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Wang L, Zheng G, Yuan Y, Wang Z, Wang Q, Sun M, Wu J, Liu C, Liu Y, Zhang B, Zhang H, Yang N, Lian L. circRUNX2.2, highly expressed in Marek's disease tumor tissues, functions in cis to regulate parental gene RUNX2 expression. Poult Sci 2024; 103:104045. [PMID: 39094493 PMCID: PMC11345620 DOI: 10.1016/j.psj.2024.104045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2024] [Revised: 06/22/2024] [Accepted: 06/25/2024] [Indexed: 08/04/2024] Open
Abstract
Marek's disease (MD), an immunosuppression disease induced by Marek's disease virus (MDV), is one of the significant diseases affecting the health and productive performance of poultry. The roles of circular RNAs (circRNAs) in MD development were poorly understood. In this study, we found a circRNA derived from exon 6 of RUNX family transcription factor 2 (RUNX2) gene, named circRUNX2.2, was highly expressed in chicken tumorous spleens (TS) induced by MDV. Through fluorescence in situ hybridization and nuclear-cytoplasmic separation assay, we determined circRUNX2.2 was mainly located in the nucleus. Knockout experiments confirmed that the flanking complementary sequences (RCMs) mediated its circularization. Gain of function assay and dual luciferase reporter gene assay revealed that circRUNX2.2 could promote the expression of RUNX2 via binding with its promoter region. RNA antisense purification assay and mass spectrometry assay showed circRUNX2.2 could recruit proteins such as CHD9 protein. Knocking down CHD9 expression decreased the expression of RUNX2 gene, which confirmed the positive regulation that circRUNX2.2 on RUNX2 expression was probably facilitated via recruiting CHD9 protein. Functional experiments showed that circRUNX2.2 promoted the proliferation of the MD lymphoma-derived chicken cell line, MDCC-MSB1, which confirmed the potential oncogenic role of circRNX2.2 in tumor development. In conclusion, we found that the RUNX2-derived circRUNX2.2 can positively regulate the transcription of the parental gene RUNX2 in a cis-acting manner. The high expression of circRUNX2.2 in MD tumor tissues indicated that it might mediate MD lymphoma progression.
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Affiliation(s)
- Lulu Wang
- Department of Animal Genetics and Breeding, College of Animal Science and Technology, China Agricultural University, Beijing 100193, China; MOE Key Laboratory of Bioinformatics, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Gang Zheng
- Department of Animal Genetics and Breeding, College of Animal Science and Technology, China Agricultural University, Beijing 100193, China
| | - Yiming Yuan
- Department of Animal Genetics and Breeding, College of Animal Science and Technology, China Agricultural University, Beijing 100193, China
| | - Ziyi Wang
- Department of Animal Genetics and Breeding, College of Animal Science and Technology, China Agricultural University, Beijing 100193, China
| | - Qinyuan Wang
- Department of Animal Genetics and Breeding, College of Animal Science and Technology, China Agricultural University, Beijing 100193, China
| | - Meng Sun
- Department of Animal Genetics and Breeding, College of Animal Science and Technology, China Agricultural University, Beijing 100193, China
| | - Junfeng Wu
- Department of Animal Genetics and Breeding, College of Animal Science and Technology, China Agricultural University, Beijing 100193, China
| | - Changjun Liu
- Division of Avian Infectious Diseases, Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences, Harbin 150001, China
| | - Yongzhen Liu
- Division of Avian Infectious Diseases, Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences, Harbin 150001, China
| | - Bo Zhang
- Department of Animal Genetics and Breeding, College of Animal Science and Technology, China Agricultural University, Beijing 100193, China
| | - Hao Zhang
- Department of Animal Genetics and Breeding, College of Animal Science and Technology, China Agricultural University, Beijing 100193, China
| | - Ning Yang
- Department of Animal Genetics and Breeding, College of Animal Science and Technology, China Agricultural University, Beijing 100193, China
| | - Ling Lian
- Department of Animal Genetics and Breeding, College of Animal Science and Technology, China Agricultural University, Beijing 100193, China.
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Emad A, El-Kenawy AA, El-Tholoth M. Molecular characterization of Marek's Disease virus reveals reticuloendotheliosis virus-long terminal repeat integration in the genome of the field isolates in Egypt. Poult Sci 2024; 103:103722. [PMID: 38626691 PMCID: PMC11036097 DOI: 10.1016/j.psj.2024.103722] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2023] [Revised: 03/02/2024] [Accepted: 03/31/2024] [Indexed: 04/18/2024] Open
Abstract
The highly contagious, immunosuppressive, and cancer-causing Marek's disease virus (MDV) infects chickens. The financial costs of Marek's disease (MD) are significant for the chicken industry. In this study, a total of 180 samples from chicken farms suspected to be MDV-infected were collected. The chickens were sampled during the period between the months of October 2016 and February 2018 at Dakahlia and Damietta Governorates, Egypt. A total of 36 pooled samples were created. The prepared samples were inoculated into embryonated chicken eggs (ECEs). Indirect fluorescent antibody technique (IFAT) and ICP4 gene-based polymerase chain reaction (PCR) were used for MDV identification. For the genetic characterization of the identified virus, The ICP4 gene sequence was identified and compared with the sequences available from various regions of the world. Furthermore, the genomes of all detected MDVs were screened for the long terminal repeat (LTR) region of reticuloendotheliosis (REV) in their genomes. The results showed that 31 out of 36 pooled samples (86.1%) inoculated into ECEs displayed the characteristic pock lesions. By using IFAT and PCR to identify MDV in ECEs, positive results were found in 27 samples (75%). The Egyptian virus is thought to be genetically closely related to MDVs circulating in Ethiopia, China, and India. REV-LTR was amplified from 6 out of 27 field isolates genomes (22.2 %) while MDV vaccine strains were free from REV-LTR insertion. The integrated REV-LTRs depicted a close genetic relationship with those integrated in fowl poxvirus (FWPV) circulating in Egypt as well as those integrated in FWPVs and MDVs from China, USA, South Africa, and Australia. To the best of our knowledge, this investigation represents the first identification and characterization of REV-LTR insertions in Egyptian MDV field isolates. Given the findings above, additional research in the future seems crucial to determine how the REV-LTR insertions affect MDV pathogenesis, virulence, and insufficient vaccination protection.
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Affiliation(s)
- Aya Emad
- Department of Virology, Faculty of Veterinary Medicine, Mansoura University, Mansoura 35516, Egypt
| | - Ali A. El-Kenawy
- Department of Virology, Faculty of Veterinary Medicine, Mansoura University, Mansoura 35516, Egypt
| | - Mohamed El-Tholoth
- Department of Virology, Faculty of Veterinary Medicine, Mansoura University, Mansoura 35516, Egypt
- Veterinary Science Program, Faculty of Health Sciences, Al Ain Men's Campus, Higher Colleges of Technology, 17155, UAE
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Oluwayinka EB, Otesile EB, Oni OO, Ajayi OL, Dunn JR. Molecular characterization and phylogenetic analysis of Marek's disease virus in chickens from Ogun State, Nigeria. Avian Pathol 2023; 52:401-411. [PMID: 37605844 DOI: 10.1080/03079457.2023.2243838] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Accepted: 07/26/2023] [Indexed: 08/23/2023]
Abstract
Marek's disease (MD) is caused by oncogenic MD virus serotype 1 (MDV1) and is characterized by lymphoproliferative lesions resulting in high morbidity and mortality in chickens. Despite being ubiquitous on poultry farms, there is a dearth of information on its molecular characteristics in Nigeria. This study aimed at characterizing three virulence genes (Meq, pp38, and vIL-8) of MDV1 from chickens in Ogun state, Nigeria. Blood, feather quill, and tumour samples of chickens from different commercial poultry farms in Ogun State were pooled, spotted on 107 FTA cards, and screened for MDV1 by polymerase chain reaction (PCR). Phylogenetic analysis was carried out to compare Nigerian MDV1 Meq, pp38, and vIL-8 genes sequences with the published references. Thirteen samples were MDV1-positive and the Meq, as well as pp38, and vIL-8 genes from the different samples were 100% identical. The Meq genes contained 339 amino acids (aa) with three PPPP motifs in the transactivation domain and two interruptions of the PPPP motifs due to proline-to-arginine substitutions at positions 176 and 217 resulting in a 20.88% proline composition. Phylogenetic analysis revealed that the Meq gene clustered with strains from Egypt and very virulent ATE2539 strain from Hungary. Mutations were observed in the pp38 protein (at positions 107 and 109) and vIL-8 protein (at positions 4 and 31). Based on the molecular analysis of the three genes, the results indicate the presence of MDV1 with virulence signatures; therefore, further studies on in vivo pathotyping of Nigerian MDV1 from all states should be performed.RESEARCH HIGHLIGHTS Meq, pp38 and vIL-8 genes were 100% identical between Nigerian MDV strains.Proline content in Nigerian meq gene was 20.88% with two PPPP motifs interruptions.Meq, pp38 and vIL-8 genes of Nigerian MDV were similar to Egyptian and Indian strains.
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Affiliation(s)
- E B Oluwayinka
- Department of Veterinary Medicine, Federal University of Agriculture Abeokuta, Abeokuta, Nigeria
| | - E B Otesile
- Department of Veterinary Medicine, Federal University of Agriculture Abeokuta, Abeokuta, Nigeria
| | - O O Oni
- Department of Veterinary Medicine, Federal University of Agriculture Abeokuta, Abeokuta, Nigeria
| | - O L Ajayi
- Department of Veterinary Pathology, Federal University of Agriculture Abeokuta, Abeokuta, Nigeria
| | - J R Dunn
- US National Poultry Research Center, Athens, GA, USA
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Kim T, Hearn CJ, Mays J, Velez-Irizarry D, Reddy SM, Spatz SJ, Cheng HH, Dunn JR. Phenotypic Characterization of Recombinant Marek's Disease Virus in Live Birds Validates Polymorphisms Associated with Virulence. Viruses 2023; 15:2263. [PMID: 38005939 PMCID: PMC10674313 DOI: 10.3390/v15112263] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Revised: 11/13/2023] [Accepted: 11/14/2023] [Indexed: 11/26/2023] Open
Abstract
Marek's disease (MD) is a highly infectious lymphoproliferative disease in chickens with a significant economic impact. Mardivirus gallidalpha 2, also known as Marek's disease virus (MDV), is the causative pathogen and has been categorized based on its virulence rank into four pathotypes: mild (m), virulent (v), very virulent (vv), and very virulent plus (vv+). A prior comparative genomics study suggested that several single-nucleotide polymorphisms (SNPs) and genes in the MDV genome are associated with virulence, including nonsynonymous (ns) SNPs in eight open reading frames (ORF): UL22, UL36, UL37, UL41, UL43, R-LORF8, R-LORF7, and ICP4. To validate the contribution of these nsSNPs to virulence, the vv+MDV strain 686 genome was modified by replacing nucleotides with those observed in the vMDV strains. Pathogenicity studies indicated that these substitutions reduced the MD incidence and increased the survival of challenged birds. Furthermore, using the best-fit pathotyping method to rank the virulence, the modified vv+MDV 686 viruses resulted in a pathotype similar to the vvMDV Md5 strain. Thus, these results support our hypothesis that SNPs in one or more of these ORFs are associated with virulence but, as a group, are not sufficient to result in a vMDV pathotype, suggesting that there are additional variants in the MDV genome associated with virulence, which is not surprising given this complex phenotype and our previous finding of additional variants and SNPs associated with virulence.
