The existence of rare monoclonal antibodies that possess broad neutralizing capability indicates that, although we have
thus far failed to achieve it, induction of such antibodies should be possible. For example, x-ray crystallography has revealed how HIV uses the CD4 receptor to enter cells and how the broadly neutralizing b12 antibody binds to part
of the CD4-binding site to neutralize HIV effectively. Determining the structure of the trimeric form of the envelope protein is currently a research priority and is expected to yield additional insights. Efforts to design novel envelope immunogens include the use of a “scaffold” protein unrelated to the HIV envelope to which conformation-dependent conserved regions of the envelope are added, ensuring their exposure to and recognition by the immune system.