WHAT: Most vaccines that protect against viruses generate infection-fighting proteins called antibodies that either block infection or help eliminate the virus before it can cause disease. Attempts to create a vaccine that induces antibodies that prevent HIV infection or disease, however, have so far been unsuccessful. But several recent studies suggest promising new research directions for the development of an antibody-based HIV vaccine, according to John R. Mascola, M.D., deputy director of the Vaccine Research Center at the National Institute of Allergy and Infectious Diseases of the National Institutes of Health, and colleagues.