Fowl adenovirus serotype 4 (FAdV-4) is the causative agent of hydropericardium-hepatitis syndrome (HHS), a disease that causes severe economic losses to the global poultry industry. MicroRNAs (miRNAs) are key regulators of host-pathogen interactions; yet, their temporal expression dynamics and functional roles during FAdV-4 replication in chicken-derived cells remain poorly defined. This study characterized the temporal expression profile of host miRNAs during FAdV-4 infection in Leghorn male hepatoma (LMH) cells to elucidate their regulatory roles in viral replication through small RNA deep sequencing and functional validation. We identified 63 and 126 differentially expressed (DE) miRNAs at 12 hpi and 24 hpi, respectively. These DE miRNAs exhibited time-dependent regulatory functions throughout FAdV-4 infection, and KEGG enrichment confirmed persistent enrichment of their potential target genes within the MAPK signaling and metabolic pathways at both 12 hpi and 24 hpi. Moreover, we also revealed that gga-miR-184-5p could inhibit FAdV-4 replication, while gga-miR-7447-3p could promote FAdV-4 replication. Dual-luciferase reporter assays demonstrated that Family with Sequence Similarity 135 Member B (FAM135B) is directly targeted by gga-miR-184-5p. Overexpression of FAM135B suppressed FAdV-4 replication, an effect that was partially reversed by the introduction of gga-miR-184-5p. These findings deepen our understanding of host-FAdV-4 interaction mechanisms and provide valuable candidate targets for future development of antiviral strategies against FAdV-4 infection in poultry.

Avian infectious bronchitis virus (IBV) is endemic in poultry flocks worldwide, posing a significant threat to the global poultry industry. Frequent mixing of free-range local chickens with introduced chickens in Yunnan Province, China, facilitates the transmission, recombination, and mutation of avian IBV, thereby complicating disease prevention and control. In this study, we aimed to investigate the presence of IBV in poultry populations in Yunnan Province. Samples were collected from live poultry markets (LPMs) and breeding farms, comprising 725 randomly sampled cloacal/fecal swabs and 55 tissue samples. IBV-positive samples were confirmed via polymerase chain reaction (PCR), with an overall positivity rate of 0.89% for all tested samples. The positivity rate was 0.35% (2/564) in Kunming, 3.7% (2/54) in Zhaotong, 20% (1/5) in Yuxi, and 12.5% (2/16) in Baoshan, while no IBV was detected in samples from Lanping, Xichou, or Ninglang. Six IBV strains, including five GI-19 strains and one GVI-1 strain, were successfully isolated. Phylogenetic analysis further showed that the Yunnan GI-19 strains predominantly clustered with strains originating from Sichuan Province. Sequencing of the S1 gene revealed 2–5 amino acid substitutions per isolate in hypervariable regions HVR1–HVR3. Notably, a valine (V) and glycine (G) insertion between amino acid positions 88 and 89 was identified exclusively in isolate F210, a feature rarely reported in IBV. Protein-protein docking analysis indicated that the unique 88–89 insertion in isolate F210 S1 may alter its binding interactions with the host receptor ANPEP. Whole-genome comparison revealed that isolate YX3 shared 97.05% nucleotide identity with strain CK/CH/GX/YL17/2017 from Guangxi, whereas isolates Q47, F13, and F210 shared 96.40%–97.27% identity with strain CK/Henan/H1036/2021 from Henan. Recombination analysis detected obvious recombination events in isolates F13, F210, Q47, and YX3, with GI-22 strains serving as the major parental donors. These genetic characteristics, recombination patterns, and structural insights demonstrate the complex evolutionary dynamics of circulating IBV strains in Yunnan. Continuous molecular epidemiological surveillance combined with functional protein analysis is essential to monitor emerging variants and formulating targeted, effective disease control strategies.

