• The knob domain of Fiber 2 protein of FAdV-4 very virulent WZ strain are expressed in Escherichia coli;. • The recombinant knob protein as the functional region of the viral surface protein Fiber 2 had good reactivity;. • The Fiber 2-knob protein provided full protection against virulent FAdV-4 challenge.

The chicken infectious anemia virus (CIAV) and fowl adenovirus serotype E8b (FAdV E8b) are pathogens that cause aplastic anemia and inclusion body hepatitis (IBH) in chickens, respectively. The co-infection of CIAV and FAdV E8b poses a significant threat to poultry health, potentially worsening clinical symptoms and increasing mortality rates. This study aimed to explore the combined pathogenic effects of FAdV E8b and CIAV co-infection on one-day-old specific pathogen-free (SPF) chickens. The results showed that co-infection led to significantly higher clinical scores and mortality rates compared to FAdV E8b infection alone. Additionally, there were different tissue distribution patterns for FAdV E8b between the single infection and co-infection groups, indicating potential changes in viral tropism. Biochemical analysis revealed elevated markers of liver and/or muscle damage in both the FAdV E8b infection group and the co-infection group, consistent with the viral infection process. These findings suggest that co-infection with FAdV E8b and CIAV can intensify clinical signs and mortality, and may potentially alter viral replication and tissue tropism in chickens. This study establishes a foundation for future investigations into the underlying mechanisms governing the interaction between CIAV and FAdV E8b during co-infection.

Since 2012, there has been a noticeable upward trend in the global incidence of inclusion body hepatitis (IBH) cases, leading to substantial economic losses in the poultry industry. In response to this trend, the current study aimed to investigate the phylogenetic information, genetic mutations, and pathogenicity of the highly pathogenic fowl adenovirus (FAdV) strain HN1472, which was isolated from liver samples obtained from a laying flock affected by IBH. This investigation was carried out using 1-day-old specific pathogen-free (SPF) chickens. Recombination and phylogenetic analyses confirmed that HN1472 is a recombinant strain derived from FAdV-8a and FAdV-8b, and exhibited significant genetic divergence in the hexon, fiber, and ORF19 genes. Notably, the phylogenetic analysis identified recombination events in these regions. Furthermore, animal experiments revealed that HN1472 is a highly pathogenic isolate, causing 80% mortality and manifesting clinical signs of IBH in SPF chickens. Furthermore, the recombinant FAdV serotype 8b (FAdV-8b) was found to be widely distributed in various tissues, with a higher concentration in the livers and gizzard tissue at 3 d postchallenge (dpc). Collectively, these findings contribute to our current understanding of the factors influencing the pathogenicity and genetic diversity of FAdV serotype 8b (FAdV-8b) in China.

According to previous studies, three representative avian adenoviral strains utilize coxsackievirus–adenovirus receptor (CAR) as a receptor and seem to exhibit diverse binding affinities and modes. Thus, further revealing the exact molecular mechanism underlying the interaction between different FAdVs and the attachment receptor CAR is necessary. In this study, we successfully solved the crystal structure of the FAdV-4 fiber1 knob at 1.6 Å resolution. The interaction between the fibre knob and different domains of CAR was verified by confocal microscopy, coimmunoprecipitation and surface plasmon resonance (SPR) analysis. The fibre knobs of the three representative fowl adenoviruses specifically recognized CAR domain 1 (D1), but the recognition of CAR domain 2 (D2) by chicken embryo lethal orphan (CELO) strains was weak. These results provide insights into the differences in adenovirus‒host cell interactions and have important implications for the exploration of viral invasion mechanisms.

Vaccination remains the primary strategy for controlling infectious diseases in farm animals. However, current conventional vaccines demonstrate clinical limitations including suboptimal immunogenicity and frequent booster requirements, which compromise disease management efficacy. This study presents an innovative vaccine platform combining yolk immunoglobulin (IgY) with inactivated antigens as co-immunization components. We developed two formulations targeting economically significant pathogens: avian Fowl Adenovirus Serotype 4 (FAdV-4) and Porcine Epidemic Diarrhea Virus (PEDV). For FAdV-4 vaccine evaluation in specific pathogen-free (SPF) chickens, the IgY-antigen complex demonstrated superior immunogenic properties compared to conventional inactivated vaccines. When administered as a single dose at 14 days of age, the experimental formulation elicited significantly stronger humoral responses as measured by both serum neutralization (SN₅₀) and ELISA. Notably, this vaccination strategy provided 100% protection against lethal FAdV-4 challenge from 0 h to 20 weeks post-vaccination, with complete absence of clinical disease manifestations. In PEDV assessment using mouse models, the IgY-antigen formulation induced significantly higher antibody titers than inactivated antigen alone at all post-immunization timepoints (p < 0.01). Comparative analysis revealed our dual-component platform enhanced both the intensity and rapidity of protective immune responses compared to traditional inactivated vaccines. These findings establish that the IgY-antigen co-immunization strategy represents a promising approach for developing new veterinary vaccines with improved protective efficacy. The platform’s ability to generate robust, rapid-onset immunity while maintaining single-dose effectiveness addresses critical limitations of current vaccine technologies.

In recent years, the prevalence and variation of goose adenoviruses, especially Goose Adenovirus Type 4 (GoAdV-4), have threatened waterfowl farming, while their genetic evolution and pathogenic mechanisms remain unelucidated. In May 2024, a novel GoAdV-4 strain (JA2485) was isolated from diseased Sanhua geese in Jian City, Jiangxi Province, China. It propagated in 11–13-day-old goose embryos, with a 50% embryo infectious dose (EID₅₀) of 10^2.2/0.1 mL. Whole-genome sequencing (GenBank Accession No. PQ152938) showed its genome is 43,030 base pairs long, containing 33 protein-coding regions and 2 fiber genes. Phylogenetic analysis revealed JA2485 is closely related to the Hungarian P29 strain and Chinese CH-FJZZ-202201 strain (nucleotide similarity: 94–96.8%), but clusters in a different branch from other avian adenoviruses. In pathogenicity tests on 1-day-old Sanhua geese, both subcutaneous injection and oral inoculation groups had 50% mortality. Infected geese showed weight loss, depression, reduced appetite, increased recumbency, and even paralysis in severe cases. Post mortem examination revealed hepatic rounded margins, yellowing, focal hemorrhages, and renal hemorrhagic lesions. Notably, viral loads were highest in the liver, duodenum, and cloacal swabs, suggesting fecal transmission. This study provides a key basis for clarifying GoAdV-4’s evolutionary characteristics and pathogenic mechanisms, and formulating targeted prevention strategies.