Radioactive weapons against AIDS?

Scientists from the U.S. and Germany have successfully used radiotherapy to eliminate HIV-infected cells in mice without killing healthy cells. Of course, clinical trials on humans will be necessary to know if this technique is safe. And the researchers warn that their 'guided missiles' are not a cure for AIDS, but a complement to current drugs.
Written by Roland Piquepaille, Inactive

You all know that radiotherapy has been used for a long time as a treatment for several types of cancer. Why not applying it to people infected with HIV, the virus that causes AIDS? Scientists from the United States and Germany have done it and they've successfully used radioimmunotherapy to eliminate HIV-infected cells in mice without killing healthy cells. Of course, more animal trials will be necessary before starting clinical trials on humans to know if this technique is safe. And they warn that their 'guided missiles' are not a cure for AIDS. Even if this works with humans, this radioimmunotherapy will only supplement antiretroviral therapy. But read more...

Here is a short excerpt from this Albert Einstein College of Medicine news release.

The Einstein researchers used a technique called radioimmunotherapy, in which radioisotopes are piggy-backed onto antibodies. Once these precision-made molecules are injected into the body, the antibodies home in on a specific protein target... and the radioisotope "warhead" destroys the cell to which that protein is attached.

Below is a diagram showing how this potential new weapon against HIV would work (Credit: Dr. Ekaterina Dadachova, via PLoS Medicine, link a to larger version).

Radiolabeled antibodies used to fight HIV

In "Radioactive antibodies hunt out HIV-infected cells," Erika Check describes for Nature how the researchers built their experiments.

First, the team constructed its weapons: radioactive chemicals joined to antibodies that recognize particular proteins displayed only on the surface of an HIV-infected cell. In tissue-culture experiments, the antibodies killed most of the HIV-infected cells.
The researchers then tested the radioactive antibodies in mice that had been specially engineered so that they contain human immune cells that HIC infects. The mice were infected with HIV and then injected with radiolabelled antibodies. The team found that the antibodies eliminated up to 99% of the HIV-infected cells from the mice, although the dose needed for almost total elimination was higher than that likely to be used in humans.

In "Radioactive Antibody 'Missiles' Home In on HIV," Scientific American gives additional details about the experiments.

[The researchers] linked radioactive bismuth 213 and rhenium 188 to antibodies designed to stick to two HIV proteins (gp41 and gp120) displayed on the surface of infected cells. To see if the antibodies would home in on the offending cells, they injected the compound into mice that contained human blood cells infected with HIV. The compound appeared to work safely: the treated mice had less than half the quantity of infected cells that their untreated counterparts did, and the animals suffered collateral damage to healthy blood cells only at the highest antibody dose, the group reports.

Now, please keep in mind that radioimmunotherapy is not a cure for AIDS as I noted above. First, it's unknown if this approach works with humans. And it's also unknown what kinds of side effects could be caused by such radioactive antibodies.

Anyway, this research work has been published by the open access journal PLoS Medicine under the name "Targeted Killing of Virally Infected Cells by Radiolabeled Antibodies to Viral Proteins" (Volume 3, Issue 11, November 2006). Here is a link to the full text of this article. Below is the opinion of the editors of the journal about these findings.

These results provide preliminary support for the idea that radioimmunotherapy might be an approach for treatment of HIV. They argue that additional experiments in animals are warranted. If those continue to be promising, it will be critical to find out whether the radioactively labeled antibodies are safe in humans, and whether they are effective. The researchers who did this study feel that the strategy, if eventually shown to be safe and effective, would likely be of most value in preventing HIV infection very shortly after someone is exposed to the virus or treating HIV-infected patients not responsive to anti-retroviral therapy.

I hate to repeat myself, but this is not a miracle cure to kill HIV. It simply can become an additional tool to help people infected with this virus.

Sources: Albert Einstein College of Medicine news release, via EurekAlert!, November 6, 2006; and various websites

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