Muscovy duck parvovirus (MDPV) and Goose parvovirus (GPV) are highly contagious waterfowl viruses causing significant harm to the poultry industry. This study designed primers and probes targeting the non-structural genomic region of MDPV and GPV, optimizing amplification for both quantitative polymerase chain reaction (qPCR) and duplex crystal digital polymerase chain reaction (dPCR). The resulting duplex crystal dPCR method showed strong specificity, detecting MDPV and GPV without cross-reactivity with other waterfowl viruses. Sensitivity tests revealed that the lower detection limit for qPCR was 11.5 copies/μL, while duplex crystal dPCR achieved a significantly lower detection limit of 0.3 copies/μL. This indicates that dPCR is approximately 38.3-fold more sensitive than qPCR in detecting MDPV and GPV The method demonstrated good repeatability with variation coefficients below 8.0%. In 52 clinical samples from Guangxi, the positive rates for MDPV and GPV were 15.38% and 23.08%, respectively, with one co-infection. This study confirms that duplex crystal dPCR is a specific, sensitive, and efficient technique for detecting MDPV and GPV, especially in the detection of samples containing low concentrations of viruses.

Avian infectious bronchitis virus (IBV) is a highly infectious pathogen, which seriously threatens the global poultry industry. Traditional Chinese Medicine (TCM) has shown some potential in the fight against IBV infection, but its application in the veterinary field is limited by the lack of systematic and massive data support. Based on the TCM inheritance computing platform, this study integrated 34,324 TCM prescriptions, 7,505 Chinese patent medicines and 4,207 platform-specific formulas, screened 336 candidate formulas consistent with IBV clinical phenotypes and obtained 5 core formulas through association rule and clustering analyses. The therapeutic effects of the IBV-infected yellow-feathered broilers were evaluated. The TCM compound had time- and group-dependent antiIBV effects. TCM-1 performed the best in alleviating clinical symptoms and restoring growth; TCM-1/2/5 alleviated symptoms on the 14th day and TCM-2/3 significantly promoted weight gain. These formulations protected the thymus and bursa of Fabricius but did not affect the spleen index. Different formulations reduced the viral load in a time- and tissue-dependent manner. TCM-2/3 significantly increased antibody levels, and all formulations balanced inflammatory cytokines and oxidative stress better than ribavirin. TCM-5 showed the best tracheal ciliary protection effect, while TCM-4 had the poorest overall efficacy. This study identified the TCM formula pattern for IBV using a data-mining approach previously established in human medicine and verified their therapeutic potential in a chicken model. The observed effects were associated with immunomodulation, antioxidation, and anti-inflammation. Although the methodology is not entirely novel in human TCM, its application to avian IBV with multi-dimensional in-vivo validation represents an advance in veterinary phytomedicine. This study provides evidence-based candidates for the clinical prevention and treatment of infectious bronchitis in chickens. This study provides evidence-based candidates for the clinical prevention and treatment of infectious bronchitis in chickens.

Two experiments were conducted to establish the prediction equations of growth performance and apparent metabolizable energy (AME) on chemical composition and enzymatic hydrolysate gross energy (EHGE) of corn, soybean meal (SBM), corn gluten meal (CGM), and wheat bran (WB) in chickens. Experiment 1 established the prediction equations of EHGE of four ingredients on chemical composition. In experiment 2, prediction equations of growth performance and AME based on EHGE of diets in chickens was developed. The variation was high for ether extract (EE) and crude protein (CP) of corn (6.78, 9.56) and WB (15.42, 10.41). The coefficient of variation of EE was higher than those of other ingredients in SBM and CGM. Two, seven, and eight equations for predicting the EHGE of corn, CGM, and WB based on dry matter (DM), GE, CP, and EE were established, respectively. However, statistical analysis showed that prediction equations of SBM were not significant. The prediction equations of ADFI, F/G and AME on EHGE of diets were ADFI = -2.143 * EHGEd + 54.066 (R2 = 0.955), F/G = -0.256 * EHGEd + 5.935 (R2 = 0.954), AME = 0.719 * EHGEd + 3.547 (R2 = 0.937), respectively. These results indicated that chemical compositions and the EHGE of corn, CGM, and WB could predict the growth performance and AME for chickens.

