Dengue Virus Envelope Dimer Epitope Monoclonal Antibodies Isolated from Dengue Patients Are Protective against Zika Virus

Abstract

Zika virus (ZIKV) is a mosquito-borne flavivirus responsible for thousands of cases of severe fetal malformations and neurological disease since its introduction to Brazil in 2013. Antibodies to flaviviruses can be protective, resulting in lifelong immunity to reinfection by homologous virus. However, cross-reactive antibodies can complicate flavivirus diagnostics and promote more severe disease, as noted after serial dengue virus (DENV) infections. The endemic circulation of DENV in South America and elsewhere raises concerns that preexisting flavivirus immunity may modulate ZIKV disease and transmission potential. Here, we report on the ability of human monoclonal antibodies and immune sera derived from dengue patients to neutralize contemporary epidemic ZIKV strains. We demonstrate that a class of human monoclonal antibodies isolated from DENV patients neutralizes ZIKV in cell culture and is protective in a lethal murine model. We also tested a large panel of convalescent-phase immune sera from humans exposed to primary and repeat DENV infection. Although ZIKV is most closely related to DENV compared to other human-pathogenic flaviviruses, most DENV immune sera (73%) failed to neutralize ZIKV, while others had low (50% effective concentration [EC50], <1:100 serum dilution; 18%) or moderate to high (EC50, >1:100 serum dilution; 9%) levels of cross-neutralizing antibodies. Our results establish that ZIKV and DENV share epitopes that are targeted by neutralizing, protective human antibodies. The availability of potently neutralizing human monoclonal antibodies provides an immunotherapeutic approach to control life-threatening ZIKV infection and also points to the possibility of repurposing DENV vaccines to induce cross-protective immunity to ZIKV.

Importance: ZIKV is an emerging arbovirus that has been associated with severe neurological birth defects and fetal loss in pregnant women and Guillain-Barré syndrome in adults. Currently, there is no vaccine or therapeutic for ZIKV. The identification of a class of antibodies (envelope dimer epitope 1 [EDE1]) that potently neutralizes ZIKV in addition to all four DENV serotypes points to a potential immunotherapeutic to combat ZIKV. This is especially salient given the precedent of antibody therapy to treat pregnant women infected with other viruses associated with microcephaly, such as cytomegalovirus and rubella virus. Furthermore, the identification of a functionally conserved epitope between ZIKV and DENV raises the possibility that a vaccine may be able to elicit neutralizing antibodies against both viruses.

FIG 1

Neutralization and binding of DENV and ZIKV by monoclonal antibodies. (A) MAbs elicited by DENV were evaluated for their ability to neutralize and bind DENV-1, DENV-2, DENV-3, DENV-4, ZIKV H/PF/2013, and ZIKV PRVABC59. (B) The ability of the EDE1 MAbs to neutralize ZIKV H/PF/2013 and ZIKV PRVABD59 was confirmed in both U937+DC-SIGN and Vero cells. (C) Binding of the neutralizing EDE1 MAbs and the nonneutralizing EDE2 B7 MAb to DENV-1, DENV-2, DENV-3, DENV-4, and ZIKV H/PF/2013 was assessed via enzyme-linked immunosorbent assay. Bars for neutralization data in panels A and B represent the means from two replicates with upper and lower 95% confidence intervals. The dotted line indicates the limit of detection for the assay. Nonneutralizing antibodies were assigned a value of twice the limit of detection for visualization. Bars for binding data in panel C represent the mean from two replicates with standard deviations.

FIG 2

EDE1 C10 protects ZIKV-susceptible mice from infection. Five-week-old type I/II interferon receptor-knockout mice on a C57BL/6 backbone received either EDE1 C10 (n = 5) or mock (n = 5) treatment and were challenged with 10² FFU of ZIKV H/PF/2013. A mock cohort (n = 2) was also included. Survival (A) and weight loss (B) were monitored, and differences between the mock-treated and EDE1 C10-treated cohorts are shown.

FIG 3

Neutralization of DENV and ZIKV by DENV primary sera. Geometric mean titers of DENV-1 primary sera (A), DENV-2 primary sera (B), DENV-3 primary sera (C), and DENV-4 primary sera (D). Colored points represent individual sera, and horizontal lines represent the geometric mean titers of all sera with upper and lower 95% confidence intervals. The dotted line indicates the limit of detection for the assay. Nonneutralizing sera were assigned a value of one-half of the limit of detection for visualization and calculation of the geometric means and confidence intervals.

FIG 4

Neutralization of DENV and ZIKV by DENV secondary sera. Geometric mean titers of DENV secondary sera. Colored points represent individual sera, and horizontal lines represent the geometric mean titers of all sera with upper and lower 95% confidence intervals. The dotted line indicates the limit of detection for the assay. Nonneutralizing sera were assigned a value of one-half of the limit of detection for visualization and calculation of the geometric means and confidence intervals.