Figure 1.

The mechanism of HMAb 1F4 neutralization of DENV1 (Western Pacific 74 strain) in Vero or DC-SIGN expressing U937 cell lines.

A, B Both HMAb 1F4 IgG (A) and its Fab fragment (B) neutralized DENV1 infection in U937 cells expressing DC-SIGN although the Fab fragment required a 4-fold higher concentration.

C HMAb 1F4 inhibited a post-attachment step of virus infection in Vero cells. HMAb 1F4 had similar neutralization activities when exposed to virus pre- (FRNT₅₀ = 0.41 μg/ml) or post-attachment (FRNT₅₀ = 0.37 μg/ml) to Vero cells. The two experiments were done with two replicates. Error bars represent standard deviations. Pre and post-attachment neutralization curves are not significantly different by a 2-way repeated measures analysis of variance (RM ANOVA).

D HMAb 1F4 prevented virus infection of DC-SIGN-expressing U937 cells by blocking both virus attachment and also a post-attachment step. Error bar represented standard deviations. Neutralization curves of pre and post-attachment groups are significantly different by 2-way RM ANOVA, with a P < 0.001.