Porcine epidemic diarrhea virus (PEDV) G2c variants have recently emerged, posing significant challenges to swine health management. As a major coronavirus affecting the swine industry, PEDV exhibits extensive genetic variability, which has greatly complicated disease control. Current vaccines provide suboptimal protection under field conditions. Therefore, the isolation of recently circulating strains and the establishment of a robust reverse genetics system are critical for advancing the study of emerging variants and facilitating rational vaccine development. In this study, a PEDV field strain designated PEDV-BJ-2023 was isolated from diarrheic piglets in Guizhou, China. Phylogenetic analysis based on the complete genome and spike gene classified PEDV-BJ-2023 within the emerging G2c lineage. To facilitate functional studies, a full-length infectious cDNA clone was constructed using transformation-associated recombination cloning in yeast. Furthermore, an enhanced green fluorescent protein reporter virus was generated via CRISPR/Cas9-assisted homologous recombination by inserting an EGFP-2A cassette upstream of the nucleocapsid gene. The recombinant viruses displayed virion morphology and plaque characteristics similar to those of the parental wild-type PEDV-BJ-2023 strain, although the parental virus exhibited faster replication during the early stage of infection in vitro. In 5-day-old piglets, all three viruses caused severe diarrhea, weight loss, and intestinal lesions; however, recombinant viruses exhibited slightly reduced viral shedding and pathogenicity, with rPEDV-EGFP being the most attenuated. Notably, rPEDV-EGFP maintained stable EGFP expression over eight serial passages. This study establishes a reverse genetics platform for an emerging G2c PEDV strain and provides a stable fluorescent reporter virus, offering valuable tools for visualizing viral infection and investigating virus–host interactions.

Porcine circovirus type 4 (PCV4) is an emerging pathogen that poses a significant potential threat to the global swine industry. The capsid (Cap) protein is the primary target for host immune responses and a critical component for diagnostic and vaccine development. However, the lack of specific monoclonal antibodies (mAbs) and defined antigenic determinants has hindered both diagnostic accuracy and pathogenesis research. In this study, we generated a highly specific, high affinity mAb, designated 6C3 (IgG2b/κ, KD = 0.29 nM) against the PCV4 dCap protein. This mAb recognizes PCV4 Cap without cross-reactivity toward PCV2, PCV3 or other swine viruses. Epitope mapping identified a minimal linear B-cell epitope spanning residues 119LDGD122. Homology modeling predicted that this motif is situated on a surface-exposed random coil loop of the PCV4 Cap. Furthermore, Alanine scanning mutagenesis revealed that residues L119, G121, and D122 were indispensable for antibody binding. Comprehensive sequence alignment revealed that the 119LDGD122 motif is completely conserved across all known global PCV4 strains but remains distinct from other PCVs due to pronounced sequence variations at the G121 and D122 positions. The development of mAb 6C3 and the characterization of this novel, highly conserved, and PCV4 specific epitope provide powerful tools for accurate serological differentiation, establishing a robust foundation for targeted diagnostic assays and future vaccine design.

Pseudorabies virus (PRV) reprograms host inflammatory responses and epitranscriptomics, yet how these processes are connected remains unclear. Here, we report a JNK-WTAP-m⁶A-DUSP5 regulatory circuit that coordinates viral replication and inflammatory responses. PRV infection activated c-Jun N-terminal kinase (JNK), which phosphorylated wilms tumor-associated protein (WTAP) to drive its nuclear export and disrupt the activity of the m⁶A methyltransferase complex. Methylated RNA immunoprecipitation sequencing (MeRIP-seq) and biochemical analyses revealed a global reduction of N6-methyladenosine (m⁶A) on host transcripts, particularly on proinflammatory cytokines, alongside widespread m⁶A modification sites on viral transcripts. Consequently, reduced m⁶A prolonged the half-lives of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-18 (IL-18) mRNAs, as well as viral transcripts, thereby synergistically promoting PRV replication. Inhibition of JNK activity or restoration of m⁶A modification suppressed PRV replication in vitro and in vivo. Moreover, the m⁶A hypomethylation stabilized dual-specificity phosphatase 5 (DUSP5) transcripts at early infection, transiently restraining JNK activation and forming a negative feedback loop. These findings demonstrate that PRV reprograms the m⁶A machinery via JNK-mediated WTAP phosphorylation and highlights RNA methylation restoration as a promising antiviral strategy.

