Abstract:Objective Porcine circovirus type 3 (PCV3) is associated with the development of reproductive disorders in sows, piglet dermatitis, and myocarditis. However, due to the difficulty in stably passaging PCV3 in vitro, the animal infection model construction and specific pathogenicity of PCV3 remain to be investigated. This study aims to solve the above problems.Methods A PCV3 strain (PCV3-HK) was successfully isolated by inoculating PK-15 cells with lymph node samples from PCV3-positive weaned piglets. The strain was identified using PCR, indirect immunofluorescence assay, and transmission electron microscopy, and its complete genome was sequenced. The whole genome of the strain was sequenced. The pathogenicity of the strain was evaluated based on the clinical symptoms, body weight changes, virus excretion, and pathological changes of 21-day-old non-weaned piglets after inoculation with the 15th-passage viral cell culture at a dose of 106.4 TCID50/mL.Results PCV3-HK had a genome length of 2 000 bp and belonged to PCV3c subtype. The viral particles were spherical, non-enveloped, about 15-20 nm in diameter, and capable of reacting specifically with the monoclonal antibody against PCV3 Cap protein. The results of infection in piglets showed that the PCV3-HK infected pigs developed obvious symptoms such as dermatitis, slow weight gain and even wasting, as well as anatomical changes such as lymph node edema and interstitial pneumonia. The viral nucleic acid was detected in oral swabs and anal swabs on day 7-21 post infection, and viremia was observed. The virus infected multiple organs, including the heart, lungs, kidneys, and lymph nodes. Notably, inflammatory cell infiltration and aggregation of necrotic cells were observed in the kidneys and lymph nodes.Conclusion We isolate a PCV3 strain with classical circovirus morphology and establish a piglet infection model, which provides key materials for pathogenic mechanism study and vaccine development regarding PCV3.
