Preparation and evaluation of the immune efficacy of an inactivated fowl adenovirus 8a serotype oil emulsion vaccine

In recent years, fowl adenovirus (FAdV) transmission has significantly increased worldwide, leading to substantial economic losses in the poultry industry. The virus causes hepatitis-hydropericardium syndrome (HHS) and inclusion body hepatitis (IBH). The prevalent FAdV strains in China are FAdV-4, FAdV-8a, FAdV-8b, and FAdV-11. Vaccines for FAdV-4 and FAdV-8b, which prevent HHS and IBH, are available commercially, but no vaccine exists for FAdV-8a. To address this issue, we developed a vaccine using an oil emulsion to inactivate the FAdV-8a serotype. Additionally, we built a fluorescence quantitative PCR for the detection of the virus. The lowest concentration detected was 4.11 × 101 copies/μL. The study's results illustrated that the FAdV-8a oil emulsion vaccine effectively produced significant antibodies and offered ample protection for poultry. This vaccine can potentially limit the transmission of IBH resulting from FAdV-8a in China.

Prevalence, genomic characteristics, and pathogenicity of fowl adenovirus 2 in Southern China

In recent years, the occurrence of fowl adenovirus 2 (FAdV-2) has been on the rise in China, posing a significant threat to the poultry industry. This study aimed to investigate the epidemiology, phylogenetic relationship, genomic characteristics, and pathogenicity of FAdV-2. The epidemiological analysis revealed the detection of multiple FAdV serotypes, including FAdV-1, FAdV-2, FAdV-3, FAdV-4, FAdV-8a, FAdV-8b, and FAdV-11 serotypes. Among them, FAdV-2 exhibited the highest proportion, accounting for 21.05% (8/38). The complete genomes of these 8 FAdV-2 strains were sequenced. Genetic evolution analysis indicated that these FAdV-2 strains formed a separate branch within the FAdV-D group, sharing 94.60 to 97.90% nucleotide similarity with the reference FAdV-2 and FAdV-11 strains. Notably, the recombination analysis revealed that 5 out of the 8 FAdV-2 strains, exhibited recombination events between FAdV-2 and FAdV-11. The recombination regions involved Hexon, Fiber, ORF19 genes and 3' end. Furthermore, pathogenicity experiments demonstrated that recombinant FAdV-2 XX strain is capable of inducing mortality rate of 66.70% and causing more severe hepatitis hydropericardium syndrome (HHS) in 6-wk-old specific-pathogen-free chickens. These findings contribute to our understanding of the prevalence, genomic characteristics, and the pathogenicity of FAdV-2, providing foundations for FAdV-2 vaccine development.

Virome Profiling of Chickens with Hepatomegaly Rupture Syndrome Reveals Coinfection of Multiple Viruses

Liver diseases seriously challenge the health of chickens raised on scaled farms and cause tremendous economic losses to farm owners. The causative agents for liver diseases are still elusive, even though various pathogens, such as the hepatitis E virus, have been reported. In the winter of 2021, a liver disease was observed on a chicken farm in Dalian, China, which increased chicken mortality by up to 18%. We conducted panvirome profiling of the livers, spleens, kidneys, and recta of 20 diseased chickens. The viromic results revealed coinfection of multiple viruses, including pathogenic ones, in these organs. The viruses were highly identical to those detected in other provinces, and the vaccine and field strains of avian encephalomyelitis virus (AEV) and chicken infectious anemia virus (CIAV) cocirculated on the farm. In particular, the liver showed higher abundance of AEV and multiple fowl adenoviruses than other organs. Furthermore, the liver also contracted avian leukemia virus and CIAV. Experimental animals with infected liver samples developed minor to medium lesions of the liver and showed a virus abundance profile for AEV across internal organs similar to that in the original samples. These results suggest that coinfection with multiple pathogenic viruses influences the occurrence and development of infectious liver disease. The results also highlight that strong farm management standards with strict biosafety measures are needed to minimize the risk of pathogenic virus introduction to the farm.

