Good-deed viruses stop mouse diabetes.

good-deed viruses stop mouse diabetes

Apparently not all viral infections are bad news. A California researcher reported last week that injecting a specific virus into mice predisposed to diabetes seems to prevent the disease. Using nonobese diabetic mice and the lymphocytic choriomeningitis virus (LCMV), Michael B.A. Oldstone of the Research Institute of Scripps Clinic in La Jolla found that the virus interacts with certain immune cells to stop the destruction of insulin-producing cells in the mice.

Because of autoimmune reactions against their own pancreatic cells, nonobese diabetic mice develop life-threatening diabetes, usually by the age of 6 months. Prompted by his earlier findings that viruses may alter the autoimmune response, Oldstone injected mice with LCMV, which can infect a range of animals that includes humans. Of the mice injected when newborn, none developed diabetes within 9 months. Of those injected at age 6 weeks, only 6 percent became diabetic within the same period of time, compared with 95 percent of the untreated mice. About 20 mice were in each of the three treatment groups.

Oldstone writes in the Jan. 29 SCIENCE that probably only a small subset of cells is involved in this type of diabetes and that the animal's immune system is still generally intact. He says evidence suggests that the helper T lymphocytes are the culprits, and that they are incapacitated by LCMV through an undetermined mechanism. "We presume the virus gets into a small subset of these helper cells...and the virus alters their function or kils them," Oldstone said in an interview.

Although the virus causes chronic infection in mice, its injurious effects on the animals are "subtle and minimal," says Oldstone. Emphasizing that he does not advocate injecting whole viruses as potential therapy, Oldstone says he is searching for a component of the virus that can give the same protection, with possible applications as a treatment for human diabetics.

Aldo A. Rossini, from the University of Massachusetts Medical Center in Worcester, told SCIENCE NEWS that the new results are "an exciting observation. But one has to be very cautious ... there are a lot more studies that have to be done." Nevertheless, Rossini says the new research direction taken by the La Jolla study could have significant implications for diabetes. "For a long time, it's been suggested that a virus plays a role in the pathogenesis of diabetes," he says. "Now, all of a sudden, we're saying a virus is important in protection from diabetes, that there are good viruses and bad viruses."