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CSIRO scientists have discovered how mosquitoes develop viral immunity, potentially leading to improved vaccines, and other control measures, for mosquito-borne viruses such as dengue and West Nile.
Published online in the prestigious Proceedings of the National Academy of Sciences of the USA (PNAS), the team from CSIRO's Australian Animal Health Laboratory, in Geelong, have shown Vago, a protein previously identified in fruit flies, is released by infected mosquito cells, providing a warning to other cells to defend against the invading virus.
Mosquito-transmitted emerging viruses, such as dengue, Japanese encephalitis and West Nile threaten the health of our people, livestock and wildlife. Globally, dengue infects 50-100 million people and results in around 22,000 deaths annually.
According to CSIRO's Professor Peter Walker, these insect vectors present a particular biosecurity risk for Australia as they are rapidly spreading into new areas driven by a number of factors including climate change and increased travel and trade.
"Difficulties in generating safe and effective vaccines for many of these pathogens present significant challenges due to their complex ecology and the range of hosts the viruses can infect," Professor Walker said.
"Until now, very little was known about the defensive anti-viral response of insects. Unlike humans and other mammals, insects lack key components of the immune response including antibodies, T-cells and many important cytokines, such as interferon."
This work is part of CSIRO's ongoing commitment to protect Australia from biosecurity problems and risks posed by serious diseases.
Using West Nile Virus as their infection model, the research team has demonstrated that, although unrelated structurally, Vago acts in mosquitoes like human interferon.
"Mosquito cells can sense the presence of a virus by detecting its small genome, stimulating the secretion of Vago. The secreted Vago then binds to receptors on other cells, signalling an anti-viral defensive response to limit the infection," Professor Walker said.
"This is the first demonstration that such a mechanism exists in mosquitoes or any other invertebrate.
"We are now looking at how viruses such as West Nile and dengue overcome the defensive response of the mosquito and how we can use this knowledge to increase resistance to infection and decrease the efficiency of disease transmission."
CSIRO will also use this new knowledge to explore the use of Vago for the control of viruses in invertebrate aquaculture species including prawns and abalone.
This work is part of CSIRO's ongoing commitment to protect Australia from biosecurity problems and risks posed by serious diseases.
Editor's Note: Original news release can be found here.
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Trying to keep an image we've just seen in memory can leave us blind to things we are 'looking' at, according to the results of a new study. (Credit: © Igor Mojzes / Fotolia)
Science Daily — Trying to keep an image we've just seen in memory can leave us blind to things we are 'looking' at, according to the results of a new study supported by the Wellcome Trust.
It's been known for some time that when our brains are focused on a task, we can fail to see other things that are in plain sight. This phenomenon, known as 'inattentional blindness', is exemplified by the famous 'invisible gorilla' experiment in which people watching a video of players passing around a basketball and counting the number of passes fail to observe a man in a gorilla suit walking across the centre of the screen.
The new results reveal that our visual field does not need to be cluttered with other objects to cause this 'blindness' and that focusing on remembering something we have just seen is enough to make us unaware of things that happen around us.
Professor Nilli Lavie from UCL Institute of Cognitive Neuroscience, who led the study, explains: "An example of where this is relevant in the real world is when people are following directions on a sat nav while driving.
"Our research would suggest that focusing on remembering the directions we've just seen on the screen means that we're more likely to fail to observe other hazards around us on the road, for example an approaching motorbike or a pedestrian on a crossing, even though we may be 'looking' at where we're going."
Participants in the study were given a visual memory task to complete while the researchers looked at the activity in their brains using functional magnetic resonance imaging. The findings revealed that while the participants were occupied with remembering an image they had just been shown, they failed to notice a flash of light that they were asked to detect, even though there was nothing else in their visual field at the time.
The participants could easily detect the flash of light when their mind was not loaded, suggesting that they had established a 'load induced blindness'. At the same time, the team observed that there was reduced activity in the area of the brain that processes incoming visual information -- the primary visual cortex.
Professor Lavie adds: "The 'blindness' seems to be caused by a breakdown in visual messages getting to the brain at the earliest stage in the pathway of information flow, which means that while the eyes 'see' the object, the brain does not."
The idea that there is competition in the brain for limited information processing power is known as load theory and was first proposed by Professor Lavie more than a decade ago. The theory explains why the brain fails to detect even conspicuous events in the visual field, like the man in a gorilla suit, when attention is focused on a task that involves a high level of information load.
The research reveals a pathway of competition in the brain between new visual information and our short-term visual memory that was not appreciated before. In other words, the act of remembering something we've seen that isn't currently in our field of vision means that we don't see what we're looking at.