Principles bacterial immunotherapy

Bacterial immunotherapy, just like modern immunotherapies, aims to activate the immune system in order for it to target cancer cells.

Both therapies also aim to (re-)activate a response by the immune system that had, prior to the immune therapy, failed to adequately respond to the developing cancer.

As described previously, modern immunotherapies aim to achieve this by either stimulating an adaptive immune response against an assumed cancer specific molecule, by activating the immune system using cytokines, or blocking defined checkpoint inhibitors.

Bacterial immunotherapy treatment consists of administering bacterial cultures to an affected cancer patient with the goal of triggering an immune response against both the bacteria as well as cancer cells.  Bacterial immunotherapy activates the entire immune system. The working mechanism of for instance BCG treatment for bladder cancer is complex and involves both the innate and adaptive immune systems. Important constituents of the immune response to BCG include so-called CD4⁺ and CD8⁺ lymphocytes, natural killer cells, and granulocytes as well as TRAIL (tumour necrosis factor-related apoptosis-inducing ligand), IL-2, IL-8, IL-18, IL-12, interferon (IFN)-γ, and tumour necrosis factor (TNF).

Just as individual patients will respond differently to a given pathogen, the mechanism of action of bacterial immunotherapy is expected to vary depending on a patient’s own immune machinery and the characteristics of his/her tumour. 

The following Nature Cancer Immunotherapy animation provides an overview of immunotherapies (including bacterial immunotherapy and references to Coley's toxins and BCG).