Jianbo Huang

We sequenced the complete genome of the pseudorabies virus (PRV) FJ epidemic strain, and we studied the characteristics and the differences compared with the classical Chinese strain and that of other countries. Third-generation sequencing and second-generation sequencing technology were used to construct, sequence, and annotate an efficient, accurate PRV library. The complete FJ genome was 143,703 bp, the G+C content was 73.67%, and it encoded a total of 70 genes. The genetic evolution of the complete genome and some key gene sequences of the FJ strain and PRV reference strains were analyzed by the maximum likelihood (ML) method of MEGA 7.0 software. According to the ML tree based on the full-length genome sequences, PRV FJ strain was assigned to the branch of genotype II, and it showed a close evolutionary relationship with PRV epidemic variants isolated in China after 2011. The gB, gC, gD, gH, gL, gM, gN, TK, gI, and PK genes of the FJ strain were assigned to the same branch with other Chinese epidemic mutants; its gG gene was assigned to the same branch with the classic Chinese Fa and Ea strains; and its gE gene was assigned to a relatively independent branch. Potential recombination events were predicted by the RDP4 software, which showed that the predicted recombination sites were between 1694 and 1936 bp, 101,113 and 102,660 bp, and 107,964 and 111,481 bp in the non-coding region. This result broke the previously reported general rule that pseudorabies virus recombination events occur in the gene coding region. The major backbone strain of the recombination event was HLJ8 and the minor backbone strain was Ea. Our results allowed us to track and to grasp the recent molecular epidemiological changes of PRV. They also provide background materials for the development of new PRV vaccines, and they lay a foundation for further study of PRV.

Pseudorabies is a disease that seriously endangers the pig industry in China. Recently, we successfully isolated a pseudorabies virus from the brain tissue of piglets at a farm in Sichuan, China, and named it the FJ62 strain. In order to understand the molecular biological characteristics of the strain, primers were designed for glycoproteins gB, gC, gD and gE, which were amplified by a polymerase chain reaction (PCR) and sequenced. After comparing the sequence with the Genbank 22 pseudorabies virus reference strains and establishing the genetic evolutionary tree, it was found that the gB gene of pseudorabies virus was highly homologous (up to 100%) with the MY‐1 strain which is isolated from a wild boar in Japan (AP018925) but that homology with other strains in China was low. The gC gene was in the same branch as most of the representative strains in China, with 99.5% homology. The gD gene is in the same branch as the domestic strain LA in China (KU552118), and the homology was 99.9%. The gE gene was in the same branch as the domestic BJ/YT strain in China (KC981239), with 99.9% homology. The results showed that the FJ62 strain of the pseudorabies virus isolated here may be a variant strain of FJ62 isolated from a domestic pig after natural recombination of pseudorabies virus genotype I from wild boar and genotype II from pigs in China. There have been no similar reports in Sichuan. The discovery of the recombinant virus strain provides a reference basis for the prevention and control of pseudorabies and a design strategy for a vaccine in Sichuan, China, in the future.