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Affiliation(s)
- Taejoong Kim
- Southeast Poultry Research Laboratory, U.S. National Poultry Research Center, Agricultural Research Service, U.S. Department of Agriculture, 934 College Station Road, Athens, GA 30605, USA; (S.J.S.); (J.R.D.)
| | - Cari J. Hearn
- Avian Diseases and Oncology Laboratory, U.S. National Poultry Research Center, Agricultural Research Service, U.S. Department of Agriculture, 4279 E. Mount Hope Road, East Lansing, MI 48823, USA; (C.J.H.); (J.M.); (D.V.-I.); (H.H.C.)
| | - Jody Mays
- Avian Diseases and Oncology Laboratory, U.S. National Poultry Research Center, Agricultural Research Service, U.S. Department of Agriculture, 4279 E. Mount Hope Road, East Lansing, MI 48823, USA; (C.J.H.); (J.M.); (D.V.-I.); (H.H.C.)
| | - Deborah Velez-Irizarry
- Avian Diseases and Oncology Laboratory, U.S. National Poultry Research Center, Agricultural Research Service, U.S. Department of Agriculture, 4279 E. Mount Hope Road, East Lansing, MI 48823, USA; (C.J.H.); (J.M.); (D.V.-I.); (H.H.C.)
| | - Sanjay M. Reddy
- Department of Veterinary Pathobiology, Texas A&M University, College Station, TX 77843, USA;
| | - Stephen J. Spatz
- Southeast Poultry Research Laboratory, U.S. National Poultry Research Center, Agricultural Research Service, U.S. Department of Agriculture, 934 College Station Road, Athens, GA 30605, USA; (S.J.S.); (J.R.D.)
| | - Hans H. Cheng
- Avian Diseases and Oncology Laboratory, U.S. National Poultry Research Center, Agricultural Research Service, U.S. Department of Agriculture, 4279 E. Mount Hope Road, East Lansing, MI 48823, USA; (C.J.H.); (J.M.); (D.V.-I.); (H.H.C.)
| | - John R. Dunn
- Southeast Poultry Research Laboratory, U.S. National Poultry Research Center, Agricultural Research Service, U.S. Department of Agriculture, 934 College Station Road, Athens, GA 30605, USA; (S.J.S.); (J.R.D.)
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Xu H, Krieter AL, Ponnuraj N, Tien YYT, Kim T, Jarosinski KW. Coinfection in the host can result in functional complementation between live vaccines and virulent virus. Virulence 2022; 13:980-989. [PMID: 35658809 PMCID: PMC9191873 DOI: 10.1080/21505594.2022.2082645] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
One of the greatest achievements of the last century is the development of vaccines against viral diseases. Vaccines are essential for battling infectious diseases and many different formulations are available, including live attenuated vaccines. However, the use of live attenuated vaccines has the potential for adverse effects, including reversion of pathogenicity, recombination, and functional complementation in the host. Marek’s disease is a serious disease in poultry controlled by live attenuated vaccines that has resulted in increased virulence over the decades. Recombination between circulating field viruses or vaccines is a proposed mechanism for the increase in virulence, however, complementation between vaccines and field strains has not been demonstrated in chickens. Here, we describe functional complementation of vaccines with virulent virus to functionally complement transmission and spread in the host. Using the natural virus-host model of Marek’s disease in chickens, our results show dual infection of target cells in chickens with vaccine and virulent virus providing the opportunity for recombination or complementation to transpire. Interestingly, our controlled results showed no evidence of recombination between vaccine and virulent virus, but functional complementation occurred in two independent experiments providing proof for complementation during natural infection in vaccinated individuals. These results suggest complementation as a potential mechanism for vaccine-mediated viral evolution and the potential for complementation should be taken into consideration when developing novel vaccines.
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Affiliation(s)
- Huai Xu
- Department of Pathobiology, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Andrea L Krieter
- Department of Pathobiology, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Nagendraprabhu Ponnuraj
- Department of Pathobiology, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Yvette Yung-Tien Tien
- Department of Pathobiology, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Taejoong Kim
- United States Department of Agriculture, Agricultural Research Service, US National Poultry Research Center, Athens, GA, USA
| | - Keith W Jarosinski
- Department of Pathobiology, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, IL, USA
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Stephan T, Burgess SM, Cheng H, Danko CG, Gill CA, Jarvis ED, Koepfli KP, Koltes JE, Lyons E, Ronald P, Ryder OA, Schriml LM, Soltis P, VandeWoude S, Zhou H, Ostrander EA, Karlsson EK. Darwinian genomics and diversity in the tree of life. Proc Natl Acad Sci U S A 2022; 119:e2115644119. [PMID: 35042807 PMCID: PMC8795533 DOI: 10.1073/pnas.2115644119] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Genomics encompasses the entire tree of life, both extinct and extant, and the evolutionary processes that shape this diversity. To date, genomic research has focused on humans, a small number of agricultural species, and established laboratory models. Fewer than 18,000 of ∼2,000,000 eukaryotic species (<1%) have a representative genome sequence in GenBank, and only a fraction of these have ancillary information on genome structure, genetic variation, gene expression, epigenetic modifications, and population diversity. This imbalance reflects a perception that human studies are paramount in disease research. Yet understanding how genomes work, and how genetic variation shapes phenotypes, requires a broad view that embraces the vast diversity of life. We have the technology to collect massive and exquisitely detailed datasets about the world, but expertise is siloed into distinct fields. A new approach, integrating comparative genomics with cell and evolutionary biology, ecology, archaeology, anthropology, and conservation biology, is essential for understanding and protecting ourselves and our world. Here, we describe potential for scientific discovery when comparative genomics works in close collaboration with a broad range of fields as well as the technical, scientific, and social constraints that must be addressed.
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Affiliation(s)
- Taylorlyn Stephan
- National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20817
| | - Shawn M Burgess
- National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20817
| | - Hans Cheng
- Avian Disease and Oncology Laboratory, Agricultural Research Service, US Department of Agriculture, East Lansing, MI 48823
| | - Charles G Danko
- Department of Biomedical Sciences, Baker Institute for Animal Health, Cornell University, Ithaca, NY 14850
| | - Clare A Gill
- Department of Animal Science, Texas A&M University, College Station, TX 77843
| | - Erich D Jarvis
- Laboratory of Neurogenetics of Language, The Rockefeller University, New York, NY 10065
- HHMI, Chevy Chase, MD 20815
| | - Klaus-Peter Koepfli
- Smithsonian-Mason School of Conservation, George Mason University, Front Royal, VA 22630
- Smithsonian Conservation Biology Institute, National Zoological Park, Washington, DC 20008
| | - James E Koltes
- Department of Animal Science, Iowa State University, Ames, IA 50011
| | - Eric Lyons
- School of Plant Sciences, BIO5 Institute, University of Arizona, Tucson, AZ 85721
| | - Pamela Ronald
- Department of Plant Pathology, University of California, Davis, CA 95616
- The Genome Center, University of California, Davis, CA 95616
- The Innovative Genomics Institute, University of California, Berkeley, CA 94720
- Grass Genetics, Joint Bioenergy Institute, Emeryville, CA 94608
| | - Oliver A Ryder
- San Diego Zoo Wildlife Alliance, Escondido, CA 92027
- Department of Evolution, Behavior, and Ecology, University of California San Diego, La Jolla, CA 92093
| | - Lynn M Schriml
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD 21201
| | - Pamela Soltis
- Florida Museum of Natural History, University of Florida, Gainesville, FL 32611
| | - Sue VandeWoude
- Department of Micro-, Immuno-, and Pathology, Colorado State University, Fort Collins, CO 80532
| | - Huaijun Zhou
- Department of Animal Science, University of California, Davis, CA 95616
| | - Elaine A Ostrander
- National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20817
| | - Elinor K Karlsson
- Bioinformatics and Integrative Biology, University of Massachusetts Medical School, Worcester, MA 01655;
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA 01655
- Broad Institute of MIT and Harvard, Cambridge, MA 02142
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Conrad SJ, Oluwayinka EB, Heidari M, Mays JK, Dunn JR. Deletion of the Viral Thymidine Kinase in a Meq-Deleted Recombinant Marek's Disease Virus Reduces Lymphoid Atrophy but Is Less Protective. Microorganisms 2021; 10:7. [PMID: 35056456 PMCID: PMC8779792 DOI: 10.3390/microorganisms10010007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2021] [Revised: 12/17/2021] [Accepted: 12/18/2021] [Indexed: 11/16/2022] Open
Abstract
Marek's disease (MD) is a ubiquitous disease of domesticated chickens and its etiologic agent is the Gallid alphaherpesvirus 2 (GaHV-2), also known as Marek's disease virus (MDV). MD is currently controlled by vaccination using live attenuated strains of MDV (e.g., CVI988/Rispens), non-pathogenic serotypes of MDV (GaHV-3), or non-pathogenic strains of the related Melagrid alphaherpesvirus 1 (MeHV-1). One attractive strategy for the production of new vaccine strains is a recombinant MDV attenuated by the deletion of the major viral oncogene meq. However, meq-deleted variants of MDV cause atrophy of the bursa and thymus in maternal antibody-negative chickens, and the resulting immunosuppression makes them unsuitable. Herein we detail our attempt to mitigate the lymphoid atrophy caused by meq-deleted MDV by further attenuation of the virus through ablation of the viral thymidine kinase (tk) gene. We demonstrate that ablation of the viral tk from the meq-deleted virus rMd5B40/Δmeq resulted in a virus attenuated for replication in vitro and which spared chickens from atrophy of the lymphoid organs in vivo. When the rMd5B40/Δmeq/Δtk/GFP was used as a vaccine it was protective against challenge with the vv+MDV strain 686, but the protection was less than that provided by the CVI988/Rispens vaccine.
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Affiliation(s)
- Steven J. Conrad
- United States Department of Agriculture, Agricultural Research Service, U.S. National Poultry Research Center, Avian Disease and Oncology Laboratory, East Lansing, MI 48823, USA; (S.J.C.); (M.H.); (J.K.M.)
| | - Eniope B. Oluwayinka
- Department of Veterinary Medicine, Federal University of Agriculture Abeokuta, Abeokuta 111101, Nigeria;
| | - Mohammad Heidari
- United States Department of Agriculture, Agricultural Research Service, U.S. National Poultry Research Center, Avian Disease and Oncology Laboratory, East Lansing, MI 48823, USA; (S.J.C.); (M.H.); (J.K.M.)
| | - Jody K. Mays
- United States Department of Agriculture, Agricultural Research Service, U.S. National Poultry Research Center, Avian Disease and Oncology Laboratory, East Lansing, MI 48823, USA; (S.J.C.); (M.H.); (J.K.M.)
| | - John R. Dunn
- United States Department of Agriculture, Agricultural Research Service, U.S. National Poultry Research Center, Avian Disease and Oncology Laboratory, East Lansing, MI 48823, USA; (S.J.C.); (M.H.); (J.K.M.)
