Location: Endemic Poultry Viral Diseases Research
2017 Annual Report
Objectives
1. Characterize the intestinal virome associated with poultry enteric diseases, including assessing the intestinal microbiome of poultry for the presence of novel enteric pathogens, and developing molecular tools to study the epidemiology, ecology, and evolution of enteric pathogens.
2. Investigate the role of the poultry gut microbiome in promoting overall health and performance gains, including defining the interactions between the gut microbiome and the host immune system that contribute to enteric diseases and performance problems and developing the microbiome as a poultry health phenotype.
3. Develop vaccine platforms that will lead to highly efficacious vaccines that have been rationally designed to control enteric diseases of poultry, including developing vaccines targeting specific enteric pathogens early during the poultry production cycle.
4. Further support annotation of functional regions of the chicken genome.
Approach
Viral infections of the avian gastrointestinal tract negatively impact poultry production; however, determining the complex etiologies of the viral enteric diseases in poultry has been difficult. Research in our Unit over the past five+ years has focused in part on the characterization of the poultry gut virus community and initial characterizations of novel viruses. The research proposed in Objective 1 will continue and expand upon this line of investigation. As a logical extension of our viral metagenomic work, we have further performed comparative metagenomic analyses of healthy and enteric disease-affected poultry flocks, leading to descriptions of potential disease-associated viruses such as the enteric picornaviruses. Objective 2 again continues and expands upon these investigations, proposing extensive flock comparisons using powerful next-generation sequencing techniques, pathogenesis work with viruses, and defining the immune response of poultry suffering from enteric maladies. Finally, the discovery of disease-associated genes and infectious agents in Objective 2 will directly inform the design of targeted interventions in Objective 3, which will use our established, efficacious recombinant vectored vaccine platforms to produce vaccines targeting enteric viruses early during the poultry production cycle.
Progress Report
Turkey enteric coronavirus (TCoV) causes clinical enteric disease in turkeys, resulting in significant economic losses to the turkey industry in the United States and abroad. Currently, there is no commercial vaccine available to prevent the disease because TCoV does not readily grow in cell culture, which hampers conventional vaccine development. To overcome this barrier to vaccine development, project scientists are developing a novel approach using an enteric Newcastle disease virus (NDV) vaccine as a vector. TCoV spike glycoprotein (S) subunit 1 (S1) and subunit 2 (S2), and nucleocapsid (N) protein genes have been cloned into the enteric NDV vaccine vector. Several NDV/TCoV recombinant viruses have been rescued and are being evaluated in vitro (cell culture) and in vivo (experimental birds) for safety and stability as vaccine candidates.
Enteric viral infections in poultry have caused a great deal of economic loss in the poultry industry worldwide. Several enteric viruses have been identified from the intestine of poultry either alone or in combination, suggesting the multicausal etiology of this disease. From our archived samples collected from field cases of diarrheic turkeys, 3 picornavirus- and 5 coronavirus-positive fecal samples were analyzed by Illumina MiSeq next generation sequencing (NGS) to determine viral community sequences and to investigate the presence of other concomitant enteric viruses. In the archived samples determined to be positive for picornavirus, metagenomic analysis of sequence reads revealed that 98, 10, and 83% of the virus reads consisted of Picornaviridae virus sequences, among which the most commonly indicated piconaviruses were turkey hepatitis virus (genus Megrivirus) and turkey gallivirus (genus Gallivirus). Other than the picornaviruses, astroviruses were the only other enteric virus reads with 0.69, 49.1, and 12.4%, respectively. In the coronavirus-positive samples, 96, 66, 97, 81, and 85% of the virus reads were identified as coronavirus, with turkey coronavirus comprising the majority of virus sequences and infectious bronchitis virus being a minor constituent. Other known enteric viruses were not indicated in 3 out of 5 coronavirus-positive samples, while a small percentage (less than 7%) of astrovirus and picornaviruses sequence reads were detected in the other 2 samples. NGS and metagenomics analyses in this study demonstrates the diversity of enteric viruses in turkey flocks with enteric problems in the U.S.
Accomplishments
1. There has been a general concern in the poultry industry that maternally derived antibodies (MDA) against Newcastle disease virus (NDV) may interfere with the protection provided by recombinant NDV-vectored vaccines against NDV as well as any targeted avian pathogens included in the recombinant system. To address this concern, ARS researchers in Athens, Georgia, evaluated NDV LaSota vaccine strain-based recombinant viruses expressing the glycoproteins B (gB) or D (gD) of infectious laryngotracheitis virus (ILTV) in broiler chickens in the presence of (MDA) against NDV. The results indicate that the presence of maternal antibodies to NDV and ILTV did not significantly interfere with the ability of the NDV LaSota strain-vectored ILTV gB and gD vaccine candidates to elicit protective immunity against infectious laryngotracheitis and Newcastle disease.
2. Our metagenomics (community-based) investigations of the enteric viral community in turkeys and chickens have revealed numerous novel viruses that may play roles in the performance problems and enteric syndromes observed in the field. Results obtained by ARS researchers in Athens, Georgia, during design of the streamlined sample preparation and the analysis pipeline have revealed novel enteric turkey and chicken picornaviruses—small RNA viruses that are common in the poultry gut and appear to be associated with enteric disease and performance problems. Phylogenetic analyses of the picornaviral RNA-dependent RNA-polymerase (RdRp) and capsid (VP3) genes suggest that flocks and even individual birds may be infected with more than one picornavirus strain. Many of these newly discovered viruses remain largely uncharacterized and may be present in some geographic regions and not others, and there may be unique and varied genotypes and pathotypes circulating in poultry flocks as well.
Review Publications
Wen, G., Li, L., Yu, Q., Wang, H., Luo, Q., Zhang, T., Zhang, R., Zhang, W., Shao, H. 2017. Evaluation of a thermostable Newcastle disease virus strain TS09-C as an in-ovo vaccine for chickens. PLoS One. 12(2):e0172812. doi:10.1371/journal.pone.0172812.
Wu, Y., He, J., Geng, J., An, Y., Ye, X., Yan, S., Yu, Q., Yin, J., Zhang, Z., Li, D. 2017. Recombinant Newcastle disease virus expressing human TRAIL as a potential candidate for hepatoma therapy. European Journal of Pharmacology. 802:85–92. doi:org/10.1016/j.ejphar.2017.02.042.
Yu, Q., Spatz, S.J., Li, Y., Yang, J., Zhao, W., Zhang, Z., Wen, G., Garcia, M., Zsak, L. 2017. Newcastle disease virus vectored infectious laryngotracheitis vaccines protect commercial broiler chickens in the presence of maternally derived antibodies. Vaccine. 35(5):789-795. doi:10.1016/j.vaccine.2016.12.038.
Zhang, Z., Zhao, W., Li, D., Yang, J., Zsak, L., Yu, Q. 2015. Development of a Newcastle disease virus vector expressing a foreign gene through an internal ribosomal entry site provides direct proof for a sequential transcription mechanism. Journal of General Virology. 96:2028-2035. doi:10.1099/vir.0.000142.
Wu, Y., He, J., An, Y., Wang, X., Liu, Y., Yan, S., Ye, X., Qi, J., Zhu, S., Yu, Q., Yin, J., Li, D., Wang, W. 2016. Recombinant Newcastle disease virus (NDV/Anh-IL-2) expressing human IL-2 as a potential candidate for suppresses growth of hepatoma therapy. Journal of Pharmacological Sciences. 132(1):24-30. doi:10.1016/j.jphs.2016.03.012.
