Genomic characterization of emergent pseudorabies virus in China reveals marked sequence divergence: Evidence for the existence of two major genotypes

Abstract

Recently pseudorabies outbreaks have occurred in many vaccinated farms in China. To identify genetic characteristics of pseudorabies virus (PRV) strains, we obtained the genomic sequences of PRV strains HeN1 and JS, which were compared to 4 PRV genomes and 729 partial gene sequences. PRV strains isolated in China showed marked sequence divergence compared to European and American strains. Phylogenetic analysis revealed that for the first time PRV can be divided into 2 distinct clusters, with Chinese strains being genotype II and PRVs isolated from other countries being genotype I. Restriction fragment length polymorphism analysis confirmed differences between HeN1 and Bartha strains, as did the presence of unique insertion/deletion polymorphisms and microsatellites. This divergence between the two genotypes may have been generated from long-term, independent evolution, which could also explain the low efficacy of the Bartha vaccine in protecting pigs infected with genotype II PRV.

Experimental Infection of Sheep With Pseudorabies Viruses Isolated In Shanghai, China, Between 2010 and 2012

“…As shown in Figure 1A, the two isolates both shared an insertion of seven amino acids (AAASTPA) between positions 63 and 69 in the gC gene, as compared to the classic PRV strains Bartha, Becker and Kaplan; only earlier Chi-nese strains, emerging variant strains, and the P-Prv strain shared these insertions. Based on a phylo-genetic analysis of the gC gene, the two major genotypes observed were designated as genotype I and genotype II ( Figure 1B); these results were similar to those reported in the literature [15]. Genotype I was composed of viruses from a wide range of geographic regions, including Europe, America, and Asia.…”

“…Furthermore, the gC gene is most widely used for phylogenetic analysis of PRV strains mainly because the sequence is prone to variation [5,11,21]. Recent reports have revealed that PRV can be classified into two major genotypes: genotype I (European and American strains) and gen-otype II (Chinese strains) [15]. The two isolates in the present study could be classified in genotype II.…”

Live attenuated pseudorabies virus developed using the CRISPR/Cas9 system

“…The PRV HeN1 strain used (GenBank accession number: KP098534.1) has been described previously Ye et al, 2015).…”

“…In a recent study, according to genome sequence analysis Ye et al demonstrated that PRV can be divided into 2 genotypes. The emergent strain belongs to genotype II, which is distinct from the European and American strains that belong to genotype I (Ye et al, 2015). The Bartha-K61 vaccine was derived from genotype I, which exhibits marked sequence divergence compared to the emergent strains.…”

“…The Bartha-K61 vaccine was derived from genotype I, which exhibits marked sequence divergence compared to the emergent strains. This lack of homology could explain the low efficacy of the Bartha vaccine in protecting pigs from emergent strains Ye et al, 2015).…”