Figure 4.

DENV-4 E VLPs elicit EDIII-directed serotype-specific neutralizing antibodies. (A) Immune sera collected 10 days after the final boost from DENV-4 E VLP-immunized BALB/c mice were evaluated for existence of neutralizing antibodies against DENV-1 (DV1, red curve), DENV-2 (DV2, green curve), DENV-3 (DV3, blue curve), and DENV-4 (DV4, black curve) by FNT on Vero cells. (B) The contribution of anti-EDIII antibodies in DENV-4 E immune serum (black solid curve) in neutralizing DENV-4 was evaluated by FNT on Vero cells after depleting it of anti-EDIII antibodies by incubating it with serotype 4 EDIII-MBP (black dotted curve). DENV-4 E immune serum was also incubated with MBP (black dashed curve) to score nonspecific depletion of antibodies (if any). The percentage of Vero cells infected with the DENV is represented on y axis, while log of reciprocal of sera dilution is represented on x axis. FNT₅₀ titers, tabulated on the top of each of the graphs, represent the sera dilution resulting in 50% neutralization of respective DENV, and are calculated from the dotted horizontal line in the graphs representing 50% infection (or 50% neutralization). DENV-4 E = dengue virus serotype 4 ectodomain; ED = envelope domain; FNT = fluorescence-activated cell sorting (FACS)-based neutralization test; MBP = maltose-binding protein; VLP = virus-like particle.