Fig. 3.

SARS-CoV-2 variants Delta and Omicron BA.2 infection induce cardiac damage in hamsters. Hamsters were inoculated intranasally with 10⁴ PFU SARS-CoV-2 Delta or Omicron BA.2 virus. At 2 days post infection (dpi), the hamsters were sacrificed. A Cryosections of the heart were stained with antibodies against the SARS-CoV-2 nucleocapsid protein (NP) in red, cardiac ventricular marker MLC2V in green, and DAPI nuclear staining in blue. Small clusters of NP⁺/MLC2V⁺ cells could be detected in Omicron BA.2 infected heart (arrow). NP⁺ cells could be detected in Delta-infected heart, but they are rarely positive for MLC2v (asterisk). B–E Paraffin sections of the heart were stained with H&E. Representative images of B myocardial blood vessel congestion and interstitial edema (green arrows), C interstitial immune cell infiltration (yellow arrows), D CM degeneration (white arrows). E CM necrosis (blue arrows). F Histological scores of pathological features scaled 0–3, where 0 indicates the absence of pathological changes. Data are presented as mean ± SEM, n = 3 for A, n = 6 for B-F . Statistical significance was calculated using Student’s t-test *p < 0.05, **p < 0.01, ****p < 0.0001. Scale bar A = 25 µM; B–E = 50 µM