Getting to the Brain by Hijacking miRNA: The EEE story

The mechanism by which Eastern Equine Encephalitis (EEE), a deadly mosquito-borne viral disease with a 50% mortality rate, causes its characteristic illness is the subject of a pathbreaking article in Nature by authors from Pitt's Center for Vaccine Research

The paper is focused on the role of miRNAs and their interaction with viral RNA. miRNAs are small pieces of RNA that cells use to regulate the expression of genes. miRNAs have not been thought to have a role in controlling viral genes. In the case of EEE, however, William Klimstra and colleagues found an miRNA that binds to the virus, blunting its ability to infect specific cells of the immune system and, consequently, stops the triggering of an immune response.

This suppression of host immune defenses by exploiting--or hijacking, as the authors put it--host miRNAs allows the virus to reek havoc in the central nervous system causing the signs and symptoms of encephalitis.

Furthermore, the viral sequences that bind the miRNA serve a dual purpose, enhancing replication in the mosquito vector.

The elegance and ingenuity of this viral mechanism is truly fascinating and it will be important to determine if other viruses use similar mechanisms.