Scientists found levels of certain cytokines spiked during disease stage
WEDNESDAY, March 18 (HealthDay News) -- Scientists in South Africa recently had the rare opportunity to follow the West Nile virus from initial infection through symptoms and recovery in a 29-year-old lab worker who had accidentally jabbed herself with an infected needle.
In particular, the researchers followed the trajectory of cytokines, a type of signaling molecule in the body, as the patient progressed through the illness.
"There are currently no specific treatments for neurological West Nile virus infections," said Marietjie Venter, head of the respiratory and emerging neurological virus program in the department of medical virology at the University of Pretoria in South Africa and co-author of a letter in the March 19 issue of the New England Journal of Medicine. "Cytokines may serve as potential targets for treatment," Venter said.
Another expert said the importance of the report lies more in the basic science knowledge it provides for West Nile, which has been endemic in North America since its first appearance in 1999.
"They were able to link the course of the infection to basic science," said Dr. Pascal James Imperato, dean and distinguished service professor at State University of New York (SUNY) Downstate Medical Center in New York City. "The interest here lies in the range of cytokines which were produced and the levels at which they were produced at different points of time."
People infected with West Nile, which is typically passed from birds to mosquitoes to humans, can experience a range of symptoms, from mild, flu-like aches and pains to life-threatening encephalitis (inflammation of the brain).
These researchers, in effect, had the opportunity to carry out a serendipitous controlled trial when the 29-year-old woman, who was HIV-negative, pricked herself with the needle.
The woman's symptoms began one week after the needle mishap and included, at first, backache and stiffness in the neck. This was soon followed by a mild fever and symptoms of meningoencephalitis (inflammation of the brain and surrounding membrane) such as severe headache, sensitivity to light and joint pain.
The symptoms subsided in about three weeks, and the woman had completely recovered by day 26 post-infection.
Blood levels of 16 cytokines were measured on the day of infection and eight subsequent days, including the day of full recovery, and compared to a blood sample taken from the patient five years after her illness.
They found that levels of the cytokines interferon-alpha and interleukin-13, both of which have effects on the immune system, were elevated.
The authors speculated that increased levels of interferon-a might help treat neurological infection from West Nile, because interferon-a has a dampening effect on the inflammatory responses of the body.
According to Venter, two patients with West Nile Virus-related encephalitis had shown improvement when treated with interferon alpha.
"Our study confirms that this cytokine increases to high levels when symptoms became apparent in our patient and supports the use of interferon alpha 2 beta as a treatment," she said. "Other cytokines that have been highlighted in the course of this neurological case that warrant further research for their role in controlling West Nile Virus infection include interferon inducible protein 10 (IP10) and interleukin 13."
"The case study also highlights that this strain of the virus, West Nile virus lineage 2, which is endemic to Southern Africa, may cause severe disease and should be considered as a cause of neurological disease to patients living here and travelers to this area," Venter added. "This contradicts the general belief that West Nile Virus lineage 2 only causes mild disease but rather suggests that it may be an underappreciated cause of neurological infection in Southern Africa."
Also, the patient had received the Yellow Fever vaccine shortly before the accident, suggesting that the vaccine is not protective against West Nile, as had been suspected.
The U.S. Centers for Disease Control and Prevention has more on West Nile virus.
SOURCES: Marietjie Venter, Ph.D., head, respiratory and emerging neurological virus program, department of medical virology, University of Pretoria, South Africa; Pascal James Imperato, M.D., dean, and distinguished service professor, graduate program in public health, State University of New York (SUNY) Downstate Medical Center, New York City; March 19, 2009, New England Journal of Medicine
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