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Integrated HIV Successfully Cut Out of Human Genome
Chris writes "German scientists have succeeded in snipping HIV out of human cells after it has integrated itself into a patient's DNA. The procedure is a breakthrough in bio-technology and fuels hope of a cure for AIDS. The group is only cautiously optimistic, though, as treating a full-on infection would be substantially different than succeeding in a controlled lab environment. 'Researchers ... began with the bacterial enzyme Cre recombinase, which exchanges any two pieces of DNA flanked on either end by a certain pattern of nucleotides (DNA subunits) known as loxP. HIV does not naturally contain loxP sites, so the team created a hybrid of the two DNA molecules, which they used to select a series of mutated Cre enzymes that were increasingly able to recognize the combined DNA. The final enzyme, Tre, removed all traces of HIV from cultured human cervical cells after about three months, the researchers report online today in Science.'"
I read about this in PhysOrg yesterday and they speak more about something the last paragraph of Scientific American only mentions. The fact that they wouldn't use this enzyme to remove HIV infections but instead to figure out which cells have been infected. The biggest problem in treating HIV is that it can go dormant and undetected for so long during which the host can infect others. It sounds horrible, but even being able to destroy all the cells infected with the virus is worth something though it may often prove fatal to the host. I don't think this is a 'cure' or 'vaccine' merely something that makes HIV treatments much much more effective.
My work here is dung.
Cre is an bacterial enzyme (a member of a family of enzymes called site specific recombinases) commonly used by researchers attempting genetic manipulations of dna. The cre enzyme recgonises a specific dna sequence (called LoxP sites) just over 30 letters (base pair) long and then catalyses a reaction which can either cut out dna, insert dna or reverse the orientation of dna flanked by loxp sites (precisely what the cre enzyme will do depends upon the number of sites and the order and orientation of the sites). The HIV virus does not contain LoxP sites so these guys "evolved" the cre enzyme by a selective process to recognise DNA sequences that were initially a hybrid of a part of the HIV virus sequence and the cre Loxp site. they continues this evolution until a modified Cre enzyme (now called Tre) could actually recognise the original HIV dna sequence. They then used this Tre enzyme to cut out the HIV virus dna that had inserted itself into the cell genomic dna, freeing the cells of the HIV virus. This is a pretty interesting article, however, as the authors state this is preliminary work. One problem i can envision stems from the fact that HIV virus often inserts itself numerous times into the host genome. When researchers are using cre they have to be careful about the number of copies of the Loxp site in the genome or it is possible for the cre enzyme to cause large deletions of genomic dna or even cause translocations (when the genomic dna found on one chromosome is erroneously attached to that of another chromosome). Such changes to the dna can be highly deleterious to the cell and initiate cancerous changes. hope this helps.
The final enzyme did work with real HIV in the lab. They identified a site in HIV similar to the cre binding motif, but which cre was not able to bind. They created intermediate sequences to bridge the gap between the cre binding site and this HIV sequence. Using directed evolution they could evolve cre to bind sites progressively more unlike the cre site and progressively more like the HIV site. The final outcome was an enzyme able to excise sequences flanked by the HIV specific pattern.
Do you, by any chance, wake up to public radio or similar? I find that sometimes the first 10 minutes or so of what is said on the radio, before I become fully cognizant, gets absorbed into my subconscious so that I think it is weird when I hear the same bit of news later in the day.
My eyes reflect the stars and a smile lights up my face.
Sure: Germans have created a variant of sed, that operates on DNA and used it to delete HIV.
Alright, I must be crazy. I was just thinking about HIV in the shower
Are you currently serving time in prison by any chance?
In Soviet Russia, Chuck Norris will still kick your ass.