Salmonella Pullorum is a host-adapted pathogen that causes Pullorum disease in chickens and can be vertically transmitted via eggs, leading to embryonic mortality. The susceptibility and vertical transmission of S. Pullorum may vary among chicken breeds, yet genomic characterization of strains from dead embryos of indigenous breeds remains limited. This study isolated and characterized a Gram-negative short rod, designated Salmonella Pullorum strain SPullorum-YN-07, from dead embryos of Yanjin black-bone chickens, a native breed in Yunnan, China. The strain formed colorless colonies on MacConkey agar and red, non-H2S colonies on XLD agar, with biochemical reactions consistent with the genus Salmonella. Whole-genome sequencing using Illumina and PacBio platforms generated a complete genome consisting of one circular chromosome and four circular plasmids; plasmid replicon types IncFII(S) and Col(pVC) were identified in two of the plasmids. On the chromosome, a total of 340 virulence-associated genes were detected, including those involved in secretion systems, adhesion, motility, and immune modulation. Resistance gene analysis identified the acquired aminoglycoside resistance gene aac(6')-Iaa, alongside multiple intrinsic resistance determinants related to efflux pumps and target alteration. Multilocus sequence typing (MLST) assigned the strain to sequence type ST92, and core-genome phylogenetic analysis confirmed its clustering within the Salmonella Pullorum lineage. In a chick infection model, the strain induced depression, white diarrhea, and growth retardation, with clinical scores peaking at 10 days post-infection and a mortality rate of 10%. Bacterial colonization was highest in the cecum, and histopathological lesions were observed in the liver, spleen, and cecum. This study provides the first complete genomic characterization and pathogenicity assessment of an S. Pullorum strain isolated from dead embryos of Yanjin black-bone chickens, offering a foundation for understanding host-pathogen interactions in indigenous breeds and assessing cross-transmission risks to commercial poultry populations.

Fowl adenovirus serotype 4 (FAdV-4) is a highly destructive pathogen that causes hepatitis-hydropericardium syndrome (HHS), leading to substantial economic losses in the global poultry industry. Interferon-stimulated genes (ISGs) play a crucial role in controlling viral infections; however, their protective potential against FAdV-4 infections remains largely unknown. In this study, we systematically identified 482 type I and 107 type III ISGs with potential anti-FAdV-4 activity in chickens using RNA sequencing (RNA-Seq), of which 98 were shared by both types, and the expression level of the two types of ISGs was different, such as interferon alpha inducible protein 6 (IFI6). Functional analysis using Gene Ontology and the Kyoto Encyclopedia of Genes and Genomes revealed that these ISGs are involved in multiple essential biological processes, metabolic activities, signaling pathways, and immune regulations, suggesting their roles in host-virus interactions and cellular regulatory mechanisms. Heatmap analysis of gene expression profiles showed significant differences in ISG expression between interferon-alpha (ChIFN-α) and interferon-lambda (ChIFN-λ) treatment groups following FAdV-4 infection. Protein interaction analysis indicated that IFI6 is highly connected to multiple immune-related proteins. Notably, IFI6 exhibited the highest expression among the co-expressed genes. Functional validation demonstrated that IFI6 overexpression significantly suppressed FAdV-4 replication, while interference with IFI6 expression enhanced viral propagation. This study provides a comprehensive ISG resource for investigating antiviral responses in chickens and is the first to identify the antiviral activity of IFI6 against FAdV-4. These findings support future antiviral development and prevention and control measures for FAdV-4 infections in poultry.

