Characterization of fowl adenoviruses associated with hydropericardium syndrome and inclusion body hepatitis in broiler chickens

Gizzard Erosion and Ulceration Syndrome in Moroccan Poultry Flocks and Molecular Characterization of Fowl Adenoviruses (FAdV)

Gizzard erosion and ulceration syndrome (GEUS) is caused by a fowl adenovirus serotype 1 (FAdV-1) and was first reported in laying hens in Japan in 1993. This syndrome has emerged as an epizootic in Morocco since 2014, causing significant economic losses for the poultry industry, but no involvement of a FAdV has been confirmed. Thus, the objective of this work was to assess GEUS cases that occurred in the country and to determine the role of FAdVs in their occurrence. Investigations were based on a retrospective reassessment of tissue sections and paraffin blocks of gizzards and livers from GEUS cases between 2014 and 2021 coupled with a prospective search of cases in 2022. Gizzards and livers were fixed in 10% neutral buffered formalin for histopathologic examinations according to standard methods and stored at -20 C for molecular analysis. After deparaffinizing, 10-µm-thick tissue sections along with fresh organs were subjected to DNA extraction using a commercial kit. A primer pair specific for the Hexon gene of FAdVs was used in conventional PCR; in contrast, for real-time PCR, a primer pair targeting the 52K gene was employed. In total, 24 flock cases with characteristic GEUS were assessed between 2014 and 2022. They were nine broiler cases aged between 11 and 39 days, 11 layer cases with an age between 17 and 29 wk, two cases in meat-type breeders aged 10 and 27 wk, and two flock cases of turkey poults aged 22 and 23 days. In most cases, microscopic lesions were consistent with an ulcerative and lymphoplasmocytic ventriculitis, and pathognomonic viral intranuclear inclusion bodies within degenerate epithelial cells were identified in four broiler flock cases, four layer cases, and one case in breeders and hence were highly suggestive of a FAdV infection. Among these nine cases that were positive at the histopathologic examination, six cases were found to be FAdV-PCR positive; another four cases were negative to histology but FAdV-PCR positive. Furthermore, a sequencing analysis was conducted, providing the initial evidence of the implication of FAdV-1 from species A as the cause of GEUS in Moroccan poultry. Additionally, a phylogenetic analysis was executed to facilitate a comparison between the strains investigated in this study and those identified in diverse geographic regions and across various time periods.

Novel pathogenic adenovirus in Timneh grey parrot (Psittacus timneh) unveils distinct lineage within Aviadenovirus

Wild birds harbour a vast diversity of adenoviruses that remain uncharacterised with respect to their genome organisation and evolutionary relatedness within complex host ecosystems. Here, we characterise a novel adenovirus type within Aviadenovirus genus associated with severe necrotising hepatitis in a captive Timneh grey parrot, tentatively named as Timneh grey parrot adenovirus 1 (TpAdV-1). The TpAdV-1 genome is 39,867 bp and encodes 46 putative genes with seven hitherto not described ones. Comparative genomics and phylogenetic analyses revealed highest nucleotide identity with psittacine adenovirus 1 and psittacine adenovirus 4 that formed a discrete monophyletic clade within Aviadenovirus lineage suggesting a deep host co-divergent lineage within Psittaciformes hosts. Several recombination breakpoints were identified within the TpAdV-1 genome, which highlighted an ancient evolutionary relationship across the genera Aviadenovirus, Mastadenovirus and Atadenovirus. This study hints towards a host-adapted sub-lineage of avian adenovirus capable of having significant host virulence in Psittaciformes birds augmented with ecological opportunity.

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.

Attenuation and molecular characterization of fowl adenovirus 8b propagated in a bioreactor and its immunogenicity, efficacy, and virus shedding in broiler chickens

Background and Aim

Live-attenuated vaccines are the most successful type of vaccine and could be useful in controlling fowl adenovirus (FAdV) 8b infection. This study aimed to attenuate, molecularly characterize, and determine the immunogenicity, efficacy, and challenge virus shedding in broiler chickens.

Materials and Methods

The FAdV 8b isolate (UPM08136) was passaged onto chicken embryo liver (CEL) cells until attenuation. We sequenced and analyzed the hexon and fiber genes of the passage isolates. The attenuated bioreactor-passage isolate was inoculated into 1-day-old broiler chickens with (attenuated and inactivated) and without booster groups and challenged. Body weight (BW), liver weight (LW), liver: body weight ratio (LBR), FAdV antibody titers, T-lymphocyte subpopulation in the liver, spleen, and thymus, and challenge virus load and shedding were measured.

Results

Typical cytopathic effects with novel genetic changes on CEL cells were observed. The uninoculated control-challenged (UCC) group had significantly lower BW and higher LW and LBR than the inoculated groups. A significantly higher FAdV antibody titer was observed in the challenged non-booster and attenuated booster groups than in the UCC group. T cells in the spleen and thymus of the liver of inoculated chickens were higher than uninoculated control group levels at all-time points and at different times. A significantly higher FAdV challenge virus load was observed in the liver and shedding in the cloaca of UCC chickens than in non-booster chickens.

Conclusion

The FAdV 8b isolate was successfully attenuated, safe, and immunogenic. It reduces virus shedding and is effective and recommended as a vaccine against FAdV infection in broiler chickens.

Development of an ELISA for the detection of fowl adenovirus serotype -4 utilizing fiber protein

Hydropericardium syndrome (HPS), caused by the Fowl adenovirus 4 (FAdV-4) has led to significant financial losses for the poultry industry globally, including Pakistan over the past few years. Conventional serological methods are time consuming, laborious and less sensitive therefore, a rapid and sensitive ELISA kit is required for the reliable detection of FAdV-4 infection. In the current research, fiber proteins (1 &2) of FAdV-4 were successfully expressed in Escherichia coli and purified using metal affinity chromatography. Using these proteins as antigens, an indirect ELISA for detecting FAdV-4 infection was developed. The developed ELISA showed superior performances upon comparison with Serum neutralization test (SNT). This ELISA also showed reliable detection of FAdV specific antibodies in experimentally infected and vaccinated chickens. This assay produced good correlation on the samples collected from the field with SNT and found essential for large scale serology of the FAdV. No cross reactivity was observed in the ELISA following the testing of the serum samples of different other avian pathogens which showed that this ELISA is specific in detecting the FAdV infection. In conclusion, the developed Fiber protein ELISA is highly sensitive and specific in the detecting the FAdV infection and can be utilized for large scale sero-epidemiology of the disease.

Efficacy, immunogenicity, and virus shedding in broiler chickens inoculated with live attenuated fowl adenovirus serotype 8b propagated a bioreactor

Background

Fowl adenovirus (FAdV) 8b causes huge economic losses in the poultry industry worldwide. Attenuated FAdV 8b could be useful in preventing FAdV infections globally and scale-up obstacles could be solved by bioreactor technology.

Aim

This study was carried out to attenuate the FAdV 8b isolate, propagate it in a bioreactor, molecularly characterize the passage isolates, and determine the immunogenicity, efficacy, and shedding of the virus of chickens.

Methods

FAdV serotype 8b (UPM11142) isolate was passaged on chicken embryo liver (CEL) cells until attenuation and propagated in a bioreactor (UPM11142P20B1). Hexon and fiber genes of the isolates were sequenced and analyzed. UPM11142P20B1 was administered to 116-day-old broiler chickens divided into four groups, A (control), B (non-booster), C (booster with UPM11142P20B1), and D (booster with inactivated UPM11142P5B1). Eight chickens from each group were challenged. Body weight (BW) and liver weight (LW), liver: BW ratio (LBR), FAdV antibody titer, T lymphocyte sub-populations in the liver, spleen and thymus; and challenge virus load in the liver and shedding in cloaca were measured at weekly intervals.

Results

The isolate caused typical cytopathic effects on CEL cells typical of FAdV. Novel molecular changes in the genes occurred which could be markers for FAdV 8b attenuation. BW, LW, and LBR were similar among groups throughout the trial but the uninoculated control-challenged group (UCC) had significantly higher LBR than the inoculated and challenged groups at 35 dpi. Non-booster group had higher FAdV antibodies at all time points than the uninoculated control group (UCG); and the challenged booster groups had higher titer at 35 dpi than UCC. T lymphocytes increased at different time-points in the liver of inoculated chickens, and in the spleen and thymus as well, and was higher in the organs of inoculated challenged groups than the UCC. There was a significantly higher challenge virus load in the liver and cloaca of UCC chickens than in the non-booster chickens.

Conclusion

UPM11142P20B1 was safe, efficacious, significantly reduced shedding, and is recommended as a candidate vaccine in the prevention and control of FAdV 8b infections in broiler chickens.

