NIAID Now | October 25, 2019
In recent months, an uptick in cases of eastern equine encephalitis virus (EEEV) infections in Connecticut, Massachusetts, Michigan, and elsewhere in the United States has raised alarm. As headlines warn of the mosquito-borne virus’ lethal symptoms, affected communities have advised people to remain indoors during peak mosquito periods, such as at dusk, and have sprayed insecticide to tamp down mosquito populations. At NIAID, researchers are working to develop both vaccines and therapeutics to fight this rare but deadly virus.
EEEV is an alphavirus which primarily infects birds. However, it can occasionally be transmitted from birds to humans by an Aedes or a Culex mosquito. Other mammals can also be infected—the virus got its name after being first recognized in horses. EEEV can cause systemic illness (which includes chills, fever, fatigue, joint pain, and muscle aches) and encephalitic illness, in which the brain is also attacked by the virus. The brain infection can be fatal: according to the Centers for Disease Control and Prevention, approximately one-third of all people with EEEV symptoms die of the disease, and many who survive have severe lingering neurological symptoms. Currently, there is no vaccine to prevent people from becoming infected with the virus, and no specific antiviral treatment for those who do.
NIAID is working to change that. For many years, NIAID’s Vaccine Research Center (VRC) has been developing a vaccine that could provide humans protection against EEEV, as well as Western Equine Encephalitis Virus (WEEV), and Venezuelan Equine Encephalitis Virus (VEEV). The vaccine, abbreviated WEVEE, is not made from actual virus. Instead, it is a virus-like particle (VLP) vaccine. These VLPs look like empty “shells” of the virus to the immune system; they cannot replicate or infect a person. The WEVEE vaccine is being assessed in a Phase 1 clinical trial to evaluate its safety and ability to induce an immune response in people. So far, it appears safe and well-tolerated in 30 healthy volunteers.
NIAID also funds a variety of researchers studying EEEV at other institutions. Some are looking into how the virus infects the brain, while others are piecing together the structure of viral proteins, looking for weaknesses that could be targeted by vaccines or drugs. Still other grants are providing support for additional approaches to an EEEV vaccine. NIAID also provides access to a suite of services that scientists can use to accelerate their own research, including the testing of compounds for their activity against EEEV. Since 2014, NIAID has completed 125 primary assays and 16 secondary assays to test compounds for EEEV activity, and demand for these services is on the rise. One early-stage candidate compound, ML336, showed activity against EEEV.
NIAID also supports research into how similar species of mosquitoes smell their prey, feed as larvae, find each other to mate, and how they could be stopped with new pesticides or repellants. For now, the best protection against EEEV is avoiding the mosquitoes that carry the virus. In areas where EEEV has been found, people can help avoid contact with mosquitoes by wearing long sleeves and mosquito repellant, and emptying pools of standing water where mosquitoes might lay their eggs.