Molecular epidemiology analysis of fowl adenovirus detected from apparently healthy birds in eastern China

BACKGROUND

Fowl adenovirus is of major concern to the poultry industry worldwidely. In order to monitor the prevalent status of Fowl adenovirus in China, a total of 1920 clinical samples from apparently healthy birds in the 25 sites of poultry flocks, Slaughterhouse and living bird markets from 8 provinces in eastern China were collected and detected by PCR, sequencing, and phylogenetic analysis.

RESULTS

The epidemiological survey showed that Fowl adenoviruses were detected in living bird markets, and circulating in a variety of fowl species, including chickens, ducks, goose and pigeons. Among the 1920 clinical samples, 166 samples (8.65%) were positive in the fowl adenovirus PCR detection. In this study, totally all the 12 serotypes (serotypes of 1, 2, 3, 4, 5, 6, 7, 8A, 8B, 9, 10 and 11) fowl adenoviruses were detected, the most prevalent serotype was serotype 1. Phylogenetic analysis indicated that 166 FAdVs of 12 serotypes were divided into 5 fowl adenovirus species (Fowl aviadenovirus A, B, C, D, E).

CONCLUSIONS

In the epidemiological survey, 8.65% of the clinical samples from apparently healthy birds were positive in the fowl adenovirus PCR detection. Totally all the 12 serotypes fowl adenoviruses were detected in a variety of fowl species, which provided abundant resources for the research of fowl adenoviruses in China. The newly prevalent FAdV serotypes provides valuable information for the development of an effective control strategy for FAdV infections in fowls.

Isolation and identification of four pathogenic bacterial strains from edible snake (Elaphe carinata and Ptyas mucosus) farms with pneumonia in China

This report describes an outbreak and treatment of pneumonia and enteritis in a snake farm with more than 3000 snakes containing Elaphe carinata (one-year-old) and Ptyas mucosus (three-month-old) seedlings in Huanggang, Hubei, China. Gentamicin was used once in the early stage as treatment, administered orally with water or feed by owners, but mortality increased. Lobar pneumonia was confirmed by dissection and histopathology in infected snakes. Four main pathogenic bacteria were isolated and identified with culture and 16S rRNA sequencing: Staphylococcus sciuri, Salmonella enteritis, Vagococcus fluvialis and Providencia vermicola. Drug susceptibility tests were performed, and amikacin, gentamicin and cefitriaxone were chosen accordingly. After two rounds of treatment, the clinical signs for Elaphe carinata were under control, and the mortality was close to 0% after treatment. However, treatments for Ptyas mucosus seedlings did not work well, potentially because of poor administration technique and weak body condition.

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.

Whole genome analysis of a novel adenovirus discovered from Oriolus chinesis

We present the first complete genome sequence of an aviadenovirus Oriolus adenovirus (OrAdV) sequenced from the cloaca of a Oriolus chinensis (a passerine bird widely distributed in Asia), which was collected from an island off the east coast of China. Thirty-one protein coding genes were predicted in this 40425-bp-long genome. OrAdV genome is highly divergent and has only 57% average protein identity compared with other aviadenovirus genomes. Comparative genomic analysis indicates that this passerine virus is a new species of aviadenovirus. One unique thymidylate kinase gene was discovered in OrAdV genome. This gene is absent in other adenovirus genomes and usually reported to occur in herpesvirus. Protein sequence alignment against all known proteins indicates that this gene may be originated from ancient horizontal gene transfer event between virus and parasitic eukaryote like protozoan. This new aviadenovirus genome enriches the genomic information of adenovirus and suggests that there is a large unknown space of adenovirus world.

