An ACE2-Based Bimodular Fusion Protein Enables Reorientation of Endogenous Anti-Epstein-Barr Virus Antibodies Toward SARS-CoV-2 Spike.

The use of soluble recombinant angiotensin-converting enzyme 2 (rACE2) as a decoy capable of blocking SARS-CoV-2 entry into cells has been envisaged as a therapeutic strategy to reduce viral loads in patients with severe COVID-19. We engineered a novel form of rACE2, fused to the Epstein-Barr virus antigen P18F3 (rACE2-P18F3), to reorient a preexisting humoral response toward Epstein-Barr virus against SARS-CoV-2 particles. Recombinant ACE2-P18F3 was able to bind to the SARS-CoV-2 spike protein, neutralize viral entry into cells, and promote the phagocytosis of spheres coated with different spike variants by monocytic cells. The results position rACE2-P18F3 as a promising therapeutic candidate to universally block coronavirus cell entry and clear viral particles.

Associations between prenatal malaria exposure, maternal antibodies at birth, and malaria susceptibility during the first year of life in Burkina Faso.

In this study, we investigated how different categories of prenatal malaria exposure (PME) influence levels of maternal antibodies in cord blood samples and the subsequent risk of malaria in early childhood in a birth cohort study (N = 661) nested within the COSMIC clinical trial (NCT01941264) in Burkina Faso. Plasmodium falciparum infections during pregnancy and infants' clinical malaria episodes detected during the first year of life were recorded. The levels of maternal IgG and IgG1-4 to 15 P. falciparum antigens were measured in cord blood by quantitative suspension array technology. Results showed a significant variation in the magnitude of maternal antibody levels in cord blood, depending on the PME category, with past placental malaria (PM) more frequently associated with significant increases of IgG and/or subclass levels across three groups of antigens defined as pre-erythrocytic, erythrocytic, and markers of PM, as compared to those from the cord of non-exposed control infants. High levels of antibodies to certain erythrocytic antigens (i.e., IgG to EBA140 and EBA175, IgG1 to EBA175 and MSP142, and IgG3 to EBA140 and MSP5) were independent predictors of protection from clinical malaria during the first year of life. By contrast, high levels of IgG, IgG1, and IgG2 to the VAR2CSA DBL1-2 and IgG4 to DBL3-4 were significantly associated with an increased risk of clinical malaria. These findings indicate that PME categories have different effects on the levels of maternal-derived antibodies to malaria antigens in children at birth, and this might drive heterogeneity to clinical malaria susceptibility in early childhood.

Evaluation of Malarial Var2CSA-Displaying Baculovirus Vector in Transduction Efficiency in Human Cancer Cells.

Baculovirus vectors (BVs) are able to use for gene transduction in mammalian cells and are recognized as growing viral vectors for cancer gene therapy applications. The transduction efficiency of BVs varies among cancer cell types. To improve the transduction efficiency of BVs in human cancer cells, BV displaying malarial variant surface antigen 2-chondroitin sulfate A (var2CSA) molecules was developed in this study. Var2CSA plays a critical role in the sequestration of Plasmodium falciparum-infected erythrocytes in the placenta. Moreover, var2CSA binds to cancer cells via placenta-like chondroitin sulfate A (CSA), but not to non-cancer cells. Var2CSA BV showed significantly higher gene transduction than control BV in HepG2 and Huh7 cells, human hepatic cancer cells as well as AsPC-1 cells, human pancreatic cancer cells. The transduction efficiency of var2CSA BV was significantly inhibited by the anti-gp64 antibody, free heparin, and CSA. The results of this study suggest that var2CSA BV would be an improved vector for cancer gene therapies, especially in the treatment of hepatic and pancreatic cancers.

An Invariant Protein That Colocalizes With VAR2CSA on Plasmodium falciparum-Infected Red Cells Binds to Chondroitin Sulfate A.

