Date of Award

Spring 5-15-2015

Author's School

Graduate School of Arts and Sciences

Author's Department

Biology & Biomedical Sciences (Molecular Microbiology & Microbial Pathogenesis)

Degree Name

Doctor of Philosophy (PhD)

Degree Type

Dissertation

Abstract

Chikungunya virus (CHIKV) is an Aedes mosquito-transmitted alphavirus that causes epidemics of a debilitating, often chronic polyarthritis in humans. Over five million people in Africa and Asia have been infected since 2005, and an outbreak occurred recently in Italy demonstrating the potential for a global epidemic. A strong antibody response is elicited during infection and the aim of this thesis was to develop a better understanding of how the humoral immune response can control CHIKV infection. We identified 230 new anti-CHIKV monoclonal antibodies (MAbs) and tested their ability to inhibit infection of strains representing all three CHIKV genotypes (East/Central/South African, West African and Asian). We identified 36 of these MAbs that inhibit Chikungunya infection; almost half of them are potently neutralizing and have EC50 values of less than 15 ng/mL (0.1 nM) against CHIKV strains representing the three genotypes. Many of these MAbs exhibit cross-reactivity with a number of related alphaviruses including O'nyong'nyong, Ross River, Semliki Forest, Mayaro, Una, Getah, Bebaru, Middleburg, Barmah Forest, Sindbis and Venezuelan equine encephalitis viruses. Four of these neutralizing MAbs provided complete protection as prophylaxis in highly susceptible immunocompromised mice and mapped to distinct antigenic epitopes on the E1 and E2 structural proteins. To define functional epitopes, we selected for escape mutants in vitro for these four MAbs. We identified most of these escape mutants in the brains and leg muscle of mice dying despite lower dose prophylaxis or monotherapy. The most protective MAb was humanized, shown to block viral fusion, and require Fc effector function for optimal activity in vivo. In post-exposure therapeutic trials, administration of a single dose of a combination of two neutralizing MAbs targeting different domains of the E2 surface glycoprotein or targeting both the E1 and E2 glycoproteins limited the development of resistance and protected immunocompromised mice against disease when given even 24 to 36 hours before CHIKV-induced death. These studies provide some insight into the location of neutralizing epitopes of CHIKV and how selected pairs of highly neutralizing MAbs may be a promising treatment option for CHIKV infection in humans.

Language

English (en)

Chair and Committee

Michael Diamond

Committee Members

Deepta Bhattacharya, Daved Fremont, Deborah Lenschow, Henry Huang, Dave Wang

Comments

Permanent URL: https://doi.org/10.7936/K7KK98X6

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