In a recent study published in lancetresearchers investigated the molecular characteristics of type 2 poliovirus (PV) isolates obtained from sewage samples (SS) to detect PV transmission within the community.
Background
PV transmission affects all countries and has been designated an international public health emergency by the World Health Organization (WHO). Global PV outbreak risk may be exacerbated in countries using inactivated polio vaccines. Inactivated polio vaccines offer strong protection against paralytic polio, but are less effective than oral vaccines against PV shedding, possibly allowing undetected PV circulation for long periods of time.
The authors of this study have previously performed PV environmental monitoring in the United Kingdom (UK) since 2014. They found that vaccine-like PV isolates could be sporadically detected in wastewater (WW) samples. It was probably imported from a country that uses oral polio vaccine for vaccination and generates an immune response.
The authors previously identified 2, 2, and 8 vaccine-like PV isolates of types 1, 2, and 3, respectively, from 2017 to 2021, none of which were genetically related. , all contained mutations and no associated viruses were detected. His subsequent WW samples show no local PV transmission.
About research
In the present study, researchers extended their previous analysis by performing an environmental surveillance analysis for the detection of PV type 2 isolates in the London sewage system.
Ribonucleic acid (RNA) was extracted from SS, subjected to polymerase chain reaction (PCR) analysis using PV-enterovirus primers and sequenced by whole-genome sequencing. SS was tested using WHO-recommended techniques, including enrichment, virus isolation in L20B mouse and rhabdomyosarcoma cells, and molecular characterization. DDNS (direct detection by nanopore sequencing) and phylogenetic analysis were also performed.
Furthermore, using a novel nanopore sequencing protocol, we directly detected PVs in fecal samples and rapidly generated whole-genome PV sequences to improve our understanding of their geographical transmission and history. The modified protocol uses type 2 PV isolate target primers to increase virus detection sensitivity by reducing VP1 sequence background from cocirculating C enterovirus species obtained using the original detection protocol. improved.
Sampling procedures were extensively performed to identify areas where PV transmission could occur. The Beckton sewage treatment plant was classified as a small sub-catchment area. Sampling was also extended to the large London sewage treatment plant beyond Beckton to investigate the possible presence of Type 2 PV in a wider geographic area.
result
Two PV type 2 vaccine-like isolates were identified in sewage samples obtained from the Beckton sewage treatment operation in London on 8 February 2022. In addition, 3 and 6 type 1 and type 3 PV vaccine-like isolates were identified in 52 SS obtained from London between 11 January and 4 July 2022, the parental Sabin strain. All consisted of several unrelated mutations, except for .
In 21 consecutive SS acquired in London between 8 February and 8 February, genetic A total of 118 genetically related PV isolates associated with . July 4, 2022. The isolates acquired an additional 11 mutations at different nt positions between 8 February and 12 April 2022, increasing the genetic diversity of PV.
The isolate was recombinant with a species C enterovirus crossover at nucleotide (nt) position 5139. Twenty isolates contained vaccine-derived PV type 2 obtained from neighboring sewage bodies with non-overlapping drainage populations, indicating localized PV transmission.
Only two samples (ENV-22-117 and ENV-22-027) constituted PV isolates with similar sequences. Since 12 April 2022, cell culture experiments performed on samples obtained from his Beckton area of ​​London have detected genetically related PV type 2 isolates in increasing concentrations.
The positive sampling locations identified indicated the presence of PV mainly in some areas within Beckton and some boroughs east and north of London. Increased sensitivity was observed when using type 2 PV isolate-specific primers in a second nested PCR test. Type 2 PV isolates were detectable from faecal samples reported as negative in virus isolation experiments.
Conclusion
Overall, the findings suggest that environmental surveillance will enable early detection of PV importation (and circulation) in London, leading to increased surveillance and inactivated polio vaccine campaigns in 1-9 years. , indicating that a rapid public health response is now possible. old kids. Viruses appear to have evolved in several directions from a common source, with multiple London sewage PV type 2 isolates sharing only one or similar VP1 nt alterations from the Sabin 2 strain. , demonstrating that genetic relatedness among isolates is not based solely on VP1. sequence.
Therefore, it may be important to refine the definition of vaccine-derived viral organisms to ensure rapid and early detection of PC infection events, especially in countries that have been polio-free for several years.
