Retrovirus marker identified in motor neuron disease

Scientists have discovered a molecular marker linked to retroviruses in the blood of people affected by motor neuron disease (MND), according to a study published in the Feb 8 issue of the journal Neurology .

The collaborative study found the marker in nearly half of all patients studied, suggesting that there might be a common basis for the development of MND, a disease which at present has no known cause for the majority of people affected.

The study, led by Dr Jeremy Garson of University College London (UCL) and Dr Ammar Al-Chalabi of King's College London (KCL), confirms their earlier work which revealed evidence of retroviral involvement in a group of 56 UK patients with MND, 59 per cent of whom were found to carry the marker. The new study, conducted with 30 US patients, identified a marker of retrovirus activity in the blood of 47 per cent of the patients.

Researchers stress that their findings do not necessarily mean that a retrovirus causes motor neuron disease, also known in the US as Lou Gehrig's disease or amyotrophic lateral sclerosis (ALS). At this stage, scientists have simply identified an association between MND and a retroviral marker. Further work will be needed to explore whether there is a possible causative link with the disease.

Retroviruses are viruses whose genome consists of RNA rather than DNA. Well known examples are HIV-1 and HIV-2, the agents that cause AIDS. HTLV is another retrovirus linked to adult T-cell leukaemia and tropical spastic paraparesis. Drs Garson and Al-Chalabi have already demonstrated that HIV and HTLV are not involved in typical MND cases.

Dr Garson says: "This is a very exciting finding that hints at the possibility of retrovirus involvement in motor neuron disease.  However, much work remains to be done to establish whether this is simply an association with or a possible cause for MND."

Dr Al-Chalabi adds: "What we have identified in the serum of some MND patients is reverse transcriptase, an enzyme associated with retroviruses. However, we don't yet know whether or not the enzyme activity we detected is linked to a so-called endogenous retrovirus - a retrovirus already present in human DNA. The alternative is that the marker is related to infection from a novel, external MND-associated retrovirus. Retroviruses are already known to be implicated in the pathogenesis of MND-like syndromes in certain strains of mice and in rare cases of individuals with HIV infection."

It is hoped that further progress in this area will lead to the development of improved diagnostic tests and novel treatments, along with greater understanding of the fundamental causes of this progressive and ultimately fatal neurological disease.

The study was funded by Project ALS, a medical research charity based in New York.

Notes for Editors

For more information, please contact Jenny Gimpel at the UCL Media Relations Office on +44 (0)20 7679 9739, Out of Hours: +44 (0)7917 271364, E-mail j.gimpel@ucl.ac.uk.

The study by Steele A, Al-Chalabi A, Ferrante K, Cudkowitcz M, Brown RH and Garson JA, is published in Neurology , 8 February 2005, vol 64, pages 454-458.