Neutralizing human monoclonal antibodies prevent Zika virus infection in macaques

Abstract

Therapies to prevent maternal Zika virus (ZIKV) infection and its subsequent fetal developmental complications are urgently required. We isolated three potent ZIKV-neutralizing monoclonal antibodies (nmAbs) from the plasmablasts of a ZIKV-infected patient-SMZAb1, SMZAb2, and SMZAb5-directed against two different domains of the virus. We engineered these nmAbs with Fc LALA mutations that abrogate Fcγ receptor binding, thus eliminating potential therapy-mediated antibody-dependent enhancement. We administered a cocktail of these three nmAbs to nonhuman primates 1 day before challenge with ZIKV and demonstrated that the nmAbs completely prevented viremia in serum after challenge. Given that numerous antibodies have exceptional safety profiles in humans, the cocktail described here could be rapidly developed to protect uninfected pregnant women and their fetuses.

Fig. 1.

The plasmablast-derived human nmAbs SMZAb1, SMZAb2, and SMZAb5 neutralize ZIKV in vitro. Ninety-one mAbs generated from a ZIKV-infected patient were screened for ZIKV-neutralization potency using Vero cell infectivity assays, and the three most potent—SMZAb1, SMZAb2, and SMZAb5, neutralized ZIKV at low concentrations. The neutralization titers were determined by focus reduction neutralization test (FRNT).

Fig. 2.

Study design and pharmacokinetics of SMZAb cocktail administration to Indian rhesus macaques. (A) We administered a cocktail containing the three nmAbs, SMZAbs 1, 2, and 5 at a dose of 20 mg kg⁻¹ each to four rhesus macaques (Group 1). A control group (Group 2) received the human CB1 isotype control at a dose of 60 mg kg⁻¹ total. All animals were challenged with 1,000 PFU of ZIKV Rio U-1 2016 one day post mAb administration. Serum was collected at the indicated time points for viral load, neutralization, IgG, and IgM measurements. (A) Serum levels of recombinant Abs were determined by ELISA. Antibody level values for each SMZAb cocktail (blue) or control mAb (open symbols) animal. (C) Median values for the Group 1 (blue) and Group 2 (open symbols). (D) ZIKV-neutralizing activity in serum post mAb infusion was determined by FRNT. Median ZIKV-foci-neutralization percentage values for each SMZAb cocktail (blue) or control mAb (open symbols) animal. (E) Median values for the Group 1 (blue) and Group 2 (open symbols).

Fig. 3.

Viral loads and humoral responses post ZIKV challenge. (A) We administered a cocktail containing the three nmAbs, SMZAbs 1, 2, and 5 at a dose of 20 mg kg⁻¹ each to four rhesus macaques (Group 1). A control group (Group 2) received the human CB1 isotype control at a dose of 60 mg kg⁻¹ total. All animals were challenged with 1,000 PFU of ZIKV Rio U-1 2016 one day post mAb administration. Serum viral loads for SZMAb- (blue) and control CB1 mAb- (open symbols) treated macaques. Dotted lines indicate the limit of detection (LOD) of the assay. (B) Humoral IgM and IgG responses of challenged animals against whole ZIKV or NS1. Serum binding (diluted 1:100) was measured by ELISA using rhesus-specific antibodies.