Novel adenovirus vaccine vectors

Thesis

Replication defective adenoviruses have emerged as promising vectors for delivery of vaccine antigens. The development of new vaccine vectors has recently focused on serotypes to which the human population is less exposed in order to circumvent pre-existing anti vector immunity. This thesis describes the construction and optimisation of ChAdOX1, a new vector based on chimpanzee adenovirus Y25, which has recently been manufactured to clinical grade for a Phase I human trial.

Comparative immunogenicity studies between vectors of different serotype were performed in mice, with careful consideration of the infectious titer of vector preparations, since this parameter can confound studies based solely on viral particle estimation. After intramuscular administration, HAdV-5 (Human adenovirus C) based vectors elicited superior transgene product specific T cell and antibody responses compared to a selection of chimpanzee adenovirus vectors (from Human adenovirus E) including ChAdOX1.

The construction of ChAdOX1 in a bacterial artificial chromosome (BAC), enabled precise and flexible modification of the genome by recombination mediated genetic engineering (recombineering). Reverse genetics was performed to identify vector determinants of immunogenicity. Chimeric ChAdOX1 vectors were created by replacement of native virus associated RNA (VA-RNA) and fiber sequences with the corresponding sequences from HAdV-5. Using these chimeric vectors, the importance of innate immunity and vector transduction in determining vector immunogenicity was investigated. Though the mechanisms responsible ultimately remain unclear, superior transgene product specific immune responses with HAdV-5 correlated with higher levels of transgene expression in vivo after vector administration. The current study has conclusively demonstrated that neither VA-RNA sequences, nor the fiber protein, are responsible for differences in immunogenicity between vectors, contrary to hypotheses based on previous studies.

Authors: Dicks, M

• Publication date: 2013
• DOI: 10.5287/ora-xoxbyyp6v
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: adenovirus; vaccines; Viral vectors
• Subjects: Biology (medical sciences); Vaccinology; Viruses