Enterococcus cecorum, long regarded as a commensal bacterium in the avian gut, has recently emerged as a significant pathogen causing enterococcal spondylitis. The widespread use of antibiotics has driven the emergence of multidrug resistance in Enterococcus, particularly linezolid-resistant strains, posing risks to poultry farming and public health. Here, we report the first isolation and characterization of a linezolid-resistant E. cecorum strain (2023EC-GS-SDAU-1) harboring the optrA/fexA resistance gene cluster from Chinese commercial broilers, and analyze its genomic profile, resistance mechanisms, and pathogenicity. Whole-genome sequencing identified 15 resistance genes, including optrA, fexA, catA8, SAT-4, AAC(6’)-Ie-APH(2’’)-Ia, and aad(6)—all newly identified in E. cecorum. The optrA/fexA/ermA cluster colocalized on chromosomal genomic island GI12 is flanked by codirectional insertion sequences (ISEfa5), forming a mobile transposon-like unit. Phylogenetic analysis placed the strain within clade F, closely related to pathogenic isolates from the U.S. and France. Antimicrobial susceptibility testing confirmed multidrug resistance to aminoglycosides, macrolides, florfenicol, and linezolid. Additionally, 31 virulence genes were identified, and experimental infections in broilers recapitulated spondylitis lesions, validating pathogenicity. This study is the first to characterize a linezolid-resistant E. cecorum strain harboring the optrA/fexA cluster in poultry in China, implicating ISEfa5-mediated mobilization in resistance dissemination. The findings underscore the poultry production chain as a critical reservoir for oxazolidinone resistance (optrA) and highlight urgent needs for enhanced surveillance to mitigate zoonotic risks.

Chicken anemia virus (CAV), when primarily transmitted through the vertical route, could result in a significant global prevalence. Specifically, vertical CAV transmission, especially in newly-hatched chicks, may cause anemia and immunosuppression, leading to significant losses in the global poultry industry. Although CAV infection of chick embryos is critical in its vertical transmission, the pathogenicity of CAV in these embryos remains unclear. Herein, CAV-infected chick embryos exhibited a reduced hatchability rate, decreased embryo weight, and anemia. Furthermore, histopathological findings revealed reduced hematopoietic foci in the yolk sac and spleen, as well as pancytopenia and cortical lymphopenia in the bone marrow and thymus, respectively. Additionally, an analysis of the relative expression of transcription factors (TFs) and cell markers demonstrated that CAV inhibited hematopoiesis and T-lymphocyte development. Moreover, the high viral loads and strong immunolabelling highlighted the hematopoietic cells of the yolk sac and bone marrow as the primary target tissues for CAV. It is also noteworthy that the detection of CAV load showed active CAV replication from Embryo Day 15 (ED15) to ED18, implying that CAV replication was activated before hatching. These findings collectively suggest that CAV inhibited hematopoiesis and development in embryos, with its replication activated before hatching. In addition to illuminating CAV pathogenesis, our findings on CAV pathogenicity and tissue tropism in embryos could also guide its prevention and control.

Indigenous chicken breeds have a large market share in China due to their superior production traits, including high meat quality and disease resistance. Yunnan Province is recognized as a major source of domestic chickens globally and boasts a diverse array of indigenous chicken resources. Avian leukosis virus (ALV) induces various tumors and immunosuppression, endangering the poultry industry. However, the prevalence of ALV infection among indigenous chickens in Yunnan Province remains unclear. In this study, we aimed to investigate the presence of ALV in these breeds. To this end, we collected 1,470 plasma samples from six indigenous chicken breeds in Yunnan province, 309 of which tested positive. The results confirmed the presence of exogenous ALV in local chicken, with a positivity rate ranging from 8.20 %-41.46 %. Furthermore, eight exogenous ALV isolates were successfully identified: four ALV subtype J (ALV-J) strains, three ALV subtype A (ALV-A) strains and one ALV subtype B (ALV-B) strain. The four ALV-J strains share relatively high sequence identity (99.55 %-99.80 %) with the GX14ZS14 strain isolated from Guangxi in 2014 and was closely related to the prototype strain HPRS103 and belongs to clade 1.1. Several substitutions were observed in gp85 proteins in the three ALV-A and ALV-B strains isolated in this study. Additionally, the four ALV-J strains exhibited 203 bp deletions in the rTM and DR1 regions, a feature commonly observed in viruses in clades 1.2 and 1.3. Overall, this study confirmed the presence of multiple ALVs in these six indigenous chicken breeds from Yunnan Province. This study provides molecular characterization of ALV in indigenous chicken breeds in Yunnan Province and provides a reference for the further eradication of ALV in China. The complex background of ALV infection highlights the urgent need for intensifying eradication efforts.