Circular RNAs (circRNAs) are dynamically remodeled during infection, yet how viruses exploit circRNA-RNA binding protein (RBP) circuits remains poorly understood. Here, we report a cGLIS3-IGF2BP2-linked TNF-α regulatory axis triggered by deltacoronavirus infection to inhibit antiviral innate immunity. The host m6A reader insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2) and viral nucleocapsid (N) protein promote biogenesis of the m6A-modified cGLIS3 by strengthening the GLIS3 exon 3 circulation. Interaction assay reveals that K-Homology domain of IGF2BP2 or the linker region of viral protein N binds to GLIS3 pre-mRNA to achieve cGLIS3 biogenesis, respectively. IGF2BP2 stabilizes the m6A-modified cGLIS3 against RNase L-mediated degradation. cGLIS3 attenuates IGF2BP2-driven TNF-α induction to facilitate deltacoronavirus replication by accelerating K48-linked ubiquitin degradation of IGF2BP2. Together, our findings uncover a coronavirus-elicited circRNA-RBP crosstalk circuit to suppress innate immunity, establishing cGLIS3 as a mechanistically defined regulator of virus-host interactions.

Virus inhibitory protein, endoplasmic reticulum-associated, interferon-inducible (Viperin), an interferon-stimulated gene (ISG) product, restricts the replication of a broad spectrum of viruses through its radical S-adenosyl methionine (SAM) enzymatic activity, which converts cytidine triphosphate (CTP) to 3'-deoxy-3',4'-didehydro-CTP (ddhCTP). This conversion leads to premature termination of RNA synthesis by the RNA-dependent RNA polymerase (RdRp) of certain RNA viruses. Coronaviruses, being RNA viruses, can be suppressed by viperin; certain strains, such as porcine epidemic diarrhea virus (PEDV), are directly influenced by ddhCTP, while others, such as Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), are inhibited by different pathways. In this study, we describe a previously unrecognized anti-coronavirus mechanism of viperin. Using Porcine Deltacoronavirus (PDCoV) as a model, we observed that viperin is strongly induced upon PDCoV infection and significantly inhibits viral replication. Furthermore, we found that viperin directly interacts with the viral non-structural protein 8 (nsp8) protein, disrupting the formation of the replication-transcription complex (RTC) and reducing RdRp activity. Our results further indicate that the central domain (residues 43-184) of viperin and the lysine 82 (K82) residue in the N-terminal domain of nsp8 are critical for this interaction and its antiviral function. We illustrate that the viperin-nsp8 interaction is preserved across all genera of α-, β-, γ-, and δ-coronaviruses. These findings reveal a unique anti-coronavirus mechanism of viperin and offer new insights into its potential as a target for inhibiting viral nsp8 function.

Pseudorabies virus (PRV), known as porcine herpesvirus type I, belongs to the α-herpesvirus subfamily of the herpesviridae family. Its virions are oval or round, with a genome of approximately 143 000 bp and a high guanine-cytosine (GC) content of 73% (Pomeranz et al., 2005). While swine are the natural host and the virus has caused significant economic loss to the pig industry, PRV can infect other mammals, causing acute infectious diseases characterized by neurological symptoms (He et al., 2019; Cheng et al., 2020). Young pigs are more susceptible to PRV and the infection in piglets is nearly 100% fatal, whereas adult pigs exhibit reproductive disorders such as abortion, stillbirths, and reduced fertility, ultimately decreasing farm productivity (Zuckermann, 2000). Due to its global impact, PRV is classified as a Class B infectious disease by the World Organization for Animal Health (WOAH).

Porcine circovirus type 2 (PCV2) is one of the main pathogens causing porcine circovirus-associated diseases (PCVAD). We recently reported the immunogenicity of the recombinant PRV with an envelope-embedded Cap protein of PCV2 (PRV-Cap) in mice. Here, we further evaluated the immunoprotective efficacy of PRV-Cap virus in pigs. Following vaccination, the PRV-Cap stimulated the production of neutralizing antibodies against PRV and PCV2, along with protected piglets from the challenge of the lethal PRV, the virulent PCV2b and PCV2d. Peripheral blood mononuclear cells analysis revealed that PRV-Cap virus effectively induced proliferation and activation of CD4 and CD8 T cells, as well as an increase in T follicular helper cells, although γδ T and B cells did not show significant differences. Compared to DMEM control piglets, the expanded CD4 and CD8 T cells exhibited an effector memory T cell phenotype, and in vitro stimulation led to PRV- and PCV2-specific IFN-γ and TNF-α secretion, peaking at 21 days post-immunization. In summary, PRV-Cap virus effectively prevents PRV, PCV2b and PCV2d challenges in piglets by simultaneously inducing both PRV- and PCV2-specific humoral and cellular immunity, indicating that PRV-Cap virus is a promising and safe candidate vaccine for combined PRV and PCV2 immunization.

