The S32 amino acid deletion in the GP5 protein modulates the infectivity of porcine reproductive and respiratory syndrome virus

The Q653R substitution in the spike protein is associated with attenuation of a GVI-1 infectious bronchitis virus strain.

Single amino acid substitution in RdRp reduces viral recombination frequency of NADC30-like porcine reproductive and respiratory syndrome virus type 2

Porcine reproductive and respiratory syndrome (PRRS) is one of the most significant diseases, causing tremendous economic losses to the global swine industry. Accumulating evidence indicates that recombination between PRRSV-2 strains, particularly those involving NADC30-like PRRSV-2 variants, has been responsible for outbreaks across several countries. However, the key proteins or amino acids associated with PRRSV-2 recombination remain unclear. In this study, two representative PRRSV-2 strains (the NADC30-like HeB108 strain from lineage 1 and the HP-PRRSV HuN4 strain from lineage 8) were serially passaged in the presence of ribavirin. Amino acid substitutions associated with ribavirin resistance were identified in the RNA-dependent RNA polymerase (RdRp) and helicase of the passaged viruses. Using the infectious clones PRRSV-2 HeB108 and HuN4, ribavirin-resistant mutants with single or multiple amino acid substitutions were generated. Notably, the mutants HeB108-VGSS and HuN4-TNII, with multiple amino acid substitutions, showed higher fidelity and lower pathogenicity in infected piglets than their parental viruses. Furthermore, the potential decreased recombination risk correlated with increased polymerase fidelity. In an inter-lineage co-infection assay on primary alveolar macrophages, the I360V substitution in RdRp reduced the recombination frequency of NADC30-like PRRSV-2 HeB108 as determined by both Sanger sequencing and nanopore long-read RNA sequencing. The results identified a key amino acid associated with viral recombination in NADC30-like PRRSV-2 and provide an editing target for developing safer vaccines that are less prone to recombination.

Characterization and pathogenicity of single-farm-isolated PRRSV 1 and PRRSV 2 strain in China

The evidence of PRRSV 1 and PRRSV 2 concurrent circulation in the single sow farm in China is provided, which highlights the ongoing evolution of both Chinese PRRSV species and underscores the urgent need for enhanced surveillance and updated control strategies.

Isolation and assessment of characterization of porcine epidemic diarrhea virus GD1 strain from China

Porcine epidemic diarrhea virus (PEDV) is an important pathogen in swine, causing severe economic losses to the global swine industry. As a coronavirus, PEDV is prone to mutations and recombination. Therefore, characterizing circulating strains is essential for disease control. In this study, a PEDV strain (GD1) was isolated from diarrheic piglets in Guangdong Province, China, and identified by RT-PCR and immunofluorescence. Pathogenicity was evaluated in piglet challenge experiment. The results showed that GD1 strain could be stably passaged in Vero cells, forming syncytia. Phylogenetic analysis based on the complete genome and spike (S) gene both placed GD1 strain within the GIIc genotype. Amino acid sequence alignment of the S protein revealed multiple amino acid mutations in the neutralizing epitopes COE, SE16, and SS6 of GD1 strain compared with the classical vaccine strain CV777. Recombination analysis suggested that GD1 may be a novel recombination strain originating from strains SD2021 and GDS28, with the recombination breakpoint located in the ORF1a region. Pathogenicity assessment demonstrated that GD1 is highly virulent, inducing severe watery diarrhea and vomiting in newborn piglets within 24 h post-inoculation, and causing histopathological lesions characterized by intestinal villous atrophy and shedding. Immunohistochemistry confirmed that PEDV antigen was predominantly distributed in the villous epithelial cells of the small intestine. The successful isolation and characterization of the GD1 strain provide important viral resources for further research on the genetic evolution of PEDV and the development of matched vaccines.

Genetic Diversity, Phylogenetic Lineages, and Antigenic Features of the PRRSV-1 GP5 Gene in China

Porcine reproductive and respiratory syndrome virus (PRRSV) poses a significant threat to the global swine industry. In this study, the genetic diversity, evolutionary dynamics, and key antigenic characteristics of the PRRSV-1 GP5 gene in China were systematically investigated. A total of 114 Chinese PRRSV-1 GP5 sequences, isolated between 1999 and 2024, were analyzed alongside global reference strains. The nucleotide and amino acid sequence similarities ranged from 60.03% to 100% and from 48.72% to 100%, respectively, with mutation and deletion hotspots concentrated in the N-terminal hypervariable region. Phylogenetic analysis further classified the Chinese strains into four major lineages: Amervac-like, BJEU06-1-like, HKEU16-like, and NMEU09-1-like. Notably, a preliminary phylogenetic observation indicated that several recent Chinese PRRSV-1 isolates clustered topologically close to PRRSV-2 strains. However, as this finding is based solely on a single-gene tree and has not been validated by formal tests for convergent evolution, homoplasy, or selection pressure, it should be interpreted with caution and warrants further investigation using whole-genome data. A Bayesian evolutionary analysis estimated the evolutionary rate at 1.94 × 10−3 substitutions per site per year and the time to the most recent common ancestor at approximately 1910. No statistically significant recombination events were identified within the GP5 gene. The transmembrane topology of GP5 was highly conserved, whereas B-cell linear epitopes were enriched in the N-terminal extracellular region. This study establishes a useful molecular foundation for understanding PRRSV-1 evolution in China and offers valuable insights for the development of broad-spectrum vaccines and effective control strategies.

PRMT3 restricts porcine epidemic diarrhea virus replication by disrupting the interaction between VAPA and the viral nucleocapsid protein

Porcine epidemic diarrhea virus (PEDV) represents a severe threat to the global swine industry. Its infection process involves intricate virus–host interactions and immune evasion mechanisms, but effective therapeutic targets remain elusive. In this study, we identified protein arginine methyltransferase 3 (PRMT3) as a novel regulatory factor that significantly modulates PEDV infection via genome-wide CRISPR/Cas9 knockout library screening. Knockout or inhibition of PRMT3 markedly enhanced PEDV infection in multiple cell lines, including LLC-PK1, IPEC-J2, and primary porcine intestinal epithelial cells. Mechanistic investigations revealed that PRMT3 can restrict PEDV infection by interacting with vesicle-associated membrane protein-associated protein A (VAPA). Further analysis revealed that VAPA facilitates cholesterol transport through binding to oxysterol-binding protein (OSBP) and inhibits the autophagic degradation of the viral nucleocapsid (N) protein, with both processes being critical for promoting PEDV infection in host cells. A detailed analysis revealed that K52 within its major sperm protein (MSP) domain interacts with D404 and D405 in the two phenylalanines in an acidic tract (FFAT)-like motifs of the N protein, and these interactions proved essential for PEDV infection. In summary, this is the first study to identify and validate the PRMT3–VAPA–N protein autophagic degradation axis as a key pathway through which PRMT3 suppresses PEDV infection, with VAPA acting as an essential host factor for PEDV pathogenesis. These findings uncover novel signaling pathways and molecular targets for the development of anti-PEDV therapeutics.