Genetic marker may identify individuals at risk of severe West Nile infection
Scientists at Baylor College of Medicine in Houston have found a genetic marker that may identify individuals at greater risk for life-threatening infection from the West Nile virus. Results of the study are reported in the Nov. 15 print edition of Journal of Infectious Diseases.
Using technology at the Human Genome Sequencing Center at BCM, infectious disease experts compared genomic sequences of patients with severe West Nile virus infections to those who were not affected by the disease. The study was funded by the Albert and Margaret Alkek Foundation.
"Why do some people who get West Nile get much sicker than others who get the virus? The answer may be in the results we obtained," said Dr. David J. Tweardy, chief of the section of infectious diseases at BCM.
Following up on the discovery of a mutation in an anti-viral gene pathway in mice that causes greater West Nile susceptibility, Baylor scientists found a single nucleotide polymorphism in this set of genes in humans who were suffering from severe symptoms of West Nile. In essence, the SNP found in patients with severe West Nile virus infection may mimic the mutation found in mice resulting in suppression of the anti-viral pathway and more severe disease.
Tweardy cited estimates from the Center for Disease Control that over 99 percent of those inoculated with the virus, which is spread by mosquito bites, develop little to no clinical symptoms or illness. Of the remainder, most manifest flu-like symptoms such as fever and malaise with a small subset of those developing meningitis and encephalitis, the latter of which can be fatal.
Because only a small fraction of those who contract the virus develop life-threatening symptoms, scientists hope to differentiate segments of the population that warrant immunization from those who are not seriously afflicted.
"We are trying to understand who would be the first group to be targeted for immunization should a vaccine become available," Tweardy said. "You might be inclined to believe that everyone needs to be vaccinated, but as we are becoming increasingly sophisticated about the genomics of individuals, we may only need to vaccinate those who have a predisposition to more severe disease.".
An outbreak of West Nile in the United States first occurred in 1999, creating a growing problem for health professionals who still have no consistently effective treatment for the virus. Those over the age of 60 are most vulnerable to becoming seriously ill.
Other contributors to the study included BCM faculty members Drs. Richard Gibbs, Imtiaz Yakub, Ana Moran, Omar Y. Gonzalez, and John Belmont. Dr. Kristy M. Lillibridge, a member of the infectious disease center at the University of Texas Health Science Center at Houston School of Public Health, also was a key participant.