BACKGROUND: Plasmodium falciparum-infected red blood cells (iRBCs) bind and sequester in deep vascular beds, causing malaria-related disease and death. In pregnant women, VAR2CSA binds to chondroitin sulfate A (CSA) and mediates placental sequestration, making it the major placental malaria (PM) vaccine target. METHODS: In this study, we characterize an invariant protein associated with PM called P falciparum chondroitin sulfate A ligand (PfCSA-L). RESULTS: Recombinant PfCSA-L binds both placental CSA and VAR2CSA with nanomolar affinity, and it is coexpressed on the iRBC surface with VAR2CSA. Unlike VAR2CSA, which is anchored by a transmembrane domain, PfCSA-L is peripherally associated with the outer surface of knobs through high-affinity protein-protein interactions with VAR2CSA. This suggests that iRBC sequestration involves complexes of invariant and variant surface proteins, allowing parasites to maintain both diversity and function at the iRBC surface. CONCLUSIONS: The PfCSA-L is a promising target for intervention because it is well conserved, exposed on infected cells, and expressed and localized with VAR2CSA.

Gravidity and malaria trends interact to modify P. falciparum densities and detectability in pregnancy: a 3-year prospective multi-site observational study.

BACKGROUND: Low-density Plasmodium falciparum infections prevail in low transmission settings, where immunity is expected to be minimal, suggesting an immune-independent effect on parasite densities. We aimed to describe parasite densities in pregnancy, and determine how gravidity and antibody-mediated immunity affect these, during a period of declining malaria transmission in southern Mozambique. METHODS: We documented P. falciparum infections at first antenatal care visits (n = 6471) between November 2016 and October 2019 in Ilha Josina (high-to-moderate transmission area), Manhiça (low transmission area), and Magude (pre-elimination area). Two-way interactions in mixed-effects regression models were used to assess gravidity-dependent differences in quantitative PCR-determined P. falciparum positivity rates (PfPRqPCR) and densities, in the relative proportion of detectable infections (pDi) with current diagnostic tests (≥ 100 parasites/µL) and in antimalarial antibodies. RESULTS: PfPRqPCR declined from 28 to 13% in Ilha Josina and from 5-7 to 2% in Magude and Manhiça. In primigravidae, pDi was highest in Ilha Josina at the first study year (p = 0.048), which declined with falling PfPRqPCR (relative change/year: 0.41, 95% CI [0.08; 0.73], p = 0.029), with no differences in antibody levels. Higher parasite densities in primigravidae from Ilha Josina during the first year were accompanied by a larger reduction of maternal hemoglobin levels (- 1.60, 95% CI [- 2.49; - 0.72; p < 0.001), than in Magude (- 0.76, 95% CI [- 1.51; - 0.01]; p = 0.047) and Manhiça (- 0.44, 95% CI [- 0.99; 0.10; p = 0.112). In contrast, multigravidae during the transmission peak in Ilha Josina carried the lowest pDi (p = 0.049). As PfPRqPCR declined, geometric mean of parasite densities increased (4.63, 95% CI [1.28; 16.82], p = 0.020), and antibody levels declined among secundigravidae from Ilha Josina. CONCLUSIONS: The proportion of detectable and clinically relevant infections is the highest in primigravid women from high-to-moderate transmission settings and decreases with declining malaria. In contrast, the falling malaria trends are accompanied by increased parasite densities and reduced humoral immunity among secundigravidae. Factors other than acquired immunity thus emerge as potentially important for producing less detectable infections among primigravidae during marked declines in malaria transmission.

Phosphorylation of the VAR2CSA extracellular region is associated with enhanced adhesive properties to the placental receptor CSA.

Plasmodium falciparum is the main cause of disease and death from malaria. P. falciparum virulence resides in the ability of infected erythrocytes (IEs) to sequester in various tissues through the interaction between members of the polymorphic P. falciparum erythrocyte membrane protein 1 (PfEMP1) adhesin family to various host receptors. Here, we investigated the effect of phosphorylation of variant surface antigen 2-CSA (VAR2CSA), a member of the PfEMP1 family associated to placental sequestration, on its capacity to adhere to chondroitin sulfate A (CSA) present on the placental syncytium. We showed that phosphatase treatment of IEs impairs cytoadhesion to CSA. MS analysis of recombinant VAR2CSA phosphosites prior to and after phosphatase treatment, as well as of native VAR2CSA expressed on IEs, identified critical phosphoresidues associated with CSA binding. Site-directed mutagenesis on recombinant VAR2CSA of 3 phosphoresidues localised within the CSA-binding region confirmed in vitro their functional importance. Furthermore, using clustered regularly interspaced short palindromic repeats/CRISPR-associated protein-9 nuclease (CRISPR/Cas9), we generated a parasite line in which the phosphoresidue T934 is changed to alanine and showed that this mutation strongly impairs IEs cytoadhesion to CSA. Taken together, these results demonstrate that phosphorylation of the extracellular region of VAR2CSA plays a major role in IEs cytoadhesion to CSA and provide new molecular insights for strategies aiming to reduce the morbidity and mortality of PM.

RTS,S/AS01E immunization increases antibody responses to vaccine-unrelated Plasmodium falciparum antigens associated with protection against clinical malaria in African children: a case-control study.

BACKGROUND: Vaccination and naturally acquired immunity against microbial pathogens may have complex interactions that influence disease outcomes. To date, only vaccine-specific immune responses have routinely been investigated in malaria vaccine trials conducted in endemic areas. We hypothesized that RTS,S/A01E immunization affects acquisition of antibodies to Plasmodium falciparum antigens not included in the vaccine and that such responses have an impact on overall malaria protective immunity. METHODS: We evaluated IgM and IgG responses to 38 P. falciparum proteins putatively involved in naturally acquired immunity to malaria in 195 young children participating in a case-control study nested within the African phase 3 clinical trial of RTS,S/AS01E (MAL055 NCT00866619) in two sites of different transmission intensity (Kintampo high and Manhiça moderate/low). We measured antibody levels by quantitative suspension array technology and applied regression models, multimarker analysis, and machine learning techniques to analyze factors affecting their levels and correlates of protection. RESULTS: RTS,S/AS01E immunization decreased antibody responses to parasite antigens considered as markers of exposure (MSP142, AMA1) and levels correlated with risk of clinical malaria over 1-year follow-up. In addition, we show for the first time that RTS,S vaccination increased IgG levels to a specific group of pre-erythrocytic and blood-stage antigens (MSP5, MSP1 block 2, RH4.2, EBA140, and SSP2/TRAP) which levels correlated with protection against clinical malaria (odds ratio [95% confidence interval] 0.53 [0.3-0.93], p = 0.03, for MSP1; 0.52 [0.26-0.98], p = 0.05, for SSP2) in multivariable logistic regression analyses. CONCLUSIONS: Increased antibody responses to specific P. falciparum antigens in subjects immunized with this partially efficacious vaccine upon natural infection may contribute to overall protective immunity against malaria. Inclusion of such antigens in multivalent constructs could result in more efficacious second-generation multistage vaccines.

Optimization of incubation conditions of Plasmodium falciparum antibody multiplex assays to measure IgG, IgG1-4, IgM and IgE using standard and customized reference pools for sero-epidemiological and vaccine studies.