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8
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Vega-Rodriguez W, Xu H, Ponnuraj N, Akbar H, Kim T, Jarosinski KW. The requirement of glycoprotein C (gC) for interindividual spread is a conserved function of gC for avian herpesviruses. Sci Rep 2021; 11:7753. [PMID: 33833367 PMCID: PMC8032754 DOI: 10.1038/s41598-021-87400-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Accepted: 03/25/2021] [Indexed: 12/12/2022] Open
Abstract
We have formerly shown that glycoprotein C (gC) of Gallid alphaherpesvirus 2, better known as Marek’s disease (MD) alphaherpesvirus (MDV), is required for interindividual spread in chickens. Since gC is conserved within the Alphaherpesvirinae subfamily, we hypothesized gC was important for interindividual spread of other alphaherpesviruses. To test this hypothesis, we first generated a fluorescent protein tagged clone of Gallid alphaherpesvirus 3 MD vaccine strain 301B/1 to track virus replication in cell culture and chickens using fluorescent microscopy. Following validation of this system, we removed the open reading frame of 301B/1 gC from the genome and determined whether it was required for interindividual spread using experimental and natural infection studies. Interindividual spread of MD vaccine 301B/1 was abrogated by removal of 301B/1 gC. Rescuent virus in which 301B/1 gC was inserted back into the genome efficiently spread among chickens. To further study the conserved function of gC, we replaced 301B/1 gC with MDV gC and this virus also efficiently spread in chickens. These data suggest the essential function of alphaherpesvirus gC proteins is conserved and can be exploited during the generation of future vaccines against MD that affects the poultry industry worldwide.
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Affiliation(s)
- Widaliz Vega-Rodriguez
- Department of Pathobiology, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Huai Xu
- Department of Pathobiology, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Nagendraprabhu Ponnuraj
- Department of Pathobiology, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Haji Akbar
- Department of Pathobiology, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Taejoong Kim
- United States Department of Agriculture, Agricultural Research Service, US National Poultry Research Center, Athens, GA, USA
| | - Keith William Jarosinski
- Department of Pathobiology, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
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Dunn JR, Mays J, Hearn C, Hartman A. Comparison of Marek's disease virus challenge strains and bird types for vaccine licensing. Avian Dis 2021; 65:241-249. [PMID: 33567073 DOI: 10.1637/aviandiseases-d-20-00122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Accepted: 02/10/2021] [Indexed: 11/05/2022]
Abstract
Marek's disease virus (MDV) is an important poultry pathogen which is controlled through widespread vaccination with avirulent and attenuated strains, but continued evolution of field viruses to higher virulence has required ongoing improvement of available vaccine strains, and these vaccine strains also offer an attractive platform for designing recombinant vector vaccines with cross-protection against MDV and additional pathogens. Recent reports of failures in vaccine licensing trials of positive controls to reach appropriately high levels of MD incidence prompted us to evaluate possible combinations of outbred specific pathogen-free (SPF) layer lines and alternative virulent challenge strains which could provide more consistent models for serotype-3 vectored vaccine development. Choice of layer line and virulent MDV challenge strain each contributed to the ability of a challenge model to reach 80 percent virulence in unvaccinated positive control groups in the majority of trials without overwhelming serotype-3 vectored vaccine protection in vaccinated groups. Conversely, reducing challenge virus dose by a factor of four, or vaccine dose by half, had no consistent effect across these models. Although MDV strain 617A had the most potential as an alternative to strains that are currently approved for licensing trials, no combination of layer line and challenge virus consistently met the goals for a successful challenge model in all study replicates, indicating that high variability is an inherent difficulty in MDV challenge studies, at least when outbred birds are used.
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Affiliation(s)
- John R Dunn
- USDA-ARS Reviewer US National Poultry Research Center 934 College Station Rd UNITED STATES Athens GA 30605 1-706-546-3642
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Abstract
The domestication of animals led to a major shift in human subsistence patterns, from a hunter-gatherer to a sedentary agricultural lifestyle, which ultimately resulted in the development of complex societies. Over the past 15,000 years, the phenotype and genotype of multiple animal species, such as dogs, pigs, sheep, goats, cattle and horses, have been substantially altered during their adaptation to the human niche. Recent methodological innovations, such as improved ancient DNA extraction methods and next-generation sequencing, have enabled the sequencing of whole ancient genomes. These genomes have helped reconstruct the process by which animals entered into domestic relationships with humans and were subjected to novel selection pressures. Here, we discuss and update key concepts in animal domestication in light of recent contributions from ancient genomics.
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Sadigh Y, Tahiri-Alaoui A, Spatz S, Nair V, Ribeca P. Pervasive Differential Splicing in Marek's Disease Virus can Discriminate CVI-988 Vaccine Strain from RB-1B Very Virulent Strain in Chicken Embryonic Fibroblasts. Viruses 2020; 12:E329. [PMID: 32197378 PMCID: PMC7150913 DOI: 10.3390/v12030329] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Revised: 03/07/2020] [Accepted: 03/10/2020] [Indexed: 12/13/2022] Open
Abstract
Marek's disease is a major scourge challenging poultry health worldwide. It is caused by the highly contagious Marek's disease virus (MDV), an alphaherpesvirus. Here, we showed that, similar to other members of its Herpesviridae family, MDV also presents a complex landscape of splicing events, most of which are uncharacterised and/or not annotated. Quite strikingly, and although the biological relevance of this fact is unknown, we found that a number of viral splicing isoforms are strain-specific, despite the close sequence similarity of the strains considered: very virulent RB-1B and vaccine CVI-988. We validated our findings by devising an assay that discriminated infections caused by the two strains in chicken embryonic fibroblasts on the basis of the presence of some RNA species. To our knowledge, this study is the first to accomplish such a result, emphasizing how relevant a comprehensive picture of the viral transcriptome is to fully understand viral pathogenesis.
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Affiliation(s)
- Yashar Sadigh
- Avian Viral Oncogenesis, The Pirbright Institute, Ash Road, Woking GU24 0NF, UK;
| | - Abdessamad Tahiri-Alaoui
- Clinical BioManufacturing Facility, The Jenner Institute, University of Oxford, Old Road, Headington, Oxford OX3 7JT, UK;
| | - Stephen Spatz
- US National Poultry Research Center, 934 College Station Road, Athens, GA 30605, USA;
| | - Venugopal Nair
- Avian Viral Oncogenesis, The Pirbright Institute, Ash Road, Woking GU24 0NF, UK;
| | - Paolo Ribeca
- Integrative Biology and Bioinformatics, The Pirbright Institute, Ash Road, Woking GU24 0NF, UK
- Biomathematics and Statistics Scotland (BioSS), James Clerk Maxwell Building, Peter Guthrie Tait Road, The King’s Buildings, Edinburgh EH9 3FD, UK
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12
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Bertzbach LD, Conradie AM, You Y, Kaufer BB. Latest Insights into Marek's Disease Virus Pathogenesis and Tumorigenesis. Cancers (Basel) 2020; 12:cancers12030647. [PMID: 32164311 PMCID: PMC7139298 DOI: 10.3390/cancers12030647] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2020] [Revised: 03/06/2020] [Accepted: 03/07/2020] [Indexed: 12/14/2022] Open
Abstract
Marek’s disease virus (MDV) infects chickens and causes one of the most frequent cancers in animals. Over 100 years of research on this oncogenic alphaherpesvirus has led to a profound understanding of virus-induced tumor development. Live-attenuated vaccines against MDV were the first that prevented cancer and minimized the losses in the poultry industry. Even though the current gold standard vaccine efficiently protects against clinical disease, the virus continuously evolves towards higher virulence. Emerging field strains were able to overcome the protection provided by the previous two vaccine generations. Research over the last few years revealed important insights into the virus life cycle, cellular tropism, and tumor development that are summarized in this review. In addition, we discuss recent data on the MDV transcriptome, the constant evolution of this highly oncogenic virus towards higher virulence, and future perspectives in MDV research.
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13
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Bailey RI, Cheng HH, Chase-Topping M, Mays JK, Anacleto O, Dunn JR, Doeschl-Wilson A. Pathogen transmission from vaccinated hosts can cause dose-dependent reduction in virulence. PLoS Biol 2020; 18:e3000619. [PMID: 32134914 PMCID: PMC7058279 DOI: 10.1371/journal.pbio.3000619] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Accepted: 01/30/2020] [Indexed: 02/07/2023] Open
Abstract
Many livestock and human vaccines are leaky because they block symptoms but do not prevent infection or onward transmission. This leakiness is concerning because it increases vaccination coverage required to prevent disease spread and can promote evolution of increased pathogen virulence. Despite leakiness, vaccination may reduce pathogen load, affecting disease transmission dynamics. However, the impacts on post-transmission disease development and infectiousness in contact individuals are unknown. Here, we use transmission experiments involving Marek disease virus (MDV) in chickens to show that vaccination with a leaky vaccine substantially reduces viral load in both vaccinated individuals and unvaccinated contact individuals they infect. Consequently, contact birds are less likely to develop disease symptoms or die, show less severe symptoms, and shed less infectious virus themselves, when infected by vaccinated birds. These results highlight that even partial vaccination with a leaky vaccine can have unforeseen positive consequences in controlling the spread and symptoms of disease.
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Affiliation(s)
- Richard I. Bailey
- Division of Genetics and Genomics, The Roslin Institute, Easter Bush, Midlothian, United Kingdom
| | - Hans H. Cheng
- USDA, Agricultural Research Service, US National Poultry Research Center, Avian Disease and Oncology Laboratory, East Lansing, Michigan, United States of America
| | - Margo Chase-Topping
- Division of Genetics and Genomics, The Roslin Institute, Easter Bush, Midlothian, United Kingdom
- Usher Institute of Population Health Sciences & Informatics, University of Edinburgh, Edinburgh, United Kingdom
| | - Jody K. Mays
- USDA, Agricultural Research Service, US National Poultry Research Center, Avian Disease and Oncology Laboratory, East Lansing, Michigan, United States of America
| | - Osvaldo Anacleto
- Division of Genetics and Genomics, The Roslin Institute, Easter Bush, Midlothian, United Kingdom
| | - John R. Dunn
- USDA, Agricultural Research Service, US National Poultry Research Center, Avian Disease and Oncology Laboratory, East Lansing, Michigan, United States of America
| | - Andrea Doeschl-Wilson
- Division of Genetics and Genomics, The Roslin Institute, Easter Bush, Midlothian, United Kingdom
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14
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Dunn JR, Black Pyrkosz A, Steep A, Cheng HH. Identification of Marek's disease virus genes associated with virulence of US strains. J Gen Virol 2019; 100:1132-1139. [PMID: 31184569 DOI: 10.1099/jgv.0.001288] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Marek's disease virus (MDV) is the most well-cited example of vaccine-driven virulence evolution. MDV induces a lymphoproliferative disease in chickens, which is currently controlled by widespread vaccination of flocks. Unfortunately, Marek's disease (MD) vaccines, while effective in preventing tumours, do not prevent viral replication and mutation, which has been hypothesized as the major driving force for increased MDV virulence of field strains during the past 40 years in US commercial flocks. To limit future virulence increases, there is interest in characterizing MDV strain genomes collected over the years and associating genetic variations with variation in virulence. In this study, we characterized 70 MDV genomes with known virulence by complete or targeted DNA sequencing, and identified genetic variants that showed association with virulence. Our results revealed a number of MDV genes as would be expected for a complex trait. In addition, phylogenetic analysis revealed a clear separation of strains that varied by virulence. Interestingly, high virulence isolates from the same farms persisted over years despite eradication attempts, which has implications on control efforts. Given the growing ability to bioengineer the MDV genome, it should be feasible to experimentally test whether these individual variants influence virulence markers alone or combinations. Once validated, these markers may provide an alternative to live bird testing for evaluating virulence of new MDV field strains.
