Evaluation and application of novel serologic tools for assessing ZIKV-specific immunity for surveillance and translational research Open Access

Abstract

Since the beginning of the Latin American Zika epidemic first recognized in 2015,

autochthonous transmission of Zika virus (ZIKV) has been reported in 87 different countries.

Although most ZIKV infections are mild or asymptomatic, there is risk of developing Guillain-

Barr. syndrome and adverse pregnancy outcomes including congenital malformations, stillbirth,

and pre-term births. Although RT-PCR testing is available, ZIKV RNA is detectable during a

narrow window in patients presenting with symptoms. Serology can detect recent or remote

infections, but traditional assays are complicated by cross-reactive antibodies elicited by other

co-circulating flaviviruses like dengue virus (DENV). Thus, there is a critical need for serologic

tools for reliable diagnosis and surveillance of ZIKV infection as well as to gain a better

understanding of protective immunity for vaccine development. We developed a blockade-ofbinding

(BOB) ELISA using A9E and G9E, two ZIKV envelope protein-binding monoclonal

antibodies (mAbs), which are strongly neutralizing against ZIKV but do not bind to DENV. We

assessed BOB performance by ROC curve analysis after running a panel of positive and negative

control sera. At the optimal cutoff, the A9E BOB ELISA has a sensitivity of 93.5% (95% CI:

79.3,98.9) and specificity 97.8 (95% CI: 92.2,99.6). The G9E BOB ELISA has a sensitivity and

specificity of 100% (95% CI: 89.0,100.0) and 100% (95% CI: 95.9,100). We then applied these

assays to test samples from surveillance cohorts in Risaralda, Colombia. Finally, the assay was

applied to samples from participants in a phase 1 randomized controlled trial for a ZIKV DNA

vaccine candidate. Serum samples collected 30-day post-vaccine administration exhibited

significantly less A9E and G9E blockade than those with natural ZIKV immunity. In conclusion,

A9E and G9E ZE-BOB are sensitive and specific assays that may be useful tools for diagnosis of

recent or remote ZIKV infections and clinical decision making. Further development of A9E and

G9E BOB assays as potential serologic correlates of protective immunity against ZIKV is well

justified.

Table of Contents

Table of Contents

Chapter I: Literature Review ................................................................................................... 1

Flaviviruses and the emergence of Zika as a public health threat ................................................................................. 1

Zika epidemiology and diagnosis ................................................................................................................................... 2

ZIKV biology ................................................................................................................................................................... 3

Complications of flavivirus cross-reactivity ................................................................................................................... 4

Features of natural immunity ........................................................................................................................................ 5

Vaccine development and challenges ............................................................................................................................ 6

A9E and G9E monoclonal antibodies and their potential use in a ZE-BOB ELISA format .............................................. 8

Chapter II: Manuscript ............................................................................................................ 9

Introduction ................................................................................................................................................................... 9

Materials and Methods ............................................................................................................................................... 11

Human serum and plasma samples ........................................................................................................................ 11

Lab Experiments ..................................................................................................................................................... 13

Statistical Analyses ................................................................................................................................................. 14

Results ......................................................................................................................................................................... 15

ZE-BOB Assay Optimization and Validation ............................................................................................................ 15

Characteristics of the A9E and G9E response ......................................................................................................... 16

Colombian Mother Surveillance Cohort ................................................................................................................. 17

VRC 320 Phase 1 Clinical Trial Recipients ............................................................................................................... 18

Discussion ................................................................................................................................................................... 19

Figures ......................................................................................................................................................................... 22

Chapter III: Public Health Implications .................................................................................. 31

References ............................................................................................................................ 32

About this Master's Thesis

Rights statement

• Permission granted by the author to include this thesis or dissertation in this repository. All rights reserved by the author. Please contact the author for information regarding the reproduction and use of this thesis or dissertation.

School	Rollins School of Public Health
Department	Epidemiology
Subfield / Discipline	Global Epidemiology - MPH & MSPH
Degree	M.P.H.
Submission	Master's Thesis
Language	English
Research Field	Health Sciences, Public Health Health Sciences, Epidemiology Health Sciences, Immunology
Keyword	Zika Infectious Disease Serology Epidemiology
Committee Chair / Thesis Advisor	Gonzalo Vasquez-Prokopec, Emory University
Committee Members	Matthew Collins, Emory University

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