An affinity-matured human monoclonal antibody targeting fusion loop epitope of dengue virus with in vivo therapeutic potency

Abstract

Dengue virus (DENV), from the genus flavivirus of the family flaviviridae, causes serious health problems globally. Human monoclonal antibodies (HuMAb) can be used to elucidate the mechanisms of neutralization and antibody-dependent enhancement (ADE) of DENV infections, leading to the development of a vaccine or therapeutic antibodies. Here, we generated eight HuMAb clones from an Indonesian patient infected with DENV. These HuMAbs exhibited the typical characteristics of weak neutralizing antibodies including high cross-reactivity with other flaviviruses and targeting of the fusion loop epitope (FLE). However, one of the HuMAbs, 3G9, exhibited strong neutralization (NT50 < 0.1 μg/ml) and possessed a high somatic hyper-mutation rate of the variable region, indicating affinity-maturation. Administration of this antibody significantly prolonged the survival of interferon-α/β/γ receptor knockout C57BL/6 mice after a lethal DENV challenge. Additionally, Fc-modified 3G9 that had lost their in vitro ADE activity showed enhanced therapeutic potency in vivo and competed strongly with an ADE-prone antibody in vitro. Taken together, the affinity-matured FLE-targeting antibody 3G9 exhibits promising features for therapeutic application including a low NT50 value, potential for treatment of various kinds of mosquito-borne flavivirus infection, and suppression of ADE. This study demonstrates the therapeutic potency of affinity-matured FLE-targeting antibodies.

New Anti-Flavivirus Fusion Loop Human Antibodies with Zika Virus-Neutralizing Potential

“…The present work contributes two additional FL-specific ZIKV neutralizing antibodies, AZ1p and AZ6m. The neutralizing potentials observed from AZ1p (397.4 ηΜ) and AZ6m (311.4 ηΜ) are lower than some previously described anti-fusion loop antibodies such as 2A10G6 with IC 50 = 1.67 µΜ [ 26 , 31 ] and C5, and IC 50 > 10 µΜ [ 32 ] against ZIKV, but they are also higher than others anti-FL antibodies such as 3G9 (0.67 ηΜ) [ 33 ] and ZAb_FLEP (33.3 ηΜ) [ 34 ], although a direct comparison is not possible due to methodological variations that exist in the PRNT and the antibody format and valence. However, the important message from our work is that it is possible to find neutralizing antibodies in naive phage libraries, and further molecular engineering and mutagenesis may help improve FL-binding properties.…”

Self-Assembling Nanovaccine Confers Complete Protection Against Zika Virus Without Causing Antibody-Dependent Enhancement

“…Additionally, after zEDIII-rHF vaccination, mice were challenged with 100 μl of DENV-2 (10 3 50% tissue culture infectious dose (TCID 50 )) by intraperitoneal injection ( 35 ). Body weight loss and survival data were collected for the next 14 days ( Figures 6B, C ).…”

Evolution of a Functionally Intact but Antigenically Distinct DENV Fusion Loop

“…For example, antibodies can be engineered to eliminate binding to the Fcγ receptor, abolishing antibody-dependent enhancement. 31 While this methodology holds potential for antibody therapeutic development and passive immunization strategies, it is not relevant for vaccination. As fusion-loop and premembrane targeting antibodies are the major species demonstrated to cause antibodydependent enhancement in vitro and are thought to be responsible for antibodydependent enhancement-driven negative outcomes after primary infection and vaccination, [10][11][12]32 we propose that genetic ablation of the fusion-loop and pre-membrane epitopes in vaccine strains will minimize the production of these subclasses of antibodies responsible for undesirable vaccine responses.…”