Rodent Malaria Erythrocyte Preference Assessment by an Ex Vivo Tropism Assay

Abstract

Circulating red blood cells consist of young erythrocytes (early and late reticulocytes) and mature erythrocytes (normocytes). The human malaria parasites, Plasmodium falciparum and P. vivax, have a preference to invade reticulocytes during blood-stage infection. Rodent malaria parasites that also prefer reticulocytes could be useful tools to study human malaria reticulocyte invasion. However, previous tropism studies of rodent malaria are inconsistent from one another, making it difficult to compare cell preference of different parasite species and strains. In vivo measurements of cell tropism are also subjected to many confounding factors. Here we developed an ex vivo tropism assay for rodent malaria with highly purified fractions of murine reticulocytes and normocytes. We measured invasion into the different erythrocyte populations using flow cytometry and evaluated the tropism index of the parasite strains. We found that P. berghei ANKA displayed the strongest reticulocyte preference, followed by P. yoelii 17X1.1, whereas P. chabaudi AS and P. vinckei S67 showed mixed tropism. These preferences are intrinsic and were maintained at different reticulocyte and normocyte availabilities. Our study shed light on the true erythrocyte preference of the parasites and paves the way for future investigations on the receptor-ligand interactions mediating erythrocyte tropism.

Host cell maturation modulates parasite invasion and sexual differentiation in Plasmodium berghei

“…In the spleen and blood, this normalization revealed a relative enrichment of intravascular reticulocytes in iRBCs, in line with the previously described preference of P. berghei for reticulocytes (Fig. 1C) ( 16 , 17 ). Although the spleen and bone marrow have high numbers of CD44 + extravascular reticulocytes, only a small fraction of these was infected in initial days of the time course.…”

“…P. berghei has a known tropism for reticulocytes (16,17); consistent with this tropism, we observed a significant enrichment of CD71 + reticulocytes in iRBCs. This host cell tropism was independent of organ, and the observed enrichment of parasites in the spleen could be attributed to the higher abundance of CD71 + reticulocytes in this organ.…”

“…It is thus not unexpected that many Plasmodium species, including the human malaria parasite P. falciparum and the rodent parasite P. berghei , preferentially invade younger RBCs. Some species, including the human malaria parasite P. vivax , are restricted to reticulocytes ( 12 – 14 , 16 , 17 ). In addition, extravascular maturation of gametocytes in the bone marrow and spleen appears to be a common feature of many Plasmodium species ( 18 – 20 ), and gametocytes can develop in erythroid precursors ( 21 , 22 ).…”

The acid ceramidase/ceramide axis controls parasitemia in Plasmodium yoelii-infected mice by regulating erythropoiesis

“…Since global Ac KO mice showed decreased parasitemia, although cell-specific Ac activity did not alter innate and T cell immune responses during P. yoelii infection per se , we analysed whether Ac deletion instead has an effect on the host cells of the parasites. Depending on the species, Plasmodium parasites prefer immature or mature red blood cells for asexual propagation (23). P. yoelii parasites primarily infect reticulocytes, which are defined as Ter119 + CD71 + (24).…”

The acid ceramidase/ceramide axis controls parasitemia in Plasmodium yoelii-infected mice by regulating erythropoiesis

“…Since global Ac KO mice showed decreased parasitemia, although cell-specific Ac activity did not alter innate and T cell immune responses during P. yoelii infection per se, we analyzed whether Ac deletion instead has an effect on the host cells of the parasites. Depending on the species, Plasmodium parasites prefer immature or mature RBCs for asexual propagation ( Leong et al, 2021 ). P. yoelii parasites primarily infect reticulocytes, which are defined as Ter119 + CD71 + ( Martín-Jaular et al, 2013 ).…”