Abstract
To understand the biological characteristics of the reemerging pseudorabies virus (PRV) strains, a total of 392 tissue samples were collected from diseased pigs during reemerging PR outbreaks between 2012 and 2019 on farms in central China where swine had been immunized with Bartha-K61 and 51 (13. 01%) were positive for the gE gene by PCR. Sixteen PRV strains were isolated and caused clinical symptoms and death in mice. Subsequently, gE, gC, gB, and gD complete genes were amplified from the 16 PRV isolates and sequenced. Phylogenetic analysis based on these four gene sequences shows that the 16 PRV isolates were more closely related to the Chinese PRV variants (after 2012) but genetically differed from early Chinese PRV isolates (before 2012). Sequence analysis reveals that PRV isolates exhibited amino acid insertions, substitutions, or deletions compared with early Chinese PRV isolates and European–American PRV strains. In addition, this is the first report that eight isolates (8/16) in this study harbor a unique amino acid substitution at position 280 (F to L) of the gC protein, and six isolates have an amino acid substitution at position 338 (A to V) of the gD protein compared with the Chinese PRV variants. The emulsion containing inactivated PRV NY isolate could provide complete protection against the NY isolate. This study might enrich our understanding of the evolution of reemerging PRV strains as well as pave the way for finding a model virus to develop a novel vaccine based on reemerging PRV strains.
Highlights
Pseudorabies (PR), or Aujeszky’s disease, is an economically important viral disease of swine worldwide and poses a great threat to the pork industry [1, 2]
Of the 392 samples, 51 were positive for the pseudorabies virus (PRV) gene, yielding an average positive rate of 13.01% (51/392), which was coincident with the reports of the prevalence of novel PR in China [6, 19, 26, 27]
PRV glycoprotein E (gE) gene–positive tissue samples were inoculated into Swine testicle (ST) cells, and distinct cytopathic effects (CPEs) characterized by cell rounding, pyknosis, and degeneration were observed after three blind passages on ST cells
Summary
Pseudorabies (PR), or Aujeszky’s disease, is an economically important viral disease of swine worldwide and poses a great threat to the pork industry [1, 2]. The glycoprotein E (gE) is a major virulence determinant of PRV but is not essential for virus replication [15] In light of this fact, gE-deleted vaccines (Bartha-K61 vaccine) were developed, and the vaccines, together with a corresponding serological test to detect antibodies against the gE protein, have played a key role in the program of the elimination of PR. For further investigating the molecular epidemiology of reemerging PRV strains, this study reports the detection and genetic analysis of PRV from pigs in central China between 2012 and 2019 and is evaluated to find a candidate virus for the development of novel and efficient PR vaccines
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