Abstract
The emergence of Zika virus (ZIKV) in the Western hemisphere in 2015 precipitated a global health crisis. ZIKV causes microcephaly and other severe congenital abnormalities in neonates of women infected while pregnant. Future prevention of ZIKV-induced birth defects will require accurate diagnostic testing to inform prospective parents of their ZIKV serostatus prior to conception. However, cross-reactivity exhibited by antibodies (Abs) against ZIKV and closely-related dengue virus (DENV) poses a significant diagnostic challenge. In this thesis project, we sought to understand the antibody response in infected individuals, rapidly isolate monoclonal (m) Abs against an emergent virus, develop a novel immunological diagnostic test capable of differentiating ZIKV and DENV seropositivity rapidly, reproducibly, and inexpensively, and field test this assay for real world use. We hypothesized that Abs recognizing epitopes only found on the ZIKV Envelope (E) protein and not on the E proteins of the closely-related DENV1-4 would be produced by individuals infected with ZIKV, but not DENV, and that these Abs would serve as a marker of prior ZIKV exposure. To detect immunodominant ZIKV-epitope-specific Abs in human plasma, we developed an Ab competition ELISA, the Z-Quick ZIKV Antibody Competition Assay (Z-ACA), where we compete the ability of patient plasma Abs to block binding of an immunodominant ZIKV-specific (P1F12) mAb to a ZIKV-specific epitope on whole virus. We found that the plasma of ZIKV-exposed individuals blocked binding of the ZIKV-specific mAb to ZIKV, whereas the plasma of DENV-exposed individuals did not. We developed the assay and field tested the assay in patients with ZIKV-like symptoms or high risk ZIKV-exposures from different locations throughout the Americas. Collectively, these results indicate that the Z-ACA test is highly specific for ZIKV and can accurately differentiate between exposure to ZIKV and other flaviviruses. These findings suggest that the test could provide a promising aide in surveillance, seroprevalence, and clinical trial programs.