Test for JC virus benefits patients with MS and other autoimmune disorders
A laboratory test developed by scientists at the National Institute of Neurological Disorders and Stroke (NINDS) is helping clinicians around the world in diagnosing a rare and potentially life-threatening brain disease called progressive multifocal leukoencephalopathy (PML). The test, or assay, can quickly and precisely detect trace amounts of the virus responsible for PML.
In recent years, cases of this little known condition have appeared in some individuals receiving certain types of monoclonal antibody therapies, cutting-edge medications that can successfully treat multiple sclerosis (MS), Crohn’s disease, rheumatoid arthritis and other autoimmune disorders. For medical teams who monitor and safeguard the health of patients on these medications, the NINDS innovation has become an important resource.
Eugene Major, Ph.D., leads the NINDS team responsible for the assay. He is chief of the Laboratory of Molecular Medicine and Neuroscience (LMMN), part of the NINDS Division of Intramural Research on the Bethesda, Md., campus of the National Institutes of Health.
Dr. Major’s work focuses on viruses affecting the human nervous system. One of these is the cause of PML: JC virus (so-named after the initials of the patient in whom it was first identified in 1971). This common virus infects an estimated 70 percent of people worldwide, but it is usually rendered harmless by healthy immune system cells. The virus, however, is never cleared entirely from the body; instead it remains latent (inactive) inside hidden reservoirs. If cancer, HIV or other serious conditions weaken immune defenses, JC virus can sometimes reactivate, resulting in PML.
Although there is no treatment for PML, doctors can take steps to help the immune system recognize the viral infection. A rapid diagnosis is critical, and the only conclusive method is to run an assay to confirm the presence of JC virus DNA. As a result, the ultrasensitive NINDS assay has emerged as a key diagnostic asset.
The NINDS test is based on quantitative polymerase chain reaction, or PCR (the same technology that sparked a genetics revolution more than three decades ago). “Through PCR we amplify copies of viral DNA from DNA templates isolated from clinical samples,” explained Dr. Major. The result is a highly specific and sensitive gauge capable of returning rapid results.
A 2009 case study in The New England Journal of Medicine(1) documented the NINDS assay’s strengths. Investigators at Sweden’s prestigious Karolinska Institute suspected PML in an MS patient treated with natalizumab, a monoclonal antibody drug. The patient was experiencing muscle problems, and brain scans revealed that his white matter lesions had grown larger.
According to the published report, even though the initial tests in Sweden had been negative for JC virus (with criteria at less than 200 copies per milliliter), the results from quantitative PCR assay at NINDS confirmed borderline positivity (at 10 copies per milliliter). The analysis validated the doctors’ suspicions. Their prompt response helped the patient recover with fewer neurological deficits than expected.
NINDS conducts the tests free of charge. Dr. Major considers it part of his lab’s translational research mission. “Our work extends from developing new technologies to enhance our basic understanding of disease mechanisms to translating that knowledge into diagnostics and therapeutic strategies to treat patients,” he said.
Dr. Major also continues to investigate underlying reasons for JC virus reactivation. In an article published in conjunction with the Karolinska case study, he mapped out a possible connection.(3)
Dr. Major remains committed to improving and broadening access to the assay. He had the test independently validated and certified through the U.S. Clinical Laboratory Improvement Amendments (CLIA). The program ensures quality standards for lab procedures.
NIH also recently licensed the assay technology, making it commercially available for scientists anywhere in the world. “This will expand opportunities for collaboration,” said Dr. Major. “We hope the assay continues to be an important resource wherever it’s needed.”
- By Gregory Roa, NINDS