Unprecedented cure after infection with the lethal Plasmodium berghei ANKA was observed in an F2 progeny generated by intercrossing the wild-derived WLA and the laboratory C57BL/6 mouse strains. Resistant mice were able to clear parasitaemia and establish immunity. The observed resistance was disclosed as a combinatorial effect of genetic factors derived from the two parental strains. Genetic mapping of survival time showed that the WLA allele at a locus on chromosome 1 (colocalizing with Berghei resistance 1 (Berr1), a locus associated with resistance to experimental cerebral malaria) increases the probability to resist early death. Also, the C57Bl/6 allele at a novel locus on chromosome 9 (Berr3) confers overall resistance to this lethal Plasmodium infection. This report underlines the value of using wild-derived mouse strains to identify novel genetic factors in the aetiology of disease phenotypes, and provides a unique model for studying parasite clearance and immunity associated with malaria.