The detection of fowl adenovirus in chickens with hydropericardium syndrome in Isfahan and Charmahal-Va-Bakhtiyari provinces, Iran

The Ascite and hydropericardium is most common in Isfahan and Chcharmahal-va-Bakhtiyari, Iran. For this, the study was achieved for investigation of AV role in induction of Ascite or hydropericardium in these regions. In this study, 20 broiler flocks suspected to Ascite and hydrpericardium were sampled from hydropericardium fluid. Then, DNA was extracted and amplified by specific primers. The amplified fragment for detection of AV was 896 bp. The results showed that 10 from 20 flocks, and 47 from 200 samples were positive to AV. The results revealed, the most of infected flocks were higher than 30 days old. In this study, the correlation between infectivity to AV and growing system were not significant. The infectivity rate in Isfahan and Chaharmahal-va-Bakhtiyari was not significant. Therefore, in addition to high altitude, AV infection can play a role in increasing the prevalence of hydropericardium syndrom in these areas.

Design and Identification of a Novel Antiviral Affinity Peptide against Fowl Adenovirus Serotype 4 (FAdV-4) by Targeting Fiber2 Protein

Outbreaks of hydropericardium hepatitis syndrome caused by fowl adenovirus serotype 4 (FAdV-4) with a novel genotype have been reported in China since 2015, with significant economic losses to the poultry industry. Fiber2 is one of the important structural proteins on FAdV-4 virions. In this study, the C-terminal knob domain of the FAdV-4 Fiber2 protein was expressed and purified, and its trimer structure (PDB ID: 7W83) was determined for the first time. A series of affinity peptides targeting the knob domain of the Fiber2 protein were designed and synthesized on the basis of the crystal structure using computer virtual screening technology. A total of eight peptides were screened using an immunoperoxidase monolayer assay and RT-qPCR, and they exhibited strong binding affinities to the knob domain of the FAdV-4 Fiber2 protein in a surface plasmon resonance assay. Treatment with peptide number 15 (P15; WWHEKE) at different concentrations (10, 25, and 50 μM) significantly reduced the expression level of the Fiber2 protein and the viral titer during FAdV-4 infection. P15 was found to be an optimal peptide with antiviral activity against FAdV-4 in vitro with no cytotoxic effect on LMH cells up to 200 μM. This study led to the identification of a class of affinity peptides designed using computer virtual screening technology that targeted the knob domain of the FAdV-4 Fiber2 protein and may be developed as a novel potential and effective antiviral strategy in the prevention and control of FAdV-4.

An Inactivated Novel Trivalent Vaccine Provides Complete Protection against FAdV-4 Causing Hepatitis-Hydropericardium Syndrome and FAdV-8b/-11 Causing Inclusion Body Hepatitis

Outbreaks of hepatitis-hydropericardium syndrome (HHS) caused by fowl adenovirus serotype 4 (FAdV-4) and inclusion body hepatitis (IBH) related to FAdV-8b and FAdV-11 have been increased in chickens in China since 2015. Clinical concurrent infections of FAdV-4, FAdV-8b, and FAdV-11 are quite common, yet there are no commercially available trivalent vaccines against infection by these three serotypes. In our previous study, a bivalent vaccine based on a recombinant FAdV-4, of which fiber-1 was replaced with the fiber of FAdV-8b, has been developed. In this study, a novel recombinant rFAdV-4-fiber/8b + 11 was constructed by inserting FAdV-11 fiber gene into the 1966-bp deletion region of rFAdV-4-fiber/8b genome. The in vitro replication ability of the rFAdV-4-fiber/8b + 11 was similar to the parental FAdV-4. One dose immunization with the inactivated rFAdV-4-fiber/8b + 11 vaccine generated robust immune responses against FAdV-4, FAdV-8b, and FAdV-11, and provided efficient clinical protection against FAdV-4, FAdV-8b, and FAdV-11 challenge. This study provides a novel strategy for developing potential trivalent vaccines for the prevention and control of HHS and IBH.

Molecular phylodynamics of fowl adenovirus serotype 11 and 8b from inclusion body hepatitis outbreaks

Fowl adenovirus (FAdV) serotypes are involved in a variety of clinical manifestations in poultry and has resulted in substantial economic loss to the poultry farmers. Despite the endemicity of Inclusion body hepatitis (IBH) in South Asian countries, including India, its etiology is not well studied. In western India, the rural poultry flocks obtained from the vaccinated parents were experiencing disease outbreaks with substantial economic losses due to heavy outbreaks and mortality. Therefore, the study was conducted to decipher the molecular epidemiology of the FAdV from field outbreaks in western India. A total of 37 commercial broiler poultry flocks and 29 village poultry flocks of western India were visited during 2019 to 2021. Out of these, 19.14% flocks showed incidence of IBH during the age of 15 to 35 days. The mortality ranged from 3.3 percent to 55.28 percent. The samples were subjected for amplification of partial hexon gene covering loop 1 and loop 2. The results revealed 48.28% positivity by PCR. The sequence analysis identified 14 isolates as species D serotype 11 with 0.97 to 0.99% divergence and two as species E serotype 8b with 0.99% divergence. The FAdV-11 isolates showed amino acid substitutions D195N, T399A, N417S, and N496H. The amino acids I188 and N195 were conserved in FAdV-11. The molecular clock in Bayesian methods was used to determine most common ancestor. The isolates MH379249 and MH379248 were determined the most recent common ancestor for FAdV-11 and FAdV-8b isolates. The analysis suggested evolution of 10 FAdV-11 strains in 2012, and four FAdV-11 strains and two FAdV-8b strains in 2018.

Fiber-1 of serotype 4 fowl adenovirus mediates superinfection resistance against serotype 8b fowl adenovirus

In recent years, hepatitis-hydropericardium syndrome (HHS) and inclusion body hepatitis (IBH) caused by serotype 4 fowl adenovirus (FAdV-4) and serotype 8b fowl adenovirus (FAdV-8b), respectively, are widely prevalent in China, causing huge economic losses to the poultry industry. Numerous studies have revealed the mechanism of the infection and pathogenesis of FAdV-4. However, little is known about the mechanism of infection with FAdV-8b. Among the major structural proteins of fowl adenoviruses, fiber is characterized by the ability to recognize and bind to cellular receptors to mediate the infection of host cells. In this study, through superinfection resistance analysis and an interfering assay, we found that Fiber-1 of FAdV-4, rather than hexon, penton, and fiber of FAdV-8b, conferred efficient superinfection resistance against the infection FAdV-8b in LMH cells. Moreover, truncation analysis depicted that the shaft and knob domains of FAdV-4 Fiber-1 were responsible for the inhibition. However, knockout of the coxsackie and adenovirus receptor (CAR) in LMH cells inhibited the replication of FAdV-8b only at early time points, indicating that CAR might not be the key cell receptor for FAdV-8b. Overall, our findings give novel insights into the infection mechanism of FAdV-8b and provide a new target for the prevention and control of both FAdV-4 and FAdV-8b.

Efficacy, humoral, and cell-mediated immune response of inactivated fowl adenovirus 8b propagated in chicken embryo liver cells using bioreactor in broiler chickens

Background and Aim

Fowl adenovirus (FAdV) 8b causes inclusion body hepatitis, resulting in major economic losses globally among chickens. The objectives were to inactivate FAdV 8b isolate propagated in chicken embryo liver (CEL) cells using a stirred tank bioreactor (UPM08136P5B1) and determine the humoral and cell-mediated immune response, efficacy, and virus shedding in broiler chickens.

Materials and Methods

The FAdV 8b isolate UPM08136P5B1 was inactivated using binary ethyleneimine, adjuvanted with Montanide 71VG, inoculated into day-old broiler chickens in a booster group (BG) and non-booster group (NBG), and challenged with a pathogenic FAdV 8b strain. Clinical signs, gross lesions, body weight (BW), liver: body weight ratio, FAdV antibody titer using enzyme-linked immunosorbent assay, and histopathological changes were recorded. The CD3+, CD4+, and CD8+ T-lymphocyte profiles of the liver, spleen, and thymus using flow cytometry, and viral load in liver and cloacal shedding using quantitative polymerase chain reaction were evaluated.

Results

Chickens in the challenged control group (CCG) exhibited mild clinical signs, gross lesions, and histopathological changes, which were absent in the inoculated groups, and had lower BW and higher liver BW ratio than chickens in the unchallenged control group (UCG); BG and NBG on 35- and 42-days post-inoculation (DPI). Chickens in NBG and BG had higher antibodies than UCG on 7, 21, 35, and 42 DPI. The challenged BG and NBG produced higher antibodies than the CCG on 35 DPI. T-lymphocytes were higher among the inoculated groups than UCG in the liver, spleen, and thymus. Inoculated challenged groups recorded higher CD3+, CD4+, and CD8+ T-lymphocytes on 35 and 42 DPI than CCG. The challenged control group had a significantly higher viral load in the liver than challenged that in BG on 35 DPI and BG and NBG on 42 DPI. The challenged control group had significantly higher challenge FAdV shedding than challenged inoculated groups on 35 and NBG on 42 DPI.

