The NS segment of H5N1 avian influenza viruses (AIV) enhances the virulence of an H7N1 AIV in chickens

Table 1 Average distribution of AIV-nucleoprotein antigen determined by immunohistochemistry (IHC) in tissue samples

VIRUS STRAIN	Time of AIV NP antigen detection				Main localization
Tissue	1 dpi	2 dpi	3 dpi	4 dpi
FPV
CNS	-	-	+	+	Neurons, glial cells
Heart	-	+	+	+	Myocytes
Kidney	-	-	−/+	+	Epithelialtubularcells
Pancreas	-	-	+	+	Exocrine acinar cells
Liver	-	-	+	+	Kupffer’s cells
Spleen	-	-	+	+	Macrophages
Thymus	-	+	+	+	Macrophages
Bursa of Fabricius	-	-	+	+	Macrophages
FPV NS GD
CNS	-	-	++	+	Neurons, glial cells, ependymalcells
Heart	-	++	+	+	Myocytes, macrophages
Kidney	-	+++	++	++	Epithelial tubular cells
Pancreas	-	-	++	+	Exocrine acinar cells
Liver	-	-	+	+	Kupffer’s cells
Spleen	-	+	+	+	Macrophages, Endothelial cells
Thymus	-	+	+	+	Macrophages, Endothelial cells
Bursa of Fabricius	-	-	+	+	Macrophages, Endothelial cells
FPV NS VN
CNS	-	-	++	+	Neurons, glial cells, ependymalcells
Heart	-	++	+	+	Myocytes, macrophages
Kidney	-	-	++	++	Epithelial tubular cells
Pancreas	-	-	++	+	Exocrine acinar cells
Liver	-	-	+	+	Kupffer’s cells
Spleen	-	-	+	+	Macrophages, Endothelial cells
Thymus	-	-	+	+	Macrophages, Endothelial cells
Bursa of Fabricius	-	-	+	+	Macrophages, Endothelial cells
Saline Solution
CNS	-	-	-	-	-
Heart	-	-	-	-	-
Kidney	-	-	-	-	-
Pancreas	-	-	-	-	-
Liver	-	-	-	-	-
Spleen	-	-	-	-	-
Thymus	-	-	-	-	-
Bursa of Fabricius	-	-	-	-	-

Chickens were inoculated with FPV, FPV NS GD or FPV NS VN and necropsies were performed at different time-points. The extension of the staining in tissues was measured by a semi-quantitative score: no positive cells (−), single positive cells (+), scattered groups of positive cells (++), and widespread positivity (+++).

ISSN: 1297-9716