Pathogenesis of highly pathogenic avian influenza A virus (H7N1) infection in chickens inoculated with three different doses

Figures & data

Table 1.  Distribution of AIV nucleoprotein antigen determined by immunohistochemistry in tissue samples from G1 chickens inoculated with H7N1 HPAIV.

	Days post infection
Tissue	1	3	4	5	6	7	10	Positive cells
Nasal cavity	−	+	+	+	+	+	−	Salivary and nasal epithelial cells (3 to 6 dpi), olfactory and respiratory epithelial cells, Bowman gland (3 to 7 dpi), trigeminal nerve branches (day 7), macrophages, heterophils, endothelial cells (3 to 7 dpi)
Trachea	−	−	−	−	−	−	−	−
Lung	−	+	+	+	+	+	−	Macrophages, endothelial cells
Heart	−	+	+	+	+	+	−	Myocytes, macrophages, endothelial cells
Skeletal muscle	−	+	+	+	−	−	−	Myocytes, endothelial cells
CNS	−	+	+	+	+	+	−	Neurons, glial cells, ependymal cells, epithelial cells of choroid plexus, endothelial cells
Oesophagus	−	+	+	+	+	−	−	Endothelial cells
Proventriculus	−	+	+	+	+	+	−	Macrophages, heterophils, endothelial cells
Gizzard	−	+	+	+	+	+		Mucosal epithelium, smooth muscle cells, macrophages, heterophils, endothelial cells
Intestine	−	+	+	+	+	−	−	Endothelial cells
Caecal tonsil	−	+	+	+	+	+	−	Macrophages, heterophils, endothelial cells
Pancreas	−	+	+	+	+	+	−	Exocrine acinar cells, Langerhans islet cells, macrophages, endothelial cells
Liver	−	+	+	+	+	+	−	Kupffer's cells, endothelial cells
Bone marrow	−	−	−	−	+	−	−	Myeloid cells
Thymus	−	+	+	+	+	−	−	Macrophages, endothelial cells
Bursa of Fabricius	−	+	+	+	+	−	−	Macrophages, endothelial cells
Spleen	−	+	+	+	+	−	−	Macrophages, endothelial cells
Kidney	−	+	+	+	+	+	−	Epithelial tubular cells, endothelial cells
Adrenal gland	−	+	+	+	+	+	−	Corticoitrophic and chromaffin cells, macrophages, endothelial cells
Skin	−	+	+	+	+	+	−	Keratinocytes, feather pulp inflammatory cells and follicular epithelial cells, macrophages, heterophils, endothelial cells

Figure 1.  Immunohistochemical detection of influenza A viral nucleoprotein in the nasal cavity of SPF chickens inoculated intranasally with 10^5.5 ELD₅₀ of H7N1 A/Chicken/Italy/5093/99 at 7 d.p.i. Epithelial necrosis in the transition between respiratory and olfactory epithelium of the nasal cavity, associated with the presence of viral antigen (brown staining) in the olfactory (arrow), and respiratory epithelial cells, Bowman glands (a), mucous glands (b) and inflammatory cells in lamina propria from a G1 chicken at 7 d.p.i.

Figure 2.  Immunohistochemical detection of influenza A viral nucleoprotein in the liver of SPF chickens inoculated intranasally with 10^5.5 ELD₅₀ (G1) of H7N1 A/Chicken/Italy/5093/99 at 5 d.p.i. Influenza A viral antigen detected in Kupffer cells, endothelial cells and mononuclear intravascular cells in the liver.

Figure 3.  Immunohistochemical detection of influenza A viral nucleoprotein in the spinal cord of SPF chickens inoculated intranasally with 10^5.5 ELD₅₀ (G1) of H7N1 A/Chicken/Italy/5093/99 at 3 d.p.i. Viral antigen was detected on ependymal cells surrounding the central canal and in the nearest glial cells and neurons in the grey matter from a G1 chicken at 3 d.p.i.

Figure 4.  Viral RNA detected by RT-qPCR expressed as log10 viral RNA copies per gram of tissue in samples of the brain, lung, intestine, and kidney collected from day 1 to day 10 in G1 (4a) birds and from day 1 to day 16 in group G2 (4b) and G3 (4c). Rates above the bars indicate the relation between positive birds and the total of birds examined. Limit of detection indicated by the dashed line (2.28 log₁₀ viral RNA copies/g tissue).

Figure 5.  Viral RNA levels detected by RT-qPCR in 1 ml oropharyngeal and cloacal swabs obtained from day 1 to day 10 in G1 (5a) birds and from day 1 to day 16 in group G2 (5b) and G3 (5c). Dotted line indicates the limit of the detection. Rates above the bars indicate the relation between positive birds and the total of birds examined. Limit of detection indicated by the dashed line (1.46 log₁₀ viral RNA copies/ml).