IFNL1 and Zika virus infectious disease: Additional TO cultures were pretreated with IFNλ-1 and IFNλ-3 neutralizing antibodies prior to ZIKV infection as a positive control, since IFNλ has been previously shown to regulate ZIKV infection of fetal trophoblasts through autocrine signaling.10–12 By measuring viral RNA via quantitative RT-PCR, we showed that TO cultures were susceptible to ZIKV infection, and that neutralization of IL-27 or IFNλ led to similar increases in TO viral RNA levels relative to control organoids (Figure 1E).