Isolation and characterization of a novel strain of duck aviadenovirus B from Muscovy ducklings with acute hepatitis in China

A new disease designated as Pale liver disease (PLD) has been circulating in Chinese Muscovy duck flocks since 2014, which is characterized by fatigue, diarrhoea, sudden death and acute hepatitis with pale and haemorrhagic liver. In this study, the etiological agents of PLD were isolated, causing a significant cytopathic effect (CPE) by cell rounding. Virus particles were observed by transmission electron microscopic (TEM) observation. The same disease was reproduced by experimental infection with the isolate BG61. The whole genomes of isolates were 43,842 nt in length with a GC content of 47.11%, similar to French Muscovy duck adenovirus strain GR with a GC content of 46.08%. The isolates shared 99.71-99.95% and 93.31-93.33% identity with Chinese Muscovy duck adenovirus isolates and GR strain, respectively. The DNA polymerase gene of all Muscovy duck adenovirus strains formed a separate genetic lineage with 99.55-100% amino acid sequence identity. All Chinese Muscovy duck adenovirus isolates contained two fibre genes. In contrast, only one fibre gene was found in GR, the only representative strain in species Duck aviadenovirus B. Anti-DAdV-2 serum antibodies had a weak neutralizing activity against Chinese Muscovy duck adenovirus isolates. The phylogenetic trees of the complete genome, hexon and fibre proteins revealed that all Muscovy duck adenovirus strains formed a major genetic lineage consisting of two clades. Thus, both GR and Chinese Muscovy duck adenovirus strains were proposed to be included in the same species of Duck aviadenovirus B belonging to the genus Aviadenovirus. The species Duck aviadenovirus B included two serotypes or genotypes, such as GR, which represents the strain of serotype 1 or genotype 1 (DAdV B1) and Chinese Muscovy duck adenovirus strains, which belong to serotype 2 or genotype 2 (DAdV B2).

Complete Genome Sequence of a Fowl Adenovirus D Strain Isolated from Chickens with Inclusion Body Hepatitis in Japan

We report the complete genome sequence of fowl adenovirus D (FAdV-D) strain JP/Tokushima/2010IBH, which was isolated from chickens with inclusion body hepatitis in Japan. This FAdV-D isolate was genetically highly similar to recent isolates from China, suggesting a common origin.

A recent perspective on fiber and hexon genes proteins analyses of fowl adenovirus toward virus infectivity-A review

Fowl adenovirus (FAdV) is a double-stranded DNA virus with a non-enveloped structure comprising three major proteins known as hexon, penton, and fiber. Molecular analysis which emphasizes on hexon and fiber proteins is currently the major focus of curiosity for FAdV antigenicity and pathogenicity. Recently, disease outbreaks associated with FAdV infections such as inclusion body hepatitis, hepatitis hydropericardium syndrome, and gizzard erosion, were commonly reported and continue to increase worldwide. Studies on the virulence gene of the virus were intensively conducted to provide a better understanding on the role of these major capsid proteins in the development of a safe and effective vaccine against the disease in the poultry industry. This paper highlights the variations of the fiber and hexon genes, their importance in genotypes and serotypes differentiation, and infectivity between FAdV strains. It appears that the L1 loop of hexon and the knob of fiber genes are the infectivity markers for FAdV infection. The fiber-2 protein plays a major role in FAdV pathogenicity than the hexon protein, while the fiber-1 protein is important for viral replication and assembly, regardless of virulence capability instead of infectivity. The hexon protein plays a major role in virus infectivity and tissue tropism. These findings could further enhance the knowledge of FAdV strains’ classification and evolution, diagnosis, and strategies to prevent and control FAdV infection and outbreaks in chicken farms.

Characterization of a fowl adenovirus 9 (FAdV-9) early promoter and its application in generating dual expression FAdV-9s

The CMV immediate early promoter from the EGFP expression plasmid pEGFP-N1 was replaced with the very left end of the fowl adenovirus 9 (FAdV-9) genome (ntds 73-574) to demonstrate and delineate the promoter function of this sequence. Expression of an EGFP ORF which replaced ORF1 and ORF2 demonstrated that the native promoter can drive down stream foreign gene expression. Replacement of ORF1 and ORF2 with a bicistronic cassette, incorporating a 493 bp IRES from an Ontario strain of avian encephalomyelitis virus (AEV) separating an EGFP ORF and mCherry ORF allowed for expression of both ORFs from a recombinant FAdV. These results provide an additional platform for multivalent vaccines development based on a native FAdV-9 promoter and an avian virus IRES.

