Radioimmunotherapy is a technique used in treating cancer , in which antibodies which have radioactive isotopes attached to them are injected into patients. These antibodies target and destroy cancer cells inside the body , by delivering the radioactive particles . The main advatage of this treatment is that it is very specific , unlike chemotherapy.
A study in mice showed that this approach could be used to treat HIV infection someday. Ekaterina Dadachova at the Albert Einstein College of Medicine in New York, US, and colleagues used specific antibodies which seek out HIV-infected cells. They did the work on mice without a functioning immune system., since normal mice cannot be infected by HIV .
The spleens of some of these rodents were injected with HIV infected cells , while others were grafted with human or liver tissue which were infected. The lack of immune systems ensured that the grafts were not rejected.
The researchers bound radioactive particles such as bismuth 213 and rhenium 188 , to the antibodies and injected them into some of the mice. These antibodies target a molecule known as GP41, specific to the HIV virus carrying cells, and deliver the radiation slowly.
Alpha or gamma particles are emitted , and either the cell membrane is ruptured or the essential DNA is damaged during this procedure. It was found that the number of HIV infected cells fell in the treated mice compared to the other mice , which had been given antibodies without a radioactive tag.
It was also seen that the higher the dose of antibodies , the greater the number of infected cells fell by . However assessment showed that the red blood cell count dropped with very high doses , making it evident that there has to be an optimum dose at which the antibodies are both selective and effective .
Some test-tube experiments on HIV infected human white blood cells were also done during the study, which showed that the technique successfully killed the cells.
It may take a while for these findings to be tranlated to humans . Other factors also have to be considered such as the fact that the GP41 molecule shows up only late in the infection cycle , so the radiation may not be as effective . Also the side effects such as blood counts dropping dangerously , have to be taken into account.
Dadachova however is optimistic because radio therapy could prove to be even more useful in HIV treatment than in cancer where the targetted molecule is not always confined to cancer cells , whereas GP41 is specific to the surface of HIV infected cells.