1. The role of specific retroviral envelope sequences in induction of brain disease has been studied in a mouse retroviral model. Comparison of two closely related viral clones has identified two different envelope regions which are important to disease induction. One region appears to influence the amount of viral protein produced and the other appears to influence the ?toxicity? of the protein in infected brain cells.2. The mouse Rfv-3 gene, which influences the ability of Friend virus infected mice to make neutralizing antibodies to Friend virus, has been mapped in more detail to a specific 0.8cM region on chromosome 15. This location is nearby, but distinct from Ly6 and Wnt7b genes but could not be separated from Il2rb, Il3rb and Pdgfb genes. - Retrovirus, immunity, brain disease, genetics