BACKGROUND: The quantitative suspension array technology (qSAT) is a useful platform for malaria immune marker discovery. However, a major challenge for large sero-epidemiological and malaria vaccine studies is the comparability across laboratories, which requires the access to standardized control reagents for assay optimization, to monitor performance and improve reproducibility. Here, the Plasmodium falciparum antibody reactivities of the newly available WHO reference reagent for anti-malaria human plasma (10/198) and of additional customized positive controls were examined with seven in-house qSAT multiplex assays measuring IgG, IgG1-4 subclasses, IgM and IgE against a panel of 40 antigens. The different positive controls were tested at different incubation times and temperatures (4 °C overnight, 37 °C 2 h, room temperature 1 h) to select the optimal conditions. RESULTS: Overall, the WHO reference reagent had low IgG2, IgG4, IgM and IgE, and also low anti-CSP antibody levels, thus this reagent was enriched with plasmas from RTS,S-vaccinated volunteers to be used as standard for CSP-based vaccine studies. For the IgM assay, another customized plasma pool prepared with samples from malaria primo-infected adults with adequate IgM levels proved to be more adequate as a positive control. The range and magnitude of IgG and IgG1-4 responses were highest when the WHO reference reagent was incubated with antigen-coupled beads at 4 °C overnight. IgG levels measured in the negative control did not vary between incubations at 37 °C 2 h and 4 °C overnight, indicating no difference in unspecific binding. CONCLUSIONS: With this study, the immunogenicity profile of the WHO reference reagent, including seven immunoglobulin isotypes and subclasses, and more P. falciparum antigens, also those included in the leading RTS,S malaria vaccine, was better characterized. Overall, incubation of samples at 4 °C overnight rendered the best performance for antibody measurements against the antigens tested. Although the WHO reference reagent performed well to measure IgG to the majority of the common P. falciparum blood stage antigens tested, customized pools may need to be used as positive controls depending on the antigens (e.g. pre-erythrocytic proteins of low natural immunogenicity) and isotypes/subclasses (e.g. IgM) under study.

Parasites Causing Cerebral Falciparum Malaria Bind Multiple Endothelial Receptors and Express EPCR and ICAM-1-Binding PfEMP1.

Background: Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) mediates the binding and accumulation of infected erythrocytes (IE) to blood vessels and tissues. Specific interactions have been described between PfEMP1 and human endothelial proteins CD36, intercellular adhesion molecule-1 (ICAM-1), and endothelial protein C receptor (EPCR); however, cytoadhesion patterns typical for pediatric malaria syndromes and the associated PfEMP1 members are still undefined. Methods: In a cohort of 94 hospitalized children with malaria, we characterized the binding properties of IE collected on admission, and var gene transcription using quantitative polymerase chain reaction. Results: IE from patients with cerebral malaria were more likely to bind EPCR and ICAM-1 than IE from children with uncomplicated malaria (P = .007). The level of transcripts encoding CIDRα1.4 and CIDRα1.5 domain subclasses was higher in patients with severe disease (P < .05). IE populations exhibiting binding to all 3 receptors had higher levels of transcripts encoding PfEMP1 with CIDRα1.4 and Duffy binding-like (DBL)-ß3 domains than parasites, which only bound CD36. Conclusions: These results underpin the significance of EPCR binding in pediatric malaria patients that require hospital admission, and support the notion that complementary receptor interactions of EPCR binding PfEMP1with ICAM-1 amplifies development of severe malaria symptoms.

Murine Model for Preclinical Studies of Var2CSA-Mediated Pathology Associated with Malaria in Pregnancy.

