A randomized first-in-human phase I trial of differentially adjuvanted Pfs48/45 malaria vaccines in Burkinabé adults.

BACKGROUNDMalaria transmission-blocking vaccines aim to interrupt the transmission of malaria from one person to another.METHODSThe candidates R0.6C and ProC6C share the 6C domain of the Plasmodium falciparum sexual-stage antigen Pfs48/45. R0.6C utilizes the glutamate-rich protein (GLURP) as a carrier, and ProC6C includes a second domain (Pfs230-Pro) and a short 36-amino acid circumsporozoite protein (CSP) sequence. Healthy adults (n = 125) from a malaria-endemic area of Burkina Faso were immunized with 3 intramuscular injections, 4 weeks apart, of 30 µg or 100 µg R0.6C or ProC6C each adsorbed to Alhydrogel (AlOH) adjuvant alone or in combination with Matrix-M (15 µg or 50 µg, respectively). The allocation was random and double-blind for this phase I trial.RESULTSThe vaccines were safe and well tolerated with no vaccine-related serious adverse events. A total of 7 adverse events, mild to moderate in intensity and considered possibly related to the study vaccines, were recorded. Vaccine-specific antibodies were highest in volunteers immunized with 100 µg ProC6C-AlOH with Matrix-M, and 13 of 20 (65%) individuals in the group showed greater than 80% transmission-reducing activity (TRA) when evaluated in the standard membrane feeding assay at 15 mg/mL IgG. In contrast, R0.6C induced sporadic TRA.CONCLUSIONAll formulations were safe and well tolerated in a malaria-endemic area of Africa in healthy adults. The ProC6C-AlOH/Matrix-M vaccine elicited the highest levels of functional antibodies, meriting further investigation.TRIAL REGISTRATIONPan-African Clinical Trials Registry (https://pactr.samrc.ac.za) PACTR202201848463189.FUNDINGThe study was funded by the European and Developing Countries Clinical Trials Partnership (grant RIA2018SV-2311).

Infected erythrocytes and plasma proteomics reveal a specific protein signature of severe malaria.

Cerebral malaria (CM), the most lethal complication of Plasmodium falciparum severe malaria (SM), remains fatal for 15-25% of affected children despite the availability of treatment. P. falciparum infects and multiplies in erythrocytes, contributing to anemia, parasite sequestration, and inflammation. An unbiased proteomic assessment of infected erythrocytes and plasma samples from 24 Beninese children was performed to study the complex mechanisms underlying CM. A significant down-regulation of proteins from the ubiquitin-proteasome pathway and an up-regulation of the erythroid precursor marker transferrin receptor protein 1 (TFRC) were associated with infected erythrocytes from CM patients. At the plasma level, the samples clustered according to clinical presentation. Significantly, increased levels of the 20S proteasome components were associated with SM. Targeted quantification assays confirmed these findings on a larger cohort (n = 340). These findings suggest that parasites causing CM preferentially infect reticulocytes or erythroblasts and alter their maturation. Importantly, the host plasma proteome serves as a specific signature of SM and presents a remarkable opportunity for developing innovative diagnostic and prognostic biomarkers.

Prospective multicentre study of host response signatures in neonatal sepsis in Sub Saharan Africa.

