Antigenic characteristics and genomic analysis of novel EV-A90 enteroviruses isolated in Xinjiang, China

Abstract

Enterovirus A90 (EV-A90) is a novel serotype of enterovirus A species that is rarely reported. Here, we isolated five enteroviruses from patients with acute flaccid paralysis in Hotan and Kashgar cities in Xinjiang, China that were identified as EV-A90 by molecular typing. The VP1 sequences of these Xinjiang EV-A90 strains showed 88.4-89% nucleotide sequence identity to the prototype EV-A90 strain; however, genome analysis indicated complex recombination events in P2 and P3 regions. Next, the seroprevalence of EV-A90 was examined in 49 serum specimens collected in Hotan and Kashgar, and 37.5% were EV-A90 antibody positive (>1:8), with a geometric mean titre (GMT) of 1:10.47. The low positive rate and GMT suggest a low-level EV-A90 epidemic in Xinjiang. Two of the five Xinjiang EV-A90 strains were temperature sensitive, and three were temperature resistant, and a comparative genomics analysis suggested that an amino acid substitution (H1799Y) in the 3D^pol region was related to temperature sensitivity. Although the epidemic strength is low, some EV-A90 strains were temperature resistant, which is suggestive of strong virulence and transmission capacity. This study expanded the number of EV-A90 in GenBank and provided basic data that may be useful for studying the molecular epidemiology of EV-A90.

Figure 1

Phylogenetic tree of global EV-A90 based on entire VP1 sequence. Isolates from Xinjiang were marked with and the prototype of EV-A90 (BAN00-10399) was marked with . The phylogenetic tree was reconstructed using neighbor-joining method with the substitution model of maximum composite likelihood model.

Figure 2

Potential recombination analysis of the whole genome of the Xinjiang EV-A90 strains. Similarity analysis (a) and bootscaning analysis (b) were performed in a 200-nt sliding window. Each point indicated similarity between the Xinjiang strain and other EV-A strains in a 20-nt moving step. Kimura (2-parameter) model was used in the analysis.

Figure 3

Phylogenetic tree of genetic fragments for EV-A90 and other similar serotypes, including P1, P2, P3 and 3CD, were illustrated in figure (a–d). Isolates in this research were marked with and the prototype of EV-A90 (BAN00-10399) was marked with . The phylogenetic tree was reconstructed using maximum likelihood method, in which GTR + I + G model was used in P1 fragment and TN93 + I + G model was used in the rest fragment. We also put forward a hypothesis between the major parental type (yellow) and the minor parental type (blue) because of recombination.

Figure 4

The viral titers of five EV-A90 strains in different time were drawn in the coordinate system. The blue line represented the growth curve in 36 °C and the red one represented the growth curve in 39.5 °C.