This invention discloses diagnostic, preventative, and treatment therapies of AIDS involving determining whether a subject exhibits an HLA-Cw7-restricted CTL response. Some methods are directed to the use of HLA-Cw7 as a genetic marker for long-term non-progression and amenability to treatment therapies. Diagnostic methods include a method for predicting long term non-progression in an HIV-infected subject. Preventative and treatment methods encompass determining whether a subject exhibits or can exhibit an HLA-Cw7-restricted CTL response. They also encompass ways of eliciting such a response, if necessary. Furthermore, some of the methods involve administering one or more HIV polypeptides or peptides, or polynucleotides encoding them, as a treatment therapy to prevent the development of AIDS.