The establishment of high sensitive detection method for various pathogenic microorganisms remains constantly concerned. In the present study, multi-probe strategy was first systematically investigated followed by establishing a highly sensitive TaqMan real-time fluorescent quantitative PCR (qPCR) method for detecting African swine fever virus (ASFV). Briefly, four probes based on the B646L gene of ASFV were designed and the effects of different combinations of the probes in a single TaqMan qPCR assay on the detection sensitivity were investigated. As less as 0.5-5 copies/μl of the ASFV gene was detected by the established TaqMan qPCR assay. Furthermore, plasmid harboring the B646L in water samples could be concentrated 1000 times by ultrafiltration to enable a highly sensitive detection of trace viral nucleic acids. Moreover, no cross-reactivity was observed with other common clinical swine viruses such as PCV2, PCV3, PCV4, PEDV, PDCoV, CSFV, PRRSV, and PRV. When detecting 173 clinical porcine serum samples, the coincidence rate between the developed method and WOAH (World Organization of Animal Health) recommended method was 100%. This study might provide an integrated strategy to achieve higher detection sensitivity of trace pathogenic microorganisms and applicably sensitive TaqMan-based qPCR assays.

IntroductionVariant pseudorabies virus (PRV) is a newly emerged zoonotic pathogen that can cause human blindness. PRV can take advantage of its large genome and multiple non-essential genes to construct recombinant attenuated vaccines carrying foreign genes. However, a major problem is that the foreign genes in recombinant PRV are only integrated into the genome for independent expression, rather than assembled on the surface of virion.MethodsWe reported a recombinant PRV with deleted gE/TK genes and an inserted porcine circovirus virus 2 (PCV2) Cap gene into the extracellular domain of the PRV gE gene using the Cre-loxP recombinant system combined with the CRISPR-Cas9 gene editing system. This recombinant PRV (PRV-Cap), with the envelope-embedded Cap protein, exhibits a similar replication ability to its parental virus.ResultsAn immunogenicity assay revealed that PRV-Cap immunized mice have 100% resistance to lethal PRV and PCV2 attacks. Neutralization antibody and ELISPOT detections indicated that PRV-Cap can enhance neutralizing antibodies to PRV and produce IFN-γ secreting T cells specific for both PRV and PCV2. Immunological mechanistic investigation revealed that initial immunization with PRV-Cap stimulates significantly early activation and expansion of CD69+ T cells, promoting the activation of CD4 Tfh cell dependent germinal B cells and producing effectively specific effector memory T and B cells. Booster immunization with PRV-Cap recalled the activation of PRV-specific IFN-γ+IL-2+CD4+ T cells and IFN-γ+TNF-α+CD8+ T cells, as well as PCV2-specific IFN-γ+TNF-α+CD8+ T cells.ConclusionCollectively, our data suggested an immunological mechanism in that the recombinant PRV with envelope-assembled PCV2 Cap protein can serve as an excellent vaccine candidate for combined immunity against PRV and PCV2, and provided a cost-effective method for the production of PRV- PCV2 vaccine.

Circular RNAs (circRNAs) exert diverse biological functions in different processes. However, the role of circRNAs during virus infection is mostly unknown. Herein, we explored the characteristics of host circRNAs using alphaherpesvirus pseudorabies virus (PRV) as a model. PRV infection upregulated the expression of circRNA circ29164, which does not encode a protein. RNA pulldown assays identified that circ29164 interacts with the microRNA ssc-miRNA-24-3p. Further analysis indicated that ssc-miR-24-3p targets the mRNA encoding kelch-like ECH-associated protein 1 (KEAP1), and circ29164 competitively binds to ssc-miR-24-3p to prevent it binding to Keap1. Apoptosis detection demonstrated that circ29164 or Keap1 overexpression, but not knockdown, induced caspase 3 activity and the release of cytochrome C from mitochondria, and inhibited PRV replication. Taken together, these data identified a previously undiscovered circRNA, circ29164, which inhibits PRV replication by competitively binding to ssc-24-3p to maintain KEAP1 levels.

lnc-AROD is a potential diagnostic and discriminative biomarker for different cancers. However, so far the mechanisms of lnc-AROD regulating virus replication are not well understood.

