An affinity-matured human monoclonal antibody targeting fusion loop epitope of dengue virus within vivotherapeutic potency

AbstractDengue virus (DENV), from the genusflavivirusof the familyflaviviridae, 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 ability (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 improved the survival rate of interferon-α/β/γ receptor knockout C57BL/6 mice after a lethal DENV challenge. Additionally, Fc-modified 3G9 molecules that had lost their in vitro ADE activity showed significantly enhanced therapeutic potencyin vivoand competed strongly with an ADE-prone antibodyin vitro. Taken together, the affinity-matured FLE-targeting antibody 3G9 exhibits several promising features for therapeutic application including a low NT50value, potential for pan-flavivirus infection treatment, and suppression of ADE. This study demonstrates the therapeutic potency of affinity-matured FLE-targeting antibodies.