FIG 3.
Immune recognition of various EV-D68 densities and characterization of membrane-associated virus. (A) The y axis represents average dilutions of anti-EV-D68 mouse serum required to neutralize virus, divided by the average TCID50 for respective viral densities (ANOVA post hoc Student'’s t test, P = 0.42, P = 0.68, P = 0.70). (B) Three viral density isolates (1.11, 1.20, and 1.24 g/cm3) were treated with 0.01 mg/mL 15C5-Chmra antibody for 1 h, then mix was put onto TCID50 plates to assess the viral titer of each isolate. Gray highlight represents detection limit. Asterisks (*) indicate statistical significance (1.11 g/cm3, P = 0.0003; 1.20 g/cm3, P < 0.0001; 1.24 g/cm3, P = 0.0064), all versus respective control, determined by Dunnett’s Method. (C) 15C5-Chmra antibody bound to magnetic beads was added to membrane-associated and naked virus. After 1 h, a magnet was used to remove antibody and the supernatant was added to a TCID50 plate to assess viral titer (15C5-Chmra versus control: *, P < 0.0005 for both membrane-associated and naked virus; Dunnett’s Method). (D) ICAM-5 or N-acetylneuraminic acid (sialic acid) were attached to magnetic beads and the antibody/bead complex was incubated with membrane-associated or naked virus samples for 1 h. Beads were rinsed twice in excess PBS and viral titer was assessed to determine how much virus was immunoprecipitated from the supernatant (control versus ICAM5 and control versus sialic acid for membrane-associated and naked virus; *, P = 0.0001 determined by Dunnett’s Method). (E) Exosome antibody array on 1.11 g/cm3 fraction, examining cytosolic proteins (FLOT1, ALIX, TSG101), transmembrane proteins (CD63, CD81, ANXA5), and cis-golgi matrix protein as markers for cellular contamination (GM130). Example blot is shown on the right and chart represents average intensity across three biological replicates. Positive control indicates detection reagents are working correctly, and do not represent an exosome-specific control. Error bars represent standard deviation. Statistics: comparison with control (blank) using Dunnett’s Method (P = 0.999 for GM130; *, P = 0.027 for FLOT1; P = 0.218 for ICAM; *, P = 0.005 for ALIX; P = 0.086 for CD81; *, P < 0.0001 for CD63; P = 0.305 for EpCAM; *, P < 0.0001 for ANXA5; *, P = 0.0008 for TSG101). Asterisks indicate statistical significance. (F) Anti-CD81 or anti-CD63 antibodies were attached to magnetic beads and incubated with membrane-associated virus. Supernatant was discarded, and beads were rinsed and treated with 0.01% NP-40 (to dissolve exosomes and release virus from bead) before TCID50 measurement. CD81 versus control: *, P = 0.0178; CD63 versus control: *, P = 0.0180 as determined by Dunnett’s Method. Gray highlight represents detection limit. (G) RD or SH-SY5Y cells in TCID50 plate were infected with MO47 with or without exosomes in the medium. The “A549 exosomes added” bar represents exosome-depleted media to which purified A549 exosomes were added. Gray panel represents TCID50 plates containing SH-SY5Y cells. Each condition represents 3 biological replicates. Error bars represent standard deviation. ANOVA: *, P < 0.05. Green panel represents TCID50 plates containing RD cells. Each condition represents 4 biological replicates. Error bars represent standard deviation. ANOVA: *, P < 0.05.