Monday, February 27, 2012

DNA injection 'weaponizes' the immune system

Scientists have found a way to make the immune system more effective against malicious cells that need to be cleared away from the body. A group of killer cells that function by helping us to combat cancer or to fight off an HIV infection can be increased in numbers with DNA injections. With this mechanism, we may be able to treat patients with cancer of HIV by enabling them to make better use of their own defence systems.

T cells
When a cell is infected by a virus or bacterium, the body needs to get rid of it. The same goes for cancer cells. For this, the immune system stocks a specialized cell type called the T lymphocyte. To be specific: a CD8+ T lymphocyte, named like that because it has the CD8 protein on its cellular surface, which other T cells don't have. It is tasked with killing badly performing cells, but those of a cancerous origin have proven to be harder, because they develop ways to evade the immune system: one of their tricks is to repress the number of T cells. Additionally, HIV attacks the immune system head on by infecting an other form of T cell, which impairs the ability to fight off the infection.

To make the T killer cells more effective in cases of cancer and HIV, scientists from Loyola University in Chicago found a way to boost them. They administered DNA to immune cells that function by 'training' T cells: normally the body finds out that something is wrong by so-called antigen-presenting cells, which basically activate the killers to let them to their job. The researchers inserted specific DNA in the helpers, which in turn made proteins that enables the immune response by making the T cells perform their job.
Interaction between T cells and antigen-presenting cells: a complex set of interactions required for activation.
Gene gun
In order to get the antigen-presenting cells to produce the right proteins, scientists needed to find a way to get the required genes, that function as a blueprint, inside the cells. To achieve this, they used a gene gun, a machine developed to get pieces of DNA in a cell. It functions by coating a heavy metal with genetic code, which can then be 'shot' at a cell culture. In turn, the pieces of DNA are supposed to be incorporated in the genome, and read by specialized cellular machinery which turns code into proteins.

After cellular transformation by the gene gun, the T cells proved to be sufficiently activated by the modified antigen-presenting cells. They didn't need any other signals in order to do their job, and they significantly increased in numbers. It shows the activation method is suitable for diseases in which T cells do not become activated.

The study reveals a novel method to deal with an insufficient immune system. Such is the case in cancer and diseases that affect the immune system. It seems that the method developed in Chicago is of higher interest than drug-based medicine, because it makes use of the body's own weapons. Clinical trials are said to be planned, but it will take about 3 years before they can start.

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