AlphaB-crystallin promotes porcine circovirus type 2 replication in a cell proliferation-dependent manner

Porcine circovirus type 2 (PCV2) is the primary causative agent of postweaning multisystemic wasting syndrome (PMWS) and causes heavy economic losses to the porcine industry worldwide. In this study, PK-15 cells were infected with PCV2 for 48 h, then harvested and subjected to label-free quantitative proteomic mass spectrometry. In total, 1212 proteins were differentially expressed in PCV2-infected cells compared with mock-infected cells, including 796 upregulated and 416 downregulated proteins. Gene ontology analysis showed that these differentially expressed proteins were involved in biological processes, cellular components and molecular functions, and these categories included cellular processes, environmental information processing, genetic information processing, disease, metabolism, and body systems. Enrichment analysis of the KEGG pathway showed that innate immune responses were significantly enriched. AlphaB-crystallin (CRYAB) interacts with desmin and cytoplasmic actin to prevent protein misfolding and aggregation, helping to maintain cytoskeletal integrity and promoting cell proliferation. In this study, CRYAB was found to effect the replication of PCV2, as verified by qRT-PCR, TCID₅₀ determination and western blot analysis. Overexpression of CRYAB significantly upregulated PCV2 capsid protein and increased viral titers in both PK-15 cells and culture supernatants, whereas the opposite results were obtained in CRYAB knockdown cells. Furthermore, we revealed that the promotion of PCV2 replication by CRYAB was dependent on cell proliferation. To our knowledge, this is the first report of the effect of CRYAB on PCV2 replication and our findings contribute to a greater understanding of the mechanism of PCV2 replication and pathogenesis, as well as the host's response to PCV2 infection.