Conclusion

UPM08136P5B1 was successfully inactivated and mixed with Montanide 71VG. The inactivated vaccine candidate that induced humoral and cellular immunity was effective, reduced FAdV load in the liver, and shedding in the cloaca, and could be useful against FAdV 8b infections in chickens.

Epidemiology, pathology, prevention, and control strategies of inclusion body hepatitis and hepatitis-hydropericardium syndrome in poultry: A comprehensive review

Infection with fowl adenoviruses (FAdVs) can result in a number of syndromes in the production of chicken, including inclusion body hepatitis (IBH), hepatitis-hydropericardium syndrome (HHS), and others, causing enormous economic losses around the globe. FAdVs are divided into 12 serotypes and five species (A-E; 1-8a and 8b-11). Most avian species are prone to infection due to the widespread distribution of FAdV strains. The genus aviadenovirus, which is a member of the adenoviridae family, is responsible for both IBH and HHS. The most popular types of transmission are mechanical, vertical, and horizontal. Hepatitis with basophilic intranuclear inclusion bodies distinguishes IBH, but the buildup of translucent or straw-colored fluid in the pericardial sac distinguishes HHS. IBH and HHS require a confirmatory diagnosis because their clinical symptoms and postmortem abnormalities are not unique to those conditions. Under a microscope, the presence of particular lesions and inclusion bodies may provide clues. Traditional virus isolation in avian tissue culture is more delicate than in avian embryonated eggs. Additionally, aviadenovirus may now be quickly and precisely detected using molecular diagnostic tools. Preventive techniques should rely on efficient biosecurity controls and immunize breeders prior to production in order to protect progeny. This current review gives a general overview of the current local and global scenario of IBH, and HHS brought on by FAdVs and covers both their issues and preventative vaccination methods.

An inactivated novel chimeric FAdV-4 containing fiber of FAdV-8b provides full protection against hepatitis-hydropericardium syndrome and inclusion body hepatitis

Fowl adenovirus serotype 4 (FAdV-4) and FAdV-8b are causative agents of hepatitis-hydropericardium syndrome (HHS) and inclusion body hepatitis (IBH), respectively. HHS and IBH co-infections were often reported in clinical, yet there are no commercially available bivalent vaccines for prevention and control of both FAdV-4 and -8b. In the present study, a chimeric FAdV-4 was firstly generated by substituting fiber-1 of FAdV-4 with fiber of FAdV-8b. The chimeric virus, rFAdV-4-fiber/8b, exhibited similar replication ability in vitro and pathogenicity in vivo to the parental wild type FAdV-4. A single dosage of vaccination with the inactivated rFAdV-4-fiber/8b induced high antibody titers against fiber-2 of FAdV-4 and fiber of FAdV-8b and provided full protection against FAdV-4 and -8b challenge. These results demonstrated that fiber of FAdV-8b could replace the role of fiber-1 of FAdV-4 in the process of viral infection, and rFAdV-4-fiber/8b could be used to make a potential bivalent vaccine for the control and prevention of HHS and IBH.

Genetic evolution of fowl adenovirus serotype 4 and its pathogenicity to Cherry Valley ducks in China

Hydropericardium hepatitis syndrome (HHS), a novel poultry disease, is caused by fowl adenovirus 4 (FAdV-4). It mainly infects 3-5-week-old broilers. In July 2015, the first outbreak of HHS occurred in the broilers in east China, which caused great economic losses to the poultry industry. In June 2019, infectious disease was detected with suspected HHS symptoms on a duck farm in Linyi City, Shandong Province. The main necropsy lesions included pericardial effusion and hepatitis. In this study, we isolated a strain of FAdV-4 from naturally infected ducks and named it SDLY190604, and the hexon gene sequence was amplified and analyzed using polymerase chain reaction (PCR). In order to study the effect of FAdV-4 on Cherry Valley ducks, we inoculated three-week-old ducks with 0.2 ml of FAdV-4 virus fluid (TCID₅₀ of 10^-6.3/0.1 ml) by orally, subcutaneously and intramuscularly. Clinical signs, gross lesions and histopathological changes, cytokines and viral load were detected and recorded within 15 days after infection. The results showed that ducks in the experimental groups exhibited typical symptoms of hydropericardium and hepatitis. The histopathological sections showed multiple-organ damage, including serious liver and kidney damage with elevated levels of inflammatory cytokines, probably due to the infection and innate immune response. Later, immunosuppression occurred, resulting in decreased levels of cytokines. The viral load indicated that the virus could be present in several organs of the ducks, with the highest viral DNA found in the liver, followed by the kidney. Compared to the subcutaneous and oral groups, the intramuscular group exhibited the highest viral load. In summary, this study can increase our understanding of the pathogenicity of FAdV-4 in ducks and provide a basis for further understanding of the virus, imparting new insights into disease research.

Complete Genome Analysis and Animal Model Development of Fowl Adenovirus 8b

Inclusion body hepatitis (IBH), hydropericardium syndrome, and gizzard erosion associated with fowl adenovirus (FAdV) infection have caused notable economic losses worldwide. In 2020, severe IBH was observed in a layer chicken farm in Hebei Province, China. Liver samples were collected from layer chickens with severe IBH and virus isolation was performed in LMH cells. DNA sequence and bioinformatics analyses were conducted to determine the phylogenetic relationship and the pathogenicity assay was conducted in specific-pathogen-free (SPF) chickens. HeB20 strain was isolated and identified as FAdV-8b, and the complete genome was successfully sequenced (GenBank No. OK188966). Although widespread recombination in clinical strains has been reported within FAdVs, HeB20 showed some novel characteristics, and did not show any recombination, highlighting that recombinant and non-recombinant FAdV-8b coexist in the clinic poultry industry. Finally, pathogenicity animal model of HeB20 was developed and showed severe IBH and 10% mortality. Collectively, a new FAdV-8b strain (HeB20) was isolated and responsible for the severe IBH in layer chickens. Complete genome of HeB20 was sequenced and valuable for future epidemiological investigations. HeB20 was capable of inducing severe IBH and 10% mortality in SPF chickens; this animal model provides a powerful tool for the future vaccine development.

The first complete genome sequence and pathogenicity characterization of fowl adenovirus serotype 2 with inclusion body hepatitis and hydropericardium in China

Since 2015, fowl adenovirus (FAdV) has been frequently reported worldwide, causing serious economic losses to the poultry industry. In this study, a FAdV-2, namely GX01, was isolated from liver samples of chickens with hepatitis and hydropericardium in Guangxi Province, China. The complete genome sequence of GX01 was determined about 43,663 base pairs (bp) with 53% G+C content. To our knowledge, this is the first FAdV-2 complete genome in China. There was a deleting fragment in ORF25 gene. Phylogenetic analysis based on the hexon loop-1 gene showed that GX01 is most closely related to FAdV-2 strain 685. Pathogenicity experiment of GX01 in 3-day-old and 10-day-old specific-pathogen-free chickens showed that although no mortality was observed within 21 days post infection (dpi), strain GX01 significantly inhibited weight gain of infected chickens. Moreover, FAdV-2 was still detectable in the anal swabs of infected chickens at 21 dpi. Necropsy analysis showed that the main lesions were observed in liver, heart, and spleen. Of note, hepatitis and hydropericardium were observed in the infected chickens. In addition, massive necrosis of lymphocyte was observed in spleen of infected 3-days-old chickens. We concluded that FAdV-2 strain GX01 is capable of causing hepatitis and hydropericardium, which will make serious impact on the growth of chickens. Our research lays a foundation to investigate the molecular epidemiology and etiology of FAdV.

