TGFB1 and infection: Compared to the infection of SARS-CoV-2 S-Vpp WT (Additional file 3: Fig. S3A), infections with BA.2 (Fig. 6B) and XBB.1 (Additional file 4: Fig. S4A) variants more obviously elicited inflammation as evidenced by the formation of granuloma (indicated with the arrow) in H&E staining and the inductions of inflammatory gene expressions, including Tnf, Infg, Il1b, Il6, Il10, and Tgfb1 in RT-qPCR analysis (Additional file 5: Figs. S5A–F).