Molecular characterization of enterovirus-A71 in children with acute flaccid paralysis in the Philippines

Lea Necitas Apostol,Maria Melissa Ann Jiao,Hiroyuki Shimizu,Amado Tandoc,Mariko Saito,Akira Suzuki,Hitoshi Oshitani,Rifqiyah Nur Umami,Socorro Lupisan

doi:10.1186/s12879-019-3955-x

Abstract

BackgroundSeveral inactivated enterovirus-A71 (EV-A71) vaccines are currently licensed in China; however, the development of additional EV-A71 vaccines is ongoing, necessitating extensive analysis of the molecular epidemiology of the virus worldwide. Until 2012, laboratory confirmation of EV-A71 for hand, foot, and mouth disease (HFMD) and other associated diseases had not occurred in the Philippines. Because EV-A71 has been linked with cases of acute flaccid paralysis (AFP), AFP surveillance is one strategy for documenting its possible circulation in the country. To expand current knowledge on EV-A71, molecular epidemiologic analysis and genetic characterization of EV-A71 isolates were performed in this study.MethodsA retrospective study was performed to identify and characterize nonpolio enteroviruses (NPEVs) associated with AFP in the Philippines, and nine samples were found to be EV-A71–positive. Following characterization of these EV-A71 isolates, the complete viral protein 1 (VP1) gene was targeted for phylogenetic analysis.ResultsNine EV-A71 isolates detected in 2000 (n = 2), 2002 (n = 4), 2005 (n = 2), and 2010 (n = 1) were characterized using molecular methods. Genomic regions spanning the complete VP1 region were amplified and sequenced using specific primers. Phylogenetic analysis of the full-length VP1 region identified all nine EV-A71 Philippine isolates as belonging to the genogroup C lineage, specifically the C2 cluster. The result indicated a genetic linkage with several strains isolated in Japan and Taiwan, suggesting that strains in the C2 cluster identified in the Asia-Pacific region were circulating in the Philippines.ConclusionThe study presents the genetic analysis of EV-A71 in the Philippines. Despite some limitations, the study provides additional genetic data on the circulating EV-A71 strains in the Asia-Pacific region, in which information on EV-A71 molecular epidemiology is incomplete. Considering that EV-A71 has a significant public health impact in the region, knowledge of its circulation in each country is important, especially for formulating vaccines covering a wide variety of strains.

Highlights

Several inactivated enterovirus-A71 (EV-A71) vaccines are currently licensed in China; the development of additional EV-A71 vaccines is ongoing, necessitating extensive analysis of the molecular epidemiology of the virus worldwide
Phylogenetic analysis of the full-length viral protein 1 (VP1) region illustrated that all nine Philippine EV-A71 isolates belonged to genogroup C, especially the C2 and C2-like clusters (Fig. 1)
The present study only examined samples from patients with acute flaccid paralysis (AFP) opposed to a diverse group of individuals presenting with other clinical conditions, this study on EV-A71–associated AFP provides a focal premise that Philippine EV-A71 strains may have neurovirulent potential as strains found in the Asia-Pacific region

Summary

Introduction

Several inactivated enterovirus-A71 (EV-A71) vaccines are currently licensed in China; the development of additional EV-A71 vaccines is ongoing, necessitating extensive analysis of the molecular epidemiology of the virus worldwide. Until 2012, laboratory confirmation of EV-A71 for hand, foot, and mouth disease (HFMD) and other associated diseases had not occurred in the Philippines. To expand current knowledge on EV-A71, molecular epidemiologic analysis and genetic characterization of EV-A71 isolates were performed in this study. EV-A71 has caused outbreaks of hand, foot, and mouth disease (HFMD) and herpangina, and as a neurotropic virus, it can cause severe neurological complications such as aseptic meningitis, encephalitis, and poliomyelitis-like acute flaccid paralysis (AFP) in infants and young children with significant mortality and morbidity [2, 6,7,8,9]. Since its first isolation in 1969 in the USA, large outbreaks have been reported in different parts of the world, and the identification of EV-A71 infection has intensified since 1997, in the Asia-Pacific region including Japan, Malaysia, Brunei, Taiwan, Australia, Singapore, China, and Vietnam [2, 10,11,12]

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Results

Discussion

Conclusion