Avian reovirus (ARV) infection is prevalent in farmed poultry and causes viral arthritis and severe immunosuppression. The spleen plays a very important part in protecting hosts against infectious pathogens. In this research, transcriptome and translatome sequencing technology were combined to investigate the mechanisms of transcriptional and translational regulation in the spleen after ARV infection. On a genome-wide scale, ARV infection can significantly reduce the translation efficiency (TE) of splenic genes. Differentially expressed translational efficiency genes (DTEGs) were identified, including 15 upregulated DTEGs and 396 downregulated DTEGs. These DTEGs were mainly enriched in immune regulation signaling pathways, which indicates that ARV infection reduces the innate immune response in the spleen. In addition, combined analyses revealed that the innate immune response involves the effects of transcriptional and translational regulation. Moreover, we discovered the key gene IL4I1, the most significantly upregulated gene at both the transcriptional and translational levels. Further studies in DF1 cells showed that overexpression of IL4I1 could inhibit the replication of ARV, while inhibiting the expression of endogenous IL4I1 with siRNA promoted the replication of ARV. Overexpression of IL4I1 significantly downregulated the mRNA expression of IFN-β, LGP2, TBK1 and NF-κB; however, the expression of these genes was significantly upregulated after inhibition of IL4I1, suggesting that IL4I1 may be a negative feedback effect of innate immune signaling pathways. In addition, there may be an interaction between IL4I1 and ARV σA protein, and we speculate that the IL4I1 protein plays a regulatory role by interacting with the σA protein. This study not only provides a new perspective on the regulatory mechanisms of the innate immune response after ARV infection but also enriches the knowledge of the host defense mechanisms against ARV invasion and the outcome of ARV evasion of the host’s innate immune response.

H9N2 avian influenza virus (AIV) is widely prevalent in poultry in China. To understand the genetic characteristics and evolution of H9N2 AIVs in Guangxi, southern China, the complete genomes of H9N2 AIVs from 1999–2023 were systematically analysed. Maximum likelihood (ML) trees indicated that H9N2 AIV gene sublineage diversity contributed to genotype diversity, yielding 17 genotypes (G1–G17). Since 2010, genotype G14 (also known as genotype S or G57) has become predominant in poultry in Guangxi. Phylogenetic analysis in the HA has resulted in the distancing of recent Guangxi isolates from the vaccine strains. This study also revealed that the genotypes of H9N2 AIVs infecting swine, equines and canines in Guangxi were consistent with those found in avian species at the same time, highlighting the capacity of H9N2 AIVs to be transmitted across species. The antigenic residues in the HA head region and NA protein of the Guangxi isolates from 2020–2023 changed significantly compared to the vaccine strains, suggesting possible antigenic drift in these viruses. Amino acid analysis of the HA protein revealed that 84.9% (73/86) of H9N2 AIV isolates from Guangxi, including those from live poultry markets, preferentially bound to α-2,6 sialic acid receptors. Considerable attention should be given to cross-species transmission of H9N2 AIV in the region. On the basis of these findings, strengthening the monitoring of H9N2 AIV in poultry in Guangxi is essential.

Interferon-inducible transmembrane protein 3 (IFITM3) is an antiviral factor that plays an important role in the host innate immune response against viruses. Previous studies have shown that IFITM3 is upregulated in various tissues and organs after avian reovirus (ARV) infection, which suggests that IFITM3 may be involved in the antiviral response after ARV infection. In this study, the chicken IFITM3 gene was cloned and analyzed bioinformatically. Then, the role of chicken IFITM3 in ARV infection was further explored. The results showed that the molecular weight of the chicken IFITM3 protein was approximately 13 kDa. This protein was found to be localized mainly in the cytoplasm, and its protein structure contained the CD225 domain. The homology analysis and phylogenetic tree analysis showed that the IFITM3 genes of different species exhibited great variation during genetic evolution, and chicken IFITM3 shared the highest homology with that of Anas platyrhynchos and displayed relatively low homology with those of birds such as Anser cygnoides and Serinus canaria. An analysis of the distribution of chicken IFITM3 in tissues and organs revealed that the IFITM3 gene was expressed at its highest level in the intestine and in large quantities in immune organs, such as the bursa of Fabricius, thymus and spleen. Further studies showed that the overexpression of IFITM3 in chicken embryo fibroblasts (DF-1) could inhibit the replication of ARV, whereas the inhibition of IFITM3 expression in DF-1 cells promoted ARV replication. In addition, chicken IFITM3 may exert negative feedback regulatory effects on the expression of TBK1, IFN-γ and IRF1 during ARV infection, and it is speculated that IFITM3 may participate in the innate immune response after ARV infection by negatively regulating the expression of TBK1, IFN-γ and IRF1. The results of this study further enrich the understanding of the role and function of chicken IFITM3 in ARV infection and provide a theoretical basis for an in-depth understanding of the antiviral mechanism of host resistance to ARV infection.

Fowl adenovirus serotype 4 (FAdV-4) causes hydropericardium-hepatitis syndrome (HHS) and has resulted in severe economic losses to the poultry industry in China since 2015. In this study, we isolated a naturally occurring strain with reduced virulence designated GXYL-03, which caused no gross or histological HHS lesions in 4-week-old specific pathogen-free (SPF) chickens infected at 10⁶ TCID₅₀, whereas clinical signs and partial mortality were observed at higher doses of 10⁷–10⁸ TCID₅₀. After a single immunization with 5 × 10⁴ TCID₅₀ of GXYL-03, all ten immunized SPF chickens survived throughout the 14-day observation following lethal GX2017-005 challenge, whereas all ten challenge-control chickens died. Integrated transcriptome and translatome analyses were performed on the livers of chickens infected with FAdV-4 strains of differing virulence by RNA sequencing (RNA-seq) and polysome profiling, with three biological replicates per group. The polysome/non-polysome (P/NP) ratio did not differ significantly among groups (p > 0.05), indicating stable global translation flux. The GXYL-03 group had 2,131 transcriptomic differentially expressed genes (DEGs) but only 71 translatomic DEGs; the GX2017-005 group had 7767 and 148, respectively, indicating that only 3.3% and 1.9% of transcriptional perturbations were transmitted to translation, revealing a pronounced translational buffering effect. Translation efficiency (TE) changes were predominantly suppressive, and downregulated genes accounted for 58.6% and 61.8% of TE changes in the two strains. The functional enrichment of genes whose expression was synchronously upregulated at both levels (TE+RNA+) revealed that GXYL-03 was enriched mainly in protein-coding genes involved in cellular stress, DNA damage repair, vesicle transport, and protein homeostasis (HSPA2, HSPB9, FANCD2, EHD2, and Vault), whereas GX2017-005 was enriched in liver injury-related genes (CD74, ATG2B, FKBP5, ND1, and COX1) that were not differentially expressed in GXYL-03. This study provides insights into the development of FAdV-4 strains with reduced virulence and virus–host interactions.