Hsp70 Inhibits the Replication of Fowl Adenovirus Serotype 4 by Suppressing Viral Hexon with the Assistance of DnaJC7

Fowl adenovirus serotype 4 (FAdV-4) infection results in serious hepatitis-hydropericardium syndrome (HHS) in broilers, which has caused great economic losses to the poultry industry; however, the specific host responses to FAdV-4 remain unknown. In this study, we identified 141 high-confidence protein-protein interactions (PPIs) between the main viral proteins (Hexon, Fiber 1, Fiber 2, and Penton bases) and host proteins via a liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay. We found that heat shock protein 70 (Hsp70), the protein with the highest score, and its cofactor DnaJ heat shock protein 40 family member C7 (DnaJC7) could negatively regulate the replication of FAdV-4. Furthermore, the nucleotide binding domain (NBD) of Hsp70 and the J domain of DnaJC7 were necessary for inhibiting FAdV-4 replication. We verified that DnaJC7 as a bridge could bind to Hsp70 and Hexon, assisting the indirect interaction between Hsp70 and Hexon. In addition, we found that FAdV-4 infection strongly induced the expression of autophagy proteins and cellular Hsp70 in a dose-dependent manner. Blockage of Hexon by Hsp70 overexpression was significantly reduced when the autophagy pathway was blocked by the specific inhibitor chloroquine (CQ). Our results showed that Hsp70 was co-opted by DnaJC7 to interact with viral Hexon and inhibited Hexon through the autophagy pathway, leading to a considerable restriction of FAdV-4 replication. IMPORTANCE FAdV-4, as the main cause of HHS, has quickly spread all over the world in recent years, seriously threatening the poultry industry. The aim of this study was to identify the important host proteins that have the potential to regulate the life cycle of FAdV-4. We found that Hsp70 and DnaJC7 played crucial roles in regulating the amount of viral Hexon and extracellular viral titers. Moreover, we demonstrated that Hsp70 interacted with viral Hexon with the assistance of DnaJC7, followed by suppressing Hexon protein through the autophagy pathway. These results provide new insight into the role of the molecular chaperone complex Hsp70-DnaJC7 in FAdV-4 infection and suggest a novel strategy for anti-FAdV-4 drug development by targeting the specific interactions among Hsp70, DnaJC7 and Hexon.

Necrotizing Salpingitis by Fowl Adenovirus in a Backyard Hen

A 3-yr-old Ameraucana hen was received for postmortem examination following a 1-day history of lethargy and death. Gross lesions observed during necropsy were limited to pulmonary congestion and a small clump of egg yolk material in the oviductal lumen. On histopathology, there was a necrotizing salpingitis of the infundibular and isthmus mucosa with amphophilic, intranuclear inclusion bodies in superficial epithelial cells. Transmission electron microscopy identified the intranuclear inclusions as aggregates of adenovirus virions. Fowl adenovirus (FAdV) type A was identified with PCR and sequencing. Although the cause of death was not determined in this case, this is the first report of FAdV type A-associated salpingitis in a hen.

First Detection and Identification of FAdV-8b as the Causative Agent of an Outbreak of Inclusion Body Hepatitis in a Commercial Broiler Farm in Greece

Inclusion body hepatitis (IBH) is an economically important disease of chickens, with a worldwide distribution, caused by Fowl Aviadenoviruses (FAdVs). Currently, the increased number of cases, the virulence of the isolate strains, as well as the lack of cross-species protection highlight that detailed in-field data are fundamental for the development of successful control strategies. This case report provides a detailed clinicopathological investigation of an unusual IBH outbreak in a commercial broiler farm in the region of Macedonia, Greece. The farm consisted of 64,000 birds, originated from the same breeder stock and placed in three different houses (Flock A–C). At 20 days of age, a sudden increase in daily mortality was recorded in Flock A. It is worth mentioning that, although all flocks were serologically (indirect ELISA) and molecularly (RT-PCR) positive for FAdV, the mortality rate, attributed to IBH, was much higher in Flock A compared to others. The clinical manifestation included non-specific symptoms such as depression, inappetence, yellowish mucoid diarrhea, and lack of uniformity. At necropsy, typically, enlarged, pale, and friable livers were dominant, while sporadically lesions were recorded in the pancreas, kidneys, skeletal muscles, and lymphoid organs. The histopathological examination of liver samples showed multifocal inflammation, necrosis, and the presence of basophilic/ eosinophilic inclusion bodies in hepatocytes. In addition, the loss of the architecture of pancreatic lobules and the presence of fibrosis and foci of mononuclear cell aggregates were suggestive of chronic pancreatic inflammation. PCR analysis confirmed the presence of FAdV, belonging to species E, serotype FAdV-8b. Performance and financial calculations revealed that IBH increased Feed Conversion Ratio (FCR), feed cost/chick as well as feed cost/kg live weight, whereas the Livability (%) and the European Production Efficiency Factor (EPEF) were decreased in the most severely affected flocks (Flock A). This study is the first report of the detection and identification of FAdV serotypes associated with IBH in commercial broiler flocks in Greece. However, there is still a lack of information about the circulating FAdV serotypes in the country, and therefore epidemiological studies are needed to establish control strategies for IBH.

Epidemiological and molecular analysis of circulating fowl adenoviruses and emerging of serotypes 1, 3, and 8b in Egypt

Fowl adenoviruses (FAdVs) are a large group of viruses of different serotypes. They are responsible for inclusion body hepatitis, adenoviral gizzard erosion, and hepatitis hydropericardium syndrome. The present study presents a comprehensive overview of FAdVs in Egypt, with a focus on the epidemiological features of virus serotypes across the country. We conducted molecular investigation of multiple FAdV species based on the genetic signature of hypervariable regions 1–4 in the loop1 (L1) region of the hexon gene. Epidemiologically, the Nile Delta governorates showed high positivity of FAdVs, which were more commonly found in broilers than in layers. Genetically, species D and serotype 8a/E dominated, and the findings also revealed the emergence of new FAdV serotypes 1, 3, and 8b. The comparative analysis of hypervariable regions in the L1 region of the hexon gene revealed variables specific to each virus serotype. In silico predictions of L1 region revealed variations in the molecular structure and predicted the antigenic epitopes which may affect the cross-antigenicity between the different FAdV species and serotypes.

Isolation and molecular characterization of fowl adenovirus and avian reovirus from breeder chickens in Japan in 2019-2021

Fowl adenoviruses (FAdVs) and avian reoviruses (ARVs) are ubiquitous in poultry farms and most of them are not pathogenic, often cause damage to chicks. A total of 104 chicken fecal samples were collected from 7 farms of breeder chickens (layers and broilers) in Japan from 2019 to 2021, and yielded 26 FAdV plus 14 ARV isolates. By sequencing, FAdV isolates were classified as FAdV-1, 5 and 8b. ARV isolates were classified as genotype II, IV and V. These results suggest that FAdVs and ARVs are resident in the breeder chicken farms in Japan.

Pathogenicity of field strain of fowl aviadenovirus serotype 11 isolated from chickens with inclusion body hepatitis in Morocco

Outbreaks of inclusion body hepatitis have emerged in Morocco since 2013 and has resulted in significant economic losses to poultry farms. Three isolates of the causative virus, Fowl adenonovirus (FAdV)were characterized from chickens with IBH, but their pathogenicity has never been investigated. In this work, the pathogenicity of an isolate FAdV 11 (MOR300315 strain) was evaluated by inoculating a group of 40 SPF chickens at 3 days of age by oral route. A group of 40 chicks injected with phosphate-buffered saline solution was used as a control group. The infected chickens showed decreased weight gain from 3dpi. Necropsy displayed pallor and enlargement in liver, swelling and slight hemorrhage in kidney and spleen at 6 dpi. Histopathological changes were mainly characterized by severe and extensive hepatic necrosis associated with the presence of basophilic intra-nuclear inclusion bodies within hepatocytes. The FAdV was reisolated in chicken embryo fibroblast cell culture from liver tissue homogenate of infected chicken from 3 to 6 dpi. Viral DNA was detected by PCR in liver, kidney, spleen and cloacal swabs from 3 to 13 dpi. Antibody response against inoculated FAdV was appeared from 9 dpi. These results confirmed that the FAdV 11 strain is pathogenic in chicken. This study is the first experimental infection of FAdV 11 in chicken in Morocco, which increase our understanding of its pathogenicity in chickens and indicate that preventive measures against FAdV infection in poultry farms should be implemented in Morocco.

Characterization of Co-infection With Fowl Adenovirus Serotype 4 and 8a

Fowl adenoviruses (FAdVs), which are distributed worldwide, have caused considerable economic losses to poultry farms. Co-infection with FAdVs and other avian pathogens has been reported previously. However, the pathogenicity of different serotypes of FAdVs causing co-infection remains unclear. Herein, strain HN from FAdV species C serotype 4 (FAdV-4) and strain AH720 from species E serotype 8a (FAdV-8a) were used to assess the pathogenicity of their co-infection in specific-pathogen-free (SPF) chickens. Compared with chickens infected with FAdV-4 alone, those co-infected with FAdV-4 and FAdV-8a showed similar clinical symptoms, mortality rates and degree of tissue lesions, and notably decreased viral loads of HN. Conversely, the viral loads of AH720 increased markedly in the co-infection group compared with that in chickens infected with AH720 strain alone. Increased viral loads of AH720 in the liver were suspected to contribute to the pathogenicity of chickens co-infected with the HN and AH720 strains. This was further investigated by histopathology and terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining analyses. Collectively, these data indicated that co-infection with FAdV-4 and FAdV-8a suppresses the replication and proliferation of FAdV-4 but enhances the replication and proliferation of FAdV-8a in chicken liver. This study will provide valuable information for the further investigation of the interactions between FAdV-4 and FAdV-8a during co-infection.

