Antibody epitopes identified in critical regions of dengue virus nonstructural 1 protein in mouse vaccination and natural human infections

Abstract

A major challenge in dengue vaccine development is that cross-reactive anti-DENV antibodies (Abs) can be protective or potentially enhance disease via antibody-dependent enhancement (ADE). We recently showed that immunization with adjuvanted recombinant NS1 from all four DENV serotypes protects against DENV2 challenge in a mouse model of lethal vascular leak syndrome. Conversely, we found that DENV NS1 by itself triggers endothelial permeability in vitro and vascular leak in vivo. Here, we evaluated survival to lethal DENV challenge in mice immunized with (1) NS1+alum; (2) NS1+Monophosphoryl Lipid A and AddaVax (MA); (3) NS1+Sigma adjuvant system and CpG DNA (SCpG); (4) ovalbumin+adjuvant (OVA); or (5) a sublethal dose of DENV2 strain PLO46.NS1. OVA or NS1+alum immunized mice were not protected, whereas immunization with NS1+MA or NS1+SCpG or DENV2-PL046 resulted in 100% survival. We characterized Ab responses to NS1 from DENV1-3 using an antigen microarray tiled with 20-mer peptides overlapping by 15 amino acids and identified 5 regions with significant levels of antibody reactivity in the NS1+MA group. We also profiled Ab responses to NS1 in humans naturally infected with DENV-2 or -3 in longitudinal serum samples from Nicaragua. One region in the NS1 “wing” domain was immunodominant in both mouse and human studies, and two regions were identified only in NS1-immunized mice; thus, vaccination can generate Abs to regions that are not targeted in natural infection and could provide additional protection against a lethal DENV infection. Overall, we identified several immunodominant regions, which were in functionally important locations on the DENV NS1 protein and are potential correlates of protection.