Plasmodium falciparum infection during pregnancy leads to abortions, stillbirth, low birth weight, and maternal mortality. Infected erythrocytes (IEs) accumulate in the placenta by adhering to chondroitin sulfate A (CSA) via var2CSA protein exposed on the P. falciparum IE membrane. Plasmodium berghei IE infection in pregnant BALB/c mice is a model for severe placental malaria (PM). Here, we describe a transgenic P. berghei parasite expressing the full-length var2CSA extracellular region (domains DBL1X to DBL6ε) fused to a P. berghei exported protein (EMAP1) and characterize a var2CSA-based mouse model of PM. BALB/c mice were infected at midgestation with different doses of P. berghei-var2CSA (P. berghei-VAR) or P. berghei wild-type IEs. Infection with 10(4) P. berghei-VAR IEs induced a higher incidence of stillbirth and lower fetal weight than P. berghei At doses of 10(5) and 10(6) IEs, P. berghei-VAR-infected mice showed increased maternal mortality during pregnancy and fetal loss, respectively. Parasite loads in infected placentas were similar between parasite lines despite differences in maternal outcomes. Fetal weight loss normalized for parasitemia was higher in P. berghei-VAR-infected mice than in P. berghei-infected mice. In vitro assays showed that higher numbers of P. berghei-VAR IEs than P. berghei IEs adhered to placental tissue. Immunization of mice with P. berghei-VAR elicited IgG antibodies reactive to DBL1-6 recombinant protein, indicating that the topology of immunogenic epitopes is maintained between DBL1-6-EMAP1 on P. berghei-VAR and recombinant DBL1-6 (recDBL1-6). Our data suggested that impairments in pregnancy caused by P. berghei-VAR infection were attributable to var2CSA expression. This model provides a tool for preclinical evaluation of protection against PM induced by approaches that target var2CSA.

Clinical development of placental malaria vaccines and immunoassays harmonization: a workshop report.

Placental malaria caused by Plasmodium falciparum infection constitutes a major health problem manifesting as severe disease and anaemia in the mother, impaired fetal development, low birth weight or spontaneous abortion. Prevention of placental malaria currently relies on two key strategies that are losing efficacy due to spread of resistance: long-lasting insecticide-treated nets and intermittent preventive treatment during pregnancy. A placental malaria vaccine would be an attractive, cost-effective complement to the existing control tools. Two placental malaria vaccine candidates are currently in Phase Ia/b clinical trials. During two workshops hosted by the European Vaccine Initiative, one in Paris in April 2014 and the other in Brussels in November 2014, the main actors in placental malaria vaccine research discussed the harmonization of clinical development plans and of the immunoassays with a goal to define standards that will allow comparative assessment of different placental malaria vaccine candidates. The recommendations of these workshops should guide researchers and clinicians in the further development of placental malaria vaccines.

High-throughput screening platform identifies small molecules that prevent sequestration of Plasmodium falciparum-infected erythrocytes.

BACKGROUND: We developed a 2-step approach to screen molecules that prevent and/or reverse Plasmodium falciparum-infected erythrocyte (IE) binding to host receptors. IE adhesion and sequestration in vasculature causes severe malaria, and therefore antiadhesion therapy might be useful as adjunctive treatment. IE adhesion is mediated by the polymorphic family (approximately 60 members) of P. falciparum EMP1 (PfEMP1) multidomain proteins. METHODS: We constructed sets of PfEMP1 domains that bind ICAM-1, CSA, or CD36, receptors that commonly support IE binding. Combinations of domain-coated beads were assayed by Bio-Plex technology as a high-throughput molecular platform to screen antiadhesion molecules (antibodies and small molecules). Molecules identified as so-called hits in the screen (first step) then could be assayed individually for inhibition of binding of live IE to receptors (second step). RESULTS: In proof-of-principle studies, the antiadhesion activity of several antibodies was concordant in Bio-Plex and live IE assays. Using this 2-step approach, we identified several molecules in a small molecule library of 10 000 compounds that could inhibit and reverse binding of IEs to ICAM-1 and CSA receptors. CONCLUSION: This 2-step screening approach should be efficient for identification of antiadhesion drug candidates for falciparum malaria.

Parity-dependent recognition of DBL1X-3X suggests an important role of the VAR2CSA high-affinity CSA-binding region in the development of the humoral response against placental malaria.

