More than one-third of the world's population is exposed to Plasmodium vivax malaria, mainly in Asia1. P. vivax preferentially invades reticulocytes (immature red blood cells)2-4. Previous work has identified 11 parasite proteins involved in reticulocyte invasion, including erythrocyte binding protein 2 (ref. 5) and the reticulocyte-binding proteins (PvRBPs)6-10. PvRBP2b binds to the transferrin receptor CD71 (ref. 11), which is selectively expressed on immature reticulocytes12. Here, we identified CD98 heavy chain (CD98), a heteromeric amino acid transporter from the SLC3 family (also known as SLCA2), as a reticulocyte-specific receptor for the PvRBP2a parasite ligand using mass spectrometry, flow cytometry, biochemical and parasite invasion assays. We characterized the expression level of CD98 at the surface of immature reticulocytes (CD71+) and identified an interaction between CD98 and PvRBP2a expressed at the merozoite surface. Our results identify CD98 as an additional host membrane protein, besides CD71, that is directly associated with P. vivax reticulocyte tropism. These findings highlight the potential of using PvRBP2a as a vaccine target against P. vivax malaria.
© 2021. The Author(s), under exclusive licence to Springer Nature Limited.

Oxidative stress perturbs vascular homeostasis leading to endothelial dysfunction and cardiovascular diseases. Vascular reactive oxygen species (ROS) reduce nitric oxide (NO) bioactivity, a hallmark of cardiovascular and metabolic diseases. We measured steady-state vascular NO levels through the quantification of heme nitrosylated hemoglobin (5-coordinate-α-HbNO) in venous erythrocytes of healthy human subjects using electron paramagnetic resonance (EPR) spectroscopy. To examine how ROS may influence HbNO complex formation and stability, we identified the pro- and anti-oxidant enzymatic sources in human erythrocytes and their relative impact on intracellular redox state and steady-state HbNO levels. We demonstrated that pro-oxidant enzymes such as NADPH oxidases are expressed and produce a significant amount of ROS at the membrane of healthy erythrocytes. In addition, the steady-state levels of HbNO were preserved when NOX (e.g. NOX1 and NOX2) activity was inhibited. We next evaluated the impact of selective antioxidant enzymatic systems on HbNO stability. Peroxiredoxin 2 and catalase, in particular, played an important role in endogenous and exogenous H2O2 degradation, respectively. Accordingly, inhibitors of peroxiredoxin 2 and catalase significantly decreased erythrocyte HbNO concentration. Conversely, steady-state levels of HbNO were preserved upon supplying erythrocytes with exogenous catalase. These findings support HbNO measurements as indicators of vascular oxidant stress and of NO bioavailability and potentially, as useful biomarkers of early endothelial dysfunction.
Copyright © 2019 The Authors. Published by Elsevier B.V. All rights reserved.

Neutrophils are short-lived cells that play important roles in both health and disease. Neutrophils and monocytes originate from the granulocyte monocyte progenitor (GMP) in bone marrow; however, unipotent neutrophil progenitors are not well defined. Here, we use cytometry by time of flight (CyTOF) and single-cell RNA sequencing (scRNA-seq) methodologies to identify a committed unipotent early-stage neutrophil progenitor (NeP) in adult mouse bone marrow. Importantly, we found a similar unipotent NeP (hNeP) in human bone marrow. Both NeP and hNeP generate only neutrophils. NeP and hNeP both significantly increase tumor growth when transferred into murine cancer models, including a humanized mouse model. hNeP are present in the blood of treatment-naive melanoma patients but not of healthy subjects. hNeP can be readily identified by flow cytometry and could be used as a biomarker for early cancer discovery. Understanding the biology of hNeP should allow the development of new therapeutic targets for neutrophil-related diseases, including cancer.
Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

In vitro erythroid differentiation from primary human cells is valuable to develop genetic strategies for hemoglobin disorders. However, current erythroid differentiation methods are encumbered by modest transduction rates and high baseline fetal hemoglobin production. In this study, we sought to improve both genetic modification and hemoglobin production among human erythroid cells in vitro. To model therapeutic strategies, we transduced human CD34+ cells and peripheral blood mononuclear cells (PBMCs) with lentiviral vectors and compared erythropoietin-based erythroid differentiation using fetal-bovine-serum-containing media and serum-free media. We observed more efficient transduction (85%-93%) in serum-free media than serum-containing media (20%-69%), whereas the addition of knockout serum replacement (KSR) was required for serum-free media to promote efficient erythroid differentiation (96%). High-level adult hemoglobin production detectable by electrophoresis was achieved using serum-free media similar to serum-containing media. Importantly, low fetal hemoglobin production was observed in the optimized serum-free media. Using KSR-containing, serum-free erythroid differentiation media, therapeutic adult hemoglobin production was detected at protein levels with β-globin lentiviral transduction in both CD34+ cells and PBMCs from sickle cell disease subjects. Our in vitro erythroid differentiation system provides a practical evaluation platform for adult hemoglobin production among human erythroid cells following genetic manipulation.

The role of Notch signaling in human innate lymphoid cell (ILC) differentiation is unclear, although IL-7 and IL-15 promote differentiation of natural cytotoxicity receptor (NCR) NKp44+ group 3 ILCs (NCR+ILC3s) and conventional NK (cNK) cells from CD34+ hematopoietic progenitor cells (HPCs) ex vivo. In this study, we analyzed the functions of Notch in the differentiation of NCR+ILC3s and cNK cells from human HPC subpopulations circulating in peripheral blood by limiting dilution and clonal assays using high-throughput flow cytometry. We demonstrated that Notch signaling in combination with IL-7 induced NCR+ILC3 differentiation, but conversely suppressed IL-15-dependent cNK cell generation in CD45RA+Flt-3-c-Kitlow, a novel innate lymphocyte-committed HPC subpopulation. In contrast, Notch signaling induced CD45RA-Flt-3+c-Kithigh multipotent HPCs to generate CD34+CD7+CD62Lhigh, the earliest thymic progenitor-like cells, which preserved high cNK/T cell potential, but lost NCR+ILC3 potential. These findings implicate the countervailing functions of Notch signaling in the fate decision between NCR+ILC3 and cNK cell lineages at different maturational stages of human HPCs. Inhibition of Notch functions by Abs specific for either the Notch1 or Notch2 negative regulatory region suggested that both Notch1 and Notch2 signals were involved in the fate decision of innate lymphocyte-committed HPCs and in the generation of earliest thymic progenitor-like cells from multipotent HPCs. Furthermore, the synergistic interaction between Notch and IL-7 in NCR+ILC3 commitment was primarily explicable by the induction of IL-7 receptor expression in the innate lymphocyte-committed HPCs by Notch stimulation, suggesting the pivotal role of Notch in the transcriptional control required for human NCR+ILC3 commitment.
Copyright © 2017 by The American Association of Immunologists, Inc.