Fig. 1.

Conditioned PHT medium and exosomes confer viral resistance to recipient cells. (A) PHT or non-PHT cells were infected with a panel of viruses, including coxsackievirus B (CVB), poliovirus (PV), vesicular stomatitis virus (VSV), vaccinia virus (VV), herpes simplex virus-1 (HSV-1), or cytomegalovirus (CMV). Non-PHT cells were as follows: HeLa (CVB, PV), U2OS (VSV, HSV-1, and VV), and human foreskin fibroblasts (HFF; CMV). Shown are the percent infected cells [assessed by immunofluorescence (IF); *P < 0.0001]. (B) Non-PHT recipient cells were exposed for 24 h to nonconditioned or conditioned PHT medium and then infected with CVB, VSV, HCV, or VV. Non-PHT cells were as follows: HFF (CVB), U2OS (VSV, VV), and Huh 7.5 (HCV). Shown are the percent of infected cells [assessed by IF (CVB, VSV), luciferase assay (HCV), or qRT-PCR (VV); *P < 0.05, **P < 0.005]. (C) (Left) Cells were exposed to nonconditioned or conditioned PHT medium for 24 h and then infected with VSV or CVB. (Right) Cells were infected with VSV following exposure to nonconditioned or conditioned PHT medium (*P < 0.05, **P < 0.005). (D) Conditioned PHT medium was subjected to heat inactivation or sonication before 24-h exposure to Vero cells and then infected with VSV. Percent infection assessed as in A (*P < 0.0001). (E) U2OS cells were exposed for 24 h to nonconditioned, conditioned, exosome-depleted conditioned medium, exosomes purified from PHT, JEG-3, or from three preparations of murine dendritic cells (DCs) and then infected with VSV. Percent infection assessed as in A (*P < 0.0005); each PHT exosome preparation was derived from a different placental preparation.