Abstract: Porcine circovirus type 2 (PCV2) is a non-enveloped single-stranded negative-strand circular DNA virus that can cause immunosuppression in infected pigs. It is the main pathogen of porcine circovirus associated diseases and is widely spread around the world. The purpose of this paper is to explore the effect of decitabine (DAC) on the proliferation of PCV2 and its mechanism. In this study, a PK-15 cell model infected with PCV2 was constructed, and the cytotoxicity of DAC to PK-15 cells was detected by CCK-8 method, and then the effect of DAC on the proliferation of PCV2 was detected by fluorescent quantitative PCR, indirect immunofluorescence and Western blot. The effect of DAC on the global methylation of cellular genomic DNA was characterized by labeling 5-methylcytosine by indirect immunofluorescence method; Dnmt1(DNA methytransferase 1), as the target of DAC in PK-15 cells, was silenced by RNA interference technology, to further explore the inhibitory effect of DAC on PCV2 proliferation. The results showed that DAC had slight cytotoxicity at 20 μmol·L^-1, and showed obvious anti-PCV2 activity at a concentration of 10 μmol·L^-1, and could inhibit the proliferation of PCV2 at different times. DAC treatment of cells can significantly reduce the methylation level of genomic DNA in PK-15 cells and induce the expression of type Ⅰ interferon (Ⅰ-IFN) and interferon-stimulated genes (ISGs). Silencing Dnmt1, the target of DAC, significantly inhibited the proliferation of PCV2 and induced the expression of I-IFN and ISGs. This study confirmed that DAC can play an anti-PCV2 function by inhibiting DNA methylation and promoting the expression of I-IFN and ISGs. Furthermore, DAC has the potential to be developed into a clinical antiviral drug against PCV2, Dnmt1 is a potential target for activating the host's innate immune antiviral pathway, providing a theoretical basis for the development of new PCV2 antiviral drugs.

Key words: decitabine, PCV2, antiviral, innate immunity