Pathogenic characteristics of Marek's disease virus field strains prevalent in China and the effectiveness of existing vaccines against them

Zhang, Yanping; Li, Zhijie; Bao, Keyan; Lv, Hongchao; Gao, Yulong; Gao, Honglei; Qi, Xiaole; Cui, Hongyu; Wang, Yongqiang; Ren, Xiangang; Wang, Xiaomei; Liu, Changjun

doi:10.1016/j.vetmic.2014.12.020

Cited by 35 publications

(28 citation statements)

References 31 publications

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“…However, vaccination failure of MD has often occurred in China in recent years [14,23,24,25,26]. Here, a field MDV strain BS/15 was isolated from a Chinese chicken flock in 2015 that had been vaccinated with the commercial vaccine CVI988 and had developed severe MD.…”

Section: Discussionmentioning

confidence: 99%

“…Feather pulps collected from the diseased chickens described above were used for viral isolation, as previously described [14]. Briefly, SPF duck or chicken embryos were obtained from the Harbin Veterinary Research Institute (HVRI), Chinese Academy of Agricultural Sciences (CAAS) for the preparation of duck embryo fibroblasts (DEFs) or chicken embryo fibroblasts (CEFs).…”

Section: Methodsmentioning

confidence: 99%

“…In addition, the body weights and immune organ (bursa, thymus, and spleen) weights of the surviving chickens at the end-point of the experiment (90 dpc) were recorded for further analysis. The MD status of the experimental animals was estimated mainly by monitoring for early mortality syndrome, immune organ damage, and tumor formation, as described previously [14]. The days that various chickens died during the experimental period in each group were recorded for survival analysis.…”

Section: Methodsmentioning

confidence: 99%

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A Chinese Variant Marek’s Disease Virus Strain with Divergence between Virulence and Vaccine Resistance

Sun

Zhang

et al. 2017

Viruses

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Marek’s disease (MD) virus (MDV) has been evolving continuously, leading to increasing vaccination failure. Here, the MDV field strain BS/15 was isolated from a severely diseased Chinese chicken flock previously vaccinated with CVI988. To explore the causes of vaccination failure, specific-pathogen free (SPF) chickens vaccinated with CVI988 or 814 and unvaccinated controls were challenged with either BS/15 or the reference strain Md5. Both strains induced MD lesions in unvaccinated chickens with similar mortality rates of 85.7% and 80.0% during the experimental period, respectively. However, unvaccinated chickens inoculated with BS/15 exhibited a higher tumor development rate (64.3% vs. 40.0%), but prolonged survival and diminished immune defects compared to Md5-challenged counterparts. These results suggest that BS/15 and Md5 show a similar virulence but manifest with different pathogenic characteristics. Moreover, the protective indices of CVI988 and 814 were 33.3 and 66.7 for BS/15, and 92.9 and 100 for Md5, respectively, indicating that neither vaccine could provide efficient protection against BS/15. Taken together, these data suggest that MD vaccination failure is probably due to the existence of variant MDV strains with known virulence and unexpected vaccine resistance. Our findings should be helpful for understanding the pathogenicity and evolution of MDV strains prevalent in China.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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A Chinese Variant Marek’s Disease Virus Strain with Divergence between Virulence and Vaccine Resistance

Sun

Zhang

et al. 2017

Viruses

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“…Secondly, MDV tumor antigens stimulate the immunological destruction of tumor cells by CTLs (Powell and Rennie 1978;Baigent et al 2006). Unfortunately, MD vaccines are incapable of inducing a sterile immunity and allow the virulent virus strains to replicate and be transmitted into the environment through the vaccinated host (Zhang et al 2015). It is believed, that keeping host alive, vaccination prolongs the infection time of virulent strains and may cause evolution of MDV with increased virulence (Witter 1997, Atkins et al 2013, Hunt and Dunn 2013.…”

