Molecular Characterization and Pathogenicity of a Novel Recombinant NADC30-Like PRRSV Strain Isolated From Piglets Inducing Intestinal Inflammation, and Construction of Its Infectious Clone.

Porcine reproductive and respiratory syndrome virus (PRRSV) causes major economic losses in swine production worldwide, characterized by reproductive failure and respiratory disease. In China, the cocirculation of diverse strains drives ongoing viral evolution and the emergence of novel recombinants, posing serious challenges for disease control. Here, we report the isolation and characterization of a novel PRRSV strain (JS-YZ/2023) from a PRRS-suspected pig farm. Genomic analysis revealed a unique recombinant pattern between NADC30-like and HP-PRRSV lineages, distinct from previously reported recombinants. Experimental infection in piglets demonstrated significant pathogenicity, with persistent fever, severe anorexia, progressive weight loss, and pathological lesions including interstitial pneumonia with lymphocyte infiltration and marked disruption of intestinal villi. Notably, JS-YZ/2023 exhibited strong intestinal tropism, inducing a local cytokine storm in the small intestine and showing PRRSV-N protein antigen accumulation in crypt epithelial cells, as detected by immunohistochemistry. In addition, we successfully constructed a full-length infectious cDNA clone of JS-YZ/2023 incorporating a green fluorescent protein (GFP) reporter gene (rGFP-JS-YZ/2023). This engineered virus provides a valuable tool for investigating the pathogenic mechanisms of NADC30-like recombinants and facilitating vaccine development.