Figure 6.

Representative photomicrographs of histopathological lesions of lung tissue sections of golden Syrian hamsters inoculated i.n. with PBS, HAd-ΔE1E3, HAd-Spike, or HAd-Spike/C5 following challenge with SARS-CoV-2

Six- to seven-week-old golden Syrian hamsters were mock inoculated (PBS) or inoculated i.n. once with 2 × 10⁸ PFUs/animal of HAd-ΔE1E3, HAd-Spike, or HAd-Spike/C5. 35 days post immunization, animal groups were challenged with 10⁵ TCID₅₀ of SARS-CoV-2 (B.1.1.28). (A) Animals were euthanized 3, 5, 7, and 14 days post challenge, and the lung lobe samples were collected and processed for histopathology. The lung tissue sections at low magnification (H&E, 1.5×) are shown as insets on the left side of each higher-magnification photo (H&E, 10×). At low magnification, darker areas correspond to areas with an increased presence of inflammatory cells (exudation). At higher magnification, the asterisks correspond to areas of exudation within the bronchiole and alveolar spaces, which are significantly reduced in the vaccinated groups (HAd-Spike and HAd-Spike/C5) 3, 5, and 7 DPI. 14 DPI, all groups present only minimal exudation. (B) Characteristic histologic features of lung vasculature after challenge with SARS-CoV-2 compared with a PBS-non-infected control (H&E, 20×). Vessels from a PBS-infected animal 3 DPI show moderate vascular changes, vasculitis (I), and endothelialitis (details in inset; H&E, 40×). Vessels from a PBS-infected animal 5 DPI show marked vascular changes, wall thickening (T), vasculitis (I), and endothelialitis (details in inset); note perivascular inflammatory infiltrate (P) and edema (E).