The subject invention pertains to materials and methods for detecting, preventing and treating retroviral infections in humans and other animals susceptible to infection by retrovirus. It has been discovered that FIV can be transmitted from cats to humans and that the FIV can infect human cells in vivo and that antibodies generated by the infected person cross-react with HIV antigens. Thus, the methods and compositions of the subject invention can be used to detect, prevent and treat FIV infection in humans and other non-feline animals that are susceptible to FIV infection. The methods and compositions of the invention can also be used to prevent and treat infection by HIV in humans.