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Affiliation(s)
- John R Dunn
- Avian Disease and Oncology Laboratory, Agricultural Research Service, United States Department of Agriculture, 4279 E. Mount Hope Road, East Lansing, MI, 48823, USA
| | - Alexis Black Pyrkosz
- Avian Disease and Oncology Laboratory, Agricultural Research Service, United States Department of Agriculture, 4279 E. Mount Hope Road, East Lansing, MI, 48823, USA
| | - Alec Steep
- Avian Disease and Oncology Laboratory, Agricultural Research Service, United States Department of Agriculture, 4279 E. Mount Hope Road, East Lansing, MI, 48823, USA.,Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, 48824, USA
| | - Hans H Cheng
- Avian Disease and Oncology Laboratory, Agricultural Research Service, United States Department of Agriculture, 4279 E. Mount Hope Road, East Lansing, MI, 48823, USA
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15
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Trimpert J, Groenke N, Jenckel M, He S, Kunec D, Szpara ML, Spatz SJ, Osterrieder N, McMahon DP. A phylogenomic analysis of Marek's disease virus reveals independent paths to virulence in Eurasia and North America. Evol Appl 2017; 10:1091-1101. [PMID: 29151863 PMCID: PMC5680632 DOI: 10.1111/eva.12515] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Accepted: 07/01/2017] [Indexed: 12/28/2022] Open
Abstract
Virulence determines the impact a pathogen has on the fitness of its host, yet current understanding of the evolutionary origins and causes of virulence of many pathogens is surprisingly incomplete. Here, we explore the evolution of Marek's disease virus (MDV), a herpesvirus commonly afflicting chickens and rarely other avian species. The history of MDV in the 20th century represents an important case study in the evolution of virulence. The severity of MDV infection in chickens has been rising steadily since the adoption of intensive farming techniques and vaccination programs in the 1950s and 1970s, respectively. It has remained uncertain, however, which of these factors is causally more responsible for the observed increase in virulence of circulating viruses. We conducted a phylogenomic study to understand the evolution of MDV in the context of dramatic changes to poultry farming and disease control. Our analysis reveals evidence of geographical structuring of MDV strains, with reconstructions supporting the emergence of virulent viruses independently in North America and Eurasia. Of note, the emergence of virulent viruses appears to coincide approximately with the introduction of comprehensive vaccination on both continents. The time‐dated phylogeny also indicated that MDV has a mean evolutionary rate of ~1.6 × 10−5 substitutions per site per year. An examination of gene‐linked mutations did not identify a strong association between mutational variation and virulence phenotypes, indicating that MDV may evolve readily and rapidly under strong selective pressures and that multiple genotypic pathways may underlie virulence adaptation in MDV.
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Affiliation(s)
- Jakob Trimpert
- Institut für Virologie Freie Universität Berlin Berlin Germany
| | - Nicole Groenke
- Institut für Virologie Freie Universität Berlin Berlin Germany
| | - Maria Jenckel
- Institute of Diagnostic Virology Friedrich-Loeffler-Institut Greifswald-Insel Riems Germany
| | - Shulin He
- Institut für Biologie Freie Universität Berlin Berlin Germany.,Department for Materials and Environment BAM Federal Institute for Materials Research and Testing Berlin Germany
| | - Dusan Kunec
- Institut für Virologie Freie Universität Berlin Berlin Germany
| | - Moriah L Szpara
- Department of Biochemistry and Molecular Biology Center for Infectious Disease Dynamics and the Huck Institutes of the Life Sciences Pennsylvania State University University Park PA USA
| | - Stephen J Spatz
- United States Department of Agriculture US National Poultry Research Center Athens GA USA
| | | | - Dino P McMahon
- Institut für Biologie Freie Universität Berlin Berlin Germany.,Department for Materials and Environment BAM Federal Institute for Materials Research and Testing Berlin Germany
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16
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Rozins C, Day T. The industrialization of farming may be driving virulence evolution. Evol Appl 2016; 10:189-198. [PMID: 28127395 PMCID: PMC5253429 DOI: 10.1111/eva.12442] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 10/03/2016] [Indexed: 02/02/2023] Open
Abstract
Farming practices have changed dramatically over the years. The industrialization of farming has provided parasites with an abundance of hosts and is thought to have influenced parasite evolution. For example, the parasite that causes the highly contagious poultry disease, Marek's disease, has evolved over the past 60 years into a highly virulent pathogen. It is assumed that the industrialization of the industry and vaccination have selected for more virulent strains of the virus. Here, with the use of an impulsive differential equation model, we investigate how modern broiler farm practices could independently lead to virulence evolution. Our model suggests that longer cohort durations and more densely stocked barns both select for less virulent strains of the virus. Our model also suggests that if intensive cleaning between cohorts does not rid the barn of disease, it may drive evolution and cause the disease to become more virulent.
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Affiliation(s)
- Carly Rozins
- Department of Mathematics and Statistics Queen's University Kingston ON Canada
| | - Troy Day
- Department of Mathematics and Statistics Queen's University Kingston ON Canada
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17
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Ralapanawe S, Walkden-Brown SW, Renz KG, Islam AFMF. Protection provided by Rispens CVI988 vaccine against Marek's disease virus isolates of different pathotypes and early prediction of vaccine take and MD outcome. Avian Pathol 2016; 45:26-37. [DOI: 10.1080/03079457.2015.1110850] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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18
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Ralapanawe S, Walkden-Brown SW, Islam AF, Renz KG. Effects of Rispens CVI988 vaccination followed by challenge with Marek’s disease viruses of differing virulence on the replication kinetics and shedding of the vaccine and challenge viruses. Vet Microbiol 2016; 183:21-9. [DOI: 10.1016/j.vetmic.2015.11.025] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2015] [Revised: 11/17/2015] [Accepted: 11/18/2015] [Indexed: 11/26/2022]
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19
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Jaganathan S, Ooi PT, Phang LY, Allaudin ZNB, Yip LS, Choo PY, Lim BK, Lemiere S, Audonnet JC. Observation of risk factors, clinical manifestations and genetic characterization of recent Newcastle Disease Virus outbreak in West Malaysia. BMC Vet Res 2015; 11:219. [PMID: 26293577 PMCID: PMC4546084 DOI: 10.1186/s12917-015-0537-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Accepted: 08/06/2015] [Indexed: 11/10/2022] Open
Abstract
Background Newcastle disease virus remains a constant threat in commercial poultry farms despite intensive vaccination programs. Outbreaks attributed to ND can escalate and spread across farms and states contributing to major economic loss in poultry farms. Results Phylogenetic analysis in our study showed that eleven of the samples belonged to genotype VIId. All farms were concurrently positive with two immunosuppressive viruses; Infectious Bursal Disease Virus (IBDV) and Marek’s Disease Virus (MDV). Amino acid sequence analysis confirmed that eleven of the samples had sequence motifs for velogenic/mesogenic strains; three were lentogenic. Conclusion In conclusion, no new NDV genotype was isolated from the 2011 NDV outbreak. This study suggests that the presence of other immunosuppressive agents such as IBD and MDV could have contributed to the dysfunction of the immune system of the chickens, causing severe NDV outbreaks in 2011. Risk factors related to biosecurity and farm practices appear to have a significant role in the severity of the disease observed in affected farms.
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Affiliation(s)
- Seetha Jaganathan
- Department of Clinical Studies, Faculty of Veterinary Medicine, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia. .,Asia-Pacific Special Nutrients Sdn. Bhd, Lot 18B, Jalan 241, Section 51A, 46100, Petaling Jaya, Selangor, Malaysia. .,Vet Food Agro Diagnostic Sdn. Bhd., Lot 18B, Jalan 241, Section 51A, 46100, Petaling Jaya, Selangor, Malaysia.
| | - Peck Toung Ooi
- Department of Clinical Studies, Faculty of Veterinary Medicine, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia.
| | - Lai Yee Phang
- Department of Biotechnology, Faculty of Biotechnology & Molecular Science, Universiti Putra Malaysia, 43400, UPM, Serdang, Selangor, Malaysia.
| | | | - Lai Siong Yip
- Rhone Ma Malaysia (M) Sdn Bhd, Lot 18B, Jalan 241, Section 51A, 46100, Petaling Jaya, Selangor, Malaysia.
| | - Pow Yoon Choo
- Rhone Ma Malaysia (M) Sdn Bhd, Lot 18B, Jalan 241, Section 51A, 46100, Petaling Jaya, Selangor, Malaysia.
| | - Ban Keong Lim
- Rhone Ma Malaysia (M) Sdn Bhd, Lot 18B, Jalan 241, Section 51A, 46100, Petaling Jaya, Selangor, Malaysia.
| | - Stephane Lemiere
- Merial S.A.S., Bio R&D, 254, Rue Marcel Merieux, 69007, Lyon, France.
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20
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Read AF, Baigent SJ, Powers C, Kgosana LB, Blackwell L, Smith LP, Kennedy DA, Walkden-Brown SW, Nair VK. Imperfect Vaccination Can Enhance the Transmission of Highly Virulent Pathogens. PLoS Biol 2015. [PMID: 26214839 PMCID: PMC4516275 DOI: 10.1371/journal.pbio.1002198] [Citation(s) in RCA: 246] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Could some vaccines drive the evolution of more virulent pathogens? Conventional wisdom is that natural selection will remove highly lethal pathogens if host death greatly reduces transmission. Vaccines that keep hosts alive but still allow transmission could thus allow very virulent strains to circulate in a population. Here we show experimentally that immunization of chickens against Marek's disease virus enhances the fitness of more virulent strains, making it possible for hyperpathogenic strains to transmit. Immunity elicited by direct vaccination or by maternal vaccination prolongs host survival but does not prevent infection, viral replication or transmission, thus extending the infectious periods of strains otherwise too lethal to persist. Our data show that anti-disease vaccines that do not prevent transmission can create conditions that promote the emergence of pathogen strains that cause more severe disease in unvaccinated hosts. A study using Marek's disease virus in poultry shows that by reducing natural selection against highly virulent strains, imperfect vaccination enables the spread of viral strains that would otherwise be too lethal to persist. There is a theoretical expectation that some types of vaccines could prompt the evolution of more virulent (“hotter”) pathogens. This idea follows from the notion that natural selection removes pathogen strains that are so “hot” that they kill their hosts and, therefore, themselves. Vaccines that let the hosts survive but do not prevent the spread of the pathogen relax this selection, allowing the evolution of hotter pathogens to occur. This type of vaccine is often called a leaky vaccine. When vaccines prevent transmission, as is the case for nearly all vaccines used in humans, this type of evolution towards increased virulence is blocked. But when vaccines leak, allowing at least some pathogen transmission, they could create the ecological conditions that would allow hot strains to emerge and persist. This theory proved highly controversial when it was first proposed over a decade ago, but here we report experiments with Marek’s disease virus in poultry that show that modern commercial leaky vaccines can have precisely this effect: they allow the onward transmission of strains otherwise too lethal to persist. Thus, the use of leaky vaccines can facilitate the evolution of pathogen strains that put unvaccinated hosts at greater risk of severe disease. The future challenge is to identify whether there are other types of vaccines used in animals and humans that might also generate these evolutionary risks.
