Abstract
Visna virus of sheep and arthritis-encephalitis virus of goats are serologically related but genetically distinct retroviruses which cause slowly progressive diseases in their natural hosts. To localize homologous regions of the DNAs of these two viruses, we constructed a physical map of caprine arthritis-encephalitis virus DNA and aligned it with the viral RNA. Cloned probes of visna virus DNA were then used to localize regions of homology with the caprine arthritis-encephalitis virus DNA. These studies showed homology in the 5' region of the genome encompassing U5 and the gag and pol genes and also in a small region in the env gene. These findings correlate with biological data suggesting that the regions of the DNA which are homologous may be responsible for virus group characteristics such as the closely related virus core antigens. Regions which did not show homology such as large sections in the env gene may represent unique sequences which control highly strain-specific characteristics such as the neutralization antigen and specific cell tropisms.