Progressive multifocal leukoencephalopathy (PML) – is a very rare and usually fatal brain disease, caused by so called John Cunningham, or JC, virus. It occurs to people who suffer from severe immune deficiency, most commonly patients with acquired immune deficiency syndrome (AIDS) are affected.
Now scientists from the University of Zurich and the University Hospital Zurich have demonstrated a novel possible treatment for this disease. These discoveries may open doors for the development of the vaccine to combat this disease.
Most of people know that human body is full of bacteria and viruses. There are many of these living creatures in human gut, on the skin and in other organs. Most of this bacterium and viruses are not harmful or actually even needed for us and performs some important functions, while others under certain conditions cause diseases. JC virus is no exception. As much as 60 % of entire human population are infected by this virus. Normally it stays in the kidneys and certain other organs. But PML is still extremely rare and people with immune deficiency are affected almost exclusively.
International team of researchers have conducted a study and revealed that the antibodies in PML patients often simply fail to recognize the JC virus they are infected with. It may be because the virus itself is so common and requires certain conditions to cause a disease.
Roland Martin, professor of neurology at the University of Zurich, explained: “In healthy people, the disease never breaks out as the immune system keeps it well under control. Once the immune system is compromised, however, such as in patients with tumours, leukaemia, AIDS, autoimmune diseases and certain immunosuppressive treatments, the JC virus is able to alter its genetic information and infect the brain”. Sometimes immune system can be supressed by drugs, treating other illnesses or diseases.
For example, there is a drug, called Tysabri, which is highly effective treating patients with multiple sclerosis. It prevents immune cells from reaching the brain, which is its main function in treating the condition. However, because immune cells cannot reach the brain, they cannot perform so called immunosurveillance.
This means that if JC virus enters the brain during the treatment with the Tysabri, it remains undetected and can cause PML. In fact, PML is regarded as the most significant side effect of the Tysabri drug.
Scientists say that over 560 patients with multiple sclerosis have already developed the PML brain infection and over 20 % of them died, because there is no effective treatment. Infection itself has a mortality rate of 30–50 % in the first few months and even those who survive can be left with varying degrees of neurological disabilities. In case of treatment with Tysabri drug, only the restoration of the immune system functions can remove the JC virus from the brain.
Researchers now revealed a potential way to vaccinate people against the PML infection. It is possible, if the brain has already been infected, to treat the disease with virus-specific human antibodies. Team of researchers already conducted several successful experiments. They vaccinated mice and a PML patient with the virus’ coating protein and got surprisingly good results. In fact, the antibody response was so strong that the patient was soon able to eliminate the JC virus from his brain. This technique, called “active vaccination method”, has already been used successfully on two more patients. Scientists are already calling this a achievement a “major breakthrough”.
And truly it is hard to overrate such achievements. Scientists managed to isolate antibody-producing cells from a patient who survived PML brain infection. Then researchers used them to produce neutralizing antibodies against the JC virus, which recognize the most important mutants of the JC virus that can cause the PML. It makes for a perfect candidate for a vaccine that could prevent PML or treatment that could help cure now mostly fatal disease.
Although very rare, PML condition is a real threat, especially to people who have damaged immune system because of AIDS or treatment drugs for other conditions (such as chemotherapy). Therefore, this is a major breakthrough which could very soon save many lives and prevent PML in cases of higher risk.