Therapeutic Effects of Monoclonal Antibody against Dengue Virus NS1 in a STAT1 Knockout Mouse Model of Dengue Infection

Abstract

Dengue virus (DENV) is the causative agent of dengue fever, dengue hemorrhagic fever, and dengue shock syndrome and is endemic to tropical and subtropical regions of the world. Our previous studies showed the existence of epitopes in the C-terminal region of DENV nonstructural protein 1 (NS1) which are cross-reactive with host Ags and trigger anti-DENV NS1 Ab-mediated endothelial cell damage and platelet dysfunction. To circumvent these potentially harmful events, we replaced the C-terminal region of DENV NS1 with the corresponding region from Japanese encephalitis virus NS1 to create chimeric DJ NS1 protein. Passive immunization of DENV-infected mice with polyclonal anti-DJ NS1 Abs reduced viral Ag expression at skin inoculation sites and shortened DENV-induced prolonged bleeding time. We also investigated the therapeutic effects of anti-NS1 mAb. One mAb designated 2E8 does not recognize the C-terminal region of DENV NS1 in which host-cross-reactive epitopes reside. Moreover, mAb 2E8 recognizes NS1 of all four DENV serotypes. We also found that mAb 2E8 caused complement-mediated lysis in DENV-infected cells. In mouse model studies, treatment with mAb 2E8 shortened DENV-induced prolonged bleeding time and reduced viral Ag expression in the skin. Importantly, mAb 2E8 provided therapeutic effects against all four serotypes of DENV. We further found that mAb administration to mice as late as 1 d prior to severe bleeding still reduced prolonged bleeding time and hemorrhage. Therefore, administration with a single dose of mAb 2E8 can protect mice against DENV infection and pathological effects, suggesting that NS1-specific mAb may be a therapeutic option against dengue disease.

Relative contribution of nonstructural protein 1 in dengue pathogenesis

“…Lack of protective NS1 immunity is independent of mouse background Previous studies that reported NS1-mediated protection were conducted in mouse strains such as IFNAR −/− ; Beatty et al, 2015) and STAT1 −/− (Wan et al, 2017;Lai et al, 2017), both on the C57BL/6 background. We thus questioned whether the discrepancy between our observations and the earlier studies could be explained by a difference in mouse background.…”

“…Beyond its role in DENV intracellular replication, recent literature has reported a critical role of NS1 in dengue pathogenesis by interacting with the endothelium and inducing vascular leakage, a clinical feature of severe dengue (Beatty et al, 2015;Modhiran et al, 2015). Consequently, NS1 immunity was found to protect against dengue disease (Beatty et al, 2015;Costa et al, 2006;Lai et al, 2017;Wan et al, 2014Wan et al, , 2017. These in vivo studies were conducted with DENV clinical isolates or mouseadapted strains which either required very high dosages to induce lethality (DENV2-454009A, D220, and DENV2-3295) or induced only mild clinical symptoms (DENV2-16681, DENV1-8700828, DENV3-8700829, DENV4-59201818, and DENV2-RJ; Orozco et al, 2012;Beatty et al, 2015;Costa et al, 2006;Lai et al, 2017;Wan et al, 2014Wan et al, , 2017Chan et al, 2019), thus implying that the in vivo fitness of these DENV strains is rather poor.…”

“…In the wake of the Dengvaxia setback and controversy, subunit vaccine candidates have regained some traction . While the envelope protein (E protein) of DENV has been the most popular subunit vaccine candidate, a number of studies have also proposed DENV nonstructural protein 1 (NS1) as a potential candidate (Schlesinger et al, 1987;Henchal et al, 1988;Falgout et al, 1990;Beatty et al, 2015;Gonçalves et al, 2015;Wan et al, 2014Wan et al, , 2017Lai et al, 2017). NS1 is a glycosylated nonstructural protein (46-55 kD) that homodimerizes after posttranslational modification, becomes membrane associated, and participates in RNA replication within membrane-bound replication complexes.…”

“…These findings thus support that NS1 represents a promising subunit vaccine candidate and a safer alternative to avoid the risk of ADE, which is a major roadblock in the development of vaccines that rely on protective immunity against the structural components of DENV. However, the role of NS1 in dengue pathogenesis and the in vivo protective efficacy of NS1 immunity had been demonstrated in mouse models that either produce mild symptoms such as local skin hemorrhage and prolonged bleeding time (Wan et al, 2014(Wan et al, , 2017Lai et al, 2017) or use mouse-adapted DENV2 strains (Schlesinger et al, 1987;Henchal et al, 1988;Falgout et al, 1990;Costa et al, 2006;Beatty et al, 2015).…”

Role of NS1 antibodies in the pathogenesis of acute dengue infection

“…Proteomics, sequence identity analyses and in vitro studies have shown that the C-terminal region of NS1 contains many cross-reactive epitopes, with sequence homology to self-antigens such as endothelial cell proteins and mediators involved in the coagulation pathways and platelet response 9,30-32 . As a result, the monoclonal antibody, which substitutes the C-terminus of dengue NS1 with that of Japanese Encephalitis NS1 was found to be 14 protective in dengue mouse models 33 . Our data show that DF patients with acute secondary DENV-1 and DENV-2 infection, had significantly higher antibody titres to the C-terminus of NS1 compared to those with severe forms of dengue (DHF).…”