Plasmodium falciparum multidomain protein VAR2CSA stands today as the leading vaccine candidate against pregnancy-associated malaria (PAM). Most of the studies aiming to decrypt how naturally acquired immunity develops have assessed the immune recognition of individual VAR2CSA Duffy-binding-like (DBL) domains, thus overlooking the presence of conformational epitopes resulting from the overall folding of the full-length protein. In order to characterize the development of humoral immunity toward VAR2CSA, we made use of a large cohort of 293 Senegalese pregnant women to assess the level of recognition by plasma IgG of the full-length VAR2CSA protein of the 3D7 parasite strain (3D7-VAR2CSA), the CSA-binding multidomains 3D7-DBL1X to -DBL3X (3D7-DBL1X-3X), and the CSA nonbinding multidomains 3D7-DBL4ε to -DBL6ε (3D7-DBL4ε-6ε), as well as individual 3D7-DBL domains. Our results revealed a parity-dependent recognition of the full-length 3D7-VAR2CSA and of the CSA-binding region, 3D7-DBL1X-3X. Indeed, multigravid women possess significantly higher levels of antibodies directed against these constructs than primigravidae. Our results suggest an important role of antibodies targeting the CSA-binding region in the development of immunity against PAM, therefore providing new insights on how natural protection might be acquired and further information for the design of VAR2CSA-based vaccines.

Beninese children with cerebral malaria do not develop humoral immunity against the IT4-VAR19-DC8 PfEMP1 variant linked to EPCR and brain endothelial binding.

BACKGROUND: Malaria is still one of the most prevalent infectious diseases in the world. Sequestration of infected erythrocytes (IEs) is the prime mediator of disease. Cytoadhesion of IEs is mediated by members of the highly diverse Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1). A restricted sub-set of var genes encoding for PfEMP1s possessing the domain cassettes DC8 and DC13 were found to bind to the endothelial protein C receptor (EPCR). These var genes were shown to be highly expressed by parasites from patients with severe malaria clinical outcomes compared to those from patients with uncomplicated symptoms. METHODS: In order to further study the molecular mechanisms underlying DC8/DC13 expressing IEs adhesion to EPCR, a method was developed to produce highly pure recombinant EPCR. The IT4 parasite strain was selected on either anti-IT4-VAR19 purified IgG, EPCR or human brain endothelial cell line and their var gene expression profiles as well as their binding phenotypes were compared. The N-terminal region of IT4-VAR19 comprising a full-length DC8 cassette as well as the single EPCR binding CIDRα1.1 domain were also produced, and their immune recognition (IgG) was assessed using plasma samples from Beninese children presenting acute mild malaria, severe malaria or cerebral malaria at the time of their admission to the clinic, and from convalescent-phase plasma collected 30 days after anti-malarial treatment. RESULTS: The multi-domain VAR19-NTS-DBLγ6 binds to EPCR with a greater affinity than the CIDRα1.1 domain alone and this study also demonstrates that VAR19-NTS-DBLγ6 binding to the EPCR-expressing endothelial cell line (HBEC5i) is more pronounced than that of the CIDRα1.1 domain alone. IT4-VAR19 represents the preferentially expressed-PfEMP1 when FCR3-IEs are selected based on their capability to bind EPCR. Notably, no significant difference in the levels of antibodies towards IT4-VAR19 antigens was observed within all clinical groups between plasma samples collected during the acute malaria phase compared to samples collected 30 days after anti-malaria treatment. CONCLUSIONS: These data indicate that even being the preferentially selected IT4-EPCR-binding variant, the IT4-VAR19-DC8 region does not appear to be associated with the acquisition of antibodies during a single severe paediatric malaria episode in Benin.

Placental cytokine and chemokine profiles reflect pregnancy outcomes in women exposed to Plasmodium falciparum infection.