Few biomarkers for sepsis diagnosis are commonly used in neonatal sepsis. While the role of host response is increasingly recognized in sepsis pathogenesis and prognosis, there is a need for evaluating new biomarkers targeting host response in regions where sepsis burden is high and medico-economic resources are scarce. The objective of the study is to evaluate diagnostic and prognostic accuracy of biomarkers of neonatal sepsis in Sub Saharan Africa. This prospective multicentre study included newborn infants delivered in the Abomey-Calavi region in South Benin and their follow-up from birth to 3 months of age. Accuracy of transcriptional (CD74, CX3CR1), proteic (PCT, IL-6, IL-10, IP-10) biomarkers and clinical characteristics to diagnose and prognose neonatal sepsis were measured. At delivery, cord blood from all consecutive newborns were sampled and analysed, and infants were followed for a 12 weeks' period. Five hundred and eighty-one newborns were enrolled. One hundred and seventy-two newborns developed neonatal sepsis (29.6%) and death occurred in forty-nine infants (8.4%). Although PCT, IL-6 and IP-10 levels were independently associated with sepsis diagnosis, diagnostic accuracy of clinical variables combinations was similar to combinations with biomarkers and superior to biomarkers alone. Nonetheless, CD74, being the only biomarkers independently associated with mortality, showed elevated prognosis accuracy (AUC > 0.9) either alone or in combination with other biomarkers (eg. CD74/IP-10) or clinical criterion (eg. Apgar 1, birth weight). These results suggest that cord blood PCT had a low accuracy for diagnosing early onset neonatal sepsis in Sub Saharan African neonates, while association of clinical criterion showed to be more accurate than any biomarkers taken independently. At birth, CD74, either associated with IP-10 or clinical criterion, had the best accuracy in prognosing sepsis mortality.Trial registration Clinicaltrial.gov registration number: NCT03780712. Registered 19 December 2018. Retrospectively registered.

SEPSIS project: a protocol for studying biomarkers of neonatal sepsis and immune responses of infants in a malaria-endemic region.

INTRODUCTION: Neonatal sepsis outreaches all causes of neonatal mortality worldwide and remains a major societal burden in low and middle income countries. In addition to limited resources, endemic morbidities, such as malaria and prematurity, predispose neonates and infants to invasive infection by altering neonatal immune response to pathogens. Nevertheless, thoughtful epidemiological, diagnostic and immunological evaluation of neonatal sepsis and the impact of gestational malaria have never been performed. METHODS AND ANALYSIS: A prospective longitudinal multicentre follow-up of 580 infants from birth to 3 months of age in urban and suburban Benin will be performed. At delivery, and every other week, all children will be examined and clinically evaluated for occurrence of sepsis. At delivery, cord blood systematic analysis of selected plasma and transcriptomic biomarkers (procalcitonin, interleukin (IL)-6, IL-10, IP10, CD74 and CX3CR1) associated with sepsis pathophysiology will be evaluated in all live births as well as during the follow-up, and when sepsis will be suspected. In addition, whole blood response to selected innate stimuli and extensive peripheral blood mononuclear cells phenotypic characterisation will be performed. Reference intervals specific to sub-Saharan neonates will be determined from this cohort and biomarkers performances for neonatal sepsis diagnosis and prognosis tested. ETHICS AND DISSEMINATION: Ethical approval has been obtained from the Comité d'Ethique de la Recherche - Institut des Sciences Biomédicales Appliquées (CER-ISBA 85 - 5 April 2016, extended on 3 February 2017). Results will be disseminated through international presentations at scientific meetings and publications in peer-reviewed journals. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov registration number: NCT03780712.

Poor maternal anthropometric status before conception is associated with a deleterious infant growth during the first year of life: a longitudinal preconceptional cohort.

BACKGROUND: According to the Developmental Origins of Health and Diseases concept, exposures in the preconception period may be critical. For the first time, we evaluated the effect of preconception poor anthropometric status on infant's growth in sub-Saharan Africa. METHODS: A mother-child cohort was followed prospectively from preconception to 1 year old in Benin. Maternal anthropometric status was assessed by prepregnancy body mass index (BMI), approximated by BMI at the first antenatal visit before 7 weeks' gestation, and gestational weight gain (GWG). BMI was categorized as underweight, normal, overweight, and obesity according to World Health Organization standards. GWG was categorized as low (<7 kg), mild (7-12 kg), and high (>12 kg). In infant, stunting and wasting were defined as length-for-age and weight-for-length z scores less than -2 SD, respectively. We evaluated the association between BMI/GWG and infant's weight and length at birth and during the first year of life, as well as with stunting and wasting at 12 months using mixed linear and logistic regression models. RESULTS: In multivariate, preconceptional underweight was associated with a lower infant's weight at birth and during the first year (-164 g; 95% CI, -307 to -22; and -342 g; 95% CI, -624 to -61, respectively) and with a higher risk of stunting at 12 months (adjusted odds ratio [aOR] = 3.98; 95% CI, 1.01-15.85). Furthermore, preconceptional obesity and a high GWG were associated with a higher weight and length at birth and during the first year. CONCLUSION: Underweight and obesity before conception as well as GWG were associated with infant's growth. These results argue for preventive interventions starting as early as the preconception period to support child long-term health.

Changes in monocyte subsets are associated with clinical outcomes in severe malarial anaemia and cerebral malaria.

Monocytes are plastic heterogeneous immune cells involved in host-parasite interactions critical for malaria pathogenesis. Human monocytes have been subdivided into three populations based on surface expression of CD14 and CD16. We hypothesised that proportions and phenotypes of circulating monocyte subsets can be markers of severity or fatality in children with malaria. To address this question, we compared monocytes sampled in children with uncomplicated malaria, severe malarial anaemia, or cerebral malaria. Flow cytometry was used to distinguish and phenotype monocyte subsets through CD14, CD16, CD36 and TLR2 expression. Data were first analysed by univariate analysis to evaluate their link to severity and death. Second, multinomial logistic regression was used to measure the specific effect of monocyte proportions and phenotypes on severity and death, after adjustments for other variables unrelated to monocytes. Multivariate analysis demonstrated that decreased percentages of non-classical monocytes were associated with death, suggesting that this monocyte subset has a role in resolving malaria. Using univariate analysis, we also showed that the role of non-classical monocytes involves a mostly anti-inflammatory profile and the expression of CD16. Further studies are needed to decipher the functions of this sub-population during severe malaria episodes, and understand the underlying mechanisms.

Maternal malaria but not schistosomiasis is associated with a higher risk of febrile infection in infant during the first 3 months of life: A mother-child cohort in Benin.

BACKGROUND: Malaria and schistosomiasis represent two of the most prevalent and disabling parasitic infections in developing countries. Few studies have evaluated the effect of maternal schistosomiasis and malaria in the peri-conceptional period on infant's risk of infection. METHODS: In Benin, women were followed from the preconception period until delivery. Subsequently, their children were followed from birth to 3 months of age. Pre-pregnancy malaria, malaria in pregnancy (MiP)-determined monthly using a thick blood smear-and urinary schistosomiasis-determined once before pregnancy and once at delivery using urine filtration-were the main maternal exposures. Infant's febrile infection (fever with respiratory, gastrointestinal and/or cutaneous clinical signs anytime during follow-up) was the main outcome. In a secondary analysis, we checked the relation of malaria and schistosomiasis with infant's hemoglobin (Hb) concentration. Both effects were separately assessed using logistic/mixed linear regression models. RESULTS: The prevalence of MiP was 35.7% with 10.8% occurring during the 1st trimester, and the prevalence of schistosomiasis was 21.8%. From birth to 3 months, 25.3% of infants had at least one episode of febrile infection. In multivariate analysis, MiP, particularly malaria in the 1st trimester, was significantly associated with a higher risk of infant's febrile infection (aOR = 4.99 [1.1; 22.6], p = 0.03). In secondary results, pre-pregnancy malaria and schistosomiasis were significantly associated with a lower infant's Hb concentration during the first 3 months. CONCLUSION: We evidenced the deleterious effect of maternal parasitic infections on infant's health. Our results argue in favor of the implementation of preventive strategies as early as in the peri-conception.

From genomic to LC-MS/MS evidence: Analysis of PfEMP1 in Benin malaria cases.

BACKGROUND: PfEMP1 is the major protein from parasitic origin involved in the pathophysiology of severe malaria, and PfEMP1 domain subtypes are associated with the infection outcome. In addition, PfEMP1 variability is endless and current publicly available protein repositories do not reflect the high diversity of the sequences of PfEMP1 proteins. The identification of PfEMP1 protein sequences expressed with samples remains challenging. The aim of our study is to identify the different PfEMP1 proteins variants expressed within patient samples, and therefore identify PfEMP1 proteins domains expressed by patients presenting uncomplicated malaria or severe malaria in malaria endemic setting in Cotonou, Benin. METHODS: We performed a multi-omic approach to decipher PfEMP1 expression at the patient's level in different clinical settings. Using a combination of whole genome sequencing approach and RNA sequencing, we were able to identify new PfEMP1 sequences and created a new custom protein database. This database was used for protein identification in mass spectrometry analysis. RESULTS: The differential expression analysis of RNAsequencing data shows an increased expression of the var domains transcripts DBLα1.7, DBLα1.1, DBLα2 and DBLß12 in samples from patients suffering from Cerebral Malaria compared to Uncomplicated Malaria. Our approach allowed us to attribute PfEMP1 sequences to each sample and identify new peptides associated to PfEMP1 proteins in mass spectrometry. CONCLUSION: We highlighted the diversity of the PfEMP1 sequences from field sample compared to reference sequences repositories and confirmed the validity of our approach. These findings should contribute to further vaccine development strategies based on PfEMP1 proteins.

