Fig. 1

Photomicrographs of H&E-stained tracheal sections of the experimental groups: A at 3dpi, CS infected group showing desquamated and inflammatory cell hanged in fibrinous exudate with syncytial cells in the tracheal lumen (H&E,100 X). RS infected group showing more fibrinous exudate in tracheal lumen admixed with syncytial cells and inflammatory cells infiltrate the tracheal mucosa along with congestion (H&E,100 X). In the VEC + CS group, mild inflammatory reaction (H&E,100 X). In VEC + RS showing deciliation with hyperplasia of glands and thickening of tracheal mucosa (H&E,100 X), CEO + CS showed mild to a moderate inflammatory reaction (H&E,100 X), while in the CEO + RS group more infiltration of inflammatory cells with edema, hyperemia, and glandular necrosis (H&E,200 X). TCO + CS shows hyperemic mucosa with inflammatory cells infiltration in its mucosa (H&E,100 X). TCO + RS shows deciliation, desquamation of tracheal lining epithelium with hyperemic mucosa, and infiltrating inflammatory cells (H&E,200 X). B at 7dpi, CS group showing severe ulceration of tracheal lining epithelium with mononuclear cells infiltration with hyperemic tracheal mucosa (H&E,200 X). RS shows a diffuse hemorrhagic cast in the tracheal lumen with the complete destruction of tracheal mucosa (H&E,100 X). VEC + CS shows hyperplasia of the mucus gland and hyperactivity with dense inflammatory cells between them (H&E,100 X). VEC + RS shows deciliation with an area of ulceration and hyperemic mucosa (H&E,200 X). CEO + CS showed mild inflammatory reaction with catarrhal exudates, with the presence of heterophils and inflammatory cells in the tracheal lumen (H&E,200 X). CEO + RS presence of a large amount of fibrinoheterophilic exudates in the tracheal lumen with syncytial cell and desquamated epithelium (H&E,100 X). TCO + CS shows a moderate inflammatory reaction of tracheal mucosa also catarrhal exudates and inflammatory cells in their lumen (H&E,100 X). TCO + RS shows severe epithelium necrosis and ulceration with thickening of tracheal mucosa and mononuclear inflammatory cells (H&E,100 X). CS: CEO like strain, RS: Recombinant strain, VEC + CS: Vector vaccinated group challenged with CEO like strain, VEC + RS: Vector vaccinated group challenged with recombinant strain, CEO + CS: CEO vaccinated group challenged with CEO like strain, CEO + RS: CEO vaccinated group challenged with recombinant strain, TCO + CS: TCO vaccinated group challenged with CEO like strain, TCO + RS: TCO vaccinated group challenged with recombinant strain