Epidemiology of fowl adenovirus (FAdV) infections in South Korean chickens during 2013-2019 following introduction of FAdV-4 vaccines

Fowl adenoviruses (FAdV) are important infectious pathogens responsible for causing substantial economic losses to the poultry industry worldwide. One hundred and forty-six FAdV strains were continuously collected and analysed from 2013 to 2019 to understand the epidemiological change and nature of the virus in South Korea from two different standpoints, before and after the release of multiple commercial FAdV-4 vaccines. Phylogenetic analysis of the hexon loop-1 gene sequences showed that 92 strains belonged to FAdV-C (63%), 35 strains to FAdV-E (24%), 18 strains to FAdV-D (12.3%), and one strain to FAdV-A (0.7%), respectively. We provide evidence that the dominant FAdV serotype has recently changed from FAdV-4 to FAdV-8b, as reflected in the proportion of each serotype in field cases in 2019 (18.5% and 77.8%, respectively). The newly emerged FAdV-8b cluster was significantly noticeable compared to the old FAdV clusters, indicating that the development of a vaccine for FAdV-8b may be necessary. Overall, this new insight into FAdV prevalence provides a foundation for strategic control and the development of efficient vaccines against FAdV cases in chickens in South Korea.RESEARCH HIGHLIGHTS The dominant FAdV serotype in South Korea shifted from FAdV-4 to FAdV-8b in 2013-2019.A new cluster of FAdV-8b has emerged in South Korea, indicating the development of new vaccines.

Molecular characterization of Malaysian fowl adenovirus (FAdV) serotype 8b species E and pathogenicity of the virus in specific-pathogen-free chicken

Background

Inclusion body hepatitis (IBH) is an economically important viral disease primarily affecting broiler and breeder chickens. All 12 serotypes of fowl adenovirus (FAdV) can cause IBH.

Objectives

To characterize FAdV isolates based on phylogenetic analysis, and to study the pathogenicity of FAdV-8b in specific-pathogen-free (SPF) chickens following virus inoculation via oral and intramuscular (IM) routes.

Methods

Suspected organ samples were subjected to virus isolation and polymerase chain reaction (PCR) for FAdV detection. Hexon gene sequencing and phylogenetic analysis were performed on FAdV-positive samples for serotype identification. One FAdV-8b isolate, UPM/FAdV/420/2017, was selected for fiber gene characterization and pathogenicity study and was inoculated in SPF chickens via oral and IM routes.

Results

The hexon gene phylogenetic analysis revealed that all isolates belonged to FAdV-8b. The fiber gene-based phylogenetic analysis of isolate UPM/FAdV/420/2017 supported the grouping of that isolate into FAdV species E. Pathogenicity study revealed that, chickens infected with UPM/FAdV/420/2017 via the IM route had higher clinical score values, higher percent mortality, higher degree of the liver lesions, higher antibody response (p < 0.05), and higher virus shedding amounts (p < 0.05) than those infected via the oral route. The highest virus copy numbers were detected in liver and gizzard.

Conclusions

FAdV-8b is the dominant FAdV serotype in Malaysia, and pathogenicity study of the FAdV-8b isolate UPM/FAdV/420/2017 indicated its ability to induce IBH in young SPF chickens when infected via oral or IM routes.

Longitudinal Serological Monitoring of Commercial Broiler Breeders for Fowl Adenoviruses (FAdVs)-Presence of Antibodies Is Linked with Virus Excretion

