coding sequences were determined from VDPV strains isolated from 34 sewage specimens. Nucleotide differences from Sabin 2 in the VP1 coding region ranged from 12.5 to 15.6 percent, and reached a maximum of 9.6 percent between the VDPV strains under study. Most of the nucleotide substitutions were synonymous but as many as 93 amino acid positions out of 301 in VP1 showed substitutions. We conclude that (1) individuals with prolonged poliovirus infection are not as rare as suggested by the studies on immune deficient patients known to the health care systems and (2) genetic divergence of VDPV strains may remain extensive during years long replication in humans.
Virology Unit, Department of Infectious Disease Surveillance and Control, National Institute for Health and Welfare, a WHO Collaborating Centre for Poliovirus Surveillance and Enterovirus Research, Helsinki, Finland. tapani.hovi@thl.fi
Tapani
T
Hovi
Anja
A
Paananen
Soile
S
Blomqvist
Carita
C
Savolainen-Kopra
Haider
H
Al-Hello
Teemu
T
Smura
Hiroyuki
H
Shimizu
Katarina
K
Nadova
Zdenka
Z
Sobotova
Eugene
E
Gavrilin
Merja
M
Roivainen
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D036022:Capsid Proteins / Q000737:chemistry / Q000235:genetics*; D002648:Child; D004783:Environmental Microbiology; D014644:Genetic Variation; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D017955:Poliovirus / Q000145:classification / Q000235:genetics* / Q000276:immunology; D011055:Poliovirus Vaccine, Oral / Q000276:immunology; D055503:Protein Multimerization; D012621:Seasons; D017386:Sequence Homology, Amino Acid; D012722:Sewage / Q000821:virology*; D018154:Slovakia; D014611:Vaccination
D000914:Antibodies, Viral; D036022:Capsid Proteins; D011055:Poliovirus Vaccine, Oral; D012722:Sewage