Key result
PCV2 ORF3 protein promotes viral replication in host cells via RIPK3 phosphorylation-dependent autophagy.
Why the study?
RIPK3 regulates necroptosis and inflammation and modulates viral infections, but its role in porcine circovirus type 2 infection was not defined.
PCV2 manipulates host cell machinery through its ORF3 protein, hijacking RIPK3 phosphorylation to activate autophagy and promote viral replication.
Answers are grounded in this paper and cite their sources.
Should not yet change PCV2 management in swine; leaves open RIPK3 inhibition as hypothesis-generating antiviral target.
Receptor-interacting protein kinase-3 (RIPK3), a critical regulator of necroptosis and inflammation, has been implicated in modulating viral infections by either promoting host defense or facilitating viral replication. In this study, it was found that porcine circovirus type 2 (PCV2) infection selectively induced RIPK3 phosphorylation in PK-15 cells without activating its canonical downstream effector MLKL. This indicated that the virus exploits RIPK3 in a necroptosis-independent manner. Inhibition of RIPK3 phosphorylation using GSK872 or RIPK3 knockdown significantly reduced viral replication, as evidenced by viral DNA levels in PK-15 cells, with a concomitant reduction in Rep protein expression. Through functional screening of viral proteins, we found that only ORF3 triggered RIPK3 phosphorylation, while capsid (Cap) and replication-associated (Rep) proteins did not. Both PCV2 infection and ORF3 could induce autophagy. RIPK3 knockdown suppressed PCV2-induced autophagy, and subsequently knockdown of the autophagy-related protein ATG7 resulted in the reduction of PCV2 replication. These findings indicated that PCV2 employed its ORF3 protein to hijack RIPK3 phosphorylation-dependent autophagy, thereby creating a promoted viral replication environment. In conclusion, this study demonstrated that PCV2 manipulated host cell machinery through its ORF3 protein, which hijacked RIPK3 phosphorylation to activate autophagy-a mechanism distinct from RIPK3's classical necroptosis function. This ORF3-RIPK3 phosphorylation-autophagy axis represented a novel therapeutic target for PCV2 control.
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Guo et al. (2026) studied Porcine circovirus type 2 (PCV2) infection. RIPK3 inhibition (GSK872 or shRNA) and ORF3 protein expression vs. Uninfected cells or empty vector (pEGFP) was evaluated on Viral replication (PCV2 DNA levels and Rep protein expression) (p=<0.01). Porcine circovirus type 2 ORF3 protein induced RIPK3 phosphorylation-dependent autophagy to significantly promote viral replication in host cells.
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