September 17, 2011

September 17, 2011
HIV Research Leads to Cancer Treatments

Welcome to another day in my life Today is Saturday and I hope you had a safe and great week. Dab the AIDS Bear and I are still having a very long and stressful week of dealing with some situations.

But I did read a bit of good news recently about HIV research leading to cancer treatments. This is especially important seeing that long term survivors of HIV/AIDS are up to 300 percent more likely to have to deal with cancer sometimes during their life.

To make T-cells search out and destroy cancer, researchers must equip them to do several tasks: recognize the cancer, attack it, multiply, and live on inside the patient. A number of research groups have been trying to do this, but the T-cells they engineered could not accomplish all the tasks. As a result, the cells’ ability to fight tumors has generally been temporary.

The University of Pennsylvania team seems to have hit all the targets at once. Inside the patients, the T-cells modified by the researchers multiplied to 1,000 to 10,000 times the number infused, wiped out the cancer and then gradually diminished, leaving a population of memory cells that can quickly proliferate again if needed.

The researchers said they were not sure which parts of their strategy made it work — special cell-culturing techniques, the use of HIV-1 to carry new genes into the T-cells, or the particular pieces of DNA that they selected to reprogram the T-cells.

The concept of doctoring T-cells genetically was first developed in the 1980s by Dr. Zelig Eshhar at the Weizmann Institute of Science in Rehovot, Israel. It involves adding gene sequences from different sources to enable the T-cells to produce what researchers call chimeric antigen receptors, or CARs — protein complexes that transform the cells into serial killers.

Chronic lymphocytic leukemia is a cancer of B-cells, the part of the immune system that normally produces antibodies to fight infection. All B-cells, whether healthy or leukemic, have on their surfaces a protein called CD19. To treat patients with the disease, the researchers hoped to reprogram their T-cells to find CD19 and attack B-cells carrying it.

But which gene sequences should be used to reprogram the T-cells, from which sources? And how do you insert them?

Various research groups have used different methods. Viruses are often used as carriers (or vectors) to insert DNA into other cells because that kind of genetic sabotage is exactly what viruses normally specialize in doing. To modify their patients’ T-cells, the researchers tried a daring approach: they used a disabled form of HIV-1. They are the first ever to use HIV-1 as the vector in gene therapy for cancer patients (the virus has been used in other diseases).

The AIDS virus is a natural for this kind of treatment because it evolved to invade T-cells. The idea of putting any form of the AIDS virus into people sounds a bit frightening, he acknowledged, but the virus used by his team was “gutted” and was no longer harmful. Other researchers had altered and disabled the virus by adding DNA from humans, mice and cows, and from a virus that infects woodchucks and another that infects cows. Each bit was chosen for a particular trait, all pieced together into a vector Rube Goldberg-like solution and truly a zoo.

It incorporates the ability of HIV to infect cells but not to reproduce itself.

To administer the treatment, the researchers collected as many of the patients’ T-cells as they could by passing their blood through a machine that removed the cells and returned the other blood components back into the patients’ veins. The T-cells were exposed to the vector, which transformed them genetically, and then were frozen. Meanwhile, the patients were given chemotherapy to deplete any remaining T-cells, because the native T-cells might impede the growth of the altered ones. Finally, the T-cells were infused back into the patients.

The patient becomes a bioreactor as the T-cells proliferate, pouring out chemicals called cytokines that cause fever, chills, fatigue and other flulike symptoms.

The treatment wiped out all of the patients’ B-cells, both healthy ones and leukemic ones, and will continue to do for as long as the new T-cells persist in the body, which could be forever (and ideally should be, to keep the leukemia at bay). The lack of B-cells means that the patients may be left vulnerable to infection, and they will need periodic infusions of a substance called intravenous immune globulin to protect them.

One thing that is not clear is why Patient 1 and Patient 3 had complete remissions, and Patient 2 did not. The researchers said that when Patient 2 developed chills and fever, he was treated with steroids at another hospital, and the drugs may have halted the T-cells’ activity. But they cannot be sure. It may also be that his disease was too severe.

The researchers wrote an entire scientific article about Patient 3, which was published in The New England Journal of Medicine. Like the other patients, he also ran fevers and felt ill, but the reaction took longer to set in, and he also developed kidney and liver trouble — a sign of tumor lysis syndrome, a condition that occurs when large numbers of cancer cells die off and dump their contents, which can clog the kidneys. He was given drugs to prevent kidney damage. He had a complete remission.

I will continue this blog tomorrow.

Hope you have a great Saturday!

big bear hug,

Daddy Dab