Currently, the poultry industry worldwide is facing an emerging trend of fowl adenovirus (FAdV)-associated diseases with a significant economic impact, especially in meat-type chickens. Vertical transmission is an important feature of all FAdVs; hence, preventive measures mostly revolve around breeding stocks. However, knowledge about temporal development of FAdV infections in modern commercial settings is rare or even nonexistent. In the present study, longitudinal monitoring for FAdV was conducted in broiler breeder flocks located in a confined geographical region with intensive poultry production in Iran. For this, the antibody status of birds from 4 to 32 wk of age was monitored with a commercial FAdV-ELISA and virus neutralization test (VNT). In parallel, fecal shedding of FAdV was determined at the peak of egg production with real-time PCR and virus isolation. Overall, the commercial ELISA showed seroconversion of flocks before onset of production. VNT resolved in detail infection patterns of individual serotypes with a primordial FAdV-D (FAdV-2/-11) infection, frequently followed by FAdV-E (FAdV-8a, -8b) superinfection. FAdV-A (FAdV-1) was traced in half of the investigated flocks, while no evidence of infection with FAdV-C (FAdV-4, -10) was noted. Common serological profiles between different houses of the same farm indicate an overarching biosecurity. Serological profiles coupled with virological findings at the peak of egg production indicated that higher antibody levels, determined by ELISA, correlated with lower amounts of viral DNA in fecal excretion. Simultaneously, the number of isolated FAdVs belonging to distinct serotypes declined in accordance with a rise of neutralizing antibodies in birds, underlining the significance of serotype-specific antibodies in the epidemiology of FAdV in breeders. Investigations in breeders were complemented with screening of FAdV-associated diseases in local broilers over a 3-yr period; 26 cases of inclusion body hepatitis with dominant involvement of FAdV-11/FAdV-8b, one outbreak of adenoviral gizzard erosion related to FAdV-1, and no evidence of hepatitis-hydropericardium syndrome suggest that identical serotypes are maintained in the local poultry industry.

Isolation and molecular characterization of Fowl adenovirus strains in Black grouse: First reported case in Poland

This article describes the isolation, molecular characterization, and genotyping of two fowl adenovirus (FAdVs) strains with GenBank Accession numbers (MT478054, JSN-G033-18-L and MT478055, JSN-G033-18-B) obtained from the internal organs of black grouse (Lyrurus tetrix). This study also reveals the first confirmation of fowl adenovirus in Poland, supporting one of the hypotheses about the probability of fowl adenovirus interspecies transmission. The adenovirus strain sequences were investigated via phylogenetic analysis and were found to have an overall mean pairwise distance of 2.189. The heterogeneity, Relative Synonymous Codon Usage (RSCU), codon composition, and nucleotide frequencies were examined. Statistical analyses and Tajima’s test for the examined sequences were carried out. The Maximum Likelihood for the examined sequences substitutions was performed. The results of the sequence analysis identified MT478054, JSN-G033-18-L and MT478055, JSN-G033-18-B as strains of fowl adenovirus 2/11/D, with the Fowl adenovirus D complete sequence showing a 93% match. Wild birds may act as a natural reservoir for FAdVs and likely play an important role in the spreading of these viruses in the environment. The findings reported here suggest horizontal transmission within and between avian species.

Development of a rapid technique for extraction of viral DNA/RNA for whole genome sequencing directly from clinical liver tissues

Characterisation of the entire genome of Fowl aviadenoviruses (FAdV) requires isolation and propagation of the virus in chicken embryo liver or kidney cells, a process which is not only time consuming but may occasionally fail to result in viral growth. Furthermore, in a mixed infection, isolation in cell culture may result in the loss of viral strains. In this study, we optimised a FAdV DNA extraction technique directly from affected liver tissues using kaolin hydrated aluminium silicate treatment. The whole genome of FAdV was sequenced directly from extracted DNA without any targetted PCR based enrichment. The extraction method was also tested on avian liver tissues affected with the RNA virus Avian hepatitis E virus and demonstrated to yield sequencing grade RNA. Therefore, the method described here is a simple technique which is potentially useful for the extraction of sequencing grade DNA/RNA from tissues with high fat content.

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.

Identification of two novel adenoviruses in smooth-billed ani and tropical screech owl

Avian adenoviruses (AdVs) are a very diverse group of pathogens causing diseases in poultry and wild birds. Wild birds, endangered by habitat loss and habitat fragmentation in the tropical forests, are recognised to play a role in the transmission of various AdVs. In this study, two novel, hitherto unknown AdVs were described from faecal samples of smooth-billed ani and tropical screech owl. The former was classified into genus Aviadenovirus, the latter into genus Atadenovirus, and both viruses most probably represent new AdV species as well. These results show that there is very limited information about the biodiversity of AdVs in tropical wild birds, though viruses might have a major effect on the population of their hosts or endanger even domesticated animals. Surveys like this provide new insights into the diversity, evolution, host variety, and distribution of avian AdVs.

