Article Figures & Data
Figures
- Figure 1. Viral load and histopathological changes in female Syrian hamsters intranasally challenged with SARS-CoV-2
.(A) Weight change profiles of hamsters that have been intranasally infected by indicated doses of SARS-CoV-2 USA/WA1-2020. (B) Subgenomic viral mRNA (sgmRNA) detected in nasal washes of SARS-CoV-2 challenged hamsters (N = 3) on 2, 5, 7 dpi. (C, D) SgmRNA and viral RNA (vRNA) (D) detected in nasal washes and the lungs of SARS-CoV-2–challenged hamsters (N = 6) on 3 dpi. (E, F) vRNA and sgmRNA detected in various organs of SARS-CoV-2–challenged hamsters (N = 4) on 5 dpi. The detection limit (25 copies for sgmRNA and 100 copies for vRNA per reaction) was shown with the dotted line. (G, H, I, J) Hematoxylin and eosin (H&E) staining of the lungs of 105 TCID50 SARS-CoV-2–challenged hamsters on 2, 5, and 7 dpi. (K, L, M, N) Lung tissues from hamsters challenged with indicated doses of virus were estimated for the percentage of consolidated areas. Scale bar in (G, H, I, J, K, L, M, N) = 500 μm. (O) Neutralizing antibody titers of each hamster at the end of the study. Blue dot denotes the hamster that received 100 TCID50; Green dot represents the hamster that received 10 TCID50.
- Figure S1. Histopathology of SARS-CoV-2 infected hamsters.
(A, B, C) Nasal turbinates of uninfected and infected hamsters on 2 and 5 dpi. (B) White dotted circle in (B) indicates the immune cell infiltration. (C) White dotted circle in (C) shows the decrease in respiratory epithelial cells in the olfactory mucosa. Scale bar = 200 μm. (D, E, F, G) Trachea of uninfected or infected hamsters on 2, 5, and 7 dpi. Black arrows indicate areas with clear loss of cilia. (H, I, J, K) Lung tissues from uninfected and infected hamsters on 2, 5, and 7 dpi. Scale bar = 60 μm. (J, L) A close-up image taken from panel (J). Green arrows indicate macrophages; red arrows indicate neutrophils; an orange arrow points to a lymphocyte; blue arrows show fibrinous exudate and edema. (M, N, O) Brain tissues from uninfected and infected hamsters on 2 and 5 dpi. (P, Q, R) Olfactory bulbs from uninfected and infected hamsters on 2 and 5 dpi. Scale bar = 100 μm in (M, N, O, P, Q, R).
- Figure S2. Efficient SARS-CoV-2 transmission in Syrian hamsters through close contact.
(A) Male Syrian hamsters (4–8 wk old) upon intranasal inoculation of SARS-CoV-2 of 105 TCID both had weight loss for up to 7 d (A). (B) Serum neutralizing antibody titers of four hamsters on 7 dpi. (C) A representative image of the consolidated region in the lung of infected hamster on 7 dpi. Scale bar = 50 μm. (D) protein fluid in airways on 7 dpi. Scale bar = 20 μm. (E) Atypical pneumocyte hyperplasia. There is also alveolar airway hemorrhage, alveolar airway proteinaceous fluid accumulation, bronchiolar mucosa hyperplasia, lumina contain foamy macrophages with fewer lymphocytes and neutrophils, a mild lymphoplasmacytic infiltrate of the interstitium, a few hyaline membranes, necrosis, and loss of terminal bronchiole mucosa. Scale bar = 50 μm. (F) perivascular lymphocytes and bronchiolar hyperplasia. Scale bar = 20 μm. (G) All lobes of the lung of the contact hamster developed consolidated regions. (H) Atypical pneumocyte hyperplasia in the lung of the contact hamster on 7 dpi. (I, J) RNAScope images of the lungs from either uninfected (I) or the contact hamster (J). The top panels show the whole lung and the bottom images are representative close-ups. The viral genomic RNA is shown as reddish dots. Scale bar = 200 μm.
- Figure 2. Prolonged virus replication in nasal cavity of aged Syrian hamsters.
(A) Weight change profile of aged hamsters after intranasal inoculation of 105 TCID50 SARS-CoV-2 isolate USA-WA1/2020. The date of birth was indicated to the right of each hamster ID. WH031 and 32 represent negative controls inoculated with media. (B) Clinical scores of hamsters. Y-axis represents day post-infection (dpi). Day 0 is the day when inoculum was given. X-axis represents the animal ID with WH031 and 032 being uninfected control. (C) Breathing rate was counted by two independent observers and averaged. (D) sgmRNA levels in uninfected (black solid circles) and infected hamsters (colored solid circles) on 2,5,7,9,14 dpi. (A) Each color corresponds to the same colored animal ID in (A). (E) Pathology of the heart of the hamster that died. The thrombus formation was noticed in the left atrium (indicated by white arrows and a small black box) with a closeup image shown to the right. Scale bar = 200 μm. (F) Pathology of the lung of the hamster that succumbed to infection. Scale bar: left = 5 mm; right = 60 μm. (G, H, I) RNAscope images of the uninfected hamster lung (negative), the lung and the brain of WH036. Red dots indicate the presence of viral genomic RNA. (G, H, J) Scale bar: 200 μm in (G), 60 μm in (H), 300 μm in (J). (J) Survival curves of four aged hamsters.
- Figure 3. Post-infection immunity protects re-challenge.
(A) Overall study design of the study. 10 hamsters Fig 1A recovered from infection were reinoculated with 105 TCID50 SARS-CoV-2 isolate USA-WA1/2020 on Day 28 post primary infection. (B) Neutralizing antibody titers of each hamster at the time of re-inoculation. (C) Weight change profile of all re-inoculated hamsters. (D) sgmRNA detected from nasal washes collected on 0, 1, 2, 3, and 7 dpi. (E) Virus titers of nasal washes collected from first (red) and second (green) infections. (F) Viral RNA (red) and sgmRNA levels (blue) in the lungs on 3, 7 dpi. (G) A representative HE image of the lung from a re-inoculated hamster. Scale bar = 60 μm.
- Figure 4. Post-infection immunity limits transmission.
The overall study design is depicted in Fig 3A. Four hamsters were paired with four naïve hamsters in clean cages on Day 29 (1 d after re-inoculation) and then another two naïve hamsters on Day 30 (2 d after re-inoculation of the transmitters). Each cage housed two hamsters (one re-inoculated and one naïve). (A) Weight change profile of contact hamsters. (B, C) sgmRNA and viral RNA (C) in nasal washes collected on 0, 1, 2, 3, 5, and 7 d post-contact. (C) Red solid circles in (C) denote two contact hamsters which were exposed to hamsters that were without prior infection but challenged with 105 TCID50 virus. Black solid circles indicate contact those hamsters that were exposed to the re-challenged hamsters. (D) Viral loads detected in the lungs. (E) Representative HE images of the lung from a contact hamster. Scale bar = 200 μm. (F) Neutralizing antibody titers of each hamster at the end of the study.
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