A novel naturally ORF3a-Deficient Porcine Transmissible Gastroenteritis Virus Field Strain HN-2012: Isolation, Pathogenicity and Reverse Genetics System Development

Transmissible gastroenteritis virus (TGEV) is an enteric coronavirus causing severe diarrhea with high mortality in suckling piglets. In this study, a field TGEV strain, designated HN-2012, was isolated from the intestinal contents of diarrheic piglets in Henan Province, China. Genomic analysis identified a continuous 140-nucleotide deletion in HN-2012 resulting in the lack of the accessory protein 3a (ORF3a) compared with other TGEV Miller strains. Experimental infection of piglets with TGEV HN-2012 induced severe diarrhea and lung injury. Simultaneously, high viral loads were detected in both the small intestines and lung tissues, demonstrating that TGEV HN-2012 exhibits dual tropism for enteric and respiratory epithelia. Furthermore, a full-length cDNA infectious clone of TGEV HN-2012 was constructed using a yeast artificial chromosome system via transformation-associated recombination. The recombinant virus was successfully rescued and exhibited similar replication kinetics comparable to the parental virus. In summary, we isolated a novel, naturally TGEV ORF3a deletion strain associated with severe enteric disease and lung injury in piglets, and establishes an efficient reverse genetic system of TGEV. This work providing a valuable tool for investigating the TGEV evolutionary and pathogenesis mechanisms.