Scrapie incubation periods and end-point titers in mouse strains differing at the H-2D locus.

In extending findings on the influence of the mouse H-2D locus on the scrapie incubation period, we showed that with the intracerebral (i.c.) route of injection, SJL and NZW mice (s and z alleles, respectively) had shorter incubation periods than C57BL mice (b allele) at several concentrations of two scrapie strains, ME7 and 139A. The three mouse strains have the same Sinc genotype, s7s7. Incubation period data among the three mouse strains after intraperitoneal (i.p.) injection revealed a different rank order of incubation periods from that seen after i.c. injection. End-point titers in the three mouse strains were similar after i.c. injection, but both scrapie strains yielded very low titers in NZW mice after i.p. injection. There were marked differences between 139A and ME7 incubation periods after both i.c. and i.p. injections in the three mouse genotypes, providing an additional parameter that distinguishes these two scrapie strains.