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. 2023 Jan 4:13:1083467.
doi: 10.3389/fmicb.2023.1083467. eCollection 2022.

Enhanced phosphatidylserine exposure and erythropoiesis in Babesia microti-infected mice

Peng Song  1   2   3   4 , Yu-Chun Cai  1   2   3 , Mu-Xin Chen  1   2   3   4 , Shao-Hong Chen  1   2   3 , Jia-Xu Chen  1   2   3   4
Affiliations

Enhanced phosphatidylserine exposure and erythropoiesis in Babesia microti-infected mice

Peng Song et al. Front Microbiol. .

Erratum in

Abstract

Introduction: Babesia microti (B. microti) is the dominant species responsible for human babesiosis, which is associated with severe hemolytic anemia and splenomegaly because it infects mammalian erythrocytes. The actual prevalence of B. microti is thought to have been substantially underestimated.

Methods: In this study, Bagg's albino/c (BALB/c) mice were intraperitoneally injected with B. microti-infected erythrocytes, and parasitemia was subsequently measured by calculating the proportion of infected erythrocytes. The ultrastructure of infected erythrocytes was observed using scanning and transmission electron microscopes. Quantifying phosphatidylserine (PS) exposure, oxidative stress, intracellular Ca2+, and erythropoiesis of erythrocytes were done using flow cytometry. The physiological indicators were analyzed using a Mindray BC-5000 Vet automatic hematology analyzer.

Results: Of note, 40.7 ± 5.9% of erythrocytes changed their structure and shrunk in the B. microti-infected group. The percentage of annexin V-positive erythrocytes and the levels of reactive oxygen species (ROS) in the erythrocytes were higher in the B. microti-infected group than in the control group at 10 dpi. Significant splenomegaly and severe anemia were also observed following B. microti infection. The parasitemia level in the B. microti-infected splenectomized group was higher than that of the B. microti-infected sham group. The population of early erythroblasts increased, and the late erythroblasts decreased in both the bone marrow and spleen tissues of the B. microti-infected group at 10 dpi.

Discussion: PS exposure and elevated ROS activities were hallmarks of eryptosis in the B. microti-infected group. This study revealed for the first time that B. microti could also induce eryptosis. At the higher parasitemia phase, the occurrence of severe anemia and significant changes in the abundance of erythroblasts in B. microti-infected mice group were established. The spleen plays a critical protective role in controlling B. microti infection and preventing anemia. B. microti infection could cause a massive loss of late erythroblasts and induce erythropoiesis.

Keywords: Babesia microti; babesiosis; eryptosis; erythrocyte; erythropoiesis.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Erythrocyte morphology as seen under a scanning electron microscope (SEM) and transmission electron microscope (TEM). (A) SEM image showing biconcave-shaped erythrocytes of mice in the control group. (B) SEM image showing membrane blebbed erythrocytes of mice in the Babesia microti(B. microti)-infected group. (C) TEM image showing regularly shaped erythrocytes of mice in the control group. (D) TEM image showing the changed shape of erythrocytes of mice in the B. microti-infected group. The scale bar is 1.0  μm. (E) Bar graph showing the arithmetic means ± SD (n = 5) of the proportion of erythrocytes with a blebbing membrane without (white bar) and with (black bars) B. microti infection.
Figure 2
Figure 2
Eryptosis assays after B. microti infection. Line graphs showing that (A) B. microti induced more PS exposure to the cell surface of erythrocytes, (B) ROS levels in the erythrocytes were higher in the B. microti -infected group at 10 dpi, and (C) Calcium ion activity of erythrocytes increased slightly in B. microti-infected group at 10 dpi, but not significantly. The results are expressed as the mean percentage of positive cells ± the standard deviation (SD) from five mice.
Figure 3
Figure 3
Changes in blood parasitemia and parameters after B. microti infection. Line graphs showing (A) the peak parasitemia level of the B. microti-infected splenectomized group was higher than that of the B. microti-infected sham group and persisted for ~6 days, (B) the red blood cell (RBC) count, (C) Hemoglobin concentration (HGB), (D) Red cell distribution width coefficient of variation (RDW-CV), and (E) Red cell distribution width standard deviation (RDW-SD). The results are expressed as the mean ± standard deviation (SD) of five mice.
Figure 4
Figure 4
Erythropoiesis of red blood cells after infection with B. microti. Line graph showing the arithmetic means ± SD of the percentage of Ter119-PE and CD71-FITC labeled bone marrow (A) and splenocytes (B) isolated from mice in the B. microti-infected group.
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