The Science


The immune system broadly has two functions: recognition & defence

Throughout life the body is exposed to viruses, bacteria, other pathogens as well as mutated cells (pre-cancerous or cancer cells). When we are exposed to foreign “organisms”, small parts of that material (antigens) are presented on the surface of special (antigen-presenting) cells. These cells will then react with immune cells that are subsequently primed to recognise and destroy cells presenting that antigen. These cells are then stored as effector (ready to act) or memory cells (reactivated on exposure).

Before viruses infect cells, they are susceptible to antibody-mediated clearance by the immune system. Traditional vaccines teach the immune system to mount an antibody response to an infectious agent before it leads to disease (such as for prophylactic and therapeutic efficacy against COVID-19, MERS and Zoster). However, once viruses enter cells, they are poorly accessible to antibodies and can be eliminated by destruction of the infected cells in which they replicate. It is the role of the cellular side of the immune system, importantly effector CD8+ T cells, to eliminate infected cells without harming healthy tissue by being highly specific. Diseases associated with persistent or chronic viral infection (Hepatitis B, Human Papillomavirus) and mutated proteins, such as cancer, therefore require treatments that create powerful and durable T cell-mediated immune responses. CD8+ T cell responses are notoriously difficult to induce in patients with common technologies. Extensive, applied research and development at the Jenner Institute has led to the design of Vaccitech’s viral vector platform – uncommon in its ability to induce not only antibodies, but also induce and maintain superior levels of disease-specific CD8+ T cells in humans.

The Vaccitech platform involves delivering either one viral vector, ChAdOx, or two heterologous viral vectors, ChAdOx + MVA, each encoding the same antigen, several weeks to months apart for the most effective T cell and antibody induction

Our immunotherapies stimulate strong, durable, and polyfunctional CD8+ and CD4+ T cell responses in humans that are leading with respect to CD8+ T cell magnitude. The responses are characterized by T cells with functional properties naturally associated with viral clearance and tumour protection that will persist for years in the immune system after induction. The treatments are also able to induce potent and durable antibody responses from the humoral arm of the immune system. The ‘prime’ component uses a non-replicating chimpanzee adenoviral vector encoding a particular pathogen antigen (the part of the invader the immune system will come to recognise) or cancer antigen (the part of a cancer cell that differs from a normal cell). The same antigen is then produced and recognised from another non-replicating viral vector Modified vaccinia Ankara (MVA) which serves to ‘boost’ an immune response to protect against or treat the target disease with exquisite specificity.