Molecular epidemiology of human enterovirus 71 in the United Kingdom from 1998 to 2006

Abstract

The last decade witnessed a significant increase in epidemic activity of human enterovirus 71 (EV71) in the Western Pacific Region (WPR). In most European countries, this risk is unrecognized despite occasional cases of severe disease and two severe outbreaks in Eastern Europe 30 years ago. In this study we report the first examination of the molecular epidemiology of EV71 in the United Kingdom from 1998 to 2006. Genomic regions encoding the 1D coat protein (VP1) and 3D polymerase (Pol) from 32 EV71 isolates associated with neurological or cutaneous manifestations were sequenced. Phylogenetic analyses of VP1 and 3D Pol sequences identified genotype C as the dominant strain. Several United Kingdom isolates had genetic linkages with predated C1 or C2 strains from Europe and the WPR. Recombination events were not detected between United Kingdom strains. However, a previously published Taiwanese strain was identified as an intergenotypic recombinant. EV71 genotype C appears to have continuous circulation in the United Kingdom from 1998 to 2006 with repeated introductions of new strains replacing previous strains. It is necessary to continuously monitor the molecular evolution and recombination events of EV71.

FIG. 1.

Phylogenetic relationship among a total of 111 worldwide EV71 strains based on alignment of complete VP1 coding sequences. Thirty-two United Kingdom strains are from the present study, and seventy-nine are from GenBank. United Kingdom strains are highlighted in bold-face. Trees were constructed by the neighbor-joining method using PHYLIP (5) and plotted by using TreeView (16). Bootstrap values of 1,000 replicates for major lineages are displayed as numbers at the nodes. CVA-16 (G-10) was used as an outgroup. The corresponding VP1 genotype and genogroup of each cluster are indicated by vertical bars. The EV71 prototype strain BrCr is the only example of genotype A, which in the absence of the intergenotypic recombinant TW/2272/98 forms an independent phylogenetic branch (data not shown).

FIG. 2.

Dendrograms showing the genetic relationships of 54 EV71 isolates based on an alignment of the complete VP1 and 3D Pol genomic sequences. Thirty-two United Kingdom strains are from the present study, and twenty-two are from GenBank. United Kingdom strains are highlighted in boldface. Trees were constructed by neighbor-joining method by using PHYLIP (5) and plotted by using TreeView (16). Bootstrap values of 1,000 replicates for major lineages are displayed as numbers at the nodes. CVA-16 (G-10) was used as an outgroup. The corresponding VP1 genotype and genogroup of each cluster are indicated by vertical bars. GenBank EV71 strain (TW/2272/98) isolated from a fatal case in Taiwan 1998 grouped as a genotype B based on VP1 analysis (asterisk) but was subsequently repositioned as a genogroup C2 when tested in the 3D Pol analysis. The EV71 prototype strain BrCr is the only example of genotype A, which in the absence of the intergenotypic recombinant TW/2272/98 forms an independent phylogenetic branch (data not shown).

FIG. 3.

Similarity analysis of complete EV71 genomes calculated by SimPlot 3.5.1 (10) using a sliding window of 200 nucleotides moving in 20-bp steps. All positions with gaps were deleted, and the similarity was plotted by using the Kimura two-parameter distance model. Each point represents the similarity between the query sequence and a given heterologous sequence. The approximate position within the EV71 genome is indicated above the similarity analysis. The plot shows a comparison of strains 2086/98, TW/2272/98, and MS/7423/87 versus NCKU9822.