ASFV antigen detection by immunohistochemistry (IHC)
ASFV antigen-labelled cells were detected in various organs and majorly
found in the mononuclear cells/macrophages. The result was tabulated in
Table 3. The labelled cells were commonly detected in the lymphoid
organs (spleen, tonsil and lymph node) as well as lung, kidney and liver
tissues. Figure 6a showed the positive cells in the background of the
haemorrhagic spleen. In the liver, positive cells were found in the
sinusoids, and they were mostly enlarged, plump Kupffer cells (Fig 6b).
In a severe case, ASFV antigen–labelled hepatocytes were found (Fig
6c). In the tonsil, positive mononuclear cells were seen in the
epithelium of the tonsillar crypt (M-cell) and mostly within the diffuse
lymphoid area surrounding the lymphoid follicles (Fig 6d). In the lymph
node, positive cells were numerous in some cases and difficult for
numeration because the cells lost their distinctive shape and blended
with the background. Figure 6e showed the ASFV antigen–positive
macrophages with many of them containing phagocytosed erythrocytes. In
the lungs, pulmonary intravascular macrophages were commonly found
positive (Fig 6f). In the cerebrum, positive cells were scarcely found.
Figures 6g and 6h showed a few positive mononuclear cells in meningitis
and perivascular cuffing lesions. In the epicardium of the heart, other
than mononuclear cells/macrophages, many spindle-shaped mononuclear
cells were positive in the haemorrhagic area (Fig 6i). In the kidney
tissue, many spindle-shaped cells were stained positive in addition to
plump-shaped macrophages within the haemorrhagic renal pelvis region
(6j). Occasionally, a few positive cells were found in the capillary of
glomeruli identified as macrophages (Fig 6k). Multifocally, the renal
tubules of the kidneys showed granular cytoplasmic staining of ASFV
antigen (Fig 6l). Tissue sections from negative control pig showed no
ASFV antigen-labelled cells or non-specific staining in all tissues.