Therapeutic vaccines and antigens

Therapeutic vaccines

Therapeutic vaccines

Therapeutic vaccines
 
Influenza A virus (Amplif. X 117000) , responsible for flu. Novel antigenic variants which escape previous acquired immunity arise every year. © Institut Pasteur
Most common vaccines are administrated to healthy people to protect them against infection. These so called prophylactic vaccines carry substantial amount of antigen (= active ingredient of the vaccine) and provoke a strong antibody response against the pathogen (that carries such an antigen on its surface). This results in the protection of the vaccinated individual against infection.

Over recent decades, a great scientific and clinical effort has been was devoted to developing a second type of vaccine - therapeutic vaccines.
Therapeutic vaccines, as their name suggests, are designed to boost the immune response to fight existing diseases as cancers, viral and bacterial infections.

Human dendritic cell infected with HIV virus (= small particles in endocytotic vesicles). The virus, once present in the cell, avoids antibody inactivation and subsequently cripples other immune responses. © Institut Pasteur

To-date there are only a small number of therapeutic vaccines which have been commercialized. This is because many pathogens are able to evade individuals’ immune defense by interfering with antibody mediated inactivation processes. They can do this by: 

    • Regularly changing antigen (recognition),
    • Escaping antibodies by entering into host cells or
    • Blocking of crucial steps in the signalling between and within host cells. Such signalling is essential for the host to launch an effective defence.

However it is now possible to design therapeutic vaccines to induce the desired immune response. This is possible today thanks to the convergence of vaccine research, immunology and genomics: biomarkers or antigen-recognition that the pathogen has not yet learned to evade can be redesigned and targeted to the appropriate immune cells that will launch either a specific antibody, a specific cytotoxic reaction or repress undesirable inflammatory responses.

Good designer vaccines may also activate so-called T helper cells, have non-specific immuno-stimulatory activity or in other ways interfere with the pathogen’s attempt to block the “danger” and identification signals.

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