Isolation and molecular characterization of fowl aviadenovirus associated with inclusion body hepatitis from poultry in Banten and West Java, Indonesia

Identification, pathogenicity and molecular characterization of a novel fowl adenovirus 8b strain

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.

Clostridium perfringens sialidase interaction with Neu5Ac α-Gal sialic acid receptors by in-silico observation and its impact on monolayers cellular behavior structure

Objective

This study aims to evaluate the effect of Clostridium perfringens sialidase treatment on monolayer cell behavior using computational screening and an in vitro approach to demonstrate interaction between enzyme-based drugs and ligands in host cells.

Materials and Methods

The in silico study was carried out by molecular docking analysis used to predict the interactions between atoms that occur, followed by genetic characterization of sialidase from a wild isolate. Sialidase, which has undergone further production and purification processes exposed to chicken embryonic fibroblast cell culture, and observations-based structural morphology of cells compared between treated cells and normal cells without treatment.

Results

Based on an in silico study, C. perfringens sialidase has an excellent binding affinity with Neu5Acα (2.3) Gal ligand receptor with Gibbs energy value (∆G)-7.35 kcal/mol and Ki value of 4.11 µM. Wild C. perfringens isolates in this study have 99.1%-100% similarity to the plc gene, NanH, and NanI genes, while NanJ shows 93.18% similarity compared to the reference isolate from GenBank. Sialidase at 750 and 150 mU may impact the viability, cell count, and cell behavior structure of fibroblast cells by significantly increasing the empty area and perimeter of chicken embryo fibroblast (CEF) cells, while at 30 mU sialidase shows no significant difference compared with mock control.

Conclusion

Sialidase-derived C. perfringens has the capacity to compete with viral molecules for attachment to host sialic acid based on in silico analysis. However, sialidase treatment has an impact on monolayer cell fibroblasts given exposure to high doses.

Potency of bacterial sialidase Clostridium perfringens as antiviral of Newcastle disease infections using embryonated chicken egg in ovo model

Background and Aim: Clostridium toxins are widely used as medicinal agents. Many active metabolic enzymes, including sialidase (neuraminidase), hyaluronidase, and collagenase, contribute to the mechanism of action of these toxins. Sialidase from Clostridium perfringens recognizes and degrades sialic acid receptors in the host cell glycoprotein, glycolipid, and polysaccharide complexes. Sialic acid promotes the adhesion of various pathogens, including viruses, under pathological conditions. This study aimed to investigate the potential of C. perfringens sialidase protein to inhibit Newcastle disease virus (NDV) infection in ovo model. Materials and Methods: C. perfringens was characterized by molecular identification through polymerase chain reaction (PCR) and is cultured in a broth medium to produce sialidase. In addition, sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis was conducted to characterize the sialidase protein. In contrast, enzymatic activity and protein concentration were carried out using a neuraminidase assay kit and Bradford to obtain suitable active substances. Furthermore, embryonated chicken egg models were used to observe the toxicity of several sialidase doses. Then, the hemagglutination (HA) titer was obtained, and absolute quantitative reverse transcription–PCR assay was performed to measure the viral replication inhibitory activity of sialidase against NDV. Results: Each isolate had a specific sialidase gene and its product. The sialidase derived from C. perfringens could hydrolyze the sialic acid receptor Neu5Ac (2,6)-Gal higher than Neu5Ac (2,3)Gal in chicken erythrocytes, as observed by enzyme-linked lectin assay. A significant difference (p = 0.05) in the HA titer in the pre-challenge administration group at dosages of 375 mU, 187.5 mU, and 93.75 mU in the competitive inhibition experiment suggests that sialidase inhibits NDV reproduction. Quantification of infective viral copy confirmed the interference of viral replication in the pre-challenge administration group, with a significant difference (p = 0.05) at the treatment doses of 750 mU, 375 mU, and 46.87 mU. Conclusion: The potency of sialidase obtained from C. perfringens was shown in this study, given its ability to reduce the viral titer and copy number in allantoic fluids without adversely impacting the toxicity of the chicken embryo at different concentrations.

Screening and purification of NanB sialidase from Pasteurella multocida with activity in hydrolyzing sialic acid Neu5Acα(2–6)Gal and Neu5Acα(2–3)Gal

Study on sialidases as antiviral agents has been widely performed, but many types of sialidase have not been tested for their antiviral activity. Pasteurella multocida NanB sialidase is one such sialidase that has never been isolated for further research. In this study, the activity of NanB sialidase was investigated in silico by docking the NanB sialidase of Pasteurella multocida to the Neu5Acα(2–6)Gal and Neu5Acα(2–3)Gal ligands. Additionally, some local isolates of Pasteurella multocida, which had the NanB gene were screened, and the proteins were isolated for further testing regarding their activity in hydrolyzing Neu5Acα(2–6)Gal and Neu5Acα(2–3)Gal. Silico studies showed that the NanB sialidase possesses an exceptional affinity towards forming a protein–ligand complex with Neu5Acα(2–6)Gal and Neu5Acα(2–3)Gal. NanB sialidase of Pasteurella multocida B018 at 0.129 U/mL and 0.258 U/mL doses can hydrolyze Neu5Acα(2–6)Gal and Neu5Acα(2–3)Gal better than other doses. In addition, those doses can inhibit effectively H9N2 viral binding to red blood cells. This study suggested that the NanB sialidase of Pasteurella multocida B018 has a potent antiviral activity because can hydrolyze sialic acid on red blood cells surface and inhibit the H9N2 viral binding to the cells.

Historical Investigation of Fowl Adenovirus Outbreaks in South Korea from 2007 to 2021: A Comprehensive Review

Fowl adenoviruses (FAdVs) have long been recognized as critical viral pathogens within the poultry industry, associated with severe economic implications worldwide. This specific group of viruses is responsible for a broad spectrum of diseases in birds, and an increasing occurrence of outbreaks was observed in the last ten years. Since their first discovery forty years ago in South Korea, twelve antigenically distinct serotypes of fowl adenoviruses have been described. This comprehensive review covers the history of fowl adenovirus outbreaks in South Korea and updates the current epidemiological landscape of serotype diversity and replacement as well as challenges in developing effective broadly protective vaccines. In addition, transitions in the prevalence of dominant fowl adenovirus serotypes from 2007 to 2021, alongside the history of intervention strategies, are brought into focus. Finally, future aspects are also discussed.