Slight correction, we'd have to introduce other human receptors that HIV binds to, not just the human CCR5 receptor. It's still not that difficult though, we can put them all on the same plasmid. New techniques, such as magnetofection (http://www.chemicell.com/products/Magnetofection/Magnetofect...) should allow almost 100% transfection (inserting a plasmid, or circular piece of DNA, into a cell) rate. Granted, this is all still theoretical and there may be something I am overlooking, but I still feel it's worth pursuing.