Since ppl w/o ccr5 receptor don't get hiv, why isn't there a way to just irreversibly block these receptors and ppl won't get hiv?

Already underway: The ccr5 blockers are part of the anti-hiv armamentarium. You will learn about Maraviroc and the others as you get farther along in med school. Of course, you can't totally remove ccr5 and not affect all sorts of other cell receptors and processes, and you'll leave "irreversible" binding back in organic chemistry class -- reagents like this will kill a person. Glad you're thinking. Good luck.