Isolation and Identification of a Genotype C Bovine Parainfluenza Virus Type 3 and Its Pathogenicity in Albino Guinea Pigs.

Bovine parainfluenza virus type 3 (BPIV3) is a significant pathogen in cattle, causing a range of respiratory symptoms from mild to severe. In this study, we isolated a BPIV3 (BPIV3/SX/2021) strain using Madin-Darby bovine kidney cells from a lung tissue sample obtained in Shaanxi province. The full length of the BPIV3/SX/2021 strain is 15,474 nt, encoding six structural and three accessory proteins. A phylogenetic analysis revealed that SX2021strain belongs to BPIV3 genotype C, and the isolate shares the highest sequence homology with the other genotype C strains isolated in China. A genetic comparison of the BPIV3c strain isolated in China showed that some amino acid residues have mutations in the F and HN genes that affect the protein structure. Animal challenge experiments showed that experimental infection of guinea pigs with the BPIV3c strain SX2021 displayed depression and dyspnea clinical signs. Histopathological analysis of the lung and trachea showed that morphological changes consisted of lesions of bronchial epithelial cell shedding, alveoli septa thickening, focal fiber hyperplasia, and macrophage infiltration. The virus load analysis indicated that the SX2021 strain displayed a higher replication level in the lungs and trachea. These results provide strong evidence that the evolution of BPIV3, and the isolated BPIV3 strain SX2021 provide useful data to determine the pathogenesis of the virus.