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Affiliation(s)
- Andrew F. Read
- Center for Infectious Disease Dynamics, Departments of Biology and Entomology, The Pennsylvania State University, University Park, Pennsylvania, United States of America
- Fogarty International Center, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail:
| | - Susan J. Baigent
- Avian Oncogenic Virus Group, The Pirbright Institute, Compton, Newbury, Berkshire, United Kingdom
| | - Claire Powers
- Avian Oncogenic Virus Group, The Pirbright Institute, Compton, Newbury, Berkshire, United Kingdom
| | - Lydia B. Kgosana
- Avian Oncogenic Virus Group, The Pirbright Institute, Compton, Newbury, Berkshire, United Kingdom
| | - Luke Blackwell
- Avian Oncogenic Virus Group, The Pirbright Institute, Compton, Newbury, Berkshire, United Kingdom
| | - Lorraine P. Smith
- Avian Oncogenic Virus Group, The Pirbright Institute, Compton, Newbury, Berkshire, United Kingdom
| | - David A. Kennedy
- Center for Infectious Disease Dynamics, Departments of Biology and Entomology, The Pennsylvania State University, University Park, Pennsylvania, United States of America
- Fogarty International Center, National Institutes of Health, Bethesda, Maryland, United States of America
| | | | - Venugopal K. Nair
- Avian Oncogenic Virus Group, The Pirbright Institute, Compton, Newbury, Berkshire, United Kingdom
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Zhang YP, Li ZJ, Bao KY, Lv HC, Gao YL, Gao HL, Qi XL, Cui HY, Wang YQ, Ren XG, Wang XM, Liu CJ. Pathogenic characteristics of Marek's disease virus field strains prevalent in China and the effectiveness of existing vaccines against them. Vet Microbiol 2015; 177:62-8. [PMID: 25770895 DOI: 10.1016/j.vetmic.2014.12.020] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Revised: 12/17/2014] [Accepted: 12/21/2014] [Indexed: 10/24/2022]
Abstract
The virulence of Marek's disease virus (MDV) is continuously evolving, and more virulent MDV pathotypes are emerging, thereby reducing the effectiveness of the existing vaccines. In this study, feather pulps were collected from diseased chickens in commercial chicken flocks in China that presented significant MD visceral tumors in 2011 and were inoculated into a monolayer of duck embryo fibroblasts (DEFs). Three field isolates of MDV were obtained by plaque cloning and identified as MDV via PCR and designated strains LCC, LLY, and LTS. Unvaccinated and CVI988 vaccine-vaccinated specific pathogen-free chickens were challenged at 7 days post vaccination (dpv) with 1000 plaque forming units of each of the respective MDV isolates. These strains induced gross MD lesions in all (100%) of the unvaccinated chickens, and the mortality rates of the unvaccinated chickens were 42.9%, 46.7%, and 23.1% by 60 days post challenge (dpc), respectively. The CVI988 vaccine induced protective indices (PIs) of 85.7, 92.3, and 66.7, respectively. These results showed that the pathogenic characteristics of the Chinese isolates were diverse and that vaccine CVI988 provided different levels of protection against them. These data indicated that the existence of variant MDV strains was a possible reason of immunity failure in China.
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Affiliation(s)
- Yan-ping Zhang
- Northeast Agricultural University, Harbin 150030, PR China; Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China
| | - Zhi-jie Li
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China
| | - Ke-yan Bao
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China
| | - Hong-chao Lv
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China
| | - Yu-long Gao
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China
| | - Hong-lei Gao
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China
| | - Xiao-le Qi
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China
| | - Hong-yu Cui
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China
| | - Yong-qiang Wang
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China
| | - Xian-gang Ren
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China
| | - Xiao-mei Wang
- Northeast Agricultural University, Harbin 150030, PR China; Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China.
| | - Chang-jun Liu
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China.
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22
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Replication kinetics and shedding of very virulent Marek's disease virus and vaccinal Rispens/CVI988 virus during single and mixed infections varying in order and interval between infections. Vet Microbiol 2014; 173:208-23. [DOI: 10.1016/j.vetmic.2014.07.027] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Revised: 07/17/2014] [Accepted: 07/27/2014] [Indexed: 11/18/2022]
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23
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Walkden-Brown SW, Islam A, Islam AFMF, Burgess SK, Groves PJ, Cooke J. Pathotyping of Australian isolates of Marek's disease virus in commercial broiler chickens vaccinated with herpesvirus of turkeys (HVT) or bivalent (HVT/SB1) vaccine and association with viral load in the spleen and feather dander. Aust Vet J 2014; 91:341-50. [PMID: 23889101 DOI: 10.1111/avj.12084] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE To pathotype Australian isolates of Marek's disease virus (MDV) in commercial broiler chickens using standard methods and to evaluate early markers of pathotype. METHODS A complete 3 × 4 factorial experiment with two replicates was conducted using 648 Cobb broiler chickens in 24 isolators. The experimental factors were vaccination (unvaccinated, herpesvirus of turkeys (HVT), bivalent (HVT + SB1 strain of serotype 2 MDV)) and MDV challenge (unchallenged or 500 plaque-forming units of isolates MFP57, 02LAR or FT158). Mortality, body weight, immune-organ weights and viral load were measured to 56 days post challenge (dpc). Vaccinal protective index (PI) and virulence rank (VR) were calculated based on gross Marek's disease (MD) pathology. RESULTS The PIs provided by the HVT and bivalent vaccines against challenge with MPF57, 02LAR, and FT158 were 84.6% 56%, 61.4% and 82.2%, 60.8%, 57.7%, respectively, leading to putative pathotypes of virulent MDV for MPF57 and very virulent MDV for 02LAR and FT158. Significantly more of the unvaccinated chickens (85.7%) had MD lesions than chickens vaccinated with either the HVT (26.8%) or bivalent vaccine (27.6%). Strong linear relationships were observed between the incidence of MD at 56 dpc and MDV load in the spleen at 7 dpc (R(2) = 0.71) and MDV load in the isolator exhaust dust at 14 dpc (R(2) = 0.57) and 21 dpc (R(2) = 0.51). Immune organ weights had a weaker association with subsequent MD incidence. CONCLUSION Pathotyping results in broiler chickens with maternal antibody broadly agreed with those in specific-pathogen-free chickens in other studies, with some important differences. MDV load in the spleen at 7 dpc and in isolator dust at both 14 and 21 dpc was a powerful early predictor of subsequent MD incidence.
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Affiliation(s)
- S W Walkden-Brown
- Animal Science, School of Environmental and Rural Science, University of New England, Armidale, New South Wales, 2351, Australia.
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24
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Davison F, Nair V. Use of Marek’s disease vaccines: could they be driving the virus to increasing virulence? Expert Rev Vaccines 2014; 4:77-88. [PMID: 15757475 DOI: 10.1586/14760584.4.1.77] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Marek's disease (MD) is an economically important neoplastic disease of poultry. MD almost devastated the poultry industry in the 1960s but the disease was brought under control after Marek's disease herpesvirus (MDV) was identified and vaccines were developed. This is the first effective use of an antiviral vaccination to prevent a naturally occurring cancer in any species. MDV infection has many effects. Initially causing a cytolytic infection in B-lymphocytes, MDV infects activated T-lymphocytes where it becomes latent. In susceptible chicken genotypes MDV transforms CD4+ lymphocytes, causing visceral lymphomas and/or neural lesions and paralysis. Fully productive infection and shedding of infectious virus only occurs in the feather-follicle epithelium. Vaccination of newly-hatched chicks with live vaccines has been widely used to successfully control MD since the early 1970s. However, vaccinated chickens still become infected and shed MDV. Vaccine breaks have occurred with regularity and there is evidence that the use of MD vaccines could be driving MDV to greater virulence. MD continues to be a threat and a number of strategies have been adopted such as the use of more potent vaccines and vaccination of the embryonic stage to provide earlier protection. Recombinant MD vaccines are useful vectors and are being exploited to carry both viral and host genes to enhance protective immune responses. The future aim must be to develop a sustainable vaccine strategy that does not drive MDV to increased virulence.
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Affiliation(s)
- Fred Davison
- Head and Avian Immunology Group, Institute for Animal Health, Compton, Newbury, Berkshire, RG20 7NN, UK.
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Abstract
This article on poultry and avian diseases assembles a brief description of the current state of the poultry industry and the economical and public health impact of different diseases on these poultry production systems. Besides, a short explanation about the sustainable methods of production has been included in this article. Additionally, a review of the most important diseases that can affect poultry and wild avian species was performed, along with a summary of preventive and control measurements directed to reduce their economic impact. For all diseases, the etiology, clinical signs, and main lesions were reviewed.
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The effectiveness of mass vaccination on Marek's disease virus (MDV) outbreaks and detection within a broiler barn: a modeling study. Epidemics 2013; 5:208-17. [PMID: 24267877 PMCID: PMC3863959 DOI: 10.1016/j.epidem.2013.10.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2013] [Revised: 10/13/2013] [Accepted: 10/14/2013] [Indexed: 11/21/2022] Open
Abstract
Mathematical model to predict the outcome of broiler chicken with and without vaccination after exposure to MDV. Chance of MDV outbreak within a barn increases with the virulence of an MDV strain. Vaccination significantly reduces the chance of an MDV outbreak. Mortality due to MDV is an insufficient metric to assess the prevalence of MDV.
Marek's disease virus (MDV), a poultry pathogen, has been increasing in virulence since the mid twentieth century. Since multiple vaccines have been developed and widely implemented, losses due to MDV have decreased. However, vaccine failure has occurred in the past and vaccine breakthroughs remain a problem. Failure of disease control with current vaccines would have significant economic and welfare consequences. Nevertheless, the epidemiology of the disease during a farm outbreak is not well understood. Here we present a mathematical model to predict the effectiveness of vaccines to reduce the outbreak probability and disease burden within a barn. We find that the chance of an outbreak within a barn increases with the virulence of an MDV strain, and is significantly reduced when the flock is vaccinated, especially when there the contaminant strain is of low virulence. With low quantities of contaminated dust, there is nearly a 100% effectiveness of vaccines to reduce MDV outbreaks. However, the vaccine effectiveness drops to zero with an increased amount of contamination with a middle virulence MDV strain. We predict that the larger the barn, and the more virulent the MDV strain is, the more virus is produced by the time the flock is slaughtered. With the low-to-moderate virulence of the strains studied here, the number of deaths due to MDV is very low compared to all-cause mortality regardless of the vaccination status of the birds. However, the cumulative MD incidence can reach 100% for unvaccinated cohorts, and 35% for vaccinated cohorts. These results suggest that death due to MDV is an insufficient metric to assess the prevalence of MDV broiler barns regardless of vaccine status, such that active surveillance is required to successfully assess the probability of MDV outbreaks, and to limit transmission of MDV between successive cohorts of broiler chickens.