Newcastle disease, caused by the Newcastle disease virus (NDV) and characterised by rapid onset and high mortality rates, is a highly contagious disease in the poultry industry. Interferons (IFN) play a key role in host defence against NDV, however, the non-structural protein V of NDV can antagonise IFN to facilitate NDV immune escape. DNA methyltransferase (DNMT)3A, an important regulator of IFN signalling molecules, may participate in the process by which the V protein inhibits IFN. Here, we found that NDV and V protein can inhibit DNMT3A expression, and DNMT3A participates in V protein inhibition of IFN expression. Further analysis revealed that the V protein interacts with DNMT3A and promotes its degradation via the K48-ubiquitin pathway. DNMT3A enhances the transcription and expression of IFN-β without altering the methylation status of the IFN-β gene. Instead, DNMT3A reduces the methylation of the CpG island in the IRF7 promoter region and increases the overall CpG island methylation within the IRF7 gene body, thereby increasing IRF7 expression and modulating IFN-β expression. Our study shows that NDV V protein can bind to and degrade DNMT3A, thereby affecting the methylation level of IRF7 and inhibiting IRF7 expression, ultimately leading to decreased IFN-β expression.

ABSTRACT A successful strategy employed by RNA viruses to achieve replication is to evade host cell RNase degradation. However, the mechanisms through which plus-strand RNA viruses effectively shield viral RNA from cellular ribonuclease degradation remain unclear. In this study, we identified the phenomenon whereby plus-strand RNA viruses, including avian leukosis virus subgroup J (ALV-J), reticuloendotheliosis virus (REV), chicken astrovirus (CAstV), and porcine epidemic diarrhea virus (PEDV), hijacked host cellular Musashi homolog 1 (MSI1). These viruses upregulated MSI1 expression and facilitated its translocation from the cytoplasmic periphery to a position proximal to and within the nucleus, thereby protecting viral RNA from degradation. Mechanistic analyses revealed that these viruses use distinct regions, the unique (U3) region or three prime untranslated region (3′UTR), to engage with MSI1, consequently shielding their viral RNA from cytoplasmic ribonuclease degradation. These results offer significant implications for understanding the replication tactics used by plus-strand RNA viruses, thereby advancing our understanding of their biological behaviors. IMPORTANCE The intricate interplay between RNA viruses and host cell RNA regulation encompasses viral mechanisms designed to circumvent RNase-mediated degradation. However, the specific strategies employed by plus-strand RNA viruses to shield their RNA from host ribonucleases remain inadequately characterized. In this study, Musashi homolog 1 (MSI1) is predominantly localized in the cytoplasm of normal cells, distinct from the nucleus. Following infection by plus-strand RNA viruses such as avian leukosis virus subgroup J (ALV-J), reticuloendotheliosis virus (REV), chicken astrovirus (CAstV), and porcine epidemic diarrhea virus (PEDV), these viruses hijack MSI1 to relocate near and within the nucleus. This hijacking is facilitated by specific regions, including unique or three prime untranslated regions, thereby preventing viral RNA from degradation by cytoplasmic ribonucleases. These findings have significant implications for elucidating the replication strategies of plus-strand RNA viruses, thereby advancing our understanding of their biological mechanisms.

