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A possible association between plaque type and pathogenicity of Marek's disease herpesvirus
Abstract:
Eighteen isolants of Marek's disease herpesvirus (MDHV) were examined for their plaque types in chicken embryo fibroblast cell cultures and their pathogenicity to an experimental line of White Leghorns highly susceptible to MD. Seven isolants (Id-1, GA, WSU-GF, and 4 field isolants) induced morphologically similar small-cell plaques (SC plaques) consisting of small round refractile cells, whereas 11 isolants (HN and 10 isolants from zoo birds) all induced large-cell plaques (LC plaques) containing large cells along with small refractile cells. The 7 SC plaque isolants all produced clinical MD with high incidences of gross MD tumors, while all 11 LC plaque isolants produced subclinical infection with only minimal histologic lesions. This observation strongly suggests a possible association between plaque type and pathogenicity of MDHV isolants.
Insights
Marek's disease herpesvirus (MDHV) isolants were classified by plaque type. Small-cell plaques correlated with virulent Marek's disease, while large-cell plaques indicated less severe infections.
Area of Science:
- Veterinary Virology
- Avian Pathology
- Herpesvirus Research
Background:
- Marek's disease is a significant lymphoproliferative disease in poultry.
- Marek's disease herpesvirus (MDHV) is the causative agent.
- Understanding MDHV pathogenicity is crucial for disease control.
Purpose of the Study:
- To investigate the relationship between Marek's disease herpesvirus (MDHV) plaque types and pathogenicity.
- To differentiate MDHV isolants based on their in vitro plaque morphology and in vivo virulence.
Main Methods:
- Eighteen MDHV isolants were cultured in chicken embryo fibroblast cells.
- Plaque morphology (small-cell vs. large-cell) was characterized for each isolant.
- Pathogenicity was assessed by challenging a highly susceptible White Leghorn chicken line.
Main Results:
- Seven MDHV isolants produced small-cell (SC) plaques and caused clinical Marek's disease with high tumor incidence.
- Eleven MDHV isolants produced large-cell (LC) plaques and resulted in subclinical infections with minimal lesions.
- A strong correlation was observed between SC plaque formation and high pathogenicity.
Conclusions:
- Plaque typing of MDHV in cell culture can serve as a reliable indicator of pathogenicity.
- SC plaque-forming MDHV isolants are associated with virulent disease, while LC plaque-forming isolants are less virulent.
- This finding aids in the rapid assessment and differentiation of MDHV strains.