Pregnancy-associated malaria (PAM) can lead to severe complications for both mother and baby. Certain placental cytokine/chemokine profiles have been shown to reflect poor pregnancy outcomes, including maternal anemia and low birth weight. In intervillous plasma samples from 400 Beninese women living in an area where Plasmodium falciparum is endemic, we quantified 16 cytokines/chemokines. We assessed their profiles in groups with PAM, with maternal anemia, with preterm births, or with a low birth weight for gestational age. Repeated ultrasound measurements ensured that prematurity and low birth weight were highly accurate. Preliminary analyses revealed trends for lower cytokine/chemokine concentrations in placental plasma associated both with babies with low birth weight for gestational age and with P. falciparum infection during pregnancy, while, as a function of the latter, the concentration of gamma interferon (IFN-γ)-inducible protein 10 (IP-10) was higher. Multivariate analyses showed that (i) higher placental plasma interleukin-10 (IL-10) levels were associated with P. falciparum infections and (ii) independently of P. falciparum infections, lower concentrations of both IFN-γ and IL-5 were associated with low birth weight for gestational age. Our data further strengthen the idea that IL-10 and IP-10 could be useful diagnostic markers of P. falciparum infection during pregnancy. The concentrations of cytokines/chemokines in placental plasma may represent previously unrecognized markers of poor fetal growth.

JK-1, a useful erythroleukemic cell line model to study a controlled erythroid differentiation from progenitors to terminal erythropoiesis.

New hematopoietic cell models have recently emerged through immortalization of CD34 cells to study and understand various molecular mechanisms of erythropoiesis. Here, we characterize the JK-1 CML-derived cell line, previously shown to spontaneously differentiate without cytokines. Using an epigenetic differentiation inhibitor that keeps JK-1 in an early differentiation phase, we characterized 2 progenitor stages: BFU-E JK-1 and CFU-E JK-1 with CD34+/CD36- and CD34-/CD36 + phenotypes respectively. Then, using the PFI-1 inducer known to synchronously control the terminal differentiation of JK-1 cells, 5 precursor stages were obtained (ProE, Baso1-2, PolyC, OrthoC) and characterized via cell morphology, CD49a and Band3 markers. Enlarged phenotyping was carried out for the earlier phase, and expression kinetics of membrane proteins such as RhAG, RhD/CE, CD47, DARC and CD44 were performed on each stage of the terminal phase. Furthermore, since JK-1 offers the unique property of covering a broad spectrum of differentiation stages, we explored deeper the GATA2/GATA1 and the non-erythroid/erythroid spectrin 'switching'. The possibility of obtaining large quantities of JK-1 cells at each stage of differentiation, as shown in this study, as well as the potential to genetically modify these cells, via CrisprCas9, makes their use of considerable interest for studying pathologies occurring during erythropoiesis.

Sustained clinical benefit of malaria chemoprevention with sulfadoxine-pyrimethamine (SP) in pregnant women in a region with high SP resistance markers.

OBJECTIVE: The effectiveness of intermittent preventive treatment of malaria in pregnancy with sulfadoxine-pyrimethamine (IPTp-SP) is threatened by increasing SP-resistance in Africa. We assessed the level of SP-resistance markers, and the clinical and parasitological effectiveness of IPTp-SP in southern Mozambique. METHODS: P. falciparum infection, antimalarial antibodies and dhfr/dhps SP-resistance mutants were detected by quantitative polymerase chain reaction (qPCR), suspension array technology and targeted deep sequencing, respectively, among 4016 HIV-negative women in Maputo province (2016-2019). Univariate and multivariate regression models were used to assess the association between taking the recommended three or more IPTp-SP doses (IPTp3+) and parasitological and clinical outcomes. RESULTS: 84.3% (3385/4016) women received three or more IPTp-SP doses. The prevalence of quintuple mutants at first antenatal care (ANC) visit was 94.2%. IPTp3+ was associated with a higher clearance rate of qPCR-detected infections from first ANC visit to delivery (adjusted odds ratio [aOR]=5.9, 95% CI: 1.5-33.3; p = 0.012), lower seroprevalence at delivery of antibodies against the pregnancy-specific antigen VAR2CSADBL34 (aOR=0.72, 95% CI: 0.54-0.95; p = 0.022), and lower prevalence of low birth weight deliveries (aOR: 0.61, 95% CI: 0.41-0.90; p = 0.013). CONCLUSION: A sustained parasitological effect of IPTp-SP contributes to the clinical effectiveness of IPTp3+ in areas with high prevalence of SP-resistance markers.

