There are many millions of people who have HIV but not AIDS. Their immune systems work well, and their viral levels are controlled by medications. These people are on US health insurance and are highly monitored already, and easy to enroll in studies, easily accessed and monitored - as they already conform to an HIV medication regimen and see their doctors regularly.

Why would a company not test a technology that may well benefit both infected and uninfected people on both populations? You would only have more data. It will take much longer to see the results if you are only studying it as a preventative measure because you have to wait (a really long time, I would suspect) to see which of your study ends up getting HIV. Additionally, you'd need to study those that do get HIV (if some do, and some probably would, as even the best vaccines aren't 100% effective) and try to see if you can tell if their infection progresses differently or if it is somehow augmented by the vaccination's boost to the immune system. I mean... your explanation doesn't actually make that much sense to me.

Why not test both populations?