[thedoc (OP)]

Frank Buckley asked the Naked Scientists:

Most viruses are cured in the body and we recover fully.

Unfortunately there are some viruses that once we are infected remain in the body for ever. Could you please explain the difference.

What areas are being explored in order to cure these viruses and what progress has been made?

I understand that after a bone-marrow transport certain individuals have been found to be free of a virus. Why should this be and does it open any avenues for treatment?

What do you think?

[Villi]

Many viruses have a dormant phase. During this phase they have usually incorporated themselves into the infected person's genome. Even if there are no virus particles in the person's body, the person is still infected because the DNA blueprints of the virus still exist. Some time later, a trigger such as stress or temperature change can reactivate the virus to produce more of itself. You remain infected forever because the virus is in your genome, it has become a part of you. The immune system does not have effective methods to fix your own genome.

A great example of recent developments in curing viral infections is in HIV/AIDs. Using the CRISPR system, scientists were able to cut out the HIV DNA from a person's genome, thus curing them. However, this is still experimental with many difficulties.

A reason why a bone-marrow transplant may work for some viral infections is that you are removing all infected cells and replacing them with cells that have been modified to recognize and attack the virus. Bone-marrow is an important source of immune system cells. If you can modify these stem cells and give them genes that code for specialized antibodies for example, you can give the person who receives these cells the ability to fight many infections.