the key to finding an HIV vaccine is to prevent the virus from binding to the T cells in the body.
there have already been cases of people who are immune to being infected because they have a genetic mutation where they lack a binding protein on the T cells (called the CCR5 coreceptor).
biologists call these 'resistance alleles' and drugs that seek to mimick their effect is going to be how they will finally create a vaccine to beat this virus.