Understanding how viral innate immune evasion strategies affect adaptive immunity, and the application to vaccine development

Vaccines are one of the best means to prevent infection and the spread of disease. Although more than 60 vaccines exist, vaccines are still needed against infections such as HIV, malaria and dengue that comprise a huge burden on global health. Contributing to this problem is our incomplete understanding of the type of immune response that provides optimal protection and how this is best evoked by vaccination. In this study vaccinia virus (VACV), the vaccine used to eradicate smallpox, will be used as a model to improve current understanding of the immune response to vaccination and this information will be used to design more potent vaccines.

There are two arms that make up our immune system. The first is the 'innate' immune system, which is quick to respond to infection but is not pathogen specific. Innate immunity helps to control the infection whilst the 'adaptive' immune response develops. Adaptive immunity is specific to the invading pathogen and is required for complete pathogen clearance. Importantly, the adaptive immune response endures as a long-lived memory immunity that protects from subsequent infection. It is the development of this long-lived, pathogen-specific memory immunity that provides the basis for vaccination.

The importance of the innate immune response in successful vaccination is becoming clear, although exactly how it contributes to memory immunity is not well understood. Cells in the body are able to detect the presence of invading microorganisms and respond by producing molecules such as cytokines and interferons - so named as they 'interfere' with viral infection. As well as limiting virus replication, these specialised proteins attract white blood cells (leukocytes) to the site of infection so that they can kill pathogen-infected cells and stimulate the activation of leukocytes that control the adaptive immune response. Viruses have counter-measures that limit the production and action of these anti-pathogenic and immune-activating molecules and VACV has numerous mechanisms to achieve this. Work in our laboratory has demonstrated that engineering VACV to remove the genes whose protein products act to limit the innate immune response, such as cytokines and interferons, can improve the potency of VACV as a vaccine. These data are valuable because they highlight the importance of innate immunity in shaping and influencing the memory immune response.

The question we aim to answer is how does the removal of these innate immune inhibitory genes from VACV positively impact on memory immunity? By answering this question we will not only be able to improve the vaccine potential of VACV, but also enhance current understanding of how the innate immune system shapes memory immune responses, information that can be used to design better vaccines in general. VACV is a good model to answer this question as it is a well-studied virus where numerous tools are already available, it has already been used as a successful vaccine for the eradication of smallpox and there is a robust mouse model of VACV infection and vaccination. Furthermore VACV is a popular candidate as a vector for the vaccination against other diseases, such as HIV and malaria, thus the data generated by this proposed study can be directly used to improve the vaccine potential of this virus.

Although many successful vaccines exist, effective vaccines against important diseases such as HIV, malaria and dengue are still lacking. Vaccine development requires a better understanding of how to elicit strong memory responses. The contribution of innate immunity to memory immunity is currently not well understood, but work in our laboratory has demonstrated that mutants of vaccinia virus (VACV) that lack innate immune inhibitory genes are more immunogenic and efficacious vaccines. These data highlight the importance of innate immunity in shaping immune memory and can be used not only to design more effective vaccines based on VACV vectors, but also to enhance current understanding of how stimulating innate immunity positively impacts on vaccine design in general.

We have demonstrated already that removal of specific immunomodulators can improve either the CD8+ T-cell or the NK-cell memory responses to immunisation. The question we will address in this study is how does the removal of these innate immune inhibitors from VACV improve memory immunity? Our hypothesis is that in the absence of innate immunomodulators the cytokine, and hence cellular, environment following vaccination is altered in a way that positively impacts on development of memory immune responses. We will characterise the immune response in detail shortly after VACV vaccination. First, we will measure which cells are infected and what cytokines are produced. Then we will determine which cells are recruited to the site of vaccination, what is their activation state and how they present antigen to activate T and B-cells. By comparing these parameters following infection with wild-type versus mutant VACVs lacking inhibitors of innate immunity we will correlate differences with enhanced immunological protection. Finally, we will use this information to improve vaccine design.

This is fundamentally a basic science project that will advance the understanding of the immune response to virus infection but can contribute more broadly to improvements in human health by assisting our ability to improve the design of future vaccines. This study will further the academic discipline through contributing to the training of researchers skilled in a wide range of techniques. The research assistant and postdoc will acquire new expertise in molecular biological, immunological and virological research that would be widely applicable in the UK biotech industry as well as contributing to training and teaching other laboratory members, such as PhD students. The PhD students in the lab over the course of the grant will also acquire both specialised and transferable skills. These lab members will improve other transferable skills via presentations and networking opportunities at conferences and writing papers and reports during the course of the grant.

Our findings will be disseminated in open access peer-reviewed journals, presentations at suitable scientific conferences, such as the Cambridge Immunology Forum, the Gordon conference on animal cells and viruses as well as other meetings that are relevant to the results of the research project. Additionally, we will advertise on-line the key facts from our research on our website that will link to any publications and will notify of MRC support. Such information will be provided in lay terms as well as more technically in such that it is suitable for all interested parties.

As a method to improve public engagement BF is a Science/Technology/Engineering and Maths (STEM) Ambassador allowing opportunities to interact with and to present this work to young people. The research assistant and postdoc will be encouraged to engage in such activities and coached by the applicant where necessary.