Figure 2. Lung microtissues can be infected with SARS-CoV-2.

(A and B) Micrographs of lung tissue stained with a 1:1 mix of antibodies for spike and nucleocapsid protein to detect SARS-CoV-2 and actin. (C and D) RNA in situ hybridization of SARS-CoV-2–infected lung tissue with a negative control probe specific for the DapB gene of Bacillus subtilis. (E–H) RNA in situ hybridization of lung tissue using a probe specific for the negative strand of the subgenomic E gene of SARS-CoV-2 at 24 hours after infection. Images are representative of microscopy performed on tissue from 2 donors. (I) Quantitative PCR for the subgenomic E gene of SARS-CoV-2 in 16 donors at 24 hours after infection. Range of uninfected samples = 0–77.2, mean = 25.8, standard deviation = 34.6. Range of infected samples = 87.4–157.4, mean = 103.1, standard deviation = 16.7. Significance was determined by the nonparametric Mann-Whitney U test. (J) Copies of SARS-CoV-2 detected in tissue culture supernatant at the indicated time after the start of infection. Samples were infected for 12 hours with 10⁴ PFU and then washed and transferred to fresh media in a new plate. At each time point40 μL aliquots were collected. Error bars are from triplicate wells collected from each donor at each time point. (K) TCID₅₀ assay of lung homogenate using tissue from the same donors as in J at 18 and 36 hours after infection. TCID₅₀ was determined by counting 6 wells per donor at each dilution.