PROS1 and infection: Furthermore, infection with both rSARS-CoV-2 Δ3a/Δ6 and rSARS-CoV-2 Δ3a/Δ7b induced significantly higher levels of IgA against full-length viral S protein in the bronchoalveolar lavage fluid (BALF) of infected mice than the rSARS-CoV-2 WT (Fig. 3G, right).