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Marek's disease virus infection in the brain: virus replication, cellular infiltration, and major histocompatibility
I M Gimeno1, R L Witter, H D Hunt
1USDA-ARS Avian Disease and Oncology Laboratory, East Lansing, MI 48823, USA.
Abstract:
Marek's disease virus (MDV) infection in the brain was studied chronologically after inoculating 3-week-old chickens of two genetic lines with two strains of serotype I MDV representing two pathotypes (v and vv+). Viral replication in the brain was strongly associated with the development of lesions. Three viral antigens (pp38, gB, and meq) were detected in the brain of infected chickens. Marked differences between v and vv+ pathotypes of MDV were identified for level of virus replication, time course of brain lesions, and expression of major histocompatibility complex (MHC) antigens. Two pathologic phenomena (inflammatory and proliferative) were detected in the brain of chickens inoculated with vv+MDV, but only inflammatory lesions were observed in those inoculated with vMDV. Inflammatory lesions, mainly composed of macrophages, CD4+ T cells, and CD8+ T cells, started at 6-10 days postinoculation (dpi) and were transient. Proliferative lesions, characterized by severe infiltrates of CD4+CD8- T cells (blasts), started at 19-26 dpi and persisted. Expression of MHC antigens in endothelial cells and infiltrating cells within the brain was influenced by MDV infection. Upregulation of MHC class II antigen occurred in all treatment groups, although it was more severe in those inoculated with vv+MDV. MHC class I antigen was downregulated only in those groups inoculated with vv+MDV. These results enhance our understanding of the nature and pattern of MDV infection in the brain and help to explain the neurovirulence associated with highly virulent MDV.
Insights
Marek's disease virus (MDV) brain infection causes distinct inflammatory and proliferative lesions, differing by viral pathotype. Highly virulent MDV strains induce more severe brain lesions and altered major histocompatibility complex (MHC) antigen expression.
Area of Science:
- Veterinary Virology
- Immunology
- Pathology
Background:
- Marek's disease virus (MDV) is a significant poultry pathogen.
- Understanding MDV neurotropism is crucial for disease control.
Purpose of the Study:
- To chronologically investigate Marek's disease virus (MDV) infection in chicken brains.
- To differentiate the neuropathogenesis of virulent (v) and very virulent plus (vv+) MDV pathotypes.
- To analyze viral replication, lesion development, and host immune responses in the brain.
Main Methods:
- Inoculation of chickens with different MDV serotype I strains (v and vv+).
- Chronological analysis of viral antigen expression (pp38, gB, meq) in brain tissue.
- Histopathological examination of brain lesions and immune cell infiltration (macrophages, CD4+, CD8+ T cells).
- Assessment of major histocompatibility complex (MHC) antigen expression on brain cells.
Main Results:
- Viral replication correlated with brain lesion development.
- vv+MDV caused both inflammatory and proliferative lesions, while vMDV induced only inflammatory lesions.
- Inflammatory lesions (macrophages, CD4+, CD8+ T cells) were transient; proliferative lesions (CD4+CD8- T cells) persisted.
- MDV infection altered MHC antigen expression; vv+MDV induced more severe MHC class II upregulation and MHC class I downregulation.
Conclusions:
- MDV pathotype dictates the nature and timing of brain lesions.
- vv+MDV exhibits greater neurovirulence, associated with persistent proliferative lesions and distinct MHC modulation.
- Findings elucidate MDV neuroinvasion mechanisms and pathotype-specific neuropathogenesis.