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Title: A study of human monoclonal antibodies to Influenza and Ebola viruses
Author: Rijal, Pramila
ISNI:       0000 0004 6495 7936
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2016
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This thesis describes an analysis of the B cell repertoire in humans in response to infection or vaccination with Influenza or Ebola. We isolated monoclonal antibodies (mAbs) from individuals using single B cell cloning and PCR technology, and defined their epitopes, binding characteristics and neutralisation properties. As summarised by Thomas Francis in 1960, we found that the secondary B cell response to Influenza is largely determined by the primary response to the virus that the donor was exposed to in childhood. In some individuals this can lead to focusing of the polyclonal antibody response to a single site on the influenza haemagglutinin. Monoclonal antibodies isolated from such focused responses selected escape mutations in vitro that matched actual antigenic drift observed in circulating viruses. Recapitulation of antigenic drift in vitro with human mAbs, in parallel with standard analysis with ferret anti-sera, may contribute to improved selection of vaccine strains by the WHO. A second consequence of preferential selection of B cell responses from memory cells laid down early in life, is the expansion of broadly cross-reactive clones during exposures to viruses that are only distantly related to the original stimulus. We have isolated many protective antibodies to conserved epitopes on both haemagglutinin and neuraminidase from individuals with appropriate exposure histories. One novel antibody binds to the conserved active site of neuraminidase. Antibodies of this type may have therapeutic potential to complement antibodies to the conserved stem of Haemagglutinin. In contrast to Influenza, the antibody response to the Ebola glycoprotein (GP) in vaccinated humans was essentially primary. The elicited antibodies were closer in sequence to germline than those to Influenza, and contained fewer somatic mutations. The response was more diverse, employing a wide selection of VH/L genes, and was directed at multiple epitopes in at least three distinct regions on the GP. Despite these features, half of the antibodies neutralised an Ebola surrogate virus in vitro, and many were therapeutic in a murine infection model. We developed a cocktail of antibodies to three non-overlapping sites for testing as a therapy in a stringent model of Ebola infection in the guinea pig. Taken together our results fit with a Darwinian model of selection of the fittest B cells in the germinal centre reaction, where memory cells have a selective advantage over naïve B cells.
Supervisor: Townsend, Alain Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available