Acute Malaria Infection Research Articles

Acute malaria suppresses the B lymphocytic niche in the bone marrow through the alteration of CXCL12-abundant reticular cells.

Bone marrow is a dynamic organ composed of stem cells that constantly receive signals from stromal cells and other hematopoietic cells in the niches of the bone marrow to maintain hematopoiesis and generate immune cells. Perturbation of the bone marrow microenvironment by infection and inflammation affects hematopoiesis and may affect immune cell development. Little is known about the effect of malaria on the bone marrow stromal cells that govern the hematopoietic stem cell (HSC) niche. In this study, we demonstrate that the mesenchymal stromal CXCL12-abundant reticular (CAR) cell population is reduced during acute malaria infection. The reduction of CXCL12 and IL-7 signals in the bone marrow impairs the lymphopoietic niche, leading to the depletion of common lymphoid progenitors, B cell progenitors and mature B cells, including plasma cells in the bone marrow. We found that IFNγ is responsible for the upregulation of Sca1 on CAR cells, yet the decline in CAR cell and B cell populations in the bone marrow is IFNγ-independent. In contrast to the decline in B cell populations, HSCs and multipotent progenitors increased with expansion of myelopoiesis and erythropoiesis, indicating a bias in the differentiation of multipotent progenitors during malaria infection. These findings suggest that malaria may affect host immunity by modulating the bone marrow niche.

Challenges in Diagnosing and Treating Acutely Febrile Children with Suspected Malaria at Health Care Facilities in the Lake Mwanza Region of Tanzania.

Acute febrile diseases transmitted by mosquitos are a diagnostic challenge for pediatricians working in sub-Saharan Africa. Misclassification due to the lack of rapid, reliable diagnostic tests leads to the overuse of antibiotics and antimalarials. Children presenting with acute fever and suspected of having malaria were examined at health care facilities in the Mwanza Region of Tanzania. The sensitivity and specificity of blood smear microscopy and malaria rapid diagnostic tests that targeted histidine-rich protein 2 and Plasmodium lactate dehydrogenase were compared with a multiplex reverse transcriptase-polymerase chain reaction (PCR)-ELISA. Six hundred ninety-eight children presented with acute fever and met the criteria for inclusion; 23% received antibiotics and 23% received antimalarials prior to admission. Subsequently, 20% were confirmed by PCR to have Plasmodium falciparum infection. Blood smear microscopy exhibited 33% sensitivity and 93% specificity. The malaria rapid test provided 87% sensitivity and 98% specificity in detecting acute malaria infections. Only 7% of malaria-negative children received antimalarials at Sengerema Designated District Hospital when treatment was guided by the results of rapid testing. In contrast, 75% of malaria-negative patients were treated with antimalarial drugs at health facilities that used blood smears as the standard diagnostic test. Misclassification and premedication of nonmalarial, febrile illnesses contribute to the emergence of antimalarial and antimicrobial resistance. The incorporation of malaria rapid diagnostic tests into the clinical routine translated into improved treatment and a significant reduction in antimalarial drug prescriptions.

Placental Malaria and Its Relationship with Neonatal Birth Weight among Primigravidae: An Analytical Cross-sectional Study.

Malaria can be fatal during pregnancy, posing a serious risk to both mothers and fetuses, especially in sub-Saharan Africa. Primigravidae are particularly susceptible to placental malaria in areas with high rates of transmission due to insufficient immunity. This study aimed to determine the prevalence of placental malaria infection, risk factors, types of Plasmodium causing malaria during pregnancy, and its relationship with neonatal birth weight among primigravidae. This was an analytical cross-sectional study involving 357 primigravidae who delivered at Abubakar Tafawa Balewa University Teaching Hospital, Bauchi, Nigeria. Placental blocks were taken from the pericentric area of the maternal surface of the placenta, and the birth weights of the neonates were recorded. The samples were fixed in 10% neutral-buffered formalin, and histopathological analysis was performed. The primary outcome measure was to determine the relationship between placental malaria and neonatal birth weight. Demographics and outcomes were analyzed using standard statistical tests. Multivariable regression models accounting for potential confounders were created for the