Molecular characteristics of VP1 region of enterovirus 71 strains in China

Abstract

Background: Enterovirus 71 (EV71) is the most commonly implicated as the causative agent of severe and fetal hand, foot, and mouth disease (HFMD) outbreaks.VP1 protein, a capsid protein of EV71, is responsible for the genotype of EV71, which is essential for vaccine development and effectiveness. However, the genotypes of EV71 isolates in China are still not completely clear.Methods: The VP1 gene sequences of 3712 EV71 virus strains from China, excluding repetitive sequences, and 30 known EV71 genotypes as reference strains, between 1986 and 2019 were obtained from GenBank. A phylogenetic tree, amino acid homology, genetic variation and genotype analysis of the EV71-VP1 protein were performed with MEGA 6.0 software.Results: The amino acid identity was 88.33%~100% among 3712 EV71 strains that was 93.47%~100% compared with vaccine strain H07, and 93.04%~100% compared with vaccine strains FY7VP5 or FY-23K-B. Since 2000, the prevalent strains of EV71 were mainly the C4 genotype. Among these the C4a subgenotype was predominant, the C4b subgenotype was the second, and other subgenotypes appeared sporadically between 2005 and 2018 in mainland China. The B4 genotype was the main genotype in Taiwan, and the epidemic strains were constantly changing. Some amino acid variations in VP1 of EV71 occurred with high frequencies: A289T (20.99%), H22Q (16.49%), A293S (15.95%), S283T (15.11%), V249I (7.76%), N31D (7.25%), and E98K (6.65%).Conclusion: The C4 genotype of EV71 in China can match the vaccine, which can effectively control EV71 epidemiology. However, the efficacy of the vaccine strain is partially affected by the continuous change in epidemic strains in Taiwan, China. These studies suggested that the genetic characteristics of the EV71-VP1 region should be continuously monitored, which is critical for epidemic control and vaccine design against EV71 infection in children.