Navigation Links
Earlier bites by uninfected mosquitoes boost West Nile deaths in lab mice

GALVESTON, Texas Theres one more reason to try to avoid being bitten by mosquitoes, scientists have discovered: bites from mosquitoes that arent infected by the West Nile virus may make the disease worse in people who acquire it later from West Nile-infected mosquitoes.

Researchers from the University of Texas Medical Branch at Galveston (UTMB) announced their discovery in a paper published online by the journal PLoS ONE. In the paper, they describe experiments showing that lab mice on which mosquitoes have previously fed are far more likely to die from West Nile infection than are mice unexposed to such mosquito bites.

The effect is induced by mosquito saliva, according to UTMB professor Stephen Higgs, one of the papers senior authors.

This virus is transmitted from mosquitoes in saliva, and wed already demonstrated that mosquito saliva has an effect on the vertebrate immune system that makes West Nile infection worse, Higgs said. What this new work shows is that the saliva delivered by even earlier feedings can also alter the course of the infection. This is important, because in natural situations in many parts of the world Southeast Texas, for example animals and some people are being exposed to mosquito feeding almost continuously.

In their experiments, researchers exposed sedated mice to feeding by between 15 and 20 Aedes aegypti mosquitoes for an hour once a week. Scientists then allowed a single West Nile virus-infected mosquito to feed once on each of these mice and also on each of a control group of mice that were previously unbitten by mosquitoes.

The results were striking: 68 percent of mice exposed to two weekly mosquito feedings died of West Nile virus, and those exposed to four weekly mosquito feedings suffered a 91 percent mortality rate. By contrast, the virus killed only 27 percent of the mice previously unexposed to saliva from mosquitoes that were free of West Nile infection. Analyses of responses of the mouse immune systems also showed a strong contrast between the previously exposed and unexposed mice.

When we examined the immune reactions, one that stood out was an increase in the immune signaling molecule interleukin-10, said Brad Schneider, the papers lead author and a UTMB alumnus who is now a postdoctoral fellow at the Institut Pasteur in Paris. This host response to the saliva of the mosquito causes a shift in the immune response at the site where the virus first contacts the host, and the virus takes advantage of this shift.

The UTMB researchers were surprised to find that mosquito bites seemed to have a detrimental effect with West Nile virus, because multiple earlier bites from other uninfected arthropods can actually protect against the parasites and bacteria carried by them. Previous work has clearly indicated that pre-exposure to the bites of uninfected sand flies has a protective effect for mice against cutaneous leishmaniasis, said Dr. Lynn Soong, the papers other senior author and an immunologist who works on the sand fly-transmitted protozoan parasite infection, dubbed Baghdad boil by American troops in the Middle East.

Since this goes against the work weve seen with both bacteria and parasites, we definitely didnt expect this result, Schneider said. But when we stood back and looked at it, it made sense. For a parasite or bacterium, the influx of immune cells brought in by this inflammatory response would be negative, but with the West Nile virus, youre just giving it more susceptible cells to infect.

Both Higgs and Schneider emphasized that the mouse experiments offered no definitive answers to the question of human responses to West Nile. This is a mouse model, but thats the best weve got at the moment, Higgs said. The thing is, it suggests that there may be yet another reason to avoid mosquitoes, to tidy up your yard and wear mosquito repellant.


Contact: Jim Kelly
University of Texas Medical Branch at Galveston

Related biology news :

1. New molecular clock from LLNL and CDC indicates smallpox evolved earlier than believed
2. Researchers detect hint of oxygen 50 to 100 million years earlier than first believed
3. Green tea boosts production of detox enzymes, rendering cancerous chemicals harmless
4. Rutgers high school outreach gets $3 million boost from NSF
5. Breast cancer research and inkjet tissue printing get NSF boost
6. Breastfeeding boost IQ in infants with helpful genetic variant
7. Small-scale fishing in Mexico rivals industrial fisheries in accidental turtle deaths
Post Your Comments:
(Date:6/27/2016)... -- Research and Markets has announced the addition of ... their offering. The report forecasts ... grow at a CAGR of 12.28% during the period 2016-2020. ... market analysis with inputs from industry experts. The report covers the ... report also includes a discussion of the key vendors operating in ...
(Date:6/22/2016)...  The American College of Medical Genetics and Genomics was ... as one of the fastest-growing trade shows during the Fastest ... in Las Vegas . ... in each of the following categories: net square feet of ... attendees. The 2015 ACMG Annual Meeting was ranked 23 out ...
(Date:6/22/2016)... ANGELES , June 22, 2016 /PRNewswire/ ... identity management and verification solutions, has partnered ... edge software solutions for Visitor Management, Self-Service ... provides products that add functional enhancements ... partnership provides corporations and venues with an ...
Breaking Biology News(10 mins):
(Date:6/27/2016)...  Alex,s Lemonade Stand Foundation (ALSF), a leading national ... a state-of-the-art bioinformatics lab, using ,big data, to advance ... as Liz Scott , co-executive director of ALSF ... in Washington, D.C. , hosted by ... advocate of pediatric cancer research and awareness. ...
(Date:6/27/2016)...  Global demand for enzymes is forecast to ... $7.2 billion.  This market includes enzymes used in ... production, animal feed, and other markets) and specialty ... and beverages will remain the largest market for ... products containing enzymes in developing regions.  These and ...
(Date:6/27/2016)... 27, 2016 /PRNewswire/ - BIOREM Inc. (TSX-V: BRM) ("Biorem" or ... its major shareholders, Clean Technology Fund I, LP and ... based venture capital funds which together hold ... a fully diluted, as converted basis), that they have ... entire equity holdings in Biorem to TUS Holdings Co. ...
(Date:6/27/2016)... , June 27, 2016  Sequenom, Inc. (NASDAQ: ... to enabling healthier lives through the development of innovative ... of the United States denied ... that the claims of Sequenom,s U.S. Patent No. 6,258,540 ... eligibility criteria established by the Supreme Court,s Mayo Collaborative ...
Breaking Biology Technology: