Important decisions need to be made about the types of antibodies and assays that have greatest relevance to HIV-1 vaccines. Validation experiments in animals models are needed to determine the potential correlative value of new assay technologies that rely on the use of genetically engineered cells lines and Envpseudotyped viruses. Ideally, this would be done by employing several different assays to study the antibody response in a clinical efficacy trial in which the vaccine was at least partially protective. Because no such vaccine is currently available for HIV-1, studies in animal models are the next best choice. In this regard, two animal models are widely used for HIV vaccine development: simian immunodeficiency virus (SIV) and chimeric simian-human immunodeficiency virus (SHIV) infection in monkeys [48] . Quantitative passive transfer experiments in either model with antibodies that exhibit different effector functions could be used to address the biological relevance of in vitro assays. Unfortunately, very few SHIVs are currently available and, among these, most are derived from a single genetic subtype (clade B) and exhibit properties that may not be well suited to assay validation [49] . The creation of new and better SHIVs from non-clade B viruses would facilitate assay standardization as well as vaccine challenge models.