Drug for MS Reactivated Virus Causing Deadly Brain Disease

Researchers from the Beth Israel Deaconess Medical Center have recently reported findings that a certain virus known to be responsible for a deadly brain disease may be reactivated in MS patients who are being treated with the drug natalizumab. The said virus, known as the JC virus, is known to be responsible for causing PML or progressive multifocal leukoencephalopathy, a rare brain disease that is usually seen to affect mostly AIDS patients as well as those with compromised immune systems.

According to Igor Koralnik, MD and Director of the Human Immunodeficiency Virus/Neurology Center at BIDMC and the senior author of the study, the JC virus is usually found in about 90 percent of the population. It usually lies dormant and causes no problems for most of the time. But according to Dr. Koralnik, the JC virus can reactivate and then travel to the brain which can then lead to the development of PML, a destructive brain disorder that may cause several symptoms such as dementia, paralysis, blindness and seizures. There is no cure currently available for PML and patients afflicted with the condition usually die within a year after diagnosis.

About four years ago, two patients who participated in the clinical trial testing of the MS treatment drug natalizumab were found to have developed PML. "This was the first time we had seen PML develop in patients with multiple sclerosis," said Dr. Koralnik. The scientists believe that the drug’ effect of preventing lymphocytes from crossing the blood-vessel wall may give the opportunity for the virus to reactivate and develop into PML. "The drug appeared to be something of a double-edged sword," observed Dr. Koralnik. "Not only was it keeping dangerous cells from entering the brain, it was also keeping out the protective virus-fighting lymphocytes, thereby leaving patients vulnerable to this dangerous infection."

"If impaired immune surveillance due to natalizumab treatment was responsible for the development of PML, we wanted to find out where in the body the JC virus reactivation was taking place," he further adds. So in order to find out, the team of scientists under Dr. Koralnik enrolled 19 MS patients for their study as they began their treatment for natalizumab. This included follow up studies in 3, 6, 12 and 18 month intervals as well as for post treatment.

The results of the study showed that urine measurements of the JC virus in the participants had a 19 percent increase during the start of the treatment. After 12 months of treatment, the measurements further increased to 63 percent. At 18 months, 60 percent of the participants showed blood samples with the JC virus entering into the blood cells, as compared to only one patient with the virus found on the blood sample after 12 months of treatment with natalizumab.

According to Dr. Koralnik, "This pilot study shows for the first time that natalizumab not only prevents the migration of protective T lymphocytes, but it also directly affects the cells’ potency against the JC virus. It further tells us that reactivation and transformation of the virus may first occur in the kidney and that once the activated virus spills into the blood it can easily spread to the brain."

Source: Beth Israel Deaconess Medical Center. "Virus Responsible For Deadly Brain Disease Found In MS Patients Treated With Natalizumab." ScienceDaily 11 September 2009. 15 September 2009 .

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