Block and lock
While the ‘shock and kill’ method continues to be explored, scientists are also investigating whether they can permanently lock up the virus hiding in the CD4 T cells and keep it there. If this succeeds, it will mean that your blood is HIV-free, but that HIV is trapped somewhere in your body.
Researchers suspect that this method will not be foolproof. They think that some virus may still escape, but in such small quantities that your immune system can clear it up itself.
This is a very simple explanation. The reality is much more complicated.