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

Authors :
Li Gao
Kai Li
Yulong Gao
Changjun Liu
Hong-chao Lv
Yanping Zhang
Yongqiang Wang
Lin-yi Zhou
Hongyu Cui
Xiaomei Wang
Guo-rong Sun
Xiaole Qi
Qing Pan
Source :
Viruses; Volume 9; Issue 4; Pages: 71, Viruses, Viruses, Vol 9, Iss 4, p 71 (2017)
Publication Year :
2017
Publisher :
MDPI AG, 2017.

Abstract

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.

Details

ISSN :
19994915
Volume :
9
Database :
OpenAIRE
Journal :
Viruses
Accession number :
edsair.doi.dedup.....bc0dcac9564bb2f6670a898fb80f8bd5
Full Text :
https://doi.org/10.3390/v9040071