BackgroundProteus mirabilis is a conditionally pathogenic bacterium that is inherently resistant to polymyxin and tigecycline, largely due to antibiotic resistance genes (ARGs). These ARGs can be horizontally transferred to other bacteria, raising concerns about the Inc plasmid-mediated ARG transmission from Proteus mirabilis, which poses a serious public health threat. This study aims to investigate the presence of Inc plasmid types in pig-derived Proteus mirabilis in Kunming, Yunnan, China.MethodsFecal samples were collected from pig farms across six districts of Kunming (Luquan, Jinning, Yiliang, Anning, Songming, and Xundian) from 2022 to 2023. Proteus mirabilis isolates were identified using IDS and 16S rRNA gene sequencing. Then, positive strains underwent antimicrobial susceptibility testing and incompatibility plasmid typing. Multi-drug-resistant isolates with positive incompatibility plasmid genes were selected for whole-genome sequencing. Resistance and Inc group data were then isolated and compared with 126 complete genome sequences from public databases. Whole-genome multi-locus sequence typing, resistance group analysis, genomic island prediction, and plasmid structural gene analysis were performed.ResultsA total of 30 isolates were obtained from 230 samples, yielding a prevalence of 13.04%. All isolates exhibited multi-drug resistance, with 100% resistance to cotrimoxazole, erythromycin, penicillin G, chloramphenicol, ampicillin, and streptomycin. Among these, 15 isolates tested positive for the IncQ1α plasmid repC gene. The two most multi-drug-resistant and repC-positive strains, NO. 15 and 21, were sequenced to compare genomic features on Inc groups and ARGs with public data. Genome analysis revealed that the repC gene was primarily associated with IncQ1α, with structural genes from other F-type plasmids (TraV, TraU, TraN, TraL, TraK, TraI, TraH, TraG, TraF, TraE/GumN, and TraA) also present. Strain NO. 15 carried 33 ARGs, and strain NO. 21 carried 38 ARGs, conferring resistance to tetracyclines, fluoroquinolones, aminoglycosides, sulfonamides, peptides, chloramphenicol, cephalosporins, lincomycins, macrolides, and 2-aminopyrimidines.ConclusionThe repC gene is primarily associated with IncQ1α, with structural genes from other F-type plasmids. A comparison with 126 public genome datasets confirmed this association.

Porcine epidemic diarrhea virus (PEDV) is a highly infectious pathogen that targets pig intestines to cause disease. It is globally widespread and causes huge economic losses to the pig industry. PEDV N protein is the protein that constitutes the core of PEDV virus particles, and most of it is expressed in the cytoplasm, and a small part can also be expressed in the nucleus. However, the role of related proteins in host nucleotide metabolic pathways in regulating PEDV replication have not been fully elucidated. In this study, PEDV-N-labeled antibodies were co-immunoprecipitated and combined with LC-MS to screen for host proteins that interact with N proteins. Bioinformatics analyses showed that the selected host proteins were mainly enriched in metabolic pathways. Moreover, co-immunoprecipitation and confocal microscopy confirmed that the second-largest subunit of RNA polymerase II (RPB2) and uridine phosphorylase 1 (UPP1) interacted with the N protein. RPB2 is the main subunit of RNA polymerase II and plays an important role in eukaryotic transcription. UPP1 is an enzyme that catalyzes reversible phosphorylation of uridine to uracil and ribo-1-phosphate to promote catabolism and bio anabolism. RPB2 overexpression significantly promoted viral replication, whereas UPP1 overexpression significantly inhibited viral replication. Studies on interactions between the PEDV N and host proteins are helpful in elucidating the pathogenesis and immune escape mechanism of PEDV.

The H9N2 subtype of the avian influenza virus (AIV) is widely prevalent in birds, threatening the poultry industry and providing genetic material for emerging human pathogens. The prevalence and genetic characteristics of H9N2 in Yunnan Province, China, are largely unknown. Samples were collected from live poultry markets (LPMs) and breeding farms in Yunnan Province. H9N2-positive samples were identified by polymerase chain reaction (PCR), with a high positivity rate of 42.86% in tissue samples. The positivity rate of swab samples in the LPMs in Kunming was 3.97% (17/564), but no AIV was detected in samples from poultry farms in Lijiang, Wenshan, and Yuxi. Evolutionary analysis and genotyping were performed for the 17 strains of isolated H9N2 virus. Phylogenetic analysis revealed that all H9N2 viral genes had 91.6%-100% nucleotide homology, belonged to the G57 genotype, and had high homology with H9N2 viruses isolated from Guangdong and Guangxi, suggesting that the H9N2 viruses in Yunnan Province may have been imported by chicks. Using a nucleotide divergence cutoff of 95%, we identified ten distinct H9N2 genotypes that continued to evolve. The surface genes of the H9N2 isolates displayed substantial genetic diversity, highlighting the genetic diversity and complexity of the H9N2-subtype AIVs in Yunnan. Molecular analysis demonstrated that all 17 strains of H9N2 isolates had mutations at H183N, Q226L, L31P, and I268V in hemagglutinin; S31N in matrix protein 2; and no replacements at positions 274 and 292 of the neuraminidase protein. Sixteen strains had the A558V mutation and one strain had the E627V mutation in polymerase basic protein 2. Analysis of these amino acid sites suggests that H9N2 influenza viruses in Yunnan continue to mutate and adapt to mammals and are sensitive to neuraminidase inhibitors but resistant to adamantanes. It is necessary to strengthen surveillance of AIV H9N2 subtypes in poultry and LPMs in Yunnan to further understand their genetic diversity.

