TABLE 1.

Cell permeabilization

Cell type	EC50a (μM)
	EBOV peptides							RESTV peptides				MelP5b
	E40ox	E40red	E23ox	E23red	E17ox	E15ox	E14ox	R42ox	R42red	R25ox	R25red
MDCK	5.5	I	11	I	14	16	I	ND	ND	ND	ND	2.8
MDCKc	25	I	72	I	ND	ND	ND	ND	ND	ND	ND	9.0
HeLa	19	I	16	I	15	21	I	ND	ND	ND	ND	3.1
Vero	20	I	22	I	52	37	I	I	I	56	I	3.6
Verod	18	ND	11	ND	ND	ND	ND	100	ND	49	ND	1.0
CHO	5.4	I	17	I	15	21	I	I	I	68	I	1.6
RBCe	>200	ND	>200	ND	>200	>200	I	I	ND	>200	ND	3.6

^aEC₅₀, concentration required for 50% lytic or toxic effect. Oxidized EBOV or RESTV peptides (ox) have a disulfide cross-link between the conserved cysteines, while reduced peptides (red) do not. Except where noted, all measurements are based on Sytox green entry into cells after 1 h of incubation of serially diluted peptide with a cell monolayer in the presence of 100 nM Sytox green. Sytox green entry, which does not occur in unperturbed cells, is measured by the dramatically increased fluorescence of the probe when it binds to nuclear DNA (Fig. 3). I, less than 5% permeabilization was observed at the highest concentration studied, 200 μM for hemolysis and 50 or 100 μM for Sytox green entry; >200, more than 5% hemolysis was observed at the highest concentration, but the EC₅₀ is greater than 200 μM peptide; ND, the experiment was not done. All values are the means of the results of ≥3 experiments. The standard deviations had an average value of 30% of the EC₅₀s listed.

^bMelP5 is a lytic control peptide derived from the bee venom toxin, melittin (23).

^cLoss of transepithelial electrical resistance in a confluent monolayer of MDCK cells.

^dCytotoxicity of peptides after 24 h of incubation with VERO cells, measured using alamarBlue fluorescence.

^eHemolysis of human erythrocytes, measured by assessing the peptide-induced release of hemoglobin.