For the first time, an allosteric interaction (that is, a regulation mechanism whereby enzymes can be activated or de-activated) between a protein, which forms part of the sheath of the Human Immunodeficiency Virus (HIV) and the antibody 2F5 (FAB), a potent virus neutralizer has been discovered. This important scientific breakthrough could help specialists to understand the mechanisms behind generating immune responses and help towards the design of future vaccines against the HIV virus.