Molecular characterization and pathogenicity of a porcine Teschovirus 5 isolate in Shandong Province in China

Porcine teschovirus (PTV), classified into the porcine enterovirus group within the Picornaviridae family, is the etiological agent of porcine polioencephalomyelitis, causing substantial economic losses to the global swine industry. This study aimed to isolate and identify a novel PTV strain from diseased pig populations in Shandong Province, China, clarify its genomic characteristics and pathogenicity, and provide a scientific basis for research on the epidemic status and virulence properties of PTV in China. Samples were collected from diseased pigs showing clinical signs in Shandong Province. Viral isolation and culture were performed using PK-15 cells, and cytopathic effects (CPE) were observed. The genetic background of the strain was analyzed via full-length genomic sequencing technology, followed by sequence alignment and recombination analysis with reference strains. Piglet challenge experiments were conducted to evaluate its pathogenicity, including the detection of clinical symptoms and pathological changes in brain tissues. A novel PTV strain (designated SD2023) was successfully isolated. This strain could induce typical cytopathic effects in PK-15 cells. Full-length genomic sequencing revealed that it belongs to genotype 5 PTV (PTV-5). Comparative analysis of the VP1 protein identified three unique amino acid substitutions and six highly variable regions in SD2023 relative to reference PTV-5 strains. These molecular features reflect the genetic divergence of the isolate, although their functional significance and potential impact on viral properties remain to be experimentally verified. Recombination analysis revealed that the SD2023 strain is a novel recombinant, featuring a P1 gene (nt 876-3372) derived from a PTV-5 HuN33-like minor parent and flanking regions from a PTV-4 10BJ02-like major parent. This structure was supported by RDP4 and SimPlot analyses. Piglet challenge experiments demonstrated that the SD2023 strain could cause mild neurological symptoms and anorexia in piglets, and lymphocyte infiltration was observed in brain tissues. This study identified a recombinant PTV-5 strain (SD2023) in Shandong Province, China. Our findings demonstrate that this strain possesses pathogenic potential, as it is capable of inducing mild clinical disease and occasional mortality under experimental conditions. Notably, the small sample size (n = 5 per group) and age mismatch between the experimental model and field cases represent key limitations for the definitive virulence assessment of this strain. The results provide important references for epidemiological monitoring, genetic evolution analysis, and the formulation of prevention and control strategies for PTV in China.