A human ex vivo dengue virus neutralization assay identifies priority antibodies and epitopes for vaccines and therapeutics

Background Dengue is the most prevalent arboviral disease, for which neither effective vaccines nor antivirals are available. Clinical trials with Dengvaxia, the first licensed dengue vaccine, show the conventional in vitro plaque reduction neutralization test (PRNT) failed to discriminate between neutralizing and non-neutralizing antibodies. A number of human monoclonal antibodies (mAbs) were characterized by PRNT as being neutralizers of virus infectivity for mammalian cells. Methodolody/Principle findings We developed a neutralization assay and tested the capacity of 12 mAbs to neutralize the infectiousness of dengue patient viremic blood in mosquitoes. We identified minimum concentrations of a subset of mAbs required to achieve dengue virus neutralization, and modelled the impact of a therapeutic mAb candidate on viremia. Five of the 12 mAbs (14c10, 2D22, 1L12, 747(4)B7, 753(3)C10), all of which target quaternary epitopes, potently inhibited dengue virus infection of Ae. aegypti . The potency of several mAbs was compromised in the context of patients with secondary serological profiles, possibly reflecting competition between the exogenously-added mAbs and the patient’s own antibody responses at or near the target epitopes. The minimum concentrations that mAbs neutralized DENV ranged from 0.1 – 5 µg/mL. An Fc-disabled variant of mAb (14c10-LALA) was as potent as its parent mAb. Within-host mathematical modelling suggests infusion of 14c10-LALA could bring about rapid acceleration of viremia resolution in a typical patient. Conclusions/Significance These data delivered a unique assessment of anti-viral potency of a panel of human mAbs. Results support the advancement of dengue virus neutralization assays, and the development of therapeutics against flaviviruses, to which dengue virus and Zika virus belong. Author summary Dengue is the most prevalent arboviral disease affecting humans. There are no therapeutics for the disease. Antibody-mediated immunity against dengue is also not well-understood, as shown by the failure of the conventional neutralization assay used to predict the efficacy of Dengvaxia, the first licensed vaccine for the disease. It is likely that the neutralization assay targets non-neutralizing antibodies, but there are no validation assays available. To this end, we developed a novel virus neutralization assay, employing Aedes aegypti mosquitoes and viremic blood from dengue patients, to examine the virus-neutralizing potency of 12 human-derived monoclonal antibodies (mAbs). While all of these mAbs neutralized dengue virus using the conventional assay, seven of them failed to block dengue virus infections of mosquitoes using our assay. The remaining five mAbs neutralized at least one serotype of dengue virus and the minimum neutralizing concentrations of range from 0.1 – 5 µg/mL. Using the minimum neutralizing concentration of a therapeutic mAb candidate, we investigated the impact of the mAb on viremia using a mathematical model and found the mAb accelerated the reduction of viremia. The results support the advancement of dengue virus neutralization assays, and the development of therapeutics for dengue.