AXL and infection: To determine whether the observed enhanced infection in differentiated cells following 2 days of RA treatment was due to increased expression of AxI, we stained differentiated and undifferentiated SH-SY5Y cells (both uninfected and after 48 hours infection by ZIKV-UG or ZIKV-PR) with an Axl-specific monoclonal antibody, which detects endogenous levels of total Axl.