Studies on the pathogenesis of a Chinese strain of bovine parainfluenza virus type 3 infection in Balb/c mice

To date, three genotypes A, B, and C of bovine parainfluenza virus type 3 (BPIV3) have been isolated from cattle and only limited studies on the pathogenesis of the genotype A of BPIV3 infection in calves and laboratory animals have been conducted. The pathogenesis of the genotypes B and C of BPIV3 infection in calves and laboratory animals have not been reported. To alleviate the difficulties associated with sourcing suitable calves for infection studies, the establishment of BPIV3 infection model using laboratory model animals could aid in increasing the knowledge of the pathogenesis of this virus. Therefore thirty Balb/c mice were intranasally inoculated with a Chinese BPIV3 strain SD0835 which was classified as genotype C. Virus replications in mice were demonstrated by using virus isolation and titration, immunofluorescent staining, and immunohistochemistry and had occurred in the respiratory tissues as early as 24h after intranasal inoculation. The results of immunofluorescent staining and IHC implicated that the lungs and tracheas might be the major tissues in which the SD0835 infected and replicated. The histopathologic examinations revealed that alveoli septa thickening and focal cellulose pneumonia were seen in the lungs of experimentally infected mice. The aforementioned results indicated that the SD0835 of the genotype C was pathogenic to Balb/c mice and the mouse infection model could cast light on the genotype C of BPIV3 infection process and pathogenesis.