West Nile virus (WNV) casts a broad net of influence, entwining itself in the mosquitoes that transmit it, the birds that carry it, the animals and people that are affected by it, and the environment it spreads through. But to understand that complex picture, you need to understand the virus itself. Kristen Bernard, DVM. MS, PhD, associate professor in the department of pathobiological sciences at the University of Wisconsin-Madison School of Veterinary Medicine, is using her research to untangle the functions of WNV."I'm trying to understand how the virus causes disease," said Bernard. "What I want is to understand each step of what the virus is doing in the body."
The virus, first seen on the east coast in 1999 before spreading rapidly across the United States, is an arthropod (insect)-borne virus. Although not common in Wisconsin, WNV presents a serious threat. The virus cycles between mosquitoes and birds, then spreads when an infected mosquito bites a healthy animal. According to Bernard, some are more affected than others, with humans, horses, and some types of birds hit the hardest.
But the common thread among all these species is one tiny buzzing insect. "In nature, there isn't any vertebrate to vertebrate transmission," Bernard said. "You need to have that mosquito."
Using a mouse model, Bernard is examining what happens after that mosquito bites. This includes interactions between the body, the virus, and even the mosquito saliva. Her work is yielding interesting findings.
"We get more virus replication when there's mosquito saliva there," said Bernard, explaining that this might indicate the presence of a protein in the saliva that changes the impact of the virus. "The long term idea is, if you could identify that protein, you could make a vaccine."
Bernard's work is also taking steps towards understanding the lasting effects of West Nile on the body. "It's typically thought that West Nile infects the host, the host mounts a response, and then it's gone," said Bernard. But her research shows that West Nile can linger, especially in the brain, long after the animal recovers from the illness. She explained that the body's immune system is responsible for eliminating the virus, but too strong of an immune response can actually damage the body's healthy tissue, especially sensitive tissue like the brain.
"That's the fine line the body's walking down," said Bernard. "In this case, it's an advantage to the virus." The body protects the brain, and accidentally leaves some virus behind.
For Bernard, this research is all about digging into the fundamental functions of the virus. She hopes that her research will pave the way for future advances in West Nile prevention and cure, with a better understanding of the disease itself. "I want to do the basic research with the goal that it will be useful in human and veterinary medicine," said Bernard.