Emerging pseudorabies virus (PRV) variant has led to frequent outbreaks of PRV infection among Bartha-K61-vaccinated swine population in Chinese swine farms and caused high mortality in pigs of all age since late 2011. Here, we generated a gE/gI-deleted PRV (rPRVXJ-delgI/gE-EGFP) based on PRV variant strain (PRV-XJ) through homologous DNA recombination. Compared to parental strain, rPRVXJ-delgI/gE-EGFP showed similar growth kinetics in vitro. Its safety and immunogenicity were evaluated in weaned piglets. Our results showed that piglets immunized with rPRVXJ-delgI/gE-EGFP did not exhibit any clinical symptoms, and a high level of gB-specific antibody was detected. After lethal challenge with variant PRV (PRV-FJ strain), all vaccinated piglets survived without showing any clinical symptoms except slight fever within 7 days post-challenge. In unvaccinated piglets, typical clinical symptoms of pseudorabies were observed, and the piglets were all died at 5 days post-challenge. These results indicated that a live rPRVXJ-delgI/gE-EGFP vaccine could be a maker vaccine candidate to control the currently epidemic pseudorabies in China.

In recent years, NADC34‐like PRRSV had a strong impact on the pig industry in the United States and Peru; it was also detected in northeastern China in 2017. In this study, we conducted a retrospective survey of NADC34‐like PRRSV in Southwest China from 2016 to 2020. Five NADC34‐like PRRSV strains were detected in samples and their whole genomes were sequenced, designated as CHSCMY‐22019, CHSCYB‐32020, CHSCMS‐42020 and CHSCLS‐22020. This is the first discovery and report of an NADC34‐like PRRSV strain in Southwest China. Phylogenetic tree analysis based on the whole genome showed that the five NADC34‐like PRRSV strains belonged to sub‐lineage 1.5 of PRRV‐2. They had 100 aa deletions in the Nsp2 hypervariable region of VR2332, located at 329–428 aa, similar to the US isolate IA/2014/NADC34. Recombination analysis showed that CHSCCD‐42020 strain was the recombinant strain of QYYZ strain and IA/2014/NADC34 strain in China. The emergence of NADC34‐like PRRSV strains in Southwest China indicates a potential threat to PRRS prevention and control in pigs. This study improves our understanding of the epidemic status and genetic variation of NADC34‐like PRRSV strains in China.

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

IntroductionPorcine circovirus type 2 (PCV2) is considered one of the viruses with substantial economic impact on swine industry in the word. Recently, porcine circovirus type 3 (PCV3) has been found to be associated with porcine dermatitis and nephropathy syndrome (PDNS)-like disease. And the two viruses were prone to co-infect clinically.MethodsTo further investigate the prevalence and genetic diversity of the two viruses, 257 pig samples from 23 different pig farms in southwest China with suspected PCVAD at different growth stages were analyzed by real-time PCR between 2020 and 2022 to determine the presence of PCV2 and PCV3.ResultsResults showed high prevalence of PCV2 and PCV3: 26.46% samples were PCV2 positive and 33.46% samples were PCV3 positive. The coinfection rate was doubled from 2020 (5.75%) to 2022 (10.45%). Subsequently, the whole genome sequences of 13 PCV2 and 18 PCV3 strains were obtained in this study. Of these, 1 strain was PCV2a, 5 strains were PCV2b and 7 strains were PCV2d, indicating that PCV2d was the predominant PCV2 genotype prevalent in the Southwest of China.DiscussionIn addition, the phylogenetic analysis of PCV3 showed high nucleotide homology (>98%) between the sequences obtained in this study and reference sequences. And 3 mutations (A24V, R27K and E128D) were found in PCV3 antibody recognition domains, which might be related to the mechanism of viral immune escape. Thus, this study will enhance our understanding of the molecular epidemiology and evolution of PCV2 and PCV3, which are conducive to the further study of the genotyping, immunogenicity and immune evasion of PCVs.

Porcine reproductive and respiratory syndrome virus (PRRSV) is an important pathogen that poses a serious threat to the global pig industry. Sichuan Province is one of the largest pig breeding provinces in China. There is a lack of reports on the continuous surveillance and systematic analysis of prevalent strains of PRRSV in Sichuan Province in recent years. To fill this gap, a total of 539 samples were collected from 13 breeding regions in Sichuan during 2012–2020. The detection result showed that the positive rate of PRRSV was 52.32% (282/539). The ORF5s and Nsp2 were obtained and further analyzed, with Chinese reference strains downloaded from the GenBank. Phylogenetic analysis showed that the PRRSV strains sequenced in this study belonged to PRRSV-1 and PRRSV-2 (lineage 1, 3, 5 and 8). In total, 168 PRRSV-2 strains were selected for ORF5 analyses, and these strains were classified into sub-lineage 8.7 (HP-PRRSV), sub-lineage 5.1 (classical PRRSV), sub-lineage 1.8 (NADC30-like), sub-lineage 1.5 (NADC34-like) and sub-lineage 3.5 (QYYZ-like), accounting for 60.71% (102/168), 11.31% (19/168), 18.45% (31/168), 2.97% (5/168) and 6.55% (11/168) of the total analyzed strains, respectively. The Nsp2 of identified PRRSV strains exhibited a nucleotide identity of 44.5–100%, and an amino acid identity of 46.82–100%. The ORF5 of the identified PRRSV strains exhibited a nucleotide identity of 81.3–100%, and an amino acid identity of 78.5–100%. A sequence analysis of ORF5 revealed that the mutation sites of GP5 were mainly concentrated in HVR1 and HVR2 and the virulence sites. In summary, the HP-PRRSV, NADC30-like PRRSV, Classic-PRRSV, QYYZ-like PRRSV, NADC34-like PRRSV and PRRSV-1 strains exist simultaneously in pigs in Sichuan. NADC30-like PRRSV was gradually becoming the most prevalent genotype currently in Sichuan province. This study suggested that PRRSV strains in Sichuan were undergoing genomic divergence.