RSAD2是一种多功能干扰素(interferon,IFN)诱导蛋白.该研究利用CRISPR/Cas9系统建立了RSAD2基因敲除的猪睾丸细胞系(swine testicular cell,ST cell)模型.应用在线工具设计了针对RSAD2基因的4条sgRNA,并将其克隆至pX459载体.经嘌吟霉素初步筛选、Western blot检测确定了 RSAD2-sgRNA-4具有最优敲除效果.该实验通过单克隆化转染RSAD2-sgRNA-4的ST细胞后成功获得RSAD2基因敲除ST细胞模型.双荧光素酶活性实验及实时荧光定量PCR实验(RT-qPCR)证明,RSAD2基因敲除对ST细胞的IFN-β、IRF3、NF-κB基因启动子活性及mRNA水平没有明显影响.该实验利用CRISPR/Cas9系统构建并获得稳定敲除RSAD2基因的ST细胞模型,为RSAD2功能研究提供有力工具.

Coronaviruses (CoVs) are a family of RNA viruses that typically cause respiratory, enteric, and hepatic diseases in animals and humans. Here, we use porcine epidemic diarrhea virus (PEDV) as a model of CoVs to illustrate the reciprocal regulation between CoV infection and pyroptosis. For the first time, we elucidate the molecular mechanism of porcine gasdermin D (pGSDMD)-mediated pyroptosis and demonstrate that amino acids R238, T239, and F240 within pGSDMD-p30 are critical for pyroptosis. Furthermore, 3C-like protease Nsp5 from SARS-CoV-2, MERS-CoV, PDCoV, and PEDV can cleave pGSDMD at the Q193-G194 junction to produce two fragments unable to trigger pyroptosis. The two cleaved fragments could not inhibit PEDV replication. In addition, Nsp5 from SARS-CoV-2 and MERS-CoV also cleave human GSDMD (hGSDMD). Therefore, we provide clear evidence that PEDV may utilize the Nsp5-GSDMD pathway to inhibit pyroptosis and, thus, facilitate viral replication during the initial period, suggesting an important strategy for the coronaviruses to sustain their infection. IMPORTANCE Recently, GSDMD has been reported as a key executioner for pyroptosis. This study first demonstrates the molecular mechanism of pGSDMD-mediated pyroptosis and that the pGSDMD-mediated pyroptosis protects host cells against PEDV infection. Notably, PEDV employs its Nsp5 to directly cleave pGSDMD in favor of its replication. We found that Nsp5 proteins from other coronaviruses, such as porcine deltacoronavirus, severe acute respiratory syndrome coronavirus 2, and Middle East respiratory syndrome coronavirus, also had the protease activity to cleave human and porcine GSDMD. Thus, we provide clear evidence that the coronaviruses might utilize Nsp5 to inhibit the host pyroptotic cell death and facilitate their replication during the initial period, an important strategy for their sustaining infection. We suppose that GSDMD is an appealing target for the design of anticoronavirus therapies.

Ubiquitination is an important reversible post-translational modification. Many viruses hijack the host ubiquitin system to enhance self-replication. In the present study, we found that Avibirnavirus VP3 protein was ubiquitinated during infection and supported virus replication by ubiquitination. Mass spectrometry and mutation analysis showed that VP3 was ubiquitinated at residues K73, K135, K158, K193, and K219. Virus rescue showed that ubiquitination at sites K73, K193, and K219 on VP3 could enhance the replication abilities of infectious bursal disease virus (IBDV), and that K135 was essential for virus survival. Binding of the zinc finger domain of TRAF6 (TNF receptor associated factor 6) to VP3 mediated K11- and K33-linked ubiquitination of VP3, which promoted its nuclear accumulation to facilitate virus replication. Additionally, VP3 could inhibit TRAF6-mediated NFKB/NF-κB (nuclear factor kappa B) activation and IFNB/IFN-β (interferon beta) production to evade host innate immunity by inducing TRAF6 autophagic degradation in an SQSTM1/p62 (sequestosome 1)-dependent manner. Our findings demonstrated a macroautophagic/autophagic mechanism by which Avibirnavirus protein VP3 blocked NFKB-mediated IFNB production by targeting TRAF6 during virus infection, and provided a potential drug target for virus infection control.Abbreviations: ATG: autophagy related; BafA1: bafilomycin A1; CALCOCO2/NDP52: calcium binding and coiled-coil domain 2; Cas9: CRISPR-associated protein 9; CHX: cycloheximide; Co-IP: co-immunoprecipitation; CRISPR: clustered regularly interspaced short palindromic repeats; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GST: glutathione S-transferase; IBDV: infectious bursal disease virus; IF: indirect immunofluorescence; IFNB/IFN-β: interferon beta; mAb: monoclonal antibody; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MOI: multiplicity of infection; MS: mass spectrometry; NFKB/NF-κB: nuclear factor kappa B; NBR1: NBR1 autophagy cargo receptor; OPTN: optineurin; pAb: polyclonal antibody; PRRs: pattern recognition receptors; RNF125: ring finger protein 125; RNF135/Riplet: ring finger protein 135; SQSTM1/p62: sequestosome 1; TAX1BP1: tax1 binding protein1; TCID50: 50% tissue culture infective dose; TRAF3: TNF receptor associated factor 3; TRAF6: TNF receptor associated factor 6; TRIM25: tripartite motif containing 25; Ub: ubiquitin; Wort: wortmannin; WT: wild type.

The highly virulent and antigenic variant of Pseudorabies virus (PRV) that emerged from classical Bartha-K61-vaccinated pig herds has caused substantial economic losses to the swine industry in China since 2011. A safe and more effective vaccine is most desirable. In this study, a gE/TK gene-deficient PRV, namely, HD/c, was constructed based on a PRV type II DX strain isolated from a commercial vaccine-immunized farm and the HD/c-based inactivated vaccine was formulated and evaluated for its safety, immunogenicity, and protective efficacy in mice and piglets. The resulting PRV HD/c strain has a similar growth curve to the parental DX strain. After vaccination, the inactivated HD/c vaccine did not cause any visible gross pathological or histopathological changes in the tissues of mice and piglets and provided rapid and potent protection against the challenge of the classical and variant PRVs at day 21 post-vaccination in mice. A single immunization of 10(8.5)TCID(50) inactivated PRV HD/c strain-elicited robust immunity with high titer of neutralizing antibody and provided complete protection from the lethal challenge of PRV DX strain in piglets. These results indicated that the inactivated PRV HD/c vaccine with the deletion of gE/TK genes was a safe and effective PRV vaccine candidate for the control of PRV.

H6-subtype avian influenza virus (AIV) was prevalent in the world and could sporadically infect humans. Here, a new chicken-derived H6N6-subtype AIV strain A/chicken/Zhejiang/49/2021 (ZJ49) was isolated in Zhejiang Province, China in 2021. Phylogenetic analysis by Maximum likelihood methods showed that H6-subtype AIVs were classed into 13 groups according to HA gene. The ZJ49 strain belonged to the G12 group, which mainly consisted of strains from Asian and dominated in recent years. Based on NA gene, H6-subtype AIVs were divided into N6.1 and N6.2 clades according to the NA gene. The ZJ49 isolate was located in the N6.2e clade, which mainly consisted of the H5N6-subtype AIVs. Phylogenetic analysis by Bayesian methods showed that the effective quantity size of H6-subtype AIVs increased around 1990, reached a peak around 2015, declined after 2015, then kept in a stable level after 2018. The reassortment analysis predicted that the PB2, PA, and NA genes of ZJ49 may recombine with H5-subtype AIVs. The amino acid at 222 position of HA gene of ZJ49 strain mutated from A to V, suggesting that ZJ49 has a potential ability to cross species barriers. The four glycosylation sites were highly conserved, implying less impact on the fold and conception of HA stem structure. Our results revealed the complicated evolution, reassortment, and mutations of receptor binding sites of H6-subtype AIVs, which emphasize the importance to continuously monitor the epidemiology and evolution of H6-subtype AIVs.

