Radiation is one of the most effective means of killing microbes, but it has been used clinically to treat only cancer. That may be about to change. For the first time, researchers have turned radiation therapy against infection.
With antibiotic resistance on the rise among bacteria, medical researchers are looking beyond traditional drug therapies. One possible source of new weapons is radioimmunotherapy (RIT), a technique used to treat cancer patients. RIT works like radiation treatment, but instead of blasting tumors with radiation from the outside, individual radioactive atoms are injected into the blood and circulated throughout the body. The trick is to attach the radiation-emitting atoms to antibody proteins designed to latch onto the surface of the tumor cell. This ensures that tumor cells become coated with the RIT molecules while normal cells are spared from the DNA-blasting radiation.
To see if RIT could be useful against an invading pathogen, Kate Dadachova, a biologist at the Albert Einstein College of Medicine in New York City, and colleagues designed antibodies to bind to the surface of Cryptococcus neoformans, a tenacious fungus that plagues AIDS patients. In a paper published online this week in the Proceedings of the National Academy of Sciences, the team shows RIT's mettle as a fungus fighter. When infected mice were injected with the antibody alone, they died just as quickly as untreated mice. But when radioactive bismuth-213 or rhenium-188 atoms were hitched onto the antibodies, the infections began to clear up and mouse survival increased up to 60% by the end of the trials. And the best news is that RIT doesn't seem to kill bone marrow, a side effect that has limited the use of RIT in cancer therapy. Given this initial success in mice, Dadachova believes that any kind of infection can potentially be treated with RIT.
"The data clearly indicate that RIT can be effectively used to treat fungal infections," says Gregory Adams, an oncologist at the Fox Chase Cancer Center in Philadelphia. Adams cautions, however, that there could be difficulty scaling the technique up from mice to humans, and there could be long-term tissue damage from the radiation.