Abstract: Methods and compositions for treatment, diagnosis, and prevention of a virus comprise administering to a patient antibodies which react with regions of viral proteins and result in neutralization of infectivity and inactivation of functionally essential events in the life cycle of the virus. The antibodies recognize viral epitopes which fail to elicit an immune response in man when encountered through infection or naturally through the environment. In a preferred embodiment, the invention provides compositions and methods useful in the treatment and diagnosis of human immunodeficiency virus (HIV) infections.