Can HIV be used as therapy for cancer?

Diagram of the HIV virus.

Diagram of the HIV virus. (Photo credit: Wikipedia)

Every so often, a report comes out in the news that grabs our attention.  Here is one of them.  The virus responsible for AIDS, a deadly disease with no real cure, has been successfully used to treat a few people with certain types of cancer.  Now wait a minute, you mean we are giving someone HIV?  Are we replacing one fatal disease (viral) for another fatal disease (cancer)?  No and no. Let me explain.

Human viruses that cause disease have successfully evolved to infect and survive in human tissues and cells.  HIV has evolved so well that it infects humans cells and avoids immune elimination and of course eventually causes death.  Other viruses are also very effective at infecting human cells and surviving to the extent that they replicate (or divide) very well in the body.  Viruses, although extremely simple in their makeup, have also evolved clever ways to manipulate the human cell’s own machinery for itself.  One of the things that the HIV viruses does very well is to integrate it’s genetic material into the human cells.  So, why not modify the virus so that it no longer kills you (we call this removing the virulent properties) but still has all the infective, survival and genetic integration properties. This is exactly what is being done.

For many years, a virus known as adenovirus has been modified to remove it’s harmful properties and keep it’s infective and replication processes.  This has been done rather successfully, but using these ‘modified viruses’ has proven rather difficult…do to a host of reasons.  What is new now is that the HIV virus was used as a viral vector in this case.  Thus, the properties that allow HIV to kill humans were removed, but the properties that allow HIV to infect human cells and integrate their genetic elements were kept.  It is perhaps not surprising that after nearly 15 years of HIV research and trillions of dollars being spent, we have now reached a stage where we know enough about the virus to start modifying it for use as therapy.

OK, so how is it being used.  Let’s first look at the cancer in question.  Leukemia is a cancer of the blood…often it is a cancer of the B cells specifically.  These B cells, instead of protecting you from pathogens by making B cells and then dying like normal cells, become transformed and keep dividing uncontrollably.  Mutations in the genome of the B cells result in a cancer of these cells that grows to such a large extent that they start preventing the normal function of the blood and the immune system.  These cancerous B cells start to overtake the body.  Getting rid of them permanently is difficult as bone marrow transplants are the best way to permanently remove them.  However, this can only be done with individuals who are healthy, and who have their cancer in remission (one must have a good heart, have a functioning normal immune system, etc.). BM transplants are still high risk and have many side effects and are very expensive, but can be life saving.  Not everyone can qualify for this procedure.  Chemotherapy often fails but is used to try and control the disease, but often as a temporary measure for many leukemias.  So, other therapies are often needed.

Using a modified and non lethal form of the HIV virus that infects T cell, scientists mixed a these cells.  However, the HIV itself was engineered to express a modified protein that allows the T cells to recognize the B cell, and then to kill it.  So, a mix of this genetically engineered HIV was allowed to infect the patients own T cells and those T cells are now able to recognize and destroy the B cells in the patient.  Confusing…yes, but don’t worry too much about the details.  In general HIV plus the patients own T cells were used to allow the T cells to kill the cancer cells.

Sounds sexy sure.  However a few things to recognize before getting too ahead of ourselves.  1) All B cells are killed not only the cancerous B cells and thus treatment makes you VERY sick as your immune system is shot for quite some time after the procedure (but this is only temporary as your immune system will recover but the cancer wont).  2) This may not work on everyone and only a small amount of people have been tested.  3) This is an example of personalized medicine and is very costly.  4) It may be years, if ever, before the FDA recognizes and approves of this type of therapy.  5) No one knows the potential dangers if any with using HIV as an infection tool.

So, interesting…let’s hope they can expand their trial and show long term studies that ‘prove’ that this works.  But for now, its a small step in the right direction!!!

 

Thank you

Dr C

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