Abstract
Simple SummaryThis article studies the local immune response in the central nervous system (CNS) in lambs experimentally infected with Spanish goat encephalitis virus. CNS sections were immunostained to detect microglia, astrocytes, T lymphocytes, and B lymphocytes. In glial foci and perivascular cuffing areas, microglia were the most abundant cell type (45.4% of immunostained cells), followed by T lymphocytes (18.6%) and B lymphocytes (4.4%). Reactive astrogliosis occurred to a greater extent in the lumbosacral spinal cord. Thalamus, hypothalamus, corpus callosum, and medulla oblongata cord contained the largest areas occupied by glial foci. Lesions were more severe in lambs than in goats.Spanish goat encephalitis virus (SGEV), a novel subtype of tick-borne flavivirus closely related to louping ill virus, causes a neurological disease in experimentally infected goats and lambs. Here, the distribution of microglia, T and B lymphocytes, and astrocytes was determined in the encephalon and spinal cord of eight Assaf lambs subcutaneously infected with SGEV. Cells were identified based on immunohistochemical staining against Iba1 (microglia), CD3 (T lymphocytes), CD20 (B lymphocytes), and glial fibrillary acidic protein (astrocytes). In glial foci and perivascular cuffing areas, microglia were the most abundant cell type (45.4% of immunostained cells), followed by T lymphocytes (18.6%) and B lymphocytes (4.4%). Thalamus, hypothalamus, corpus callosum, and medulla oblongata contained the largest areas occupied by glial foci. Reactive astrogliosis occurred to a greater extent in the lumbosacral spinal cord than in other regions of the central nervous system. Lesions were more frequent on the side of the animal experimentally infected with the virus. Lesions were more severe in lambs than in goats, suggesting that lambs may be more susceptible to SGEV, which may be due to species differences or to interindividual differences in the immune response, rather than to differences in the relative proportions of immune cells. Larger studies that monitor natural or experimental infections may help clarify local immune responses to this flavivirus subtype in the central nervous system.
Highlights
Louping ill is a vector-borne disease endemic of the British Isles and Ireland, which is caused by the louping ill virus (LIV) [1]
The immune response to Spanish goat encephalitis virus (SGEV) in lambs appears to involve a combination of microglia and T
The proportion of microglia among immune cells was higher in SGEV-infected lambs than in goats, which may reflect the greater lesion severity in sheep
Summary
Louping ill is a vector-borne disease endemic of the British Isles and Ireland, which is caused by the louping ill virus (LIV) [1]. SGEV induced clinical signs (febrile illness and neurological signs such as muscular tremors—mainly located in the neck—ataxia, and/or incoordination) and histopathological lesions in the nervous system in experimentally infected goats and lambs [3,4]. In those studies, lambs developed more severe histological lesions in the central nervous system (CNS) than goats, suggesting greater susceptibility to SGEV [4]. The response to SGEV in goat CNS has been shown to comprise microglia,
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