Phenotypic expression of pyruvate kinase deficiency and protection against malaria in a mouse model

Abstract

The recombinant congenic mouse strains AcB55 and AcB61 are extremely resistant to malaria (Plasmodium chabaudi AS) despite the presence of susceptibility alleles at the known Char1/Char2 resistance loci. Resistance in AcB55 and AcB61 is controlled by a locus on chromosome 3 (Char4) shown to be allelic with or tightly linked to a loss-of-function mutation in pyruvate kinase (Pklr). AcB55 and AcB61 show important splenomegaly prior to infection caused by the expansion of the red pulp, and display histological signs of extramedullary erythropoiesis in the liver. Examination of splenic cell populations by flow cytometry demonstrates elevated numbers of TER119-positive erythroid precursor cells (430% of total spleen cells), while RNA expression studies show elevated expression of erythrocyte-specific transcripts such as globin, transferrin receptor, and Nramp2/Slc11a2 in the spleen of both strains. Hematological profiling in both strains is consistent with the presence of anemia as evidenced by low total erythrocyte counts, decreased hemoglobin, as well as abnormally high numbers of circulating reticulocytes (15-20%). These results strongly suggest that the mutant Pklr allele (Pklr 269A ) of AcB55/61 strains causes hemolytic anemia compensated by constitutive erythropoiesis, which in turn protects the mice against P. chabaudi infection. The possible molecular basis of the Pklr protective effect is discussed and is under current investigation in these two strains.

Incremental expression of Tlr4 correlates with mouse resistance to Salmonella infection and fine regulation of relevant immune genes

“…42 The various cell populations were determined by singlecolor staining of the cells with fluorescein isothiocyanateor phytoerythrin-conjugated monoclonal antibodies against Mac-1 (CD11b, clone M1/70, rat IgG2b), Gr-1 (Ly-6G and Ly-6C, clone RB6-8C5, rat IgG2b), CD3e (clone 145-2C11, hamster IgG1), CD11c (clone HL3, hamster IgG1), CD49b/Pan-NK (clone DX5, rat IgM), I-A b (clone AF6-120.1, mouse (BALB/c) IgG2a) and IgM (clone R6-60.2, rat IgG2a). CD16/CD32 (clone 2.4G2, rat IgG2b) was used before staining to block the nonspecific binding by Fc receptors.…”

Cysteamine, the natural metabolite of pantetheinase, shows specific activity against Plasmodium

“…in (Hernandez-Valladares et al, 2005)]. Using positional cloning, we have shown that the protective effect of the Char4 locus is caused by a loss-of-function mutation in the erythrocyte form of pyruvate kinase ( Pklr I90N ) (Min-Oo et al, 2003; Min-Oo et al, 2004). Likewise, we observed that homozygosity and heterozygosity for mutant alleles at the human PKLR gene also protect against Plasmodium falciparum malaria in erythrocytes ex vivo (Ayi et al, 2008).…”

Mapping of Char10, a novel malaria susceptibility locus on mouse chromosome 9

“…Splenomegaly was apparent and histological analysis revealed breakdown of normal splenic architecture and massive expansion of the red pulp in AcB62 (Figure 2a), all known consequences of PK deficiency. 11 Compared with A/J, AcB62 and AcB55 showed elevated spleen cell counts (twofold to fourfold increase; Figure 2b), and a higher fraction of CD71 þ /TER119 þ doubly positive erythroid precursors (Figure 2c). Owing to an RBC lysis step of spleen cell suspensions performed before labeling, the percentage of erythroid precursor cells is likely under-represented, but nevertheless indicates higher levels of erythroid progenitors in the PK mutant strains compared with A/J mice.…”

“…These parameters suggest the presence of a slightly more severe anemia in AcB62 compared to that which we have reported earlier for AcB55 and AcB61. 11 Like AcB55, and as opposed to A/J controls, AcB62 mice show signs of compensatory erythropoietic activity in the spleen ( Figure 2) and liver (not shown). Splenomegaly was apparent and histological analysis revealed breakdown of normal splenic architecture and massive expansion of the red pulp in AcB62 (Figure 2a), all known consequences of PK deficiency.…”

“…AcB55/AcB61 show signs of anemia even in the absence of P. chabaudi infection, manifested by splenomegaly, extramedullary erythropoiesis, and high levels of reticulocytes in the peripheral blood. 11 Using parasitemia and reticulocyte levels as quantitative traits in informative F2 populations derived from AcB55/ AcB61, a major locus (Char4) was identified that controlled both traits and mapped to the same segment of Chr. 3.…”