Quantum dots are fluorescent crystals in which the color of the emitted light is dependent on the size of the crystal. Credit: Richard E. Cruise, University of Leeds
University of Leeds researchers have observed for the first time how HIV and Ebola viruses attach to cells to spread infection. The findings offer a new way of treating such viruses: instead of destroying the pathogens, introduce a block on how they interact with cells. They used ‘quantum dots’ that mimicked the shape of the viruses and acted as technological stand-ins in experiments to reveal how they bind to cells.
Quantum dots are fluorescent crystals in which the colour of the emitted light is dependent on the size of the crystal – one of several properties that has led to them becoming the most desirable component for the latest generation of televisions. They have also emerged as an advanced type of fluorescent probe for biomolecular and cellular imaging, making them useful for studying how viruses spread.
Using the fluorescence of the quantum dots, they illuminated the physical binds that attach them to the cells, also revealing how the viruses would bond. In order to allow the quantum dots to bind to cells, they first had to be coated in sugar – a new technique that was developed at the University of Leeds. Dr Bruce Turnbull said: “…all of our cells are coated in sugar and they interact with other cells by proteins binding with these sugars. Indeed, the reason why we have different blood types is because of the different types of sugar coating on our red blood cells.”
“Viruses also attach to the surface of healthy cells through interactions between proteins and sugars. These interactions are weak individually, but can be reinforced by forming multiple contacts to offer the viruses a ‘way in’. We want to understand what factors control this binding process and, eventually, develop a range of inhibitors designed to target specific viral bindings.”
The study has already revealed the different ways in which 2 cell surface sugar binding proteins that were previously thought to be almost indistinguishable – ‘DC-SIGN’ and ‘DC-SIGNR’ – bind to the HIV and Ebola virus surface sugars, thereby spreading the viruses. Dr Dejian Zhou said: “These proteins are like twins with different personalities. Their physical make-up is almost identical, yet the efficiency with which they transmit different viruses, such as HIV and Ebola, varies dramatically and the reason behind this had been a mystery.
“Our study has revealed a way to differentiate between these proteins, as we have found that the way in which they bind to virus surface sugars is very different. They both attach via 4 binding sites to strengthen the bond, but the orientation of these binding pockets differs.” http://www.eurekalert.org/pub_releases/2016-03/uol-sd031016.php
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