Circovirus is the smallest virus to cause immune suppression in pigs. The capsid protein (Cap) is the only viral structural protein that is closely related to viral infection. ABSTRACT Nuclear entrance and stability of porcine circovirus type 2 (PCV2), the smallest virus in mammals, are crucial for its infection and replication. However, the mechanisms are not fully understood. Here, we found that the PCV2 virion maintains self-stability via the host importin 5 (IPO5) during infection. Coimmunoprecipitation combined with mass spectrometry and glutathione S-transferase pulldown assays showed that the capsid protein (Cap) of PCV2 binds directly to IPO5. Fine identification demonstrated that the N-terminal residue arginine(24) of Cap is the most critical to efficient binding to the proline(709) residue of IPO5. Detection of replication ability further showed that IPO5 supports PCV2 replication by promoting the nuclear import of incoming PCV2 virions. Knockdown of IPO5 delayed the nuclear transport of incoming PCV2 virions and significantly decreased the intracellular levels of overexpressed PCV2 Cap, which was reversed by treatment with a proteasome inhibitor or by rescuing IPO5 expression. Cycloheximide treatment showed that IPO5 increases the stability of the PCV2 Cap protein. Taken together, our findings demonstrated that during infection, IPO5 facilitates PCV2 replication by directly binding to the nuclear localization signal of Cap to block proteasome degradation. IMPORTANCE Circovirus is the smallest virus to cause immune suppression in pigs. The capsid protein (Cap) is the only viral structural protein that is closely related to viral infection. The nuclear entry and stability of Cap are necessary for PCV2 replication. However, the molecular mechanism maintaining the stability of Cap during nuclear trafficking of PCV2 is unknown. Here, we report that IPO5 aggregates within the nuclear periphery and combines with incoming PCV2 capsids to promote their nuclear entry. Concurrently, IPO5 inhibits the degradation of newly synthesized Cap protein, which facilitates the synthesis of virus proteins and virus replication. These findings highlight a mechanism whereby IPO5 plays a dual role in PCV2 infection, which not only enriches our understanding of the virus replication cycle but also lays the foundation for the subsequent development of antiviral drugs.

伪狂犬病病毒(Pseudorabies virus,PRV)感染猪(Sus scrofa)可引起烈性接触性传染病,即伪狂犬病(Pseudorabies,PR),临床上主要通过疫苗免疫进行防控.PRV变异株(PRVⅡ型)的流行使传统疫苗失去有效保护.近年来出现PRV跨宿主感染人(Homo sapiens)的案例,更使PRV成为全球公共卫生威胁,但其感染致病机制仍不完全清楚.为从分子水平上全面了解PRV感染宿主细胞引起的变化,本研究以PRVⅡ型毒株PRV-DX感染猪肾细胞PK-15,通过高通量测序获得PRV感染后全部的细胞差异转录组数据,并对差异表达基因进行功能富集.结果表明,PRV-DX感染PK-15可引起3595条基因表达上调、3604条基因表达下调.通过qPCR验证随机选择的12条差异表达基因,其变化趋势与转录组数据一致.GO注释和KEGG信号通路富集将差异表达基因聚焦在代谢、基因表达、免疫等信号通路.本研究为深入解析PRV感染的致病机制提供了重要基础数据及研究方向.

Circular RNAs (circRNAs) are a newly discovered class of noncoding RNAs (ncRNAs) present in various tissues and cells. However, the functions of most circRNAs have not been verified experimentally. Here, using deltacoronavirus as a model, differentially expressed circRNAs in cells with or without deltacoronavirus infection were analyzed by RNA sequencing to characterize the cellular responses to RNA virus infection. More than 57,000 circRNA candidates were detected, and seven significantly dysregulated circRNAs were quantitated by real-time reverse transcription-PCR. We discovered a previously unidentified circRNA derived from the TNFAIP3 gene, named circTNFAIP3, which is distributed and expressed widely in various tissues. RNA viruses, including deltacoronaviruses, rather than DNA viruses tend to activate the expression of endogenous circTNFAIP3. Overexpression of circTNFAIP3 promoted deltacoronavirus replication by reducing the apoptosis, while silencing of circTNFAIP3 inhibited deltacoronavirus replication by enhancing the apoptosis. In summary, our work provides useful circRNA-related information to facilitate investigation of the underlying mechanism of deltacoronavirus infection and identifies a novel circTNFAIP3 that promotes deltacoronavirus replication via regulating apoptosis. IMPORTANCE CircRNAs, a new class of ncRNAs, play important roles in cell growth, neural development, carcinogenesis, and anticarcinogenesis. Porcine deltacoronavirus is an emerging enteropathogenic coronavirus that causes diarrhea, but the role of host circRNAs in regulating its infection is unknown. Here, we performed expression profiling of circRNAs in mock- and deltacoronavirus- infected cells and identified the novel differentially expressed circular RNA circTNFAIP3. We demonstrate that circTNFAIP3 promotes deltacoronavirus replication by inhibiting apoptosis. Our findings first illustrate that circRNA can act as an apoptosis negative regulator during RNA virus infection and help to explore the underlying mechanism of deltacoronavirus infection.