This week’s science news is a relatively old story with a new twist: in the journal Blood, scientists in Germany report a possible “cure” for infection with the human immunodeficiency virus (HIV), the virus which causes the disease acquired immunodeficiency syndrome (AIDS).
An American living in Germany became ill with the rare and unfortunate combination of AIDS and leukemia. Doctors carried out a standard, but radical and dangerous, therapy to treat the leukemia: they destroyed his native immune system and replaced it with a new one transplanted from another patient’s stem cells. As a result, it seems as though the HIV infection has been completely eliminated from the patient’s body.
Now that you’ve survived the jump, here’s some backstory.
The immune system is extraordinarily complex, but to simplify, there are two main kinds of cells that mount an immune defense.
The B cells are called “B” because they mature in the chicken’s bursa of Fabricius. Luckily, in humans, the equivalent of the bursa also starts with the letter B—bone marrow. These cells are born in the bone marrow and stay in the bone marrow to mature. They release a special kind of protein called an antibody that binds to invaders. Like Boys, they spit out these antibodies without regard to what happens to them; they just release their antibodies into the bloodstream on command.
The T cells (called this because they mature in the human thymus) are also born in the bone marrow, travel to the thymus to mature, and then travel the body to fight infection using cooperative methods. The T cells collaborate with each other by plotting, planning and scheming to destroy invaders.
This film shows a light-hearted treatment of how T cells are like the girls in the movie Mean Girls. (If you’re interested in the subject, there is a longer version with more information.)
There are several main types of T cells:
- T helper (more about these below)
- T suppressor (also called T regulator, “peacemaker” T cells), “Amanda Seyfried cells”
- T cytotoxic (i.e. “cell killing” T cells), “Lacey Chabert cells”
- T natural killer cells (Played by Lizzy Caplan. I call these “ninja” cells, because they talk invaders into dying.)
T helper cells direct the immune attack, and are the queen bees or quarterbacks of the immune system. They carry a surface protein called CD4, so these are also called “CD4+ cells”. These are the cells that are infected and destroyed by HIV, which renders the immune system leaderless and rudderless.
Leukemias are cancers of the immune system which cause uncontrolled division in one or more of these immune cells. The standard treatment is to kill off the entire immune system, then find someone else’s immune system to start over again. The problem is that the transplanted immune system wants to go out and attack everything in the recipient’s body, because it’s all foreign. This is called “graft vs host disease” and this, plus the other possible complications (e.g. the new immune system doesn’t “take root”, or an infection kills the patient while their immune system is incapacitated) means that only about half of the patients who undergo this treatment survive.
In the present case, the doctor who found a compatible immune stem cell donor found a donor whose cells were naturally resistant to HIV. So, the former AIDS patient not only got a new immune system, but his new immune system repelled any remaining HIV in his bloodstream and tissues.
Current estimates are that 33 million people worldwide and well over a million US citizens are infected by HIV. The problem is finding a compatible donor match and getting over the expense (in dollars and health) of such a treatment. Just for starters, there’s the extended hospitalization under absolutely sterile conditions; the lost time and health of the bone marrow donor; the cost of the “biologics“, drugs made from living organisms which are more expensive than synthetic drugs. For example, treatment for childhood respiratory syncytial virus (RSV) with the biologic palivizumab costs $5,000 per infant treated. Understandably, many have questioned the cost-benefit ratio, but if it were my infant, I’d pay for the treatment. The biggest problem with health care is that its pricing is what economists call inelastic.
Let’s say this treatment is improved to the point where it represents a “cure” for AIDS. An estimate of $1 million treatment cost per patient is not out of line. How are we going to calculate the cost-benefit ratio of such a treatment? In other words, how do we ration health care?
Each medical advance we make forces us closer to a point where we have to make this calculation. You can call them “death panels”, but someone has to make this decision. Right now, we ration health care based on who can afford to pay the bill, or who can manage to stiff their insurance company with a bill. Is that the fairest, or the best, system to ration health care?
Because of total inelasticity, the question is not whether to ration health care or not. The question is how that rationing is to be done.
- Report: Scientists finally cure HIV with stem cells? (hotair.com)
- Cure for HIV Claimed But Not Proven (livescience.com)
- Possible HIV infection cure reported (cnn.com)