Molecular detection of fowl adenovirus 7 from slaughtered broiler chickens in Iran: the first report

Background

Fowl adenoviruses (FAdVs) are responsible for a variety of clinical symptoms, with an increasing significance in the poultry industry throughout the world. Typical diseases caused by FAdVs include inclusion body hepatitis (IBH), hepatitis-hydropericardium syndrome (HHS), gizzard erosion (GE), respiratory disease, and hemorrhage in muscles and organs.

Aims

During 2020, broiler chickens from the north of Iran showed ecchymotic and petechial hemorrhages in thigh and breast muscles at the slaughterhouse. Hemorrhages were observed in 10% to 60% (with an average of 20-30%) of chicks per flock. To find out the etiology of these lesions, the present study was conducted.

Methods

Different environmental factors were investigated, and FAdV, infectious bursal disease virus (IBDV), and chicken infectious anemia virus (CIAV) were detected using molecular assays.

Results

Among the viruses tested, FAdV was detected by polymerase chain reaction (PCR), and sequence analysis clustered the virus into species E, serotype 7.

Conclusion

This is the first report on FAdV-7 existence among poultry in Iran. Effective screening of the chicks at slaughtering age should be performed from the whole country.

Detection and Typing of a Fowl Adenovirus Type 1 Agent of Pancreatitis in Guinea Fowl

Adenoviral pancreatitis has been amply described for decades in guinea fowl. Although its pathologic picture has been characterized fairly well, its etiology still remains only partially clarified. Based on several outbreaks diagnosed on commercial guinea flocks raised in France since 2017, we performed direct whole-genome sequencing from pancreatic lesional tissue by using the Oxford Nanopore Technologies (ONT) sequencing method. We generated 4781 viral reads and assembled a whole genome of 43,509 bp, clustering within fowl adenovirus type 1 (FAdV-1). A phylogenetic analysis based on a partial sequence of the hexon and short fiber genes on viruses collected in France showed 98.7% and 99.8% nucleotide identity, respectively. Altogether, these results confirm that an FAdV-1 closely related to chicken and other avian strains is the agent of pancreatitis in guinea fowl. This study illustrates the potential of ONT sequencing method to achieve rapid whole-genome sequencing directly from pathologic material.

Fowl adenovirus strains 1/A and 11/D isolated from birds with reovirus infection

Inclusion body hepatitis (IBH) is, in some cases, a fatal disease affecting fowl by adenovirus strains which are subdivided into 5 species (A-E). In the current study, we investigated sequences from the Loop L1 region of the hexon gene of sequences of adenovirus field stains 1/A and 11/D isolated from a poultry flock co-infected with IBH and avian reoviruses ARVs. In early 2021, an epidemiologic survey highlighted the coinfection adenoviruses with other viruses (orthoreovirus infection) as being particularly deleterious within the poultry industry. Here, we investigated the Loop L1 HVR1-4 region of the hexon gene with relative synonymous codon usage (RSCU) designation and RSCU inclusive of all the mutations. These are the first results that have been presented on fowl adenovirus species A and D with simultaneous reovirus infection in 38-days old broiler chickens in Poland.

Transcriptome Analysis Reveals the Potential Role of Long Noncoding RNAs in Regulating Fowl Adenovirus Serotype 4-Induced Apoptosis in Leghorn Male Hepatocellular Cells

Hepatitis-hydropericardium syndrome (HHS) is caused by fowl adenovirus serotype 4 (FAdV-4) and has resulted in considerable economic losses to the poultry industry globally. FAdV-4 elicits apoptosis in host cells. Long noncoding RNAs (lncRNAs) have emerged as important regulatory RNAs with profound effects on various biological processes, including apoptosis. However, it remains unknown whether lncRNAs participate in FAdV-4-induced apoptosis. In this study, RNA sequencing was applied to determine the transcription of cellular lncRNA in leghorn male hepatocellular (LMH) cells infected with FAdV-4. Cellular RNA transcription analysis demonstrated that FAdV-4 infection elicited 1798 significantly differentially expressed (DE) lncRNAs in infected LMH cells at 24 h post-infection (hpi) compared to mock control infection. In addition, 2873 DE mRNAs were also found. Target prediction and analyses revealed that 775 DE lncRNAs whose 671 target mRNAs were among the DE mRNAs were involved in several signaling pathways, including the AMPK signaling pathway, p53 signaling pathway and insulin signaling pathway. From these 775 DE lncRNAs, we identified 71 DE lncRNAs related to apoptosis based on their target gene functions. Subsequently, lncRNA 54128 was selected from the 71 identified DE lncRNAs, and its role in FAdV-4-induced apoptosis was verified. LncRNA 54128 interference significantly suppressed the rate of apoptosis, which was accompanied by reduced BMP4 transcription levels. To the best of our knowledge, this is the first study to analyze host lncRNA transcription during FAdV-4 infection. Our findings provide a better understanding of host responses to FAdV-4 infection and provide new directions for understanding the potential association between lncRNAs and FAdV-4 pathogenesis.

Molecular typing and pathogenicity assessment of fowl adenovirus associated with inclusion body hepatitis in chicken from India

Recently, inclusion body hepatitis (IBH) outbreaks have been increasingly reported in different regions of India, particularly in broiler flocks. The present study was undertaken to characterize fowl adenovirus associated with IBH in chicken and assessment of its pathogenicity. Liver samples were collected from fowl adenovirus (FAdV) suspected 100 commercial broiler and six broiler breeder flocks from eleven different States of India from 2016 to 2019. All the samples were subjected to 897-bp FAdV hexon gene-specific PCR for confirmation and primary chicken liver cells were used to isolate the field FAdVs. Sequencing and phylogenetic analysis of 897-bp FAdV hexon gene revealed that all the isolates have showed close evolutionary relationship with fowl adenovirus serotype 11 of species D. For pathogenicity assessment, 0.5 ml of 10^6.5 TCID₅₀/ml of field FAdV serotype 11 isolate was orally inoculated in 1-day-old SPF chicks and observed for 21 days. This experimental study revealed that there was no mortality in infected chicks and showed clinical signs of dullness, depression and diarrhoea between third and fifth day of oral inoculation. The FAdV was reisolated and confirmed by PCR from experimentally infected chicken. Based on this study, among all serotypes, FAdV serotype 11 is involved in pathogenesis of inclusion body hepatitis in broiler-type chickens in India.

Emergence of fowl aviadenovirus C-4 in a backyard chicken flock in California

Fowl aviadenovirus (FAdV) species D and E are associated with inclusion body hepatitis (IBH); species C, serotype 4 (hereafter, FAdV4) is associated with hepatitis-hydropericardium syndrome (HHS) in young chickens. Outbreaks of HHS have led to significant losses in the poultry industry in several countries, predominantly in China. In April 2020, FAdV4 was detected in a remote backyard flock in California. In a mixed flock of chickens of various breeds and ages (6 mo to 2 y old), 7 of 30 were found dead within a week without premonitory signs. One additional bird died after the flock was relocated to fresh pasture, bringing the total mortality to 8 of 30 (27%). Postmortem examination of 3 birds revealed good body condition scores and active laying. One chicken had subtle hemorrhages throughout the liver, and the other 2 had diffusely dark mahogany livers. On histopathology, 2 chickens had hepatic necrosis with hepatocytes containing large, mostly basophilic, intranuclear inclusion bodies, identified by electron microscopy as 82.2-nm diameter adenoviral particles. Virus isolation and genomic sequencing performed on a liver sample revealed strains with 99.9% homology to FAdV4 isolates reported from China. To our knowledge, FAdV4 has not been reported in the United States to date. Furthermore, the chickens affected here were all adults and exhibited a variation of serotype 4 disease in which IBH was present but not hydropericardium.

Age-dependence of hypervirulent fowl adenovirus type 4 pathogenicity in specific-pathogen-free chickens

Hypervirulent fowl adenovirus serotype 4 (hvFAdV-4) has emerged as a major pathogen of hepatitis-hydropericardium syndrome (HHS) with increased mortality in chickens, resulting in economic losses to the Chinese poultry industry since June 2015. Here, we isolated a hypervirulent FAdV-4 (hvFAdV-4) strain (designated GD616) from 25-day-old meat-type chickens with severe HHS in Guangdong Province China in June 2017. The whole genome of the strain GD616 shares high homology with those in the recently-reported hvFAdV-4 isolates in China, with natural deletions of ORF19 and ORF27. A comparative analysis of Hexon and Fiber-2 proteins revealed that 2 unique amino acid residues at positions 378 and 453 of the Fiber-2 protein might be associated with virulence due to their occurrences in all the hvFAdV-4 isolates only. To systemically evaluate the effect of age on the susceptibility of chickens to hvFAdV-4, we used this hvFAdV-4 strain to intramuscularly inoculate 7- to 180-day-old specific-pathogen-free chickens for the evaluation of pathogenicity. These results showed that the pathogenicity of the hvFAdV-4 strain GD616 to chickens exhibited age-relatedness, with younger than 59-day-old chickens showing 100% morbidity and mortality, while 180-day-old chickens still exhibited a hydropericardium syndrome-like clinicopathology with 60% morbidity and 20% mortality. These findings enrich the current available knowledge regarding the pathogenicity of the hypervirulent FAdV-4 virus in chickens with a wide range of ages, which assists with the selection of suitable-aged chickens for the evaluation of hvFAdV-4 vaccines.