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Walkden-Brown SW, Islam AFA, Groves PJ, Rubite A, Sharpe SM, Burgess SK. Development, application, and results of routine monitoring of Marek's disease virus in broiler house dust using real-time quantitative PCR. Avian Dis 2013; 57:544-54. [PMID: 23901774 DOI: 10.1637/10380-92112-reg.1] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Results are presented from four studies between 2002 and 2011 into the feasibility of routinely monitoring Marek's disease virus serotype 1 (MDV-1) in broiler house dust using real-time quantitative PCR (qPCR) measurement. Study 1 on two farms showed that detection of MDV-1 occurred earlier on average in dust samples tested using qPCR than standard PCR and in spleen samples from five birds per shed assayed for MDV-1 by qPCR or standard PCR. DNA quality following extraction from dust had no effect on detection of MDV-1. Study 2 demonstrated that herpesvirus of turkeys (HVT) and MDV serotype 2 (MDV-2) in addition to MDV-1 could be readily amplified from commercial farm dust samples, often in mixtures. MDV-2 was detected in 11 of 20 samples despite the absence of vaccination with this serotype. Study 3 investigated the reproducibility and sensitivity of the qPCR test and the presence of inhibitors in the samples. Samples extracted and amplified in triplicate showed a high level of reproducibility except at very low levels of virus near the limit of detection. Mixing of samples prior to extraction provided results consistent with the proportions in the mixture. Tests for inhibition showed that if the template contained DNA in the range 0.5-20 ng/microl no inhibition of the reaction was detectable. The sensitivity of the tests in terms of viral copy number (VCN) per milligram of dust was calculated to be in the range 24-600 VCN/mg for MDV-1, 48-1200 VCN/mg for MDV-2, and 182-4560 VCN/mg for HVT. In study 4 the results of 1976 commercial tests carried out for one company were analyzed. Overall 23.1% of samples were positive for MDV-1, 26.1% in unvaccinated and 16.4% in vaccinated chickens. There was marked regional and temporal variation in the proportion of positive samples and the MDV-1 load. The tests were useful in formulating Marek's disease vaccination strategies. The number of samples submitted has increased recently, as has the incidence of positive samples. These studies provide strong evidence that detection and quantitation of MDV-1, HVT, and MDV-2 in poultry house dust using qPCR is robust, sensitive, reproducible, and meaningful, both biologically and commercially. Tactical vaccination based on monitoring of MDV-1 rather than routine vaccination may reduce selection pressure for increased virulence in MDV-1.
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Affiliation(s)
- Stephen W Walkden-Brown
- Animal Science, School of Environmental and Rural Science, University of New England, Armidale, NSW Australia.
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Hall RN, Meers J, Mitter N, Fowler EV, Mahony TJ. The Meleagrid herpesvirus 1 genome is partially resistant to transposition. Avian Dis 2013; 57:380-6. [PMID: 23901750 DOI: 10.1637/10339-082912-reg.1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The propagation of herpesvirus genomes as infectious bacterial artificial chromosomes (iBAC) has enabled the application of highly efficient strategies to investigate gene function across the genome. One of these strategies, transposition, has been used successfully on a number of herpesvirus iBACs to generate libraries of gene disruption mutants. Gene deletion studies aimed at determining the dispensable gene repertoire of the Meleagrid herpesvirus 1 (MeHV-1) genome to enhance the utility of this virus as a vaccine vector have been conducted in this report. A MeHV-1 iBAC was used in combination with the Tn5 and MuA transposition systems in an attempt to generate MeHV-1 gene interruption libraries. However, these studies demonstrated that Tn5 transposition events into the MeHV-1 genome occurred at unexpectedly low frequencies. Furthermore, characterization of genomic locations of the rare Tn5 transposon insertion events indicated a nonrandom distribution within the viral genome, with seven of the 24 insertions occurring within the gene encoding infected cell protein 4. Although insertion events with the MuA system occurred at higher frequency compared with the Tn5 system, fewer insertion events were generated than has previously been reported with this system. The characterization and distribution of these MeHV-1 iBAC transposed mutants is discussed at both the nucleotide and genomic level, and the properties of the MeHV-1 genome that could influence transposition frequency are discussed.
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Affiliation(s)
- Robyn N Hall
- School of Veterinary Science, The University of Queensland, Gatton, QLD 4343, Australia
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Sorci G, Cornet S, Faivre B. Immunity and the emergence of virulent pathogens. INFECTION GENETICS AND EVOLUTION 2013; 16:441-6. [PMID: 23333337 DOI: 10.1016/j.meegid.2012.12.031] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Revised: 12/24/2012] [Accepted: 12/27/2012] [Indexed: 12/28/2022]
Abstract
The emergence/re-emergence of infectious diseases has been one of the major concerns for human and wildlife health. In spite of the medical and veterinary progresses as to prevent and cure infectious diseases, during the last decades we have witnessed the emergence/re-emergence of virulent pathogens that pose a threat to humans and wildlife. Many factors that might drive the emergence of these novel pathogens have been identified and several reviews have been published on this topic in the last years. Among the most cited and recognized drivers of pathogen emergence are climate change, habitat destruction, increased contact with reservoirs, etc. These factors mostly refer to environmental determinants of emergence. However, the immune system of the host is probably the most important environmental trait parasites have to cope with. Here, we wish to discuss how immune-mediated selection might affect the emergence/re-emergence of infectious diseases and drive the evolution of disease severity. Vaccination, natural (age-associated) and acquired immunodeficiencies, organ transplantation, environmental contamination with chemicals that disrupt immune functions form populations of hosts that might exert specific immune-mediated selection on a range of pathogens, shaping their virulence and evolution, and favoring their spread to other populations of hosts.
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Affiliation(s)
- Gabriele Sorci
- Biogéosciences, UMR CNRS 6282, Université de Bourgogne, Dijon, France.
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Atkins KE, Read AF, Savill NJ, Renz KG, Islam AFMF, Walkden-Brown SW, Woolhouse MEJ. Vaccination and reduced cohort duration can drive virulence evolution: Marek's disease virus and industrialized agriculture. Evolution 2012; 67:851-60. [PMID: 23461333 DOI: 10.1111/j.1558-5646.2012.01803.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Marek's disease virus (MDV), a commercially important disease of poultry, has become substantially more virulent over the last 60 years. This evolution was presumably a consequence of changes in virus ecology associated with the intensification of the poultry industry. Here, we assess whether vaccination or reduced host life span could have generated natural selection, which favored more virulent strains. Using previously published experimental data, we estimated viral fitness under a range of cohort durations and vaccine treatments on broiler farms. We found that viral fitness maximized at intermediate virulence, as a result of a trade-off between virulence and transmission previously reported. Our results suggest that vaccination, acting on this trade-off, could have led to the evolution of increased virulence. By keeping the host alive, vaccination prolongs infectious periods of virulent strains. Improvements in host genetics and nutrition, which reduced broiler life spans below 50 days, could have also increased the virulence of the circulating MDV strains because shortened cohort duration reduces the impact of host death on viral fitness. These results illustrate the dramatic impact anthropogenic change can potentially have on pathogen virulence.
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Affiliation(s)
- Katherine E Atkins
- Centre for Infectious Diseases, University of Edinburgh, West Mains Road, EH9 3JT, United Kingdom.
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31
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An assessment of opportunities to dissect host genetic variation in resistance to infectious diseases in livestock. Animal 2012; 3:415-36. [PMID: 22444313 DOI: 10.1017/s1751731108003522] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
This paper reviews the evidence for host genetic variation in resistance to infectious diseases for a wide variety of diseases of economic importance in poultry, cattle, pig, sheep and Atlantic salmon. Further, it develops a method of ranking each disease in terms of its overall impact, and combines this ranking with published evidence for host genetic variation and information on the current state of genomic tools in each host species. The outcome is an overall ranking of the amenability of each disease to genomic studies that dissect host genetic variation in resistance. Six disease-based assessment criteria were defined: industry concern, economic impact, public concern, threat to food safety or zoonotic potential, impact on animal welfare and threat to international trade barriers. For each category, a subjective score was assigned to each disease according to the relative strength of evidence, impact, concern or threat posed by that particular disease, and the scores were summed across categories. Evidence for host genetic variation in resistance was determined from available published data, including breed comparison, heritability studies, quantitative trait loci (QTL) studies, evidence of candidate genes with significant effects, data on pathogen sequence and on host gene expression analyses. In total, 16 poultry diseases, 13 cattle diseases, nine pig diseases, 11 sheep diseases and three Atlantic salmon diseases were assessed. The top-ranking diseases or pathogens, i.e. those most amenable to studies dissecting host genetic variation, were Salmonella in poultry, bovine mastitis, Marek's disease and coccidiosis, both in poultry. The top-ranking diseases or pathogens in pigs, sheep and Atlantic salmon were Escherichia coli, mastitis and infectious pancreatic necrosis, respectively. These rankings summarise the current state of knowledge for each disease and broadly, although not entirely, reflect current international research efforts. They will alter as more information becomes available and as genome tools become more sophisticated for each species. It is suggested that this approach could be used to rank diseases from other perspectives as well, e.g. in terms of disease control strategies.
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Renz KG, Cooke J, Clarke N, Cheetham BF, Hussain Z, Fakhrul Islam AFM, Tannock GA, Walkden-Brown SW. Pathotyping of Australian isolates of Marek's disease virus and association of pathogenicity with meq gene polymorphism. Avian Pathol 2012; 41:161-76. [PMID: 22515535 DOI: 10.1080/03079457.2012.656077] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
We report the pathotyping of six Australian isolates of Marek's disease virus-1 (MDV1) isolated between 1992 and 2004 and association of virulence with meq gene polymorphism. Unvaccinated and herpesvirus of turkeys (HVT)-vaccinated specific pathogen free chickens were challenged at day 5 with 500 plaque forming units of Marek's disease virus. The isolates induced gross Marek's disease lesions in 53 to 94% of unvaccinated chickens, and HVT induced a protective index ranging from 38 to 100% by 56 days post challenge. This experiment provides evidence that current Australian isolates of MDV1 vary significantly in pathogenicity. However, there was no clear evidence that the most virulent recent isolates were more pathogenic than isolates from the 1980s or that any of the isolates belong to the highest pathotype category of very virulent plus. Evidence is presented that virulence can be predicted by measurements taken as early as 13 days post challenge. The meq gene sequences of five of the isolates used in the experiment were determined. When compared with the very virulent US isolate Md5, there was a 177 base-pair insertion and distinct point mutations in each of the five isolates. There were no individual mutations in the meq sequences that correlated with levels of virulence. However, amino acid alignment of the five Australian and 14 international isolates revealed that the number of repeat sequences of four prolines (PPPP repeats) in the meq gene (overall range 2 to 8) was strongly associated with virulence across all isolates, with the most pathogenic isolates having the fewest number of repeats. The results suggest that the presence of the 177 base-pair insertion alone is not an indicator of attenuation. Rather, the number of PPPP repeats, independent of the presence of the insertion, is a better indicator of pathogenicity.
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Affiliation(s)
- Katrin G Renz
- School of Animal and Veterinary Sciences, Charles Sturt University, Wagga Wagga, NSW 2678, Australia.
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Atkins KE, Read AF, Savill NJ, Renz KG, Walkden-Brown SW, Woolhouse MEJ. Modelling Marek's disease virus (MDV) infection: parameter estimates for mortality rate and infectiousness. BMC Vet Res 2011; 7:70. [PMID: 22078942 PMCID: PMC3226581 DOI: 10.1186/1746-6148-7-70] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2010] [Accepted: 11/11/2011] [Indexed: 11/12/2022] Open
Abstract
Background Marek's disease virus (MDV) is an economically important oncogenic herpesvirus of poultry. Since the 1960s, increasingly virulent strains have caused continued poultry industry production losses worldwide. To understand the mechanisms of this virulence evolution and to evaluate the epidemiological consequences of putative control strategies, it is imperative to understand how virulence is defined and how this correlates with host mortality and infectiousness during MDV infection. We present a mathematical approach to quantify key epidemiological parameters. Host lifespan, virus latent periods and host viral shedding rates were estimated for unvaccinated and vaccinated birds, infected with one of three MDV strains. The strains had previously been pathotyped to assign virulence scores according to pathogenicity of strains in hosts. Results Our analyses show that strains of higher virulence have a higher viral shedding rate, and more rapidly kill hosts. Vaccination enhances host life expectancy but does not significantly reduce the shedding rate of the virus. While the primary latent period of the virus does not vary with challenge strain nor vaccine treatment of host, the time until the maximum viral shedding rate is increased with vaccination. Conclusions Our approach provides the tools necessary for a formal analysis of the evolution of virulence in MDV, and potentially simpler and cheaper approaches to comparing the virulence of MDV strains.