Atypical porcine pestivirus (APPV) can cause congenital tremor type A-II in neonatal piglets, posing a significant threat to swine herd health globally. Our previous study demonstrated that the Mut domains, comprising 112 amino acids at the N-terminus, are the primary functional regions of the E2 protein of APPV. This study identified 14 host cellular proteins that exhibit potential interactions with the Mut domains of the E2 protein using yeast two-hybrid screening. Using bioinformatics analysis, we discovered that the Mut domains of the E2 protein might exert regulatory effects on apoptosis by modulating energy metabolism within the mitochondria. We also conducted co-immunoprecipitation, glutathione S-transferase pull-down, and immunofluorescence assays to confirm the interaction between the Mut domains of the E2 protein and cathepsin H and signal sequence receptor subunit 4 (SSR4). Ultimately, SSR4 enhanced APPV replication in vitro. In summary, our study successfully elucidated the interactions between the Mut domains of the E2 protein and host cell protein, predicted the potential pathways implicated in these interactions, and demonstrated SSR4 involvement in APPV infection. These significant findings contribute valuable knowledge toward a deeper understanding of APPV pathogenesis and the role of the Mut domains of the E2 protein in this intricate process.

Introduction:Bacillus licheniformis (B.licheniformis) was widely used in poultry feeds. However, it is still unclear about how B.licheniformis regulates the growth and development of Pekin ducks.Methods: The experiment was designed to clarify the effect and molecular mechanism of B. licheniformis on the lipid metabolism and developmental growth of Pekin ducks through multiomics analysis, including transcriptomic and metabolomic analyses.Results: The results showed that compared with the control group, the addition of 400 mg/kg B. licheniformis could significantly increase the body weight of Pekin ducks and the content of triglyceride (p < 0.05), at the same time, the addition of B. licheniformis could affect the lipid metabolism of liver in Pekin ducks, and the addition of 400 mg/kg B. licheniformis could significantly increase the content of lipoprotein lipase in liver of Pekin ducks. Transcriptomic analysis revealed that the addition of B. licheniformis primarily impacted fatty acid and glutathione, amino acid metabolism, fatty acid degradation, as well as biosynthesis and elongation of unsaturated fatty acids. Metabolomic analysis indicated that B. licheniformis primarily affected the regulation of glycerol phospholipids, fatty acids, and glycerol metabolites. Multiomics analysis demonstrated that the addition of B. licheniformis to the diet of Pekin ducks enhanced the regulation of enzymes involved in fat synthesis via the PPAR signaling pathway, actively participating in fat synthesis and fatty acid transport.Discussion: We found that B. licheniformis effectively influences fat content and lipid metabolism by modulating lipid metabolism-associated enzymes in the liver. Ultimately, this study contributes to our understanding of how B. licheniformis can improve the growth performance of Pekin ducks, particularly in terms of fat deposition, thereby providing a theoretical foundation for its practical application.Conclusion:B. licheniformis can increase the regulation of enzymes related to fat synthesis through PPAR signal pathway, and actively participate in liver fat synthesis and fatty acid transport, thus changing the lipid metabolism of Pekin ducks, mainly in the regulation of glycerol phospholipids, fatty acids and glycerol lipid metabolites.