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Title: Antibody correlates of protection for Ebola virus infection : effects of mutations within the viral glycoprotein on immune escape
Author: Steeds, Kimberley
ISNI:       0000 0004 7964 2152
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2019
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Ebola virus (EBOV) is an enveloped, single-stranded RNA virus that can cause Ebola virus disease (EVD), a highly lethal illness with up to 90% mortality. It is thought that EVD survivors are protected against subsequent infection with EBOV and that neutralising antibodies to the viral surface glycoprotein (GP) are potential correlates of protection. Serological studies are vital to assess neutralising antibodies targeted to GP; however handling of EBOV is limited to containment level 4 laboratories. Pseudotyped viruses can be used as alternatives to live infectious viruses that require high levels of bio-containment in serological and receptor binding and assays. Neutralisation capacity can differ among pseudotyped virus platforms. The ability of EBOV GP pseudotyped lentivirus and vesicular stomatitis virus (VSV) systems to measure the neutralising ability of EVD convalescent plasma were compared. The results demonstrate that the sensitivity, specificity and correlation with live EBOV neutralisation are greater for the VSV-based pseudotyped virus system. The extensive human-to-human transmission of EBOV observed during the 2013-2016 EVD epidemic in West Africa resulted in an accumulation of mutations within the EBOV genome. The current study undertook to assess how these might impact upon immune escape. Specifically, the influence of mutations within the EBOV GP on escape from neutralising antibodies derived from EVD convalescent individuals was assessed. Site-directed mutagenesis was performed to introduce specific mutations that occurred during the 2013-2016 EVD outbreak into EBOV GP expression plasmids, which were subsequently used to generate a panel of mutant EBOV GP pseudotyped viruses. The effect of these mutations on neutralisation by polyclonal and monoclonal antibody (mAb) samples was assessed. Overall, the results suggest that multiple naturally occurring amino acid changes in EBOV GP do not have a significant impact on polyclonal neutralising antibodies derived from EVD convalescent volunteers or EBOV GP vaccinated individuals. However these mutations can result in reduced neutralisation by certain EBOV GP-specific mAbs. Specifically, a G74R mutation located in the receptor binding domain (RBD) of EBOV GP is associated with partial escape from neutralisation by a human anti-EBOV GP mAb, KZ52. Sequencing studies and pseudotyped viruses represent an opportunity to study the possible impact of naturally occurring EBOV GP mutations on immune escape, which in turn has the potential to provide a better understanding of EVD vaccine efficacy and correlates of protection against EBOV.
Supervisor: Carroll, Miles ; Pollakis, Georgios ; Hiscox, Julian ; Hewson, Roger Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral