April 26, 2005 -- An antibiotic is getting attention for its possible protective effects against brain disease linked to HIV, the virus that causes AIDS.
In a study in The Journal of the American Medical Association, researchers report that the antibiotic minocycline helped curb brain inflammation and protect brain tissue in monkeys with an HIV-like infection.
So far, minocycline has not been tested against HIV-related brain disease in people. The researchers do not make recommendations for people with HIV.
Instead, they say their findings "provide evidence for designing human studies" to examine minocycline further, suggesting that it might be useful in addition to the drugs prescribed to manage HIV.
The researchers believe this is the first report demonstrating anti-inflammatory and nerve-protecting activity of an antibiotic against a highly pathogenic virus.
Given that the prevalence of HIV-related central nervous system disease (that of the brain and spinal cord) has not declined, this finding may have important implications for future studies on the prevention and treatment of HIV, they say.
HIV can trigger disease in many parts of the body, including the brain and spinal cord. Diseases such as encephalitis -- inflammation of the brain -- are usually seen in the later stages of HIV infection.
Minocycline is inexpensive, widely available, considered safe, and has been around for years, say M. Christine Zink, DVM, PhD, and colleagues in the April 27 issue of The Journal of the American Medical Association.
The anti-inflammatory and nerve-protective effects of minocycline have also been studied in other conditions, such as Parkinson's disease, Huntington's disease, and multiple sclerosis. Those studies, reported in 2000 and 2001, were conducted in rats and mice, not people.
Zink tells WebMD that she's particularly excited about the antibiotic's potential to suppress HIV replication and "many other organisms that are a significant problem in the developing world. People in the U.S. need to remember that there are 39 million people infected with HIV who don't have the same access to highly active antiretroviral drugs" and that the antibiotic should be investigated further.
Zink's study focused on monkeys. Five monkeys with an HIV-like infection were given two tablets of minocycline per day. The dose was 4 milligrams/kilogram, split between the two pills and given 21 days after being infected with the HIV-like virus.
That's within the tolerable dose range for humans, but it's hard to make dose comparisons between species, the researchers write.
Six other monkeys with the same infection did not get minocycline. After 84 days, three untreated monkeys had moderate encephalitis, two had severe encephalitis, and one did not have inflammation of the brain.
Among the monkeys that got the antibiotic (minocycline), three out of five did not develop encephalitis, and the other two had mild encephalitis. The number of monkeys was small, but the difference was significant in terms of disease reduction, according to the study. The minocycline-treated monkeys also had fewer signs of brain inflammation.
The drug may not take on the virus directly but instead may make the environment "nonpermissive" for the virus to replicate, write the researchers. It prevents the production of chemicals that help recruit cells of the immune system that cause inflammation.
They write that minocycline might also deserve study to see if it can help in "maintaining low viral loads in patients for whom highly active antiretroviral therapy must be discontinued."