Can we target the unchanging portion of virusí genetic material?
Chris - What heís getting at is that some viruses change bits of themselves like the flu, changes its H genes (haemagglutinin genes) on the surface coat of the virus looks a little bit different. This is called genetic drift and this is down to genetic mutation when the RNA copies itself it makes mistakes and this translates into a slightly different structure for the virus. This is useful to the virus because it makes it look different so the immune system struggles to recognise it a second time.
Some bits of the virus do such a crucial job that they canít afford to change because if they did they would impair themselves. There are some un-variable bits of the virus that donít change. What heís asking is could we exploit that to make better treatments for viruses?
The answer is yes.
A good example is in flu itself. There was a recent study that was published in PNAS where researchers looked at the way in which a flu vaccine worked. Flu vaccines are based on the haemagglutinin coats on the virus. You make a coat on the virus, put it in a egg, you get some virus shrapnel and you can inject that into people. If you watch how the flu changes over time a vaccine that works against one type of flu might not work against another. If you get lots of examples of flu virus, compare the genetically you can find elements of the surface coat of the virus that have never changed over that time. If you make a vaccine out of that then in the case of the paper Iím referring to these people did it with a DNA vaccine. They just injected the DNA from that little bit of the virus coat. That hadnít changed and it was very effective against a broad repertoire of viruses so that might be a better way of doing it.
Another good example is HIV which has to bind onto CD4 receptors on our immune cells. If the virus were to mutate that bit of itself too much then it wouldnít be able to infect anymore because it wouldnít be able to recognise the target. Researchers are now looking at ways to specifically target the structure on the virus which the virus keeps very hidden but which doesnít change in order to block HIV.
Ivan Doykov asked the Naked Scientists: I love the show. I never miss a podcast. My question is the following. We know that the HIV virus is a RNA based and that gives it the ability to mutate at extraordinary rate which is the reason why is so elusive to drugs. The thing that bothers me is that even after it mutate it is still HIV so logic demand that there is a portion of RNA that is unchanged. If that is true can we use this to better control the virus? Thank you in advance for your time Ivan Doykov from London PS: I apologize for any writing mistakes but English is not my first language. What do you think? Ivan Doykov , Sat, 13th Dec 2008
The answer is definitely, and this is how some vaccines and and diagnostic tests work; scientists are seeking to do the same thing with HIV by exploiting the fact that the CD4 receptor cannot change. We discussed this in a programme about emerging diseases: