Unlike so many other deadly viruses, HIV still lacks a vaccine. The virus has proven especially tricky to prevent with conventional antibodies, in part because it evolves so rapidly in the body. A solution would require coaxing the body into producing a special type of antibody that can act broadly to defeat multiple strains of the virus at once. Scientists have moved closer to attaining that goal with an approach that would rely on genetically engineered immune cells from the patient’s body.