Vaccitech Technology

TECHNOLOGY

How a ChAdOx based vaccine works

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1. ChAdOx and antigen design

Our ChAdOx vector platform is a modified version of an adenovirus isolated from a chimpanzee.

We insert precise genetic instructions for making one or more antigens, proteins specific to a  pathogen or cancer, into the ChAdOx vector.

ChAdOx vector particles are formulated into a vaccine or immunotherapy to deliver the genetic blueprints for the antigen into cells of the body, to induce a robust immune response against the targeted disease.

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2. ChAdOx expresses the antigens but cannot make copies of itself

ChAdOx’s natural biological ability to stimulate multiple immune pathways makes it an ideal delivery system for inducing targeted, long-lived immune responses.

  1. After injection of the vaccine or immunotherapy, ChAdOx binds to the surface of cells at the site of injection.​
  2. ChAdOx enters the cell and uses the cell’s own protein​ production machinery to generate many thousands of copies of​ the antigens.
  3. The antigens are processed by the cells into proteins and peptides, which induce immune responses involving B cells and T cells.
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3. CD4+ helper T cells and CD8+ cytotoxic T cells are activated upon recognition of antigenic peptides

T cells are a key component of effective immune responses against pathogens and cancer. CD8+ cytotoxic T cells are classically activated when presented with antigenic peptides associated with MHC class I molecules. CD4+ helper T cells activate when presented with antigenic peptides associated with MHC class II molecules.

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4. Activated CD8+ cytotoxic T cells control and eliminate diseased cells such as virally infected cells or tumor cells

When activated CD8+ cytotoxic T cells encounter diseased cells with their cognate MHC class I associated antigenic peptide displayed on the cell surface, the CD8+ cytotoxic T cells identify the diseased cells and release molecules to selectively eliminate them.

ChAdOx is one of only a few immunotherapy and vaccine​ technologies that induces high levels of CD8+ cytotoxic T cells​ in addition to CD4+ T cells.

Vaccitech’s heterologous prime-boost regimen involves​ two different vectors, ChAdOx and MVA, that encode the same antigens.​ 

A first immunisation with ChAdOx potently primes T cells against the target antigen. A second immunisation with MVA boosts and expands the T cell response against the target antigen. 

This approach reproducibly achieves immune responses that are differentiated by their high magnitude, high quality, and highly durable antigen-specific CD4+ helper and CD8+ cytotoxic T cell​s. These characteristics are ideal for T cell-based immunotherapies designed to treat infectious disease and cancer.