Vanderbilt University Medical Center researchers, in collaboration with investigators at Johns Hopkins University, are beginning a Phase I trial to test a new vaccine against the West Nile virus.
The mosquito-borne virus, which can cause serious illness, is making its yearly appearance in Middle Tennessee. While no human cases of West Nile have been reported in the state so far this season, mosquitoes collected from around Nashville have tested positive for the virus.
"When West Nile virus first appeared in the United States five or six years ago, it spread remarkably quickly across the country," said Peter Wright, M.D., professor of Pediatrics, Microbiology and Immunology, and Pathology, who is heading up Vanderbilt's efforts in the trial. "There's no part of the country that has not experienced human and bird cases of West Nile."
Although around 80 percent of people infected by West Nile virus show no symptoms, up to 20 percent can experience moderate or severe symptoms ranging from fever, headaches and neck stiffness to neurological problems, paralysis and coma. About one in 150 people infected develop severe illness. People over the age of 50 are at the highest risk, but even healthy people can experience debilitating symptoms lasting several weeks.
There are currently no specific treatments or vaccines to combat West Nile infection, so those infected are consigned to letting the illness run its natural course.
While it is not clear who would most benefit from a West Nile vaccine, Wright suggests that it could be beneficial to certain high-risk populations, such as the elderly, people who work outside and have frequent exposure to mosquitoes, or those in specific geographic regions where West Nile cases are detected.
Finding an effective vaccine against West Nile could also open doors to developing vaccines for other insect-borne illnesses like Dengue fever, which are a priority for vaccine development because of their considerable global impact.
"We would love to get a vaccine developed for viruses in this class, called arthropod-borne, or as they are commonly called, arboviruses," Wright said. "If we could get one for West Nile, it could be a model for other vaccines."
The vaccine under investigation is built on a backbone of the Dengue virus with bits of the West Nile virus inserted. This method, called a chimeric vaccine, is a relatively new way to engineer a vaccine, Wright said.
"It's conceptually a very interesting vaccine," he said. "It's live but weakened, which has recently been postulated to be the ideal form of immunization...in terms of its broad stimulation of the immune response."
The researchers will test the safety of this vaccine as well as its ability to induce an immune response in healthy volunteers age 18 to 50. The study will also help identify an optimal dosage of the vaccine.
"We can learn a lot from it, and we can measure a lot of things that will inform us about how these vaccines work," Wright said.
Until an effective vaccine is found, public health officials urge the public to take steps to prevent mosquito bites. This includes using insect repellent when outdoors, limiting time spent outside around dawn and dusk when mosquitoes are most active, and getting rid of standing water where mosquitoes breed.