An efficient peptide-based ELISA for differentiating fowl adenovirus 4-infected chickens from vaccinated chickens

Fowl adenovirus serotype 4 (FAdV4), the causative agent of hepatitis-hydropericardium syndrome (HPS), has caused major economic losses to the poultry industry worldwide. Although inactivated vaccines have been deployed widely against FAdV4, a DIVA (differentiating infected from vaccinated animals) test specific for FAdV4 has not been available. We synthesized an immunogenic peptide, corresponding to regions 66-88 aa of the 22K nonstructural protein of FAdV4, and used the peptide as coating antigen to develop an indirect ELISA for a DIVA test specific to FAdV4. Specificity analysis showed that the ELISA only reacted with sera against FAdV4, and not with sera against other pathogens tested. Moreover, the ELISA could effectively differentiate FAdV4-infected chickens from vaccinated chickens. In a test of sera from experimentally infected chickens, the ELISA had 95% and 85% concordance with an indirect immunofluorescence assay (indirect IFA) and a commercial ELISA, respectively, and the concordance was 80.5% between the ELISA and the indirect IFA in detecting clinical infection samples. Our peptide-based ELISA provides an efficient DIVA test for FAdV4 in clinical samples.

Fowl adenovirus (FAdV) fiber-based vaccine against inclusion body hepatitis (IBH) provides type-specific protection guided by humoral immunity and regulation of B and T cell response

A recombinant fowl adenovirus (FAdV) fiber protein, derived from a FAdV-8a strain, was tested for its efficacy to protect chickens against inclusion body hepatitis (IBH). FAdV-E field isolates belonging to both a homotypic (FAdV-8a) and heterotypic (-8b) serotype were used as challenge. Mechanisms underlying fiber-induced protective immunity were investigated by fiber-based ELISA, virus neutralization assays and flow cytometry of peripheral blood mononuclear cells, monitoring the temporal developments of humoral and cellular responses after vaccination and challenge exposure. Birds were clinically protected from the homologous challenge and showed a significant reduction of viral load in investigated target organs, whereas fiber-based immunity failed to counteract the heterologous serotype infection. These findings were supported in vitro by the strictly type-specific neutralizing activity of fiber immune sera. In protected birds, fiber vaccination prevented a post-challenge drop of peripheral B cells in blood. Furthermore, fiber immunization stimulated CD4⁺ T lymphocyte proliferation while moderating the CD8α⁺ T cell response and prevented challenge-induced changes in systemic monocytes/macrophages and γδ⁺ T cell subpopulations. Both vaccinated and adjuvant-only injected birds experienced a priming of systemic B cells and TCRγδ⁺ T lymphocytes, which masked possible pre-challenge effects due to the antigen. In conclusion, within FAdV-E, recombinant fiber represents a vaccine candidate to control the adverse effects of homotypic infection by eliciting an effective humoral immunity and regulating B and T cell response, whereas the failure of heterotypic protection suggests a primordial role of humoral immunity for this vaccine.

Genetic Characterization and Pathogenicity Analysis of Recently Isolated Fowl Adenovirus 8b in Korea

A Korean field strain of fowl adenovirus (FAdV) 8b was isolated from chickens showing high mortality. Isolated FAdV-8b strains with the hexon and fiber genes were genetically analyzed. The Korean FAdV-8b (K194/19) strain isolated in 2019 showed higher sequence identity with the FAdV-8b strain isolated in China but lower sequence identity with the Korean FAdV-8b (K187/08) strain isolated in 2008. The K194/19 strain formed a distinct subcluster within the FAdV-8b cluster in a phylogenetic tree based on hexon and fiber genes. FAdV can infect day-old chicks through vertical transmission, and so blood samples were obtained from 54-, 60-, and 63-wk-old parent chickens. FAdV-specific antibody levels were investigated with ELISA and virus neutralization (VN) tests with the K194/19 and K187/08 strains as antigens. In VN tests, all sera neutralized the K187/08 strain. However, the K194/19 strain was neutralized by sera collected from 60- and 63-wk-old chickens but not sera obtained from 54-wk-old chickens, indicating natural infection. Finally, to determine the pathogenicity of the K194/19 strain, 1-day-old and 4-wk-old specific-pathogen-free birds were infected with the K194/19 and K187/08 strains. No significant difference in pathogenicity was observed between the two strains. Although the K194/19 strain showed similar pathogenicity with the K187/08 strain, differences in nucleotide and amino acid sequences of the hexon and fiber genes may determine the evasion ability of the K187/08 neutralizing antibody, indicating the need for development of a novel FAdV vaccine.

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

Background and Aim:

Fowl avidenoviruses (FAdVs) are generally considered ubiquitous, but certain serotypes and strains are known to be associated with primary diseases, such as inclusion body hepatitis (IBH). Since 2018, the outbreak of IBH has been reported in part provinces of Indonesia. This study aimed to isolate and molecularly characterize the FAdV from Banten and West Java Provinces of Indonesia and described the phylogenetic relationship with the FAdV that has been characterized in other countries.

Materials and Methods:

A total of 25 FAdV archive samples have been collected from January to August 2019 from clinical cases of FAdV infection in Banten and West Java Provinces, Indonesia. Collected samples were inoculated in 10-day-old specific-pathogenic-free chicken embryonated eggs. Hexon gene of FAdV was detected using polymerase chain reaction (PCR) with a primer set from previous study. To gain a better understanding of the FAdV genetic properties and construct the phylogeny tree, the PCR products were sequenced and subjected to a BLAST search and inferred using the neighbor-joining method by bootstrap test 1000×.

Results:

FAdV-D and FAdV-E are present in Banten, Indonesia. The phylogenetic analysis of 850 nucleotides that encode 289 amino acid of the partial hexon gene shows that the isolates Broiler/MSL/Ciputat-149/18, Broiler/MSL/Lebak-151/18, and Broiler/MSL/Ciputat-29/19 have 100% homology with FAdV-E TR/BVKE/R/D-1 from Turkey, whereas the isolates Layer/MSL/Ciputat-20/19 and Broiler/MSL/Ciputat-30/19 have 100% homology with FAdV-D strain 685 from Canada.

Conclusion:

The present study provides updates of the circulating FAdV in commercial poultry flocks in Banten and West Java Provinces, Indonesia. Since the FAdV vaccine was unavailable in Indonesia, this result might be used as guidance to select a proper FAdV vaccine strain. Our result indicates that at least two FAdV species were circulating among poultry in Banten and West Java Provinces, Indonesia; they are FAdV-D and FAdV-E.

Fiber-1, Not Fiber-2, Directly Mediates the Infection of the Pathogenic Serotype 4 Fowl Adenovirus via Its Shaft and Knob Domains

Recently, the disease of hepatitis-hydropericardium syndrome (HPS) caused by serotype 4 fowl adenovirus (FAdV-4) has spread widely and resulted in huge economic losses to the poultry industry. Although the genome of FAdV-4 has two fiber genes (fiber-1 and fiber-2), the exact role of the genes in the infection of FAdV-4 is barely known. In this study, through superinfection resistance analysis and an interfering assay, we found that fiber-1, but not fiber-2, was the key factor for directly triggering the infection of FAdV-4. The truncation analysis further revealed that both of the shaft and knob domains of fiber-1 were required for the infection. Moreover, the sera against the knob domain were able to block FAdV-4 infection, and the knob-containing fusion protein provided efficient protection against the lethal challenge of FAdV-4 in chickens. All the data demonstrated the significant roles of fiber-1 and its knob domain in directly mediating the infection of FAdV-4, which established a foundation for identifying the receptor of FAdV-4 and developing efficient vaccines against FAdV-4.IMPORTANCE Among 12 serotypes of fowl adenovirus (FAdV), FAdV-1, FAdV-4, and FAdV-10 all carry two fiber genes (i.e., fiber-1 and fiber-2), whereas other serotypes have only one. As important viral surface proteins, the fibers play vital roles in the infection and pathogenesis of FAdV. However, the importance of the fibers to the infection and pathogenesis of FAdV may be different from each other. Recent studies reveal that fiber-2 is identified as a determinant of virulence, but which fiber triggers the infection of FAdV-4 remains unknown. In this study, fiber-1 was identified as a key factor for directly mediating the infection of FAdV-4 through its shaft and knob domains, whereas fiber-2 did not play a role in triggering FAdV-4 infection. The results suggest that fiber-1 and its knob domain may serve as a target for identifying the receptor of FAdV-4 and developing efficient drugs or vaccines against FAdV-4.