Fowl Adenovirus (FAdV) Recombination with Intertypic Crossovers in Genomes of FAdV-D and FAdV-E, Displaying Hybrid Serological Phenotypes

After analyzing 27 new genomes from fowl adenovirus (FAdV) field isolates and so-far unsequenced prototypes, we report the first evidence for recombination in FAdVs. Recombination was confined to species FAdV-D and FAdV-E, accommodating the largest number of, and the intraspecies-wise most differentiated, types. The majority of detected events occurred in FAdV-E, involving segments with parental origin of all constitutive types. Together with the diversity of breakpoints, this suggests widespread recombination in this species. With possible constraints through species-specific genes and diversification patterns, the recombinogenic potential of FAdVs attains particular interest for inclusion body hepatitis (IBH), an important disease in chickens, caused by types from the recombination-prone species. Autonomously evolving, recombinant segments were associated with major sites under positive selection, among them the capsid protein hexon and fiber genes, the right-terminal ORFs 19, 25, and the ORF20/20A family. The observed mosaicism in genes indicated as targets of adaptive pressures points toward an immune evasion strategy. Intertypic hexon/fiber-recombinants demonstrated hybrid neutralization profiles, retrospectively explaining reported controversies on reference strains B3-A, T8-A, and X11-A. Furthermore, cross-neutralization supported sequence-based evidence for interdomain recombination in fiber and contributed to a tentatively new type. Overall, our findings challenge the purported uniformity of types responsible for IBH, urging more complete identification strategies for FAdVs. Finally, important consequences arise for in vivo studies investigating cross-protection against IBH.

Characterization and pathogenicity of fowl adenovirus serotype 4 isolated from eastern China

BACKGROUND

Fowl adenovirus outbreaks have occurred in China since June 2015. This virus is an emerging infectious disease that causes hydropericardium syndrome and inclusion body hepatitis (HPS-IBH), resulting in significant economic loss to poultry farmers. Five fowl adenovirus (FAdV) strains (HN, AQ, AH726, JS07 and AH712) were isolated from Jiangsu and Anhui provinces.

RESULTS

Phylogenetic analysis revealed that the five isolates belonged to species C fowl adenovirus serotype 4. An 11 amino-acid deletion in ORF29, relative to an older viral isolate, JSJ13, was observed for all five strains described here. In chicken experiments, 80-100% birds died after intramuscular inoculation and displayed lesions characteristic of HPS-IBH. The viral DNA copies were further detected by hexon-probe based real-time polymerase chain reaction (PCR) in the chicken samples. The viral loads and cytokine profiles were recorded in all the organs after infections. Despite minor genetic differences, the 5 strains displayed significantly different tissue tropisms and cytokine profiles.

CONCLUSIONS

Our data enhance the current understanding some of the factors involved in the pathogenicity and genetic diversity of the FAdV serotype 4 (FAdV-4) in China. Our work provides theoretical support for the prevention and control of HPS-IBH in chickens.

Unconventional gene arrangement and content revealed by full genome analysis of the white sturgeon adenovirus, the single member of the genus Ichtadenovirus

Adenoviruses are commonly found in members of almost every vertebrate lineage except fish and amphibians, from each of which only a single isolate is available as yet. In this work, the complete genomic sequence of a fish adenovirus, originating from the white sturgeon (Acipenser transmontanus), was determined and analyzed. Several exceptional features were observed including the longest hitherto known genome size (of 48,395 bp) and a strange location of the putative fiber genes resulting in an unconventional organization pattern. The left genome end contained four fiber-like genes, three of them in a tandem position on the r (rightward transcribed) strand, followed by a fourth one on the l strand. Rightward from these, the conserved adenoviral gene cassette, encompassing 16 family-common genes, was identified. In the right-hand part, amounting for >42% of the entire genome, the presence of 28 ORFs, with a coding capacity of larger than 50 amino acids, was revealed. Interestingly, most of these showed no similarity to any adenoviral genes except two ORFs, resembling slightly the parvoviral NS gene, homologues of which occur in certain avian adenoviruses. These specific traits, together with the results of phylogeny reconstructions, fully justified the separation of the white sturgeon adenovirus into the recently established new genus Ichtadenovirus. Targeted attempts to find additional adenoviruses in any other fish species were to no avail as yet. Thus the founding member, WSAdV-1 still remains the only representative of ichtadenoviruses.

