Figure 6. SBV tropism in the central nervous system of naturally in utero infected lambs and calves.

A. Stillborn lamb showing signs of congenital SBV infection including artrogryposis, brachygnatia inferior and torticollis. B–D: Tissue sections stained with hematoxylin and eosin derived from brain of a lamb congenitally infected with SBV. Panel B illustrates cerebral cortex with porencephaly. The white matter is lacking as indicated by (*). Adjacent grey matter is reduced in thickness (bar = 2 mm). C. Higher magnification micrographs showing areas of malacia and the presence of myelin laden macrophages (arrow; bar = 20 µm). D. Glial nodule (arrow) and mild lymphohistiocytic perivascular infiltrate (bar = 50 µm). E–L: Immunohistochemistry of tissue sections derived from brain (E–H) or spinal cord (I–J) of lambs congenitally infected with SBV. In sections shown in panels E, F, I and J a SBV N polyclonal rabbit antiserum was used, while panels G–H show instead serial sections (of E and F) incubated with the pre-immune serum. The use of SBV N antiserum reveals a strong positive reaction (characterized by the intracytoplasmic dark brown staining) in the cell body and processes of neurons of the grey matter, while no staining was observed with serial sections incubated with the pre-immune serum. K–L: Immunohistochemistry of control tissue sections derived from brains of sheep reared in Scotland and probed with the antiserum towards the SBV N protein showed no immunoreactive cells.