Epizootiology, Clinical Signs, and Phylogenetic Analysis of Fowl Adenovirus in Chicken Farms in Indonesia from 2018 to 2019

Fowl adenovirus (FAdV) infection is an emerging problem in the world poultry industry, especially in broilers, as the causal agent of inclusion body hepatitis or hepatitis-hydropericardium syndrome. From December 2017 to January 2019, we recorded 116 cases of suspected hepatitis-hydropericardium syndrome in chicken farms throughout Indonesia. Necropsy was done on each farm site with three to five freshly dead birds per farm. Tissue samples were collected in virus transport medium and frozen at -20 C. The virus was cultivated in 9-day-old fertilized specific-pathogenic-free chicken eggs. FAdV was detected using polymerase chain reaction with a published primer set. The polymerase chain reaction products were sequenced and subjected to a BLAST search. The phylogeny was inferred using the neighbor-joining method and tested using the bootstrap test. FadV-D and -E are present in Indonesia and confirmed in 40 of 116 suspected cases. The affected chicken ages were 27.27 ± 8.94 days. Most affected farms were raising broiler chickens. The only typical clinical sign was unusual daily mortality of >1%, while the three most frequent pathologic lesions were swelling and hemorrhage of kidney and liver, as well as hydropericardium. To reduce economic loss, a vaccine should be developed immediately.

Characterisation of Fowl Adenovirus (FAdV-8b) Strain Concerning the Geographic Analysis and Pathological Lesions Associated with Inclusion Body Hepatitis in Broiler Flocks in Turkey

Introduction

Fowl adenovirus can cause important diseases in chickens such as inclusion body hepatitis, hepatitis hydropericardium syndrome, and gizzard erosion and ulceration. Inclusion body hepatitis has been regularly reported from many countries. This is the first case report from Turkey, describing an outbreak of inclusion body hepatitis in broiler farms due to fowl adenovirus-8b (FAdV-8b).

Material and Methods

Broiler flocks with mortality about 10% were visited in Turkey, and necropsy was performed on dead birds. Samples were subjected to PCR assay to detect FAdV and other viral pathogens. After sequencing, phylogenetic analysis was performed and the nucleotide sequences of hexon genes were compared with the FAdV sequences data available in GenBank.

Results

Clinical signs such as anorexia, depression, ruffled feathers, huddling, and greenish diarrhoea were observed. Mortality started at the 8^th day of age and ranged from 10% to 14%. Necropsy showed severe hepatitis, jaundice, and pancreatitis. The main necropsy findings included a pale, enlarged, haemorrhagic, and friable liver along with swollen and haemorrhagic kidneys and spleen. PCR and sequence analysis revealed the presence of fowl adenovirus serotype 8b (FAdV-E).

Conclusion

This is the first report on characterisation and the pathological lesions associated with FAdV in broilers in Turkey. Our findings suggest that FAdV strains could be an emerging pathogen in Turkish broilers and could actively contribute to hepatitis and immunosuppression.

The first complete genome sequence and pathogenicity characterization of fowl adenovirus 11 from chickens with inclusion body hepatitis in Pakistan

Inclusion body hepatitis (IBH), hydropericardium syndrome, and gizzard erosion associated with fowl adenovirus (FAdV) infections are reported globally and resulted in significant poultry industry economic losses. In 2018, severe IBH appeared in Pakistan in a 17-week-old layer flock. Subsequently, a FAdV-11 strain (designated as PKFAd18) was isolated from liver samples and identified based on phylogenetic analyses of the serotype-specific L1 region of the capsid hexon gene. There is no complete genome sequence of the Pakistani FAdV-11. This study successfully sequenced the complete genome of PKFAd18. The full genome of PKFAd18 contains 43 840 base pairs (bp) with a G + C content of 53.9 %, which is comparable to other FAdV serotypes. Similar to other FAdV-11 strains, PKFAd18 has only one fiber, while FAdV-1 and FAdV-4 have two fibers. Notably, PKFAd18 showed unique characteristics compared to other FAdV-11 strains. A natural large genomic deletion (1215 bp) appeared in tandem repeat region two, relative to the ON-NP2 strain. Phylogenetic analyses of the PKFAd18 penton gene showed higher homology with FAdV-9, highlighting potential natural recombination between FAdV-11 and FAdV-9. Moreover, the pathogenicity of PKFAd18 studied in specific-pathogen-free chickens showed that PKFAd18 is capable of inducing severe IBH and could be responsible for IBH in Pakistan. Thus, the first complete genome of FAdV-11 in Pakistan was sequenced in this study, which enriches the diversity of knowledge about FAdV-11 and is useful for developing diagnostics and vaccines for IBH induced by FAdV-11 in Pakistan.

An efficient fiber-based ELISA for detection of antibody against fowl adenovirus serotypes 7 and 8

An outbreak of inclusion body hepatitis caused by fowl adenovirus serotype 8 (FAdV-8) has caused significant economic losses in the poultry industry worldwide. However, a rapid serology test kit specific to FAdV-8 is not available to date. We developed a fiber-based ELISA using the purified GST-fiber of FAdV-8 as coating antigen to measure antibodies against FAdV-8. Specificity analysis showed that our ELISA could react with sera against FAdV-7, -8a, and -8b, but not with sera against the other pathogens tested. Moreover, detection of positive sera with our ELISA had 83% and 94% agreement with an indirect immunofluorescence assay (IFA) and a commercial ELISA from BioChek, respectively. Our ELISA was also effective in the detection of antibodies against FAdV-8 in sera from both experimentally infected and clinically vaccinated chickens. Our FAdV-8 fiber-based ELISA can be a valuable tool to specifically and sensitively detect antibodies against FAdV-7 and/or -8 in infected or vaccinated chickens.

Pathogenicity of an FAdV-4 isolate to chickens and its genomic analysis

Fowl adenovirus serotype 4 (FAdV-4) strain SD1511 was isolated from chickens with severe inclusion body hepatitis and hydropericardium syndrome in Shandong Province, China. The isolate was cultured in primary chicken embryo kidney cells. A study of pathogenicity indicated that SD1511 readily infected 7-35-d-old chickens by intramuscular injection and intranasal and oral routes, causing 50%-100% mortality. The 35-d-old chickens suffered more severe infection than 7- and 21-d-old chickens with mortality highest in the intramuscular injection group. The serum from surviving chickens showed potent viral neutralizing capability. The complete genome of SD1511 was sequenced and analyzed. The strain was found to belong to the FAdV-4 cluster with more than 99% identity with the virulent FAdV-4 strains isolated in China in recent years except for some distinct variations, including deletions of open reading frame 27 (ORF27), ORF48, and part of ORF19. Our findings suggest that SD1511 might be used as a prototype strain for the study of pathogenesis and vaccine development.

Transcriptome Analysis Reveals New Insight of Fowl Adenovirus Serotype 4 Infection

Since 2015, Fowl adenovirus serotype 4 (FAdV-4) infection has caused serious economic losses to the poultry industry worldwide. We isolated and identified the FAdV-4 strain NP, from infected chickens on a layer farm, using chicken embryo allantoic cavity inoculation, electron microscopy, viral genome sequencing, and regression analysis. To explore the pathogenesis of FAdV-4 infection, we conducted transcriptome sequencing analysis of the liver in chickens infected with FAdV-4, using the Illumina® HiSeq 2000 system. Two days after infection with the FAdV-4 NP strain, 13,576 differentially expressed genes (DEGs) were screened in the liver, among which, 7,480 were up-regulated and 6,096 were down-regulated. Gene ontology (GO) analysis indicated that these genes were involved in 52 biological functions. Furthermore, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that those DEGs were involved in 33 pathways. We then focused on the KEGG pathway of phagosome and found that mRNA levels of the 25 DEGs in that pathway were up-regulated, and seven DEGs were down-regulated. Real-time quantitative polymerase chain reaction (qPCR) confirmed the accuracy and reliability of these findings. Moreover, 24 h after LMH cells were infected with FAdV-4, the mRNA levels of F-actin, Rab7, TUBA, and DVnein were significantly increased. These four genes were all subsequently silenced by RNA interference, and viral replication of FAdV-4 was then significantly down-regulated. These findings demonstrate the isolation and identification of the FAdV-4 NP strain, and the DEGs in KEGG pathway of phagosome were utilized by FAdV-4 to benefit its infection.