Vaccination with FAdV-8a induces protection against inclusion body hepatitis caused by homologous and heterologous strains

Fowl aviadenoviruses (FAdV) are important avian pathogens, responsible for several poultry diseases prevalent worldwide, including inclusion body hepatitis (IBH). FAdV intraspecies cross-protection has been clearly demonstrated, but there is little evidence that any interspecies cross-protection exists. The present study aimed to assess the inter- and intraspecies protection between three FAdV field isolates (FAdV-8a, FAdV-8b, FAdV-11) identified in association with severe IBH outbreaks. Inocula prepared using inactivated plaque-purified virus with adjuvant Montanide™ ISA 71VG, were injected intramuscularly into 3-week-old SPF chickens. At 6-weeks of age, the birds were challenged with 10⁶ TCID₅₀ of homologous or heterologous virus intraperitoneally, and full post mortem examination performed at 4 days post-challenge. Various tissues were examined for gross and histological lesions and assessed for the presence of virus by PCR-HRM. All homologous-type vaccine/challenge groups exhibited protection against IBH lesions with no virus detected in the tissues. Unvaccinated groups challenged with virus showed evidence of FAdV-induced lesions; however, FAdV-8a demonstrated lower pathogenicity compared with FAdV-8b and FAdV-11. In the heterologous-type vaccine/challenge groups, FAdV-8a vaccine was shown to protect against challenge with both FAdV-8b and FAdV-11. FAdV-8a and 8b belong to species E and were therefore anticipated to cross-protect. However, FAdV-11 belongs to species D and therefore cross-protection by FAdV-8a was an uncharacteristic and unique finding of this study. Further research is required to disseminate the molecular basis for the interspecies cross-protection between FAdV-8a and FAdV-11. Nonetheless, the FAdV-8a isolate was shown to have substantial potential as a vaccine candidate in countries where FAdV-8a, 8b or 11 are prevalent.

Identification of four serotypes of fowl adenovirus in clinically affected commercial poultry co-infected with chicken infectious anaemia virus in Trinidad and Tobago

Fowl adenovirus (FAdV), which causes the high-impact diseases such as inclusion body hepatitis and hepatitis-hydropericardium syndrome, is of major concern to the poultry industry internationally. This study was carried out in direct response to mortality rates of up to 75% in commercial broiler flocks in Trinidad, West Indies. Symptoms in 3- to 8-week-old broilers and 13- to 18-week-old pullets pointed to infection with an immunosuppressive viral pathogen. The objectives of the study were to determine whether the infectious agent FAdV, along with other viral pathogens, was responsible for the clinical disease, and to obtain information on the serotypes of FAdV that were infecting the birds. Tissue samples from clinically affected birds from eight different farms were tested for chicken infectious anaemia virus (CIAV) and infectious bursal disease virus (IBDV) by real-time reverse transcription polymerase chain reaction (PCR) and for FAdV by conventional PCR. The birds tested positive for FAdV and CIAV, but negative for IBDV. The gene corresponding to the L1 loop of the hexon protein for FAdV was amplified and sequenced. Phylogenetic analysis of seven FAdV strains inferred that four serotypes were likely to be circulating in the chickens. Well supported genetic relatedness was observed for serotype 8a (97.8%), 8b (97.8%), 9 (95.8%) and 11 (98.8%-99.5%). This is the first published report from Trinidad and Tobago on the presence and circulation of pathogenic FAdV strains, in combination with CIAV, in poultry. The data demonstrate a possible need for the introduction of serotype-specific vaccines against FAdV, as well as vaccines against CIAV, in broilers in the region and emphasize the importance of maintaining high levels of biosecurity on farms to prevent the spread of these potentially devastating viruses between farms.

