Mechanisms of Antibody Mediated Neutralization of Dengue Virus Public Deposited

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  • March 20, 2019
Creator
  • Zhou, Yang
    • Affiliation: School of Medicine, Department of Microbiology and Immunology
Abstract
  • Dengue virus (DENV) is the most significant arthropod-borne virus in this world, affecting 2.5 billion people. Pre-existing sub-neutralizing antibodies (Abs) can enhance virus infection, leading to severe disease. Thus a better understanding of the interaction between humoral immunity and dengue virus is imperative. In this thesis I characterized 37 human monoclonal Abs (hMAbs) cloned from human PBMC. The majority of these MAbs were broadly cross-reactive and capable of enhancement of infection in vitro; few exhibited serotype-specific neutralizing activity. I next studied the mechanism and stoichiometry of Ab mediated neutralization of DENV and found that MAbs displaying threshold stoichiometry all neutralize post-attachment steps while MAbs neutralizing pre-attachment step display linear stoichiometry, indicating that different neutralization mechanisms are associated with different stoichiometric models respectively. I also studied the neutralization using multiple MAbs mixed together and demonstrated that the neutralization two MAbs are independent of each other in the mixture. It was previously found that MAb 8A1 displays variable neutralizing activity against different DENV-3 genotypes. My results demonstrated that EDIII mutations at 301 and 383 alter the ability of 8A1 to bind and neutralize different genotypes of DENV-3. Besides genetic mutation, non-genetic variation such as maturation state of the dengue virion can also modulate neutralization. I found that monocytic cell derived dengue virions were more mature than mosquito cell derived virions. Using a panel of MAbs and sera, I demonstrated that maturation reduces virus sensitivity to neutralization mediated by weakly neutralizing cross-reactive MAbs or sera but it does not affect sensitivity to type-specific and strongly neutralizing MAbs or sera. Most interestingly, maturation enhanced virus sensitivity to neutralization of certain MAbs and sera. Further study indicated that preferential binding of immature virions by weakly neutralizing MAbs and furin cleavage of partially mature virions inside endosome are responsible for the maturation dependent differential neutralization. These results offer new insight into how humoral immunity neutralizes dengue viruses and how viruses evade the immunity. These discoveries may also shed light on rational design of dengue vaccine and antibody therapy.
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  • In Copyright
Advisor
  • De Silva, Aravinda Manu
Degree
  • Doctor of Philosophy
Graduation year
  • 2013
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