Isolation and characterization of fowl aviadenovirus serotype 11 from chickens with inclusion body hepatitis in Morocco

The present study was conducted in order to isolate, identify and characterize fowl aviadenovirus associated with inclusion body hepatitis (IBH) in three poultry farms (two of broiler chickens and one of breeder broiler chickens) in Morocco during 2015. Liver samples collected from affected three poultry farms were examined by histopathological examination. Tissue samples showing necrosis of hepatocytes associated with basophilic intranuclear inclusion bodies were homogenized and submitted to FAdV isolation in chicken embryo fibroblast (CEF) cell cultures and in SPF embryonated eggs. The cytopathic effect (CPE) was observed in the second passage with swelling and rounding of infected cells. The inoculated embryos were hemorrhagic and showed hepatitis with the presence of basophilic intra-nuclear inclusion bodies within hepatocytes. The presence of the virus was confirmed by conventional polymerase chain reaction based on hexon gene from all investigated samples. Moreover, phylogenetic analysis of the hexon gene revealed that FAdVs isolated from different affected poultry belonged to FAdV 11 serotype of the D genotype group. This work is the first isolation in cell culture and SPF embryonated eggs of FAdV from Moroccan broilers and breeder broiler chickens with IBH.

Development and application of a novel ELISA for detecting antibodies against group I fowl adenoviruses

Since 2015, outbreaks of hepatitis-hydropericardium syndrome (HPS) caused by a novel genotype of fowl adenovirus 4 (FAdV-4) infection have created serious economic losses in China. Given that other serotypes of hypervirulent FAdVs have also been reported in poultry around the world, a common ELISA for all serotypes within the group I fowl adenoviruses (FAdV-I) is urgently needed, especially for clinical epidemic serotypes. In this study, we used high purity and concentration virions of FAdV-4 and developed a common ELISA for detecting antibodies against 12 FAdV-I serotypes. The developed ELISA was able to distinguish between antibodies against FAdV-I, FAdV-III, and other heterologous viruses without any cross-reaction. Furthermore, the ELISA showed higher sensitivity than the FAdV-1-based ELISA to the novel FAdV-4 found in China. Moreover, since there are no commercial vaccines against FAdVs in China, the ELISA was applied to detect sera samples from specific pathogen-free chickens inoculated with inactivated FAdV-1, FAdV-4, and FAdV-8a. The assay showed high sensitivities for all three detected serotypes within FAdV-I. In conclusion, a novel, common ELISA for FAdV-I was developed in this study and could be a powerful tool for seroepidemiological investigations and FAdVs vaccine development.

Identification of novel B cell epitopes in the fiber protein of serotype 8 Fowl adenovirus

In recent years, hepatitis-hydropericardium syndrome (HHS) and inclusion body hepatitis (IBH) caused by fowl adenovirus (FAdV) infection have resulted in significant economic losses to the poultry industry worldwide. Epidemiological analysis revealed that serotype FAdV-8 is one of the major pathogenic FAdVs currently prevalent in domestic flocks. Although the fiber protein of FAdV plays vital roles in viral infection and pathogenesis, the B cell epitope in the fiber protein is less known. In this study, two monoclonal antibodies (mAbs) specific to fiber protein of FAdV-8, designated as 4D9 and 5F10, were prepared. Although the mAb 4D9 and 5F10 could not neutralize FAdV-8 infection, 4D9 and 5F10 showed good activities of indirect immunofluorescence, western blot and immunoprecipitation. Epitope analysis revealed that mAb 5F10 recognized 187-219aa in the fiber whereas mAb 4D9 recognized 113-149aa in the fiber. Sequence analysis showed that the epitope recognized by mAb 5F10 was conserve across serotypes FAdV-7, 8a and 8b whereas that for mAb 4D9 was only conserve in FAdV-8b. The generation of mAbs specific to fiber of FAdV-8 and the identification of the novel B cell epitopes here lay the foundation for further studying the antigenicity of the fiber and developing specific diagnosis for FAdV-8.

The fowl adenovirus (Fadv-11) outbreak in Iranian broiler chicken farms: The first full genome characterization and phylogenetic analysis

Fowl adenoviruses D and E (FAdV-D and E) can cause inclusion body hepatitis (IBH) in commercial chicken flocks. Recently, IBH outbreaks have been increasingly reported in different regions of Iran, particularly in broiler farms. The present study was conducted to perform, for the first time, a complete genome characterization of a FAdV isolate from an IBH outbreak in Iran. Briefly, liver samples were collected from affected broiler flocks and following viral DNA extraction and confirming by PCR technique; one positive sample was selected from an affected flock to conduct a complete genome sequencing. The current FAdV, named "Fowl_Adenovirus_D_isolate_iran/UT-Kiaee_2018", was placed into FAdV-11 serotype (D species). According to the complete genome sequence analysis, UT-Kiaee had high homology with Chinese and Canadian FAdV. The partial sequence of the hexon gene revealed that UT-Kiaee shared 100% identity with previous Iranian FAdVs. The present study was the first to report full genome FAdV in Iran and complete the puzzle of molecular epidemiology of FAdV in Iran through determining the possible origin of Iranian FAdvs, which are the causative agents of recent IBH outbreaks in Iran.

Pathogenicity of fowl adenovirus serotype 4 (FAdV-4) in chickens

Hepatitis-hydropericardium syndrome (HHS) is an acute infectious disease caused by fowl adenovirus serotype 4 (FAdV-4), which mainly infects broilers aged 3-5 weeks. In March 2018, a pathogenic disease, which was characterized by symptoms similar to HHS, broke out in 10-day-old broiler flocks in Shandong province. In this study, a strain of FAdV-4 (SDSG) was isolated from naturally infected broilers. To assess its pathogenicity, 10-day-old and 20-day-old specific pathogen-free (SPF) chickens were inoculated separately with the FAdV-4 virus fluid via oral and intramuscular injection routes. The results show that typical hydropericardium and hepatitis were observed in experimental chickens. The titer levels of the virus antibody and the levels of inflammatory cytokines were upregulated, which may be caused by the infection and innate immune response. The detection of viral load showed that the presence of virus was detected in multiple organs, in which the liver contained the highest concentration of viral DNA, and the virus content in the intramuscular injection group was higher than that of the oral injection group. In summary, these findings increase our understanding of the pathogenicity of FAdV-4 (SDSG) in chickens. The established model will be valuable for anti-viral drug testing and vaccine evaluation, which can prevent and reduce the spread of HHS in the poultry industry.

Epidemiological investigation of fowl adenovirus infections in poultry in China during 2015-2018

Background

Fowl adenoviruses (FAdVs) are associated with many diseases, resulting in huge economic losses to the poultry industry worldwide. Since 2015, outbreaks of FAdV infections with high mortality rates have been reported in China. A continued surveillance of FAdVs contributes to understand the epidemiology of the viruses.

Results

We isolated 155 FAdV strains from diseased chickens from poultry in China between 2015 and 2018. PCR analysis determined that 123 samples were FAdV species C, 27 were FAdV species E, and five contained two different FAdV strains. The phylogenetic analysis demonstrates that these sequences of hexon regions were clustered into three distinct serotypes: FAdV-4 (79.4%, 123/155), FAdV-8a (13.5%, 21/155) and FAdV-8b (3.9%, 6/155), of which FAdV-4 was the dominant serotype in China.

Conclusions

The characterization of newly prevalent FAdV strains provides valuable information for the development of an effective control strategy for FAdV infections in chickens.

Electronic supplementary material

The online version of this article (10.1186/s12917-019-1969-7) contains supplementary material, which is available to authorized users.

Two novel monoclonal antibodies against fiber-1 protein of FAdV-4 and their application in detection of FAdV-4/10

BACKGROUND

Recently, serotype 4 fowl adenovirus (FAdV-4) has spread widely and caused huge economic loss to poultry industry. However, little is known about the molecular pathogenesis of FAdV-4. Fiber protein is thought to be vital for its infection and pathogenesis.

RESULTS

Two novel monoclonal antibodies (mAbs) targeting the fiber-1 protein of FAdV-4 were generated, designated as mAb 3B5 and 6H9 respectively. Indirect immunofluorescence assay (IFA) showed that both mAbs only reacted with the FAdV-4 and FAdV-10, not with other serotypes including FAdV-1, FAdV-5, FAdV-6, FAdV-7, FAdV-8 and FAdV-9 tested. Although both mAbs did not recognize the linear epitopes, they could efficiently immunoprecipitate the fiber-1 protein in LMH cells either infected with FAdV-4 or transfected with pcDNA3.1-Fiber-1. Moreover, mAb 3B5 as a capture antibody and HRP-conjugated mAb 6H9 as a detection antibody, a novel sandwich ELISA for efficient detection of FAdV-4 was generated. The limit of detection of the ELISA could reach to 1000 TCID₅₀/ml of FAdV-4 and the ELISA could be efficiently applied to detect FAdV-4 in the clinical samples.

CONCLUSION

The two mAbs specific targeting fiber-1 generated here would pave the way for further studying on the role of fiber-1 in the infection and pathogenesis of FAdV-4, and the established mAb based sandwich ELISA would provide an efficient diagnostics tool for detection of FAdV-4/10.