Production, crystallization and X-ray diffraction analysis of two nanobodies against the Duffy binding-like (DBL) domain DBL6ℇ-FCR3 of the Plasmodium falciparum VAR2CSA protein.

The VAR2CSA protein has been closely associated with pregnancy-associated malaria and is recognized as the main adhesin exposed on the surface of Plasmodium falciparum-infected erythrocytes. Chondroitin sulfate A was identified as the main host receptor in the placenta. Single-domain heavy-chain camelid antibodies, more commonly called nanobodies, were selected and produced against the DBL6ℇ-FCR3 domain of VAR2CSA. Crystals of two specific nanobodies, Nb2907 and Nb2919, identified as strong binders to DBL6ℇ-FCR3 and the full-length VAR2CSA exposed on the surface of FCR3 P. falciparum-infected erythrocytes, were obtained. Crystals of Nb2907 diffract to 2.45 Šresolution and belong to space group C2 with unit-cell parameters a=136.1, b=78.5, c=103.4 Å, ß=118.8°, whereas Nb2919 crystals diffract to 2.15 Šresolution and belong to space group P43212 with unit-cell parameters a=b=62.7, c=167.2 Å.

Full-length extracellular region of the var2CSA variant of PfEMP1 is required for specific, high-affinity binding to CSA.

Pregnancy-associated malaria (PAM) is a serious consequence of sequestration of Plasmodium falciparum-parasitized erythrocytes (PE) in the placenta through adhesion to chondroitin sulfate A (CSA) present on placental proteoglycans. Recent work implicates var2CSA, a member of the PfEMP1 family, as the mediator of placental sequestration and as a key target for PAM vaccine development. Var2CSA is a 350 kDa transmembrane protein, whose extracellular region includes six Duffy-binding-like (DBL) domains. Due to its size and high cysteine content, the full-length var2CSA extracellular region has not hitherto been expressed in heterologous systems, thus limiting investigations to individual recombinant domains. Here we report for the first time the expression of the full-length var2CSA extracellular region (domains DBL1X to DBL6epsilon) from the 3D7 parasite strain using the human embryonic kidney 293 cell line. We show that the recombinant extracellular var2CSA region is correctly folded and that, unlike the individual DBL domains, it binds with high affinity and specificity to CSA (K(D) = 61 nM) and efficiently inhibits PE from binding to CSA. Structural characterization by analytical ultracentrifugation and small-angle x-ray scattering reveals a compact organization of the full-length protein, most likely governed by specific interdomain interactions, rather than an extended structure. Collectively, these data suggest that a high-affinity, CSA-specific binding site is formed by the higher-order structure of the var2CSA extracellular region. These results have important consequences for the development of an effective vaccine and therapeutic inhibitors.

Expression and Purification of scFv2H7-P18F3, a Bi-Modular Fusion Protein (BMFP) Targeting Human CD20.

P18F3-based bi-modular fusion proteins (BMFPs), designed to re-direct pre-existing anti-Epstein-Barr virus (EBV) endogenous polyclonal antibodies towards defined target cells, demonstrated efficient biological activity in a mouse tumor model and could potentially represent a universal and versatile platform to develop novel therapeutics against a broad range of diseases. This protocol provides step-by-step instructions for expressing scFv2H7-P18F3, a BMFP targeting human CD20, in Escherichia coli (SHuffle®), and for purifying soluble proteins using a two-step process, namely immobilized metal affinity chromatography (IMAC) followed by size exclusion chromatography. This protocol can also be used for expression and purification of other BMFPs with alternative binding specificities.