Abstract: This invention provides methods for preventing or treating any disease arising from HIV infection, including AIDS and AIDS-related complex (ARC). The method comprises screening a plurality of donors to identify stem cells with a beneficial gene or genes and then transplanting the therapeutic stem cells into a patient. In preferred embodiments, the beneficial gene encodes a polymorphism that renders cells refractory to HIV infection. The polymorphism may be for a gene that encodes a ligand of a receptor for HIV entry, a product of the HLA complex, or a receptor for HIV entry. The Invention also provides isolated populations of stem cells with beneficial genes for resisting infections.