FIG 2.

Viral burden in tissues of the mice infected by SARS-CoV-2 ancestral strain and Delta variant. Eight-week-old female K18-hACE2 mice were intranasally inoculated with PBS (mock group) or 10⁴ PFU of SARS-CoV-2 ancestral or Delta strain (n = 5). At 6 dpi, the titers of infectious virus in the lung (A), brain (B), intestine (C), and kidney (D) were determined by plaque assay. The copy numbers of viral genome in lung (E), brain (F), intestine (G), kidney (H), heart (I), and serum (J) were determined by probe-based qRT-PCR. Each symbol represents the mean titer for one mouse. Data were analyzed by Mann-Whitney test (**, P < 0.01; ns, not significant).