Immunization with recombinant bovine but not mouse prion protein delays the onset of disease in mice inoculated with a mouse-adapted prion.

Host tolerance to endogenous prion protein (PrP) has hampered the development of prion vaccines as PrP is a major component of prions. Indeed, we show that immunization of mice with mouse recombinant PrP elicited no prophylactic effect against a mouse-adapted prion. However, interestingly, mice immunized with recombinant bovine PrP developed the disease significantly later than non-immunized mice after inoculation of a mouse prion. Sheep recombinant PrP exhibited variable prophylactic effects. Mouse recombinant PrP stimulated only very weak antibody responses. In contrast, bovine recombinant PrP was higher immunogenic and produced variable amounts of anti-mouse PrP autoantibodies. Sheep recombinant PrP was also immunogenic but produced more variable amounts of anti-PrP autoantibodies. These results might open a new way for development of prion vaccines.