The invention provides a polynucleotide comprising portions of the genomes of caprine arthritis-encephalitis virus and HIV-1, resulting in a chimeric retrovirus referred to as a "CHIV. " The invention also provides a vaccine comprising a CHIV immunogen and a pharmaceutically acceptable carrier. A method of stimulating an immune response in an individual-against human immunodeficiency virus-1 infection by administering a therapeutically effective amount of a CHIV immunogen is also provided. The invention further provides a method of stimulating an immune response in vitro by contacting a lymphocyte with a therapeutically effective amount of a CHIV immunogen.