Finally, both recombinant proteins had been purified through a Ni-NTA affinity chromatography column in non-denaturing state based on the Ni-NT purification kit instructions. == Immunogenicity dedication == About 2025 g, six-week-old BALB/c mice purchased from the Center for Experimental Animals of Jiangxi Traditional Medical University were kept under normal conditions in the animal care facility of Jiangxi Agricultural University. for antibody prevalence of PCV4, and 17 (3.35%) and 36 (7.10%) of the samples were Cap and Rep antibody positive, respectively. In summary, our founded ELISA kit could be used to detect PCV4 antibodies in serum with good repeatability and high specificity. In addition, field samples detection results showed the antibody of PCV4 was poorly distributed (Rac)-Antineoplaston A10 in rigorous pig farms in Jiangxi Province, China. Keywords:porcine circovirus 4, ELISA, Cap protein, Rep protein, antibody, serum epidemiology == Intro == Porcine circovirus (PCV) is definitely a member of genus Circovirus that belongs to the Circoviridae family (Lefkowitz et al.,2018). The virion of PCV is definitely a small, icosahedral and non-enveloped disease comprising a single-stranded, closed-circular DNA (ssDNA) (Tischer et al.,1982; Reuter et al.,2014). The space of genome of Capn3 PCVs is about 1.72.0 kb (Tischer et al.,1974). To day, four genotypes of PCVs, PCV1, PCV2, PCV3, and PCV4 have been recognized and isolated (Zhang H. H. et al.,2020; Hou et al.,2022). PCV1 was first isolated in cultured porcine kidney (PK-15) cell lines without pathogens (Kim and Chae,2002; Hirai et al.,2006). Unlike PCV1, PCV2 still poses a danger to the rigorous swine market because PCV2 is the main pathogenic virus causing porcine circovirus-related diseases (PCVAD) (Saporiti et al.,2020; Sibila et al.,2021). (Rac)-Antineoplaston A10 PCV3 (Rac)-Antineoplaston A10 has been recognized in both diseased and healthy pigs (Jiang et al.,2019). In addition, PCV3 has been reported to be associated with porcine dermatitis and nephropathy syndrome (PDNS) (Jiang et al.,2019). From 2019 to 2021, PCV4 was identified as a distinct circovirus varieties and associated with severe medical disease with respiratory PDNS via standard PCR or qPCR in both China and South Korea with low positive rates (Franzo et al.,2020; Ha et al.,2021; Sun R. et al.,2021; Tian et al.,2021; Hou et al.,2022; Kim et al.,2022; Nguyen et al.,2022). Genetically, PCV4 shared the closest relationship and similarity to a mink circovirus with 67% genomic identity, which is higher than PCV1PCV3 with 52% genomic identity (Zhang H. H. et al.,2020). Much like additional PCVs, the genome of PCV4 is definitely a 1,770 nt circular single-stranded DNA comprising two large open reading frames (ORFs): ORF1 is definitely 891 nt encoding the putative replicase protein (Rep); ORF2 is definitely 687 nt encoding the putative capsid protein (Cap) (Kim et al.,2022). Relating to a earlier statement on PCV2, the Cap protein is an important viral affect involved in sponsor cell access (Cao et al.,2015). The Cap protein mediates the binding of the virus to the cell surface during the invasion process (Ren et al.,2016; Zhang Y. et al.,2020; Sun W. et al.,2021). The literature has shown the Cap protein takes on a crucial biological role in the process of entering sponsor cells via binding to the receptors (Khayat et al.,2011). In addition, the Cap protein is an antigenic epitope that supports the formation of antibodies in the sponsor, thereby revitalizing the sponsor to recognize invasive viruses (Kekarainen and (Rac)-Antineoplaston A10 Segales,2015; Park et al.,2021). The Rep protein of PCVs is the major protein that replicates the viral genome and is included in adult virions. The (Rac)-Antineoplaston A10 Rep protein is definitely highly indicated during the process of PCV replication, which could promote the production of specific antibodies.