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Affiliation(s)
- Katherine E Atkins
- Centre for Infectious Diseases, University Of Edinburgh, West Mains Road, Edinburgh, UK. .
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Jin YC, Wei P, Wei XX, Zhao ZY, Li Y. Marek's disease resistant/susceptible MHC haplotypes in Xiayan chickens identified on the basis of BLB2 PCR-RFLP and BLB2/BF2 sequence analyses. Br Poult Sci 2011; 51:530-9. [PMID: 20924848 DOI: 10.1080/00071668.2010.508489] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
1. The aim was to analyse the variability of the BLB2/BF2 genes of Xiayan chickens to identify homozygous birds with resistance or susceptibility to Marek's disease (MD). 2. The experiment used two lines: birds from a common line were divided into Group A (unvaccinated) and Group B (vaccinated with herpesvirus of turkeys (HVT)); and birds from an MD-resistant line were divided into Group C (unvaccinated) and Group D (vaccinated with HVT). They were challenged intra-abdominally with Marek's disease virus (MDV) and genomic DNA extracted from peripheral blood lymphocytes so that polymorphism of the BLB2/BF2 genes could be analysed using polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) and nucleotide sequence analysis. 3. A 374-bp fragment of the BLB2 gene was amplified from the samples and, after digesting with restriction enzymes Alu I, Cai I, Cfr I, Hin1 I, Hinf I and Rsa I for RFLP analysis, the 6 electrophoretic patterns were analysed. Seven homozygous genotypes were found and used tentatively to identify alleles of the BLB2 gene. 4. A 765-bp fragment of the BF2 gene was amplified from the 7 samples for cloning and sequencing. 5. Six homozygous birds were confirmed from the sequenced BLB2/BF2 gene. Four birds were resistant to MD. Three birds had identical nucleotide sequences and were highly homologous with MHC haplotype B⁶, which is MD resistant. One bird had high homology with the highly MD-resistant B²¹ haplotype, and two birds were susceptible and highly homologous to the B¹⁹ haplotype, which is highly MD susceptible.
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Affiliation(s)
- Y-C Jin
- Guangxi University, Nanning, China
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Pathogenicity of a very virulent strain of Marek's disease herpesvirus cloned as infectious bacterial artificial chromosomes. J Biomed Biotechnol 2010; 2011:412829. [PMID: 21127705 PMCID: PMC2992818 DOI: 10.1155/2011/412829] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2010] [Accepted: 09/27/2010] [Indexed: 11/18/2022] Open
Abstract
Bacterial artificial chromosome (BAC) vectors containing the full-length genomes of several herpesviruses have been used widely as tools to enable functional studies of viral genes. Marek's disease viruses (MDVs) are highly oncogenic alphaherpesviruses that induce rapid-onset T-cell lymphomas in chickens. Oncogenic strains of MDV reconstituted from BAC clones have been used to examine the role of viral genes in inducing tumours. Past studies have demonstrated continuous increase in virulence of MDV strains. We have previously reported on the UK isolate C12/130 that showed increased virulence features including lymphoid organ atrophy and enhanced tropism for the central nervous system. Here we report the construction of the BAC clones (pC12/130) of this strain. Chickens were infected with viruses reconstituted from the pC12/130 clones along with the wild-type virus for the comparison of the pathogenic properties. Our studies show that BAC-derived viruses induced disease similar to the wild-type virus, though there were differences in the levels of pathogenicity between individual viruses. Generation of BAC clones that differ in the potential to induce cytolytic disease provide the opportunity to identify the molecular determinants of increased virulence by direct sequence analysis as well as by using reverse genetics approaches on the infectious BAC clones.
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Jin YC, Wei P, Liang WF, Li Y, Niu BX, Yang XR. The protective effect of MD-resistant breeding and HVT vaccination against immunosuppression caused by MDV infection in chickens. FOOD AGR IMMUNOL 2010. [DOI: 10.1080/09540101003674342] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
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Fakhrul Islam AFM, Walkden-Brown SW, Groves PJ, Underwood GJ. Kinetics of Marek's disease virus (MDV) infection in broiler chickens 1: effect of varying vaccination to challenge interval on vaccinal protection and load of MDV and herpesvirus of turkey in the spleen and feather dander over time. Avian Pathol 2009; 37:225-35. [DOI: 10.1080/03079450701802230] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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38
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Abstract
We present a brief review of some of the empirical evidence of parasite evolution in response to vaccination. The available data shows that very different pathogen strategies can be selectively favored as a result of vaccination. However, this data often lacks a qualitative and/or quantitative assessment of the benefits and the costs associated with these alternative strategies. Without this type of information to calibrate theoretical models it will be difficult to predict the potential risks associated with vaccine-induced evolution. Our purpose here is therefore to stimulate future research into quantifying these effects.
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Affiliation(s)
- Sylvain Gandon
- CEFE-UMR 5175, 1919 Route de Mende, F-34293 Montpellier Cedex 5, France.
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39
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Changes in lymphatic organs of layer chickens following vaccination against Marek’s disease: Histological and stereological analysis. ACTA VET-BEOGRAD 2008. [DOI: 10.2298/avb0801003m] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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40
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Islam AFMF, Walkden-Brown SW, Groves PJ, Underwood GJ. Effects of vaccine dose, virus challenge dose and interval from vaccination to challenge on protection of broiler chickens against Marek's disease virus challenge. Aust Vet J 2007; 85:348-55. [PMID: 17760936 DOI: 10.1111/j.1751-0813.2007.00195.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OBJECTIVES To examine the effects of varying the doses of turkey herpesvirus (HVT) vaccine and Marek's disease virus (MDV) challenge at two intervals after vaccination on the protection of chickens against challenge with MDV. DESIGN AND PROCEDURE Experiment 1, a dose response study, consisted of 11 doses of HVT vaccine administered at hatch followed by challenge with 100 plaque forming units (pfu) of MDV 5 days post vaccination. Experiment 2, a 2 x 6 x 2 factorial design, included two HVT vaccine types, six different doses of HVT vaccine and 50 pfu and 200 pfu of MDV challenge 2 days post vaccination. All chickens were reared up to day 56 post challenge when all survivors were killed humanely. Dead and killed chickens were examined for gross MD tumours. RESULTS Experiment 1 showed a significant positive linear relationship between dose of HVT vaccine and protective index in chickens challenged 5 days post vaccination. However the range of protective index observed was limited. In Experiment 2 neither HVT vaccine provided significant protection at any dose. There was no significant effect of vaccine type or MDV challenge dose on overall protection against challenge. Chickens challenged with 200 pfu of MDV had significantly higher mortality and MD incidence than those with 50 pfu. CONCLUSIONS HVT vaccine dose had a significant impact on protective index, but vaccination to challenge interval appeared to have greater impact on the protective efficacy of vaccination. A fourfold increase in challenge dose increased mortality rate and incidence of MD.
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Affiliation(s)
- A F M F Islam
- Centre for Animal Health and Welfare, School of Rural Science and Agriculture, The University of New England, Armidale NSW 2351, Australia.
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41
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Islam A, Walkden-Brown SW. Quantitative profiling of the shedding rate of the three Marek's disease virus (MDV) serotypes reveals that challenge with virulent MDV markedly increases shedding of vaccinal viruses. J Gen Virol 2007; 88:2121-2128. [PMID: 17622613 DOI: 10.1099/vir.0.82969-0] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The shedding profile of Marek's disease virus serotype 1 (MDV1, virulent), serotype 2 (MDV2, vaccinal) and herpesvirus of turkeys (HVT, vaccinal) in commercial broiler chickens was determined by measuring the daily rate of production of feather dander from chickens housed in isolators and by quantifying the viral load of each of these serotypes in the dander using quantitative real-time PCR (qPCR). MDV1 and HVT viruses were detectable in dander filtered from isolator exhaust air from day 7 and MDV2 from day 12 after infection and thereafter until the end of the experiment at 61 days of age of the chickens. There was no difference in shedding rate among the three MDV1 isolates. Daily shedding of MDV1 increased sharply between days 7 and 28 and stabilized thereafter at about 109 virus copies per chicken per day, irrespective of vaccination status. Challenge with the three different MDV1 isolates markedly increased shedding of the vaccinal viruses HVT and MDV2 in dander by 38- and 75-fold, respectively. These results demonstrate the utility of qPCR for the differentiation and quantification of different MDV serotypes in feather dander and have significant implications for the routine monitoring of Marek's disease using qPCR assays of dust, for epidemiological modelling of the behaviour and spread of MDVs in chicken populations and for studies into the evolution of virulence in MDV1 in the face of blanket vaccination with imperfect vaccines that ameliorate disease but do not prevent infection and replication of virulent virus.
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Affiliation(s)
- Aminul Islam
- Centre for Animal Health and Welfare, School of Rural Science and Agriculture, University of New England, Armidale, NSW 2351, Australia
| | - Stephen W Walkden-Brown
- Centre for Animal Health and Welfare, School of Rural Science and Agriculture, University of New England, Armidale, NSW 2351, Australia
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Butter C, Staines K, Baaten B, Smith L, Davison TF. Route of challenge is critical in determining the clinical outcome of infection with a very virulent oncogenic herpesvirus, Marek's disease virus. Avian Pathol 2007; 36:93-9. [PMID: 17479368 DOI: 10.1080/03079450601156075] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The majority of experimental studies examining Marek's disease virus infection have used parenteral injection of cell-associated virus. The aim of this study was to examine whether the route of entry of virus was critical in determining the outcome of infection. Susceptible (L7) and resistant (L6) White Leghorn chickens were infected with a very virulent Marek's disease virus, RB1B, by either the intra-abdominal or intra-tracheal route. Birds infected by the intra-tracheal route had earlier, higher or more sustained blood, spleen and lung viral concentrations than those infected by the intra-abdominal route. L7 birds had higher viral loads than L6 birds infected by the same route. Clinical outcomes reflected these data. Resistant birds infected by the intra-tracheal route had an increased prevalence of tumours and shorter survival times compared with those infected by the intra-abdominal route. Susceptible birds infected by the intra-tracheal route became paralysed 10 days after infection. L7 birds had shorter survival times and increased prevalences of tumours than L6 birds. The pathology and viraemia seen with intra-tracheal infection could not be fully replicated by increasing the dose in intra-abdominal infections. We conclude that instillation of infective dust produces a more aggressive infection that depends on the route of entry and form of virus, and not just on the challenge dose.
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Affiliation(s)
- Colin Butter
- The Institute for Animal Health, Compton, Newbury, Berkshire, UK.
