Abstract
ABSTRACTOral poliovirus vaccine can mutate to regain neurovirulence. To date, evaluation of these mutations has been performed primarily on culture-enriched isolates by using conventional Sanger sequencing. We therefore developed a culture-independent, deep-sequencing method targeting the 5′ untranslated region (UTR) and P1 genomic region to characterize vaccine-related poliovirus variants. Error analysis of the deep-sequencing method demonstrated reliable detection of poliovirus mutations at levels of <1%, depending on read depth. Sequencing of viral nucleic acids from the stool of vaccinated, asymptomatic children and their close contacts collected during a prospective cohort study in Veracruz, Mexico, revealed no vaccine-derived polioviruses. This was expected given that the longest duration between sequenced sample collection and the end of the most recent national immunization week was 66 days. However, we identified many low-level variants (<5%) distributed across the 5′ UTR and P1 genomic region in all three Sabin serotypes, as well as vaccine-related viruses with multiple canonical mutations associated with phenotypic reversion present at high levels (>90%). These results suggest that monitoring emerging vaccine-related poliovirus variants by deep sequencing may aid in the poliovirus endgame and efforts to ensure global polio eradication.
Highlights
Oral poliovirus vaccine can mutate to regain neurovirulence
This success is due in large part to the widespread use of Sabin oral poliovirus vaccine (OPV), which has been the backbone of polio eradication efforts worldwide due to its ease of administration, immunogenic potential, and low cost [2]
OPV can develop into vaccine-derived polioviruses (VDPVs), mutated vaccine strains with the potential to behave like wild-type neurovirulent poliovirus
Summary
Oral poliovirus vaccine can mutate to regain neurovirulence. To date, evaluation of these mutations has been performed primarily on culture-enriched isolates by using conventional Sanger sequencing. Sequencing of viral nucleic acids from the stool of vaccinated, asymptomatic children and their close contacts collected during a prospective cohort study in Veracruz, Mexico, revealed no vaccine-derived polioviruses. We identified many low-level variants (Ͻ5%) distributed across the 5= UTR and P1 genomic region in all three Sabin serotypes, as well as vaccine-related viruses with multiple canonical mutations associated with phenotypic reversion present at high levels (Ͼ90%). These results suggest that monitoring emerging vaccinerelated poliovirus variants by deep sequencing may aid in the poliovirus endgame and efforts to ensure global polio eradication. A few studies have sequenced vaccine-related viruses isolated from asymptomatic individuals or their contacts after OPV vaccination; these studies relied upon tissue culture amplification, which may on its own introduce mutations, and Sanger sequencing technology, which is insensitive to low-level variants [12,13,14,15]
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