Section: Introductionmentioning

confidence: 99%

“…It is believed, that keeping host alive, vaccination prolongs the infection time of virulent strains and may cause evolution of MDV with increased virulence (Witter 1997, Atkins et al 2013, Hunt and Dunn 2013. This is why more virulent MDV pathotypes emerge, reducing the effectiveness of existing vaccines (Davison and Nair 2005, Hunt and Dunn 2015, Zhang et al 2015. Witter (1997) proposed a classification system where virulent MDV (vMDV) induced lesions in turkey herpesvirus (HVT) vaccinated chickens at a rate comparable to the JM/102W virus strain infected.…”

Section: Introductionmentioning

confidence: 99%

Morphology of immune organs after very virulent plus strain of Marek’s disease virus infection in vaccinated hens

Madej¹,

Woźniakowski²,

Gaweł³

2016

Polish Journal of Veterinary Sciences

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Marek's disease (MD) outbreaks in poultry flocks may be associated with overriding of vaccine immune protection by very virulent (vvMDV) or very virulent plus (vv+MDV) strains. This paper presents the study on lymphoid organ morphology in the latent phase of MD caused by vv+MDV which break post-vaccinal protection in hens. We also immunohistochemically examined B and T populations as well as B/T and CD4 + /CD8+ ratio of lymphocytes in lymphatic organs and, as a background, in MD lymphomas from non-lymphatic organs. The number of antigen expressed cells was evaluated as a percentage of positive cells in the one power field. Organ samples were collected from 24 dead reproductive hens (Ross 308 line) in age between 35-56 weeks, infected with vv+MDV. The hens originated from farms with MD outbreaks, despite earlier routine vaccination with CVI988/Rispens + HVT. The control organ samples originated from 15 clinically healthy hens at the same age and line, subjected to the same vaccination schedule. The number of CD3 + , CD8 + and TCRγδ + cells was significantly lower in MDV infected thymus, spleen and cecal tonsils in comparison to that found in the control organs. The proportion of CD4 + was also distinctly reduced in the thymus and limited in the spleen of MDV infected hens. This study revealed that infection with field vv+MDV isolates might break post-vaccinal protection and influence the central and peripheral immune system. The decrease in CD8 + and TCRγδ + cell number in the thymus, spleen and cecal tonsils suggests that primarily these cells are involved in cell-mediated cytotoxicity against MDV transformed cells during latency.

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Revisiting cellular immune response to oncogenic Marek’s disease virus: the rising of avian T-cell immunity

Yang

Dong

Hao

et al. 2020

Cell. Mol. Life Sci.

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Marek's disease virus (MDV) is a highly oncogenic alphaherpesvirus that causes deadly T-cell lymphomas and serves as a natural virus-induced tumor model in chickens. Although Marek's disease (MD) is well controlled by current vaccines, the evolution of MDV field viruses towards increasing virulence is concerning as a better vaccine to combat very virulent plus MDV is still lacking. Our understanding of molecular and cellular immunity to MDV and its immunopathogenesis has significantly improved, but those findings about cellular immunity to MDV are largely out-of-date, hampering the development of more effective vaccines against MD. T-cell-mediated cellular immunity was thought to be of paramount importance against MDV. However, MDV also infects macrophages, B cells and T cells, leading to immunosuppression and T-cell lymphoma. Additionally, there is limited information about how uninfected immune cells respond to MDV infection or vaccination, specifically, the mechanisms by which T cells are activated and recognize MDV antigens and how the function and properties of activated T cells correlate with immune protection against MDV or MD tumor. The current review revisits the roles of each immune cell subset and its effector mechanisms in the host immune response to MDV infection or vaccination from the point of view of comparative immunology. We particularly emphasize areas of research requiring further investigation and provide useful information for rational design and development of novel MDV vaccines.

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Pathogenic characteristics of Marek's disease virus field strains prevalent in China and the effectiveness of existing vaccines against them

Cited by 35 publications

References 31 publications

A Chinese Variant Marek’s Disease Virus Strain with Divergence between Virulence and Vaccine Resistance

A Chinese Variant Marek’s Disease Virus Strain with Divergence between Virulence and Vaccine Resistance

Morphology of immune organs after very virulent plus strain of Marek’s disease virus infection in vaccinated hens

Revisiting cellular immune response to oncogenic Marek’s disease virus: the rising of avian T-cell immunity

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