Article

Recombinant vaccine-derived poliovirus in Madagascar.

Emerging infectious diseases (Impact Factor: 5.99). 08/2003; 9(7):885-7. DOI:10.3201/eid0907.020692
Source: PubMed
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    ABSTRACT: Vaccine-derived polioviruses (VDPVs) are associated with polio outbreaks and prolonged infections in individuals with primary immunodeficiencies. VDPV-specific PCR assays for each of the three Sabin oral poliovirus vaccine (OPV) strains were developed, targeting sequences within the VP1 capsid region that are selected for during replication of OPV in the human intestine. Over 2,400 Sabin-related isolates and identified 755 VDPVs were screened. Sensitivity of all assays was 100%, while specificity was 100% for serotypes 1 and 3, and 76% for serotype 2. The assays permit rapid, sensitive identification of OPV-related viruses and flag programmatically important isolates for further characterization by genomic sequencing.
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    ABSTRACT: Polioviruses isolated from 70 acute flaccid paralysis patients from the Democratic Republic of Congo (DRC) during 2004-2011 were characterized and found to be vaccine-derived type 2 polioviruses (VDPV2s). Partial genomic sequencing of the isolates revealed nucleotide sequence divergence of up to 3.5% in the viral protein 1 capsid region of the viral genome relative to the Sabin vaccine strain. Genetic analysis identified at least 7 circulating lineages localized to specific geographic regions. Multiple independent events of VDPV2 emergence occurred throughout DRC during this 7-year period. During 2010-2011, VDPV2 circulation in eastern DRC occurred in an area distinct from that of wild poliovirus circulation, whereas VDPV2 circulation in the southwestern part of DRC (in Kasai Occidental) occurred within the larger region of wild poliovirus circulation.
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    ABSTRACT: The oral poliovaccine, a live vaccine made of attenuated poliovirus strains, is the main tool of the vaccination campaigns organised for eradicating poliomyelitis. these campaigns had led to the decline and, thereafter, to the disappearance of wild poliovirus strains of the three serotypes (1-3) in most parts of the world. However, when the poliovaccine coverage becomes too low, vaccine polioviruses can circulate in insufficiently immunized populations and become then pathogenic by mutations and genetic recombination with other enteroviruses of the same species, in particular some coxsackievirus A. These mutated and recombinant vaccine strains have been implicated in several epidemics of paralytic poliomyelitis. Two polio outbreaks associated with these pathogenic circulating vaccine-derived poliovirus (cVDPV) occurred in 2001-2002 and 2005 in the South of Madagascar where vaccine coverage was low. These cVDPV, of serotype 2 or 3, were isolated from paralyzed children and some of their healthy contacts. Other cVDPV were isolated in the same region from healthy children in 2011, indicating that these viruses were circulating again. Vaccination campaigns could stop the outbreaks in 2002 and 2005, and most probably prevent another one in 2011. Therefore, the genetic plasticity of poliovaccine strains that threatens the benefit of vaccination campaigns is the target of an accurate surveillance and an important theme of studies in the virology laboratories of the Institut Pasteur international network.
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