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Jarosinski KW, Tischer BK, Trapp S, Osterrieder N. Marek's disease virus: lytic replication, oncogenesis and control. Expert Rev Vaccines 2007; 5:761-72. [PMID: 17184215 DOI: 10.1586/14760584.5.6.761] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Marek's disease (MD) is caused by a ubiquitous, lymphotropic alphaherpesvirus, MD virus (MDV). MD has been a major concern in the poultry industry owing to the emergence of increasingly virulent strains over the last few decades that were isolated in the face of comprehensive vaccination. The disease is characterized by a variety of clinical signs; among them are neurological symptoms, chronic wasting and, most notably, the development of multiple lymphomas that manifest as solid tumors in the viscera and musculature. Much work has been devoted to study MD-induced oncogenesis and the genes involved in this process. Among the many genes encoded by MDV, a number have been shown recently to affect the development of tumors in chickens, one protein directly causing transformation of cells (Meq) and another being involved in maintaining transformed cells (vTR). Other MDV gene products modulate and are involved in early lytic in vivo replication, thereby increasing the chance of transformation occurring. In this review, we will summarize specific genes encoded by MDV that are involved in the initiation and/or maintenance of transformation and will focus mostly on current vaccination and control strategies against MD, particularly how modern molecular biological methods may be used to improve strategies to combat the disease in the future.
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Affiliation(s)
- Keith W Jarosinski
- Cornell University, Department of Microbiology and Immunology, College of Veterinary Medicine, Ithaca, NY 14853, USA.
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Abdul-Careem MF, Hunter BD, Parvizi P, Haghighi HR, Thanthrige-Don N, Sharif S. Cytokine gene expression patterns associated with immunization against Marek's disease in chickens. Vaccine 2006; 25:424-32. [PMID: 17070626 DOI: 10.1016/j.vaccine.2006.08.006] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2006] [Revised: 08/02/2006] [Accepted: 08/07/2006] [Indexed: 11/26/2022]
Abstract
The present study explored the immunological correlates of protection mediated by a live bivalent vaccine consisting of herpesvirus of turkeys (HVT) and SB-1 against infection with the RB1B strain of Marek's disease virus (MDV). Compared to unvaccinated infected chickens, vaccinated protected birds had lower expression of interleukin (IL)-6, IL-10 and IL-18 genes in spleen. However, there was no difference between these two groups of birds in the expression of interferon (IFN)-gamma, IL-4, IL-12 and inducible nitric oxide synthase (iNOS) genes on day 21 post-infection. Furthermore, protection was associated with lower MDV genome load in spleen but not in feather tips, suggesting that vaccination had little or no effect on curtailing virus transmission. In conclusion, vaccination with a bivalent MD vaccine was associated with distinct cytokine expression patterns in spleen and modulation of cytokine responses by the vaccine may play a role in mediation of protection.
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Osterrieder N, Kamil JP, Schumacher D, Tischer BK, Trapp S. Marek's disease virus: from miasma to model. Nat Rev Microbiol 2006; 4:283-94. [PMID: 16541136 DOI: 10.1038/nrmicro1382] [Citation(s) in RCA: 297] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Marek's disease virus (MDV) is an oncogenic herpesvirus that causes various clinical syndromes in its natural host, the chicken. MDV has long been of interest as a model organism, particularly with respect to the pathogenesis and immune control of virus-induced lymphoma in an easily accessible small-animal system. Recent advances in MDV genetics and the determination of the chicken genome sequence, aided by functional genomics, have begun to dramatically increase our understanding not only of lytic MDV replication, but also of the factors and mechanisms leading to latency and tumour formation. This new information is helping to elucidate cellular signalling pathways that have undergone convergent evolution and are perturbed by different viruses, and emphasizes the value of MDV as a comparative biomedical model. Furthermore, the door is now open for rational and efficient engineering of new vaccines against one of the most important and widespread infectious diseases in chickens.
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Affiliation(s)
- Nikolaus Osterrieder
- Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853, USA.
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Baigent SJ, Petherbridge LJ, Smith LP, Zhao Y, Chesters PM, Nair VK. Herpesvirus of turkey reconstituted from bacterial artificial chromosome clones induces protection against Marek's disease. J Gen Virol 2006; 87:769-776. [PMID: 16528024 DOI: 10.1099/vir.0.81498-0] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Herpesvirus of turkey (HVT) is an alphaherpesvirus that is widely used as a live vaccine against Marek's disease because of its antigenic relationship with Marek's disease virus (MDV). In spite of a similar genome structure, HVT has several unique genes, the functions of which are not completely understood. As a first step in carrying out detailed analysis of the functions of the HVT genes, a full-length infectious bacterial artificial chromosome (BAC) clone of HVT was constructed. DNA from two independent BAC clones, upon transfection into chicken embryo fibroblasts, produced plaques similar to those produced by the wild-type virus. Viruses derived from the BAC clones were stable during in vitro passage, but showed differences in in vitro growth kinetics compared with the wild-type virus. Using a one-step mutagenesis protocol to delete the essential glycoprotein B gene from the HVT genome, followed by construction of the revertant virus, BAC clones of HVT were shown to be amenable to standard mutagenesis techniques. In spite of the difference in in vitro growth, viruses from both clones induced 100 % protection against infection by the virulent MDV strain RB-1B, indicating that the BAC-derived viruses could be used as vaccines with efficacies similar to that of the parental virus. The construction of HVT BAC is a major step in understanding the functions of HVT genes by exploiting the power of BAC technology. Furthermore, the availability of the BAC clones enables use of HVT as a vector for expressing foreign genes.
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Affiliation(s)
- Susan J Baigent
- Institute for Animal Health, Compton Laboratory, Compton, Newbury, Berkshire RG20 7NN, UK
| | | | - Lorraine P Smith
- Institute for Animal Health, Compton Laboratory, Compton, Newbury, Berkshire RG20 7NN, UK
| | - Yuguang Zhao
- Institute for Animal Health, Compton Laboratory, Compton, Newbury, Berkshire RG20 7NN, UK
| | - Peter M Chesters
- Institute for Animal Health, Compton Laboratory, Compton, Newbury, Berkshire RG20 7NN, UK
| | - Venugopal K Nair
- Institute for Animal Health, Compton Laboratory, Compton, Newbury, Berkshire RG20 7NN, UK
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Baaten BJG, Butter C, Davison TF. Study of host-pathogen interactions to identify sustainable vaccine strategies to Marek's disease. Vet Immunol Immunopathol 2004; 100:165-77. [PMID: 15207454 DOI: 10.1016/j.vetimm.2004.04.009] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Marek's disease virus is a highly cell-associated, lymphotropic alpha-herpesvirus that causes paralysis and neoplastic disease in chickens. The disease has been contained by vaccination with attenuated viruses and provides the first evidence for a malignant cancer being controlled by an antiviral vaccine. Marek's disease pathogenesis is complex, involving cytolytic and latent infection of lymphoid cells and oncogenic transformation of CD4+ T cells in susceptible chickens. Innate and adaptive immune responses develop in response to infection, but infection of lymphocytes results in immunosuppressive effects. The remarkable ability of MDV to escape immune responses by interacting with, and down-regulating, some key aspects of the immune system will be discussed in the context of genetic resistance. Resistance conferred by vaccination and the implications of targeting replicative stages of the virus will also be examined.
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Affiliation(s)
- B J G Baaten
- Institute for Animal Health, Compton, Newbury RG20 7NN, Berkshire, UK.
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Garcia-Camacho L, Schat KA, Brooks R, Bounous DI. Early cell-mediated immune responses to Marek's disease virus in two chicken lines with defined major histocompatibility complex antigens. Vet Immunol Immunopathol 2003; 95:145-53. [PMID: 12963275 DOI: 10.1016/s0165-2427(03)00140-5] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
N2a and P2a chickens, resistant and susceptible to Marek's disease (MD), respectively, were used to examine relationships between major histocompatibility complex (MHC)-restricted cytotoxic T lymphocytes (CTL) and natural killer (NK)-like cell activity with resistance to infection with Marek's disease virus (MDV). Ten-day-old chickens were infected with MDV and euthanatized at selected times to evaluate for NK cell and MHC-restricted cytotoxicity. The N2a MDV-infected chickens had an early cell-mediated immune response characterized by a sustained NK-like cytotoxicity that coincided with a measurable MHC-cytotoxicity that was lower than controls. Although MHC-restricted and NK cell cytotoxicity was demonstrated in P2a MDV-infected chickens at 8 dpi, both abruptly decreased and remained low for the remainder of the 20-day experiment. The critical time point that may determine the resistance to MD appears to be within the first 2 weeks post-infection. Improvement of the chicken NK cell activity may be a good candidate for both selection and immunomodulation MD control programs.
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Affiliation(s)
- Lucia Garcia-Camacho
- Department of Pathology, College of Veterinary Medicine, The University of Georgia, Athens, GA 30602, USA
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Gandon S, Mackinnon M, Nee S, Read A. Imperfect vaccination: some epidemiological and evolutionary consequences. Proc Biol Sci 2003; 270:1129-36. [PMID: 12816650 PMCID: PMC1691350 DOI: 10.1098/rspb.2003.2370] [Citation(s) in RCA: 140] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
An aim of some vaccination programmes is to reduce the prevalence of an infectious disease and ultimately to eradicate it. We show that eradication success depends on the type of vaccine as well as on the vaccination coverage. Vaccines that reduce the parasite within-host growth rate select for higher parasite virulence and this evolution may both increase the prevalence of the disease and prevent disease eradication. By contrast, vaccines that reduce the probability of infection select against virulence and may lead more easily to eradication. In some cases, epidemiological feedback on parasite evolution yields an evolutionary bistable situation where, for intermediate vaccination coverage, parasites can evolve towards either high or low virulence, depending on the initial conditions. These results have practical implications for the design and use of imperfect vaccines in public- and animal-health programmes.
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Affiliation(s)
- Sylvain Gandon
- Institute of Cell, Animal and Population Biology, The University of Edinburgh, Edinburgh EH9 3JT, UK.
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Abstract
The incidence of Marek's disease (MD), an important neoplastic disease of chickens, suddenly increased in 1997 in Korea. Most MD cases of this country were detected in chickens over 20 wk of age. Five MD viruses were isolated from field flocks in which severe MD losses had occurred, and one of the viruses was studied to compare its pathotype with the prototype JM strain. The isolate KOMD-IC induced severe depression not only in body weight but also in relative bursal weight, and the depression by KOMD-IC was more severe than that induced by JM strain. In addition, the incidence of MD tumor caused by KOMD-IC was higher than that caused by the JM strain. The protective capacity of several MD vaccines was studied against challenge with KOMD-IC. The protective levels of several MD vaccines such as herpesvirus of turkeys (HVT), HVT plus SB1, and Rispens were usually lower against challenge with KOMD-IC than those challenged with JM strain, even if the chickens vaccinated with serotype 1 were not completely protected against challenge with KOMD-IC. The above results indicate that the virulence of KOMD-IC isolated recently was increased, and the increase of MD outbreak in Korea may be related to the virulence increase of the virus. Various MD vaccine programs were applied to reduce MD loss to a broiler breeder farm where severe MD loss had occurred. Serotype 1 vaccine could dramatically decrease the mortality due to MD, and the best results were obtained from the flocks vaccinated with bivalent vaccine of Rispens and HVT.
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Affiliation(s)
- H W Sung
- National Veterinary Research and Quarantine Service, Ministry of Agriculture and Forestry, Anyang, Korea
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