To expand our understanding of the epidemiology of avian coronavirus (ACoV) in China, the risk-based active surveillance was carried out in China in 2024. A total of 7,699 avian swab samples were collected from 153 sampling sites in 13 provinces. One thousand fifty hundred and eighty-six ACoVs were detected and identified by RT-PCR and sequencing with a positive rate of 20.60 %, including 1,125 strains of avian infectious bronchitis virus (IBV), 278 strains of duck coronavirus (DuCoV), 182 strains of pigeon coronavirus (PiCoV), and 1 strain of deltacoronavirus. Most ACoVs were detected from chickens, followed by pigeons, while others were collected from ducks and geese. The positivity rates for ACoV in poultry ranged from 2.91 % to 32.27 %. The viruses were detected from 86 sampling sites (56.21 %) in all 13 provinces surveyed. The positivity rates of ACoV in retail markets (98.08 %) and wholesale markets (100 %) were much higher than those in slaughterhouses (80.00 %) and poultry farms (20.25 %). 231 representative IBV strains from different regions were selected for S1 gene sequencing and genetic evolution analysis. The results revealed that the prevalent IBV in China comprised ten genotypes, meanwhile the recombinant variants were also detected. The viruses in GI-19 (35.06 %) and GVI-1 (33.77 %) were the predominant strains in China. Importantly, no cases of SARS-CoV-2 were found in the detected poultry samples. This study reveals the prevalence, distribution, genetic and phylogenetic characteristics of ACoV in China, and extends our understanding of the epidemiological context of ACoV in China.

Pigeon Newcastle disease, caused by pigeon paramyxovirus type 1 (PPMV-1), is a significant infectious disease in pigeons that can result in substantial mortality and poses a severe threat to the pigeon industry. The rapid and accurate onsite diagnosis of pigeon disease is crucial for timely diagnosis and the implementation of effective prevention and control measures. In this study, we established a rapid detection method for PPMV-1 based on recombinase-aided amplification (RAA) and CRISPR/Cas12a. The RAA primers target the conserved regions of the L gene for preamplification in clinical nucleic acid samples, followed by CRISPR/Cas12a detection of the target gene. Visualization could be achieved by combination with a lateral flow dipstick (LFD). This method demonstrated high specificity, showing no cross-reactivity with non-PPMV-1 samples. The sensitivity of the method assessed by fluorescence analysis reached 10⁰ copies/µL, and when it was combined with an LFD, the sensitivity was 10³ copies/µL. The constructed RAA-CRISPR/Cas12a-LFD visual detection method was applied to clinical sample testing and was found to enable the rapid and accurate detection of swab samples and tissue specimens. Its sensitivity was consistent with the current gold standard, quantitative real-time PCR results. The RAA-CRISPR/Cas12a-LFD detection method we developed provides a novel approach for the rapid, simple, precise, and specific onsite diagnosis of pigeon Newcastle disease.

The peroxisomal biogenesis factor 19 (PEX19) is necessary for early peroxisomal biogenesis. PEX19 has been implicated in the replication of a variety of viruses, but the details pertaining to the mechanisms of how PEX19 engages in the life cycle of these viruses still need to be elucidated. Here, we demonstrated that the C terminus of PEX19 interacted with the cytoplasmic tail region of the M2 protein of the influenza A virus (IAV) and inhibited the viral growth titers. IAV infection or PEX19 knockdown triggered a reduction in the peroxisome pool and led to the accumulation of ROS and cell damage, thereby creating favorable conditions for IAV replication. Moreover, a reduction in the peroxisome pool led to the attenuation of early antiviral response mediated by peroxisome MAVS and downstream type III interferons. This study also showed that the interaction between IAV M2 and PEX19 affected the binding of PEX19 to the peroxisome-associated protein PEX14 and peroxisome membrane protein 24 (PMP24). Collectively, our data demonstrate that host factor PEX19 suppresses the replication of the IAV, and the IAV employs its M2 protein to mitigate the restricting role of PEX19.

Avian infectious bronchitis virus (IBV), a major pathogen in the poultry industry, evolves rapidly via genetic mutations and recombination. While recombination between field and live vaccine strains is well-documented, its direct role in viral virulence remains unclear. In this study, four novel IBV field strains (SX/2407, SX/2408, SX/2409, SX/2410) were isolated from a single layer farm in Shanxi Province, China, and genetically characterized. Comprehensive genomic analysis revealed that SX/2409 is a natural recombinant, with SX/2408 (co-isolated) as the major parent and a 4/91-like vaccine lineage as the minor parent. To assess the functional impact of this recombination, pathogenicity was compared in chicks. Notably, SX/2409 exhibited markedly enhanced virulence, with a significantly higher mortality rate (60%) than its major parent SX/2408 (20%). The other isolates, SX/2407 and SX/2410, caused 50% and 0% mortality, respectively. Our findings provide compelling field evidence that recombination with a live vaccine strain can directly drives the evolution of a more virulent IBV phenotype. These results highlight the potential evolutionary risks of current vaccination strategies and emphasize the critical need for robust molecular surveillance and development of safer next-generation vaccines.

Porcine circovirus type 3 (PCV3) infection can cause symptoms similar to those of porcine circovirus type 2 (PCV2) infection, and coinfections with both PCV2 and PCV3 are observed in the swine industry. Consequently, developing chimeric vaccines is essential to prevent and control porcine circovirus infections. In this study, we used both E. coli and mammalian expression systems to express PCV3 Cap (Cap3) and a chimeric gene containing the PCV2-neutralizing epitope within the PCV3 Cap (Cap3-Cap2E), which were assembled into virus-like particle (VLP) vaccines. We found that Cap3 lacking nuclear localization signal (NLS) could not form VLPs, while Cap3 with a His-tag successfully assembled into VLPs. Additionally, the chimeric of PCV2-neutralizing epitopes did not interfere with the assembly process of VLPs. Various immunization approaches revealed that pCap3-Cap2E VLP vaccines were capable of activating high PCV3 Cap-specific antibody levels and effectively neutralizing both PCV3 and PCV2. Furthermore, pCap3-Cap2E VLPs demonstrated a potent ability to activate cellular immunity, protecting against PCV3 infection and preventing lung damage in mice. In conclusion, this study successfully developed a PCV3 Cap VLP vaccine incorporating chimeric PCV2-neutralizing epitope genes, providing new perspectives for PCV3 vaccine development.

Coinfections with porcine circovirus types 2, 3, and 4 (PCV2, PCV3, and PCV4) are increasingly being detected in the swine industry. However, there is no commercially available vaccine which prevents coinfection with PCV2, PCV3, and PCV4. The development of a vaccine expressing capsid (Cap) fusion proteins of multiple PCVs represents a promising approach for broadly preventing infection with PCVs. In this study, we developed a PCV subunit vaccine candidate (Cap 2-3-4) by predicting, screening, and fusing antigenic epitopes of Cap proteins of PCV2, PCV3, and PCV4. Immunoprotection assays showed that the prokaryotic expression of Cap 2-3-4 could effectively induce high levels of PCV2, PCV3, and PCV4 Cap-specific antibodies and successfully neutralize both PCV2 and PCV3. Furthermore, Cap 2-3-4 demonstrated a potent ability to activate cellular immunity and thus prevent lung damage in mice. This study provides a new option for the development of broad vaccines against PCVs.