Enhancing immune stimulation for novel anti-cancer viral vaccine vectors
Application deadline: 23 November 2018
Start date: October 2019
Research theme: Infection, immunity and repair
Human cytomegalovirus (HCMV) is an exciting vaccine vector. This comes from the demonstration that it can protect against both HIV and TB in macaque models, the only vaccine vector to ever achieve this impressive feat. Its efficacy arises from its ability to induce unique T-cell responses; it induces the highest number of T-cells of any vector, and these T-cells are polyfunctional effector memory T-cells. Thus, they can actively migrate to infected tissues and control infection. Such properties are highly desirable in cancer vaccines, and we are developing HCMV vectors to induce anti-tumour T-cells.
Although the ability of HCMV vectors to induce these responses is impressive, the virus is a pathogen, and ‘safe’ versions do not exist. Furthermore, how such effective T-cell responses are induced is unclear. If the mechanisms underlying the induction of these T-cells can be determined, the ability could be replicated in other vaccine vectors (e.g. recombinant adenovirus) that have proven safety records. A potential explanation for the unique T-cell induction by HCMV is that in vivo, HCMV infects and modulates the key antigen-presenting cells (APCs) that are responsible for controlling T-cell responses - dendritic cells (DCs). Yet these cells cannot be infected in vitro, preventing characterisation of T-cell induction by HCMV infected APCs.
We have made three key breakthroughs that permit us to interrogate this process:
- We developed virological systems that enable us to infect DCs in vitro and perform functional experiments to characterise the ways in which infection manipulates DC function.
- We developed multiplexed proteomics combined with RNAseq, enabling us to determine how the entire proteome of the DC (up to 8,000 proteins at a time), is affected by infection.
- We have created a bank of HCMV mutants which each lack a contiguous block of 5-8 genes.
Between these viruses, nearly all non-essential genes are knocked out. Crucially, immune-modulators are generally found in these knocked-out regions. This bank of ‘knock-out’ viruses is complemented by a bank of 180 RAds expressing each HCMV gene individually, enabling rapid screening for both loss of function (HCMV mutants) and gain of function (RAds). We have previously used these techniques to determine how HCMV affects NK cell function during infection of fibroblasts.
Project aims and methods
We will now use them to uncover how HCMV manipulates DCs to affect T-cell induction. We will infect DCs with our knock-out viruses, perform functional assessment of the ability of each virus to induce a T-cell response, before using proteomics/RNAseq to determine how each virus manipulates the infected cell.
When combined, this information will identify how particular HCMV genes manipulate individual DC proteins in order to induce T-cell responses that are so much more potent than alternative vectors. This understanding can then be used to replicate the potency of HCMV vectors in other widely used vectors.
Dr David Matthews, University of Bristol.