Researchers at the National Institute of Neurological Disorders and Stroke (NINDS) have discovered that a dormant retrovirus may have been responsible for causing neuronal damage in a number of patients with ALS – amyotrophic lateral sclerosis. Their findings raise hope that finding a way to block the virus with antiretroviral drugs may be of benefit to some ALS patients.
The research was led by Avindra Nath, MD, and was prompted by a case seen over 10 years ago, where a patient infected with HIV also went on to develop symptoms of ALS. It was found that once the patient was given antiretroviral drugs to treat the HIV infection, the ALS also improved. This caused the researchers to wonder whether ALS also involved some kind of retrovirus.
More than 8% of our DNA is made up of human endogenous retroviruses, which are leftover infections that occurred several million years ago. Over time mutations have meant that most of these retroviruses are defective. However, the researchers believe that they may become active once again during ALS.
Human endogenous retrovirus K evident in brains of ALS patients
During their study, Nath and his team discovered that the human endogenous retrovirus K was evident in autopsied brain of ALS patients, but did not feature in brains in healthy people, or those with Alzheimer’s. Furthermore, during in vitro tests with the genes of this retrovirus and healthy human neurons, it was seen that the retrovirus killed the neuronal cells. To further determine the role of the retrovirus, transgenic mice were developed which grew to exhibit ALS-like symptoms, such as problems with balance and walking. The also died earlier than normal mice. Upon inspection of the mice brains, spinal cords and muscles, they found that only the cells involved in ALS were affected, while other cells in the nervous system remained unaffected, thus showing that during ALS, motor neurons may be susceptible to the activation of these genes.
Their findings may lead to the development of drugs to stop the virus from replicating
As a result of their findings, the researchers are now looking at ways to block the activation and replication of this virus, by using drugs that are currently used to control HIV infections. It’s hoped that the results will go some way to finding an effective treatment for ALS.
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