The Natural Large Genomic Deletion Is Unrelated to the Increased Virulence of the Novel Genotype Fowl Adenovirus 4 Recently Emerged in China

Since 2015, severe hydropericardium-hepatitis syndrome (HHS), caused by a highly pathogenic fowl adenovirus 4 (FAdV-4), emerged in China. In our previous study, the FAdV-4 has been identified as a novel genotype with a unique 1966-bp nucleotide deletion (1966Del) between open reading frame 42 and 43. In this study, the natural 1966Del was frequently identified among 17 clinical isolates and other reported Chinese clinical strains. To investigate the relationship between 1966Del and the increased virulence of the novel FAdV-4, a CRISPR/Cas9 operating platform for FAdV-4 was developed for the first time in this study. Based on this platform, a Re1966 strain was rescued, inserted the relative 1966Del sequence of a nonpathogenic strain KR5. In the pathogenicity study, the Re1966 strain retained high virulence for specific-pathogen-free chickens, similar to the parental wild-type HLJFAd15, although the survival time of chickens infected with Re1966 was much longer. Therefore, the natural 1966Del was identified as a non-essential site for the increased virulence of the emerged novel FAdV-4. Although further research on the virulence-determining region or point within the genome of the novel FAdV-4 is needed, the CRISPR/Cas9 operating platform for the novel FAdV-4 was developed and successfully applied to edit the genomic DNA for the first time, and it provides a novel powerful tool for both basic virology studies and vaccine vector development of FAdVs.

Fiber-based fluorescent microsphere immunoassay (FMIA) as a novel multiplex serodiagnostic tool for simultaneous detection and differentiation of all clinically relevant fowl adenovirus (FAdV) serotypes

The recent emergence of fowl aviadenovirus (FAdV) induced disease outbreaks in chicken flocks worldwide, with distinct aetiologies confined to particular FAdV species and serotypes, is increasingly urging the need for specific and mass-applicable antibody screening systems. Despite this exigency, there are to date no available serological procedures which satisfactorily combine the criteria for sensitive detection of antibodies against FAdVs, diagnostic reliability in face of cross-reactions and requirements for a rapid and large-scale application. In order to address this gap, a multiplexed fluorescent microsphere immunoassay (FMIA) based on recombinant FAdV fiber proteins from six different serotypes FAdV-1, -2, -4, -8a, -8b and -11 was developed, which enabled simultaneous detection of antibodies against all clinically relevant serotypes in a single reaction within a high throughput setting. Based on a panel of >300 monospecific antisera raised against each of the 12 FAdV serotypes, 100% serotype-specificity was demonstrated for FAdV-1 (FAdV-A) and FAdV-4 (FAdV-C) fiber-based analytes. Analytes based on serotypes affiliated to FAdV-D and FAdV-E exhibited moderately lower specificities of 91.2-95.7%. This was attributed almost exclusively to mutual recognition between FAdV-2 and -11 field strains and to a much lesser extent to reference strains, supporting earlier proposals to merge them into a single serotype. Similarly, extensive cross-reactions between FAdV-8a and -8b were noted. Altogether intraspecies cross-reactions can be attributed to viruses with a close etiological intersection. Antisera against other important avian viruses remained negative by the FMIA, further validating its specificity. Compared to the virus-neutralization (VN) test, FMIA and individual fiber-based enzyme-linked immunosorbent assays (ELISAs) were equally sensitive in the detection of sera against FAdV-2 and -11, as well as FAdV-8a and -8b field strains, while they were even superior to VN test in detection of FAdV-1 and FAdV-4 responses, likely attributed to a relative abundance of fiber antibodies early upon infection. Moreover, application of the FMIA on field samples comprising a diversified response against all 12 FAdV serotypes further consolidated its specificity and agreement with VN test.