MX1 and infection: Interestingly, starting from 6 hpi, the innate immune response related effectors (MX1/2, GBP1, HERC5, IFIT2/3/5 and PML) in cluster I and II were early upregulated in HuB20 infected cells while were inhibited or slowly rising in SY18 infected cells (Figure 6B), suggesting that the low virulent HuB20 strain could stimulate a rapid immune and defense response in the early stages of infection.