The course of infections and pathology in immunomodulated NOD/LtSz-SCID mice inoculated with Plasmodium falciparum laboratory lines and clinical isolates

Human chimeras are potentially invaluable models for hemoprotozoan parasites such as Plasmodium falciparum. The work presented assesses the susceptibility of immunomodulated NOD/LtSz-SCID mice to genetically distinct P. falciparum parasites. To this end, mice grafted with human erythrocytes were inoculated with two P. falciparum laboratory lines, 3D7 and Dd2 and four clinical isolates, ISCIII-230, ISCIII-231, ISCIII-381 and ISCIII-399. The results showed that, without a previous period of parasite adaptation, 100% of the inoculated mice developed an infection, generally self-limited, though some mice died. The parasitemias ranged from 0.05 to 8% and lasted an average of 19 days (15-26 days) depending on the line or isolate studied. Sexual forms of different maturity, stage II-IV and mature gametocytes were observed in the peripheral blood of mice in 22, 50, 25, 72 and 80% of the mice infected with Dd2, ISCIII-399, ISCIII-230, ISCIII-231 and ISCIII-381 isolates, respectively. The study of the clinical symptoms, the haematological parameters and the histopathological changes in the infected mice showed that most of the malaria features were present in the infected mice except that the sequestration of infected erythrocytes was absent or at most a minor phenomenon, as also indicated by the presence of mature forms of the parasites in the peripheral blood. This study shows that the human chimeras allow the complete asexual and sexual erythrocytic cycle of different P. falciparum lines and clinical isolates to be observed in vivo. It opens a new way to investigate any parasite population in terms of infectivity, transmission, and drug resistance.