Identification and vaccine efficacy evaluation of a canine coronavirus isolated in central China.

Canine coronavirus (CCoV) is a significant enteric pathogen in dogs, particularly in group-housed conditions. Although it is classically associated with mild enteritis, its high mutation rate drives genetic diversification, influencing virulence and reducing the effectiveness of traditional vaccines. To address this challenge, a novel CCoV strain, WH2023, was isolated from a breeding facility in Wuhan, Central China. Phylogenetic analysis of the spike (S) gene suggested that WH2023 is the predominant CCoV-IIa subtype. Pathogenicity studies in puppies revealed high virulence, with 100 % morbidity after a high challenge dose (106 TCID50/mL), severe diarrhea and lethargy, intestinal lesions in the jejunum and ileum, and high viral loads consistent with typical CCoV pathogenesis. An inactivated vaccine based on WH2023 and formulated with the GEL02 adjuvant was developed and evaluated in beagle puppies. Safety assessments revealed an excellent profile, and immunogenicity studies revealed strong neutralizing antibody responses, reaching titers of 1:5404 (12.4 log2) one week after booster vaccination. Vaccinated dogs were fully protected against the WH2023 challenge, whereas unvaccinated controls developed gastroenteritis. Neutralizing antibody titers in vaccinated dogs remained above 1:32 for up to 300 days and significantly exceeded those induced by commercial vaccines available in China. These findings indicate that WH2023 is a highly virulent CCoV-IIa strain and a promising candidate for vaccine development, providing enhanced safety and long-lasting protection against canine coronavirus infection.