PFI1785w: A highly conserved protein associated with pregnancy associated malaria.

Pregnancy-associated malaria (PAM) is one of the severe forms of Plasmodium falciparum infection. The main antigen VAR2CSA is the target of vaccine development. However, the large size of VAR2CSA protein and its high degree of variability limit to the efficiency of the vaccination. Using quantitative mass spectrometry method, we detected and quantified proteotypic peptides from 5 predicted PAM associated proteins. Our results confirmed that PFI1785w is over-expressed in PAM samples. Then, we investigated PFI1785w variability among a set of parasite samples from various endemic areas. PFI1785w appear to be more conserved than VAR2CSA. PFB0115w, another PAM associated protein, seems also associated with the pathology. Further vaccination strategies could integrate other proteins in addition to the major VAR2CSA antigen to improve immune response to vaccination.

Clinical development of a VAR2CSA-based placental malaria vaccine PAMVAC: Quantifying vaccine antigen-specific memory B & T cell activity in Beninese primigravidae.

BACKGROUND: The antigen VAR2CSA plays a pivotal role in the pathophysiology of pregnancy-associated malaria (PAM) caused by Plasmodium falciparum. A VAR2CSA-based vaccine candidate, PAMVAC, is under development by an EU-funded multi-country consortium (PlacMalVac project). As part of PAMVAC's clinical development, we quantified naturally acquired vaccine antigen-specific memory B and T cell responses in Beninese primigravidae recruited at the beginning of pregnancy and followed up to delivery and beyond. METHODS: Clinical and parasitological histories were compiled from monthly clinic visits. On 4 occasions (first and fifth month of pregnancy, delivery, 6months post-delivery) peripheral blood mononuclear cells were isolated for in vitro assays. PAMVAC-specific memory B cells as well as those specific for a PAM unrelated P. falciparum antigen (PfEMP1-CIDR1a) and for tetanus toxoid were quantified by ELISpot. Memory T cell responses were assessed by quantifying cytokines (IL-5, IL-6, IL-10, IL-13, IFN-γ, TNF-α) in supernatants of cells stimulated in vitro either with PAMVAC, or mitogen (PHA). RESULTS: Both tetanus toxoid- and PAMVAC-specific memory B cell frequencies increased to reach peak levels in the 5th month and at delivery, respectively and persisted post-delivery. The frequency of CIDR1a-specific memory B cells was stable during pregnancy, but declined post-delivery. The cumulated prevalence of infection with P. falciparum during pregnancy was 61% by microscopy. In women with a history of such infections, a significantly higher frequency of PAMVAC-specific memory B cells was observed at delivery. PAMVAC-specific pro-inflammatory (IFN-γ, TNF) responses tended to be higher at delivery in those with a history of infection. Mitogen-induced IL-5/IL-13 responses were significantly enhanced in the same women. CONCLUSIONS: PAMVAC-specific memory B cells are induced during first pregnancies and are maintained post-delivery. Women with a T helper cell profile biased towards production of Th2-type cytokines have a greater risk of infection with P. falciparum.

Proteomic analysis of Plasmodium falciparum parasites from patients with cerebral and uncomplicated malaria.

Plasmodium falciparum is responsible of severe malaria, including cerebral malaria (CM). During its intra-erythrocytic maturation, parasite-derived proteins are expressed, exported and presented at the infected erythrocyte membrane. To identify new CM-specific parasite membrane proteins, we conducted a mass spectrometry-based proteomic study and compared the protein expression profiles between 9 CM and 10 uncomplicated malaria (UM) samples. Among the 1097 Plasmodium proteins identified, we focused on the 499 membrane-associated and hypothetical proteins for comparative analysis. Filter-based feature selection methods combined with supervised data analysis identified a subset of 29 proteins distinguishing CM and UM samples with high classification accuracy. A hierarchical clustering analysis of these 29 proteins based on the similarity of their expression profiles revealed two clusters of 15 and 14 proteins, respectively under- and over-expressed in CM. Among the over-expressed proteins, the MESA protein is expressed at the erythrocyte membrane, involved in proteins trafficking and in the export of variant surface antigens (VSAs), but without antigenic function. Antigen 332 protein is exported at the erythrocyte, also involved in protein trafficking and in VSAs export, and exposed to the immune system. Our proteomics data demonstrate an association of selected proteins in the pathophysiology of CM.

Infants' Peripheral Blood Lymphocyte Composition Reflects Both Maternal and Post-Natal Infection with Plasmodium falciparum.

Maternal parasitoses modulate fetal immune development, manifesting as altered cellular immunological activity in cord blood that may be linked to enhanced susceptibility to infections in early life. Plasmodium falciparum typifies such infections, with distinct placental infection-related changes in cord blood exemplified by expanded populations of parasite antigen-specific regulatory T cells. Here we addressed whether such early-onset cellular immunological alterations persist through infancy. Specifically, in order to assess the potential impacts of P. falciparum infections either during pregnancy or during infancy, we quantified lymphocyte subsets in cord blood and in infants' peripheral blood during the first year of life. The principal age-related changes observed, independent of infection status, concerned decreases in the frequencies of CD4+, NKdim and NKT cells, whilst CD8+, Treg and Teff cells' frequencies increased from birth to 12 months of age. P. falciparum infections present at delivery, but not those earlier in gestation, were associated with increased frequencies of Treg and CD8+ T cells but fewer CD4+ and NKT cells during infancy, thus accentuating the observed age-related patterns. Overall, P. falciparum infections arising during infancy were associated with a reversal of the trends associated with maternal infection i.e. with more CD4+ cells, with fewer Treg and CD8+ cells. We conclude that maternal P. falciparum infection at delivery has significant and, in some cases, year-long effects on the composition of infants' peripheral blood lymphocyte populations. Those effects are superimposed on separate and independent age- as well as infant infection-related alterations that, respectively, either match or run counter to them.

Nrf2-driven CD36 and HO-1 gene expression in circulating monocytes correlates with favourable clinical outcome in pregnancy-associated malaria.

BACKGROUND: Pregnancy-associated malaria (PAM) constitutes one of the most severe forms of malaria infection leading to fetal growth restriction and high risk of infant death. The severity of the pathology is largely attributed to the recruitment of monocytes and macrophages in the placenta which is evidenced by dysregulated inflammation found in placental blood. Importantly, CD36(+) monocytes/macrophages are also thought to participate in the tight control of the pro- and anti-inflammatory responses following Plasmodium detection through elimination of apoptotic cells and malaria-infected erythrocytes, internalization and recycling of oxidized forms of low-density lipoprotein and collaboration with TLR2 in pro-inflammatory response. Interestingly, previous work demonstrated that CD36 expression was upregulated on inflammatory macrophages following stimulation of the Nrf2 transcription factor, whilst the PPARγ pathway was inhibited and non-functional in the same inflammatory conditions. This current study examined the possible role of Nrf2-driven gene expression, CD36 and Haem-Oxygenase-1 (HO-1), in PAM clinical outcomes. METHODS: Clinical data and biological samples including peripheral blood mononuclear cells were collected from 27 women presenting PAM. Polychromatic flow cytometry was used to characterize innate immune cell subpopulations and quantify CD36 protein expression level on monocytes. mRNA levels of CD36, PPARγ, Nrf2 and HO-1 were determined by qPCR and related to clinical outcomes. Finally, the capacity of monocytes to modulate CD36 expression upon rosiglitazone or sulforaphane treatment, two respective PPARγ or Nrf2 activators, was also investigated. RESULTS: The CD36 receptor, mostly expressed by CD14(+) circulating monocytes, statistically correlated with increased infant birth weights. Interestingly, mRNA levels of the transcription factor Nrf2 and the enzyme HO-1 also correlated with lower parasitaemia and increased infant birth weight, while PPARγ mRNA levels did not. Finally, monocytes isolated from low infant birth weight pregnant women were capable of up-regulating CD36 via the Nrf2 pathway ex vivo. CONCLUSIONS: Altogether these results suggest that Nrf2-driven CD36 and HO-1 expression on innate immune cells could contribute to a protective and detoxifying mechanism during PAM. More powered and mechanistical studies are however needed to strengthen the conclusions of this study.

Insights Into Circulating Cytokine Dynamics During Pregnancy in HIV-Infected Beninese Exposed to Plasmodium falciparum Malaria.

We investigated the circulating plasma levels of Th1- (Interleukin-2 [IL-2], tumor necrosis factor-α [TNF-α], interferon-gamma [IFN-γ]) and Th2-type (IL-4, IL-5, IL-10) cytokines in human immunodeficiency virus (HIV)-infected pregnant women living in a malaria-endemic area. We analyzed samples from 200 pregnant women included in the prevention of pregnancy-associated malaria in HIV-infected women: cotrimoxazole prophylaxis versus mefloquine (PACOME) clinical trial who were followed until delivery. Cytokine concentrations were measured by flow cytometry-based multiplex bead array. Significantly elevated levels of IL-10 and lower levels of TNF-α were observed at delivery compared with inclusion (P = 0.005). At inclusion, the presence of circulating IFN-γ, a higher CD4(+) T cell count and having initiated intermittent preventive treatment of malaria with sulfadoxine pyrimethamine (SP-IPTp) were all associated with a lower likelihood of Plasmodium falciparum infection. At delivery, the inverse relationship between the presence of infection and circulating IFN-γ persisted, although there was a positive association between the likelihood of infection and the presence of circulating TNF-α. Initiation of antiretroviral therapy was associated with elevated IL-5 production. Consistent with our own and others' observations in HIV seronegative subjects, this study shows circulating IL-10 to be a marker of infection with P. falciparum during pregnancy even in HIV-infected women, although plasma IFN-γ may be a marker of anti-malarial protection in such women.

Plasmodium falciparum Polymorphisms associated with ex vivo drug susceptibility and clinical effectiveness of artemisinin-based combination therapies in Benin.

Artemisinin-based combination therapies (ACTs) are the main option to treat malaria, and their efficacy and susceptibility must be closely monitored to avoid resistance. We assessed the association of Plasmodium falciparum polymorphisms and ex vivo drug susceptibility with clinical effectiveness. Patients enrolled in an effectiveness trial comparing artemether-lumefantrine (n = 96), fixed-dose artesunate-amodiaquine (n = 96), and sulfadoxine-pyrimethamine (n = 48) for the treatment of uncomplicated malaria 2007 in Benin were assessed. pfcrt, pfmdr1, pfmrp1, pfdhfr, and pfdhps polymorphisms were analyzed pretreatment and in recurrent infections. Drug susceptibility was determined in fresh baseline isolates by Plasmodium lactate dehydrogenase enzyme-linked immunosorbent assay (ELISA). A majority had 50% inhibitory concentration (IC50) estimates (the concentration required for 50% growth inhibition) lower than those of the 3D7 reference clone for desethylamodiaquine, lumefantrine, mefloquine, and quinine and was considered to be susceptible, while dihydroartemisinin and pyrimethamine IC50s were higher. No association was found between susceptibility to the ACT compounds and treatment outcome. Selection was observed for the pfmdr1 N86 allele in artemether-lumefantrine recrudescences (recurring infections) (4/7 [57.1%] versus 36/195 [18.5%]), and of the opposite allele, 86Y, in artesunate-amodiaquine reinfections (new infections) (20/22 [90.9%] versus 137/195 [70.3%]) compared to baseline infections. The importance of pfmdr1 N86 in lumefantrine tolerance was emphasized by its association with elevated lumefantrine IC50s. Genetic linkage between N86 and Y184 was observed, which together with the low frequency of 1246Y may explain regional differences in selection of pfmdr1 loci. Selection of opposite alleles in artemether-lumefantrine and artesunate-amodiaquine recurrent infections supports the strategy of multiple first-line treatment. Surveillance based on clinical, ex vivo, molecular, and pharmacological data is warranted.

Differential adhesion-inhibitory patterns of antibodies raised against two major variants of the NTS-DBL2X region of VAR2CSA.

BACKGROUND: VAR2CSA is a large polymorphic Plasmodium falciparum protein expressed on infected erythrocytes (IE) that allows their binding in the placenta, thus precipitating placental malaria (PM). The N-terminal part of VAR2CSA that contains the binding site to placental chondroitin sulfate A (CSA) is currently recognized as the most attractive region for vaccine development. An ultimate challenge is to define epitopes in this region that induce a broad cross-reactive adhesion inhibitory antibody response. METHODS: Based on phylogenetic data that identified a dimorphic sequence motif in the VAR2CSA DBL2X, we raised antibodies against the NTS-DBL2X constructs containing one sequence or the other (3D7 and FCR3) and tested their functional properties on P. falciparum isolates from pregnant women and on laboratory-adapted strains. RESULTS: The CSA binding inhibitory capacity of the antibodies induced varied from one parasite isolate to another (range, 10%­100%), but the combined analysis of individual activity highlighted a broader functionality that increased the total number of isolates inhibited. Interestingly, the differential inhibitory effect of the antibodies observed on field isolates resulted in significant inhibition of all field isolates tested, suggesting that optimal inhibitory spectrum on field isolates from pregnant women might be achieved with antibodies targeting limited variants of the N-terminal VAR2CSA. CONCLUSIONS: Our findings indicate that the NTS-DBL2X region of VAR2CSA can elicit strain-transcending anti-adhesion antibodies and suggest that the combination of the two major variants used here could represent the basis for an effective bivalent VAR2CSA-based vaccine.

Differential protein expression profiles between Plasmodium falciparum parasites isolated from subjects presenting with pregnancy-associated malaria and uncomplicated malaria in Benin.

BACKGROUND: Plasmodium falciparum is responsible for severe malaria, including pregnancy-associated malaria (PAM). During intra-erythrocytic maturation, the infected erythrocyte (iE) membrane is modified by insertion of parasite-derived proteins, primarily consisting of variant surface antigens such as P. falciparum erythrocyte membrane protein-1. METHODS: To identify new PAM-specific parasite membrane proteins, we conducted a mass spectrometry-based proteomic study and compared the protein expression profiles of 10 PAM and 10 uncomplicated malaria (UM) samples. RESULTS: We focused on the 454/1139 membrane-associated and hypothetical proteins for comparative analysis. Using filter-based feature-selection methods combined with supervised data analysis, we identified a subset of 53 proteins that distinguished PAM and UM samples. Up to 19/20 samples were correctly assigned to their respective clinical group. A hierarchical clustering analysis of these 53 proteins based on the similarity of their expression profiles revealed 2 main clusters of 40 and 13 proteins that were under- or over-expressed, respectively, in PAM. CONCLUSIONS: VAR2CSA is identified and associated with PAM, validating our experimental approach. Other PAM-predictive proteins included PFI1785w, PF14_0018, PFB0115w, PFF0325c, and PFA_0410w. These proteomics data demonstrate the involvement of selected proteins in the pathophysiology of PAM, providing new insights for the definition of potential new targets for a vaccine against PAM.

Malaria modifies neonatal and early-life toll-like receptor cytokine responses.

Protection from infections in early life relies extensively on innate immunity, but it is unknown whether and how maternal infections modulate infants' innate immune responses, thereby altering susceptibility to infections. Plasmodium falciparum causes pregnancy-associated malaria (PAM), and epidemiological studies have shown that PAM enhances infants' susceptibility to infection with P. falciparum. We investigated how PAM-mediated exposures in utero affect innate immune responses and their relationship with infection in infancy. In a prospective study of mothers and their babies in Benin, we investigated changes in Toll-like receptor (TLR)-mediated cytokine responses related to P. falciparum infections. Whole-blood samples from 134 infants at birth and at 3, 6, and 12 months of age were stimulated with agonists specific for TLR3, TLR4, TLR7/8, and TLR9. TLR-mediated interleukin 6 (IL-6) and IL-10 production was robust at birth and then stabilized, whereas tumor necrosis factor alpha (TNF-α) and gamma interferon (IFN-γ) responses were weak at birth and then increased. In multivariate analyses, maternal P. falciparum infections at delivery were associated with significantly higher TLR3-mediated IL-6 and IL-10 responses in the first 3 months of life (P < 0.05) and with significantly higher TLR3-, TLR7/8-, and TLR9-mediated TNF-α responses between 6 and 12 months of age (P < 0.05). Prospective analyses showed that higher TLR3- and TLR7/8-mediated IL-10 responses at birth were associated with a significantly higher risk of P. falciparum infection in infancy (P < 0.05). Neonatal and infant intracellular TLR-mediated cytokine responses are conditioned by in utero exposure through PAM late in pregnancy. Enhanced TLR-mediated IL-10 responses at birth are associated with an increased risk of P. falciparum infection, suggesting a compromised ability to combat infection in early life.

Peripheral blood cell signatures of Plasmodium falciparum infection during pregnancy.

Sequestration of Plasmodium falciparum-infected erythrocytes in placental intervillous spaces causes inflammation and pathology. Knowledge of the profiles of immune cells associated with the physiopathology of pregnancy-associated malaria (PAM) is scarce. We conducted a longitudinal, prospective study, both in Benin and Tanzania, including ∼1000 pregnant women in each site with systematic follow-up at scheduled antenatal visits until delivery. We used ex vivo flow cytometry to identify peripheral blood mononuclear cell (PBMC) profiles that are associated with PAM and anaemia, determining the phenotypic composition and activation status of PBMC in selected sub-groups with and without PAM both at inclusion and at delivery in a total of 302 women. Both at inclusion and at delivery PAM was associated with significantly increased frequencies both of B cells overall and of activated B cells. Infection-related profiles were otherwise quite distinct at the two different time-points. At inclusion, PAM was associated with anaemia, with an increased frequency of immature monocytes and with a decreased frequency of regulatory T cells (Treg). At delivery, infected women presented with significantly fewer plasmacytoid dendritic cells (DC), more myeloid DC expressing low levels of HLA-DR, and more effector T cells (Teff) compared to uninfected women. Independent associations with an increased risk of anaemia were found for altered antigen-presenting cell frequencies at inclusion, but for an increased frequency of Teff at delivery. Our findings emphasize the prominent role played by B cells during PAM whenever it arises during pregnancy, whilst also revealing signature changes in other circulating cell types that, we conclude, primarily reflect the relative duration of the infections. Thus, the acute, recently-acquired infections present at delivery were marked by changes in DC and Teff frequencies, contrasting with infections at inclusion, considered chronic in nature, that were characterized by an abundance of immature monocytes and a paucity of Treg in PBMC.

First-trimester Plasmodium falciparum infections display a typical "placental" phenotype.

BACKGROUND: Plasmodium falciparum-infected erythrocytes (IEs) adhere to host cell receptors, allowing parasites to sequester into deep vascular beds of various organs. This defining phenomenon of malaria pathogenesis is key to the severe clinical complications associated with cerebral and placental malaria. The principal ligand associated with the binding to chondroitin sulfate A (CSA) that allows placental sequestration of IEs is a P. falciparum erythrocyte membrane protein 1 (PfEMP1) family member encoded by the var2csa gene. METHODS: Here, we investigated the transcription pattern of var genes by real-time polymerase chain reaction, the expression of VAR2CSA, protein by flow cytometry, and the CSA-binding ability of IEs collected at different stages of pregnancy using a static-based Petri dish assay. RESULTS: Through comparison with the profiles of isolates from nonpregnant hosts, we report several lines of evidence showing that parasites infecting women during pregnancy preferentially express VAR2CSA protein, and that selection for the capacity to adhere to CSA via VAR2CSA expression occurs early in pregnancy. CONCLUSIONS: Our data suggest that the placental tropism of P. falciparum is already established in the first trimester of pregnancy, with consequent implications for the development of the pathology associated with placental malaria.