FIG 2.

Axl augments ZIKV infection of human SC. (A) ZIKV progeny titers measured in the supernatant of SC treated with anti-Gas6 neutralizing antibody (50 μg/ml) or anti-Axl blocking antibody (10 μg/ml) or goat IgG control (50 μg/ml) by plaque assay at 24 h postinfection. (B) ZIKV progeny titers were also determined 24 h postinfection in SC grown in the presence of serum (FBS) or absence of serum (−FBS) and compared to serum-deprived SC treated with rhGas6 (5 nM) upon infection (−FBS +rhGas6). (C) ZIKV RNA copies measured in infected SC in the presence and absence of Axl kinase inhibitor R428 (1 μM) by qRT-PCR and expressed as ZIKV PFU equivalents per microgram of RNA. (D) ZIKV progeny titers measured by plaque assay at 24 h and 72 h postinfection of SC treated with R428. (E) ZIKV infection of SC treated with R428 (1 μM) was also determined by IFA via staining of ZIKV (anti-ZIKV-E [green]) at 48 h postinfection. (F) Cell viability was evaluated following R428 treatment (1 μM) in mock-infected and infected SC by CellTiter 96 AQueous One Solution at 48 h postinfection, and the percent cell viability was calculated by comparison to the value for mock-infected cells at the corresponding time point. DMSO vehicle was used as untreated control for R428 experiments. Values are averages ± standard deviations (SD) (error bars) from 3 to 5 independent experiments with cells infected at an MOI of 1. Values that are significantly different are indicated by a bar and asterisks as follows: *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001.