Spontaneous Borna disease in sheep and horses: immunophenotyping of inflammatory cells and detection of MHC-I and MHC-II antigen expression in Borna encephalitis lesions.

The research is focused on understanding the immune response and possible pathogenesis of Borna Disease (BD) in sheep and horses, which targets their Central Nervous System (CNS). This was achieved by studying their brain lesions and the inflammation cells within, alongside the identification of MHC-I and MHC-II antigen expressions.

Introduction and Background

• The study examines Borna Disease (BD), a viral infection that causes immunological disorders in the central nervous system (CNS). Although extensively studied in rats, little was known concerning the progression of this disease in other animals, specifically sheep and horses.
• The central objective was to observe and understand the brain lesions resulting from BD in sheep and horses as well as to identify the inflammatory cells active in these lesions, with a specific focus on the MHC-I and MHC-II antigen expressions.

Methods and Results

• The researchers utilized a set of monoclonal and polyclonal antibodies to explore the MHC-I and MHC-II antigens’ expressions in the brains of the animals affected by BD.
• The study examined twelve ovine (sheep) and eleven equine (horse) cases, with each showing similar reaction patterns such as those previously reported in rats during the acute phase of BD.
• Specific inflammatory cells, mostly classified as CD3+, were found in the infiltrates within the meninges, perivascular areas, and parenchymal areas of the animals’ brains, with CD4+ cells exceeding CD8+ cells in both areas.
• Macrophages were less prominent, identified by their lysozyme immunoreactivity, and B-cells or plasma cells were seen in reduced numbers. TCR-1+ cells were found, albeit very rarely, in some sheep’s perivascular infiltrates.

Discussion

• The study showed consistent MHC-I and MHC-II antigen expressions on inflammatory cells, but these expressions were not uniformly observed on astrocytes and neurons.
• Interestingly, neuronal degeneration was not a major feature in the cases studied, which deviates from the expected results considering BD’s known effects on the central nervous system.
• The research provides some much-needed data related to spontaneous BD in animals apart from rats and contributes to a deeper understanding of the progression and immune responses of this disease. This, however, calls for further studies to explore these findings in greater depth.