Comparative genomics and proteomic analyses between lethal and nonlethal strains of Plasmodium berghei

Plasmodium berghei (Pb) XAT, a rodent malaria parasite, is an irradiation-attenuated variant derived from the lethal strain Pb NK65. Differences in genome sequence, protein structure and function between Pb XAT and Pb NK65 are currently unknown. In this study, to investigate genetic alterations in Pb XAT, we performed comparative genomics and proteomics analyses of nonlethal and lethal strains of Pb. We found mutations, such as a deletion mutation in rhoptry-associated protein (rap) 1, and deletion of rap2/3 and skeleton-binding protein 1 (sbp1), in Pb XAT. RAP1 is required for targeting of RAP2 to the rhoptries. However, the contribution of RAP2/3 to the lethality of Plasmodium is unclear. Therefore, we generated RAP1- and RAP2/3-deficient mutants of Pb ANKA, a reference strain of P. berghei. Furthermore, we investigated the effect of RAP1 and RAP2/3 deficiency on the outcome of infection. The parasitemia in mice infected with RAP1-deficient parasites was increased compared to that in control parasite-infected mice during the early phase of infection. However, mice infected with RAP1-deficient parasites survived longer than did control parasite-infected mice. Moreover, mice infected with RAP2/3-deficient parasites showed low levels of parasitemia and ultimately recovered from the infection The aim of this study was to investigate the effect of RAP2/3 expression on the outcome of infection with Pb XAT using a RAP2/3-expressing Pb XAT. Results showed that complementation of RAP2/3 expression in Pb XAT partially restored virulence. Our findings suggest that RAP1 and RAP2/3 contribute to virulence and a decrease in their expression explains the loss of virulence of the Pb XAT strain.