Furthermore, induction of IFN-β mRNA expression in productively infected MDMs was detected at 3 days post infection (Fig. 1d), which was coincident with the upregulation of CD169 and other ISGs (Supplementary Fig. 1i, j), further supporting the hypothesis that a late event in the virus replication cycle induces IFN-I responses. This evidence concerns the gene SIGLEC1 and infection.