By Kirsten Sandgren
From PHN Issue 36, Spring 2018
The human body has a truly amazing set of defenses against infection. Considering how much our bodies are exposed to in the course of our day-to-day lives, it’s a pretty rare occurrence for us to get sick. Even when we do become ill, the immune system is able to recognize the invader, signal to the many different cells that are responsible for keeping us healthy, and almost always come out victorious. Despite this, Human Immunodeficiency Virus (HIV) is able to cause lifelong infection. HIV affects over one million Americans and more than 37 million people around the world.There is no cure for HIV/AIDS currently, but there is promising research being done to improve treatment and hopefully find a cure in the future.
Why is a cure for HIV/AIDS so difficult to find?
HIV is a tiny particle, which allows it to live inside of our immune cells. That makes it difficult for the immune system to detect that the virus is present. HIV specifically infects helper T-cells, which play an important role in mobilizing an immune response to disease-causing agents. Without properly functioning T-cells, the body’s response to infections becomes much less powerful than it should be. This causes people living with HIV who are not on successful treatment to become vulnerable to many more illnesses than people without HIV or those with HIV whose treatment has kept the virus undetectable.
HIV can live in a person’s body for years without making them particularly sick. This is because the virus has a mechanism that allows it to insert the blueprint to make more viruses directly into the DNA blueprint of our cells. Cells that have this hidden copy of HIV virus DNA embedded in them can work normally for years, so they are called latent reservoirs. Since these cells are not actively producing viruses particles, they’re nearly impossible to find and destroy. There is only one case in history where these latent reservoirs have been successfully destroyed, the case of Timothy Brown. Brown received bone marrow transplants to treat a very aggressive cancer. The donor who gave bone marrow for Brown happened to have a mutation that prevents HIV from taking control of T-cells. Since the transplant, Brown has had no detectable viral load. Scientists do not believe that the results of Brown’s transplant can be replicated.
Another reason a cure is so hard to find is that HIV is constantly changing. These changes, or mutations, happen randomly as the virus is being copied. This means that researchers — and doctors treating HIV — are trying to hit a moving target.
What are researchers working on now?
Medical technology is advancing quickly, and HIV researchers have new tools every day that may help them find a cure. A cure is not impossible, but it is not here yet. We are taking several pathways that can get us there. Researchers are currently investigating these approaches:
- Gene therapy is an exciting technology that attempts to enhance the immune system and has been successful in the treatment of some cancers. Some research aims to use gene therapy to directly cut out the copies of viral DNA in latent reservoirs. Other researchers are trying to make a change to the T-cells that prevent HIV from entering them, like locking a door. Even if you already have HIV, having enough T-cells that are locked against HIV infection could have the effect of eventually ending the infection. This is what scientists believe happened with Timothy Brown.
- Researchers are developing drugs that could trick the virus into revealing hidden reservoirs. The idea is to find the latent cells of HIV that are not active but are hidden, usually in the lymph nodes or the liver, brain or lungs. The HIV medications we have now can’t reach those places to kill the virus completely. But if a new drug is developed that can “wake up” the hidden HIV, then other drugs can destroy all the HIV in a person’s body and cure it.
- Immunotherapies attempt to train the immune system to operate more effectively. Immunotherapies have made a lot of progress in treating cancer, and researchers are using the lessons they’ve learned to combat HIV. The idea is that scientists would genetically change a patient’s T-cells to recognize the HIV virus or cells infected with the virus that the immune system cannot “see” on its own. Once the immune system can recognize infected cells, the body’s natural defenses may be able to overcome the infection.
When will a cure be available?
Unfortunately, there is no clear answer as to when a cure for HIV will be available. Many of the approaches described above are in very early stages, which means that researchers are using animal models to assess the safety of the treatments. There are some human trials in progress, and it is possible that the cure will be a combination of the strategies outlined. In the meantime, HIV treatment is getting more effective, with fewer side effects. It is important for people living with HIV to be as consistent as possible with the treatment prescribed by their doctor.