I'm no expert, but I assumed that HIV meds damage the kidneys, making treatment a balancing act of too aggressive treatment killing the kidneys vs not addressive enough allowing the virus to do its damage. Being able to grow a replacement kidney would allow more aggressive treatments. I think this would be true of many diseases, though, not just HIV. I know my mother-in-law has to live with the knowledge that the meds she takes to manage her bipolar disorder may eventually be what kills her, due to kidney disease. EDIT: I said kidney because the first couple comments referenced kidneys. Could apply to other organs. The basic idea is that meds often damage organs as a side effect, so being able to replace the organ opens up more possibilities for aggressive treatments.