C2 and infection: Except for a C2 VP1-145G mutant in one of the two infections, infectious viral particle shedding in the medium was only detected for VP1-145Q variants (average titers of 102.5, 103.8, and 105.0 CCID50/ml for C1, C2, and B3, respectively), confirming that VP1-145Q is a key determinant of increased infectivity in airway organoids (Fig. 5b).