Genetic and antigenic characterization of enterovirus 71 in Ho Chi Minh City, Vietnam, 2011

Abstract

Enterovirus 71 (EV71) frequently causes fatal infections in young children in Asia. In 2011, EV71 epidemics occurred in southern Vietnam. We conducted genetic and antigenic analysis of the EV71 isolates and found that 94% of them were genotype C4a related to two lineages circulating in China and 6% were genotype C5 which have circulated in Vietnam since 2003. Antigenic variants were not detected. EV71 vaccines are being developed. Longitudinal enterovirus surveillance data are critical to formulate vaccination policy in Vietnam.

Figure 1. Phylogenetic relationships of EV71 viruses isolated in this study and reference strains using VP1 sequences (A) and full genomes (B).

Backgrounds of the EV71 viruses genotyped in this study and the reference viruses were provided in Table 1 and Table S1 [15], respectively. The prototype coxsackievirus A16 (CA16G10) was used as the outgroup virus. The phylogenetic tree was constructed using the neighbor-joining method. Bootstrap values (>70%) are shown as percentage derived from 1,000 sampling at the nodes of the tree. Scale bar denotes number of nucleotide substitutions per site along the branches. Red dot indicates the viruses isolated and sequenced in this study.

Figure 2. SimPlot analysis of EV71 C5 virus isolated in HCM City, Vietnam, 2011.

The query virus is HCM84-VNM-2011 and four potential parental (EV71 genotype C1, C2 and C3, and CA8) viruses identified through BLAST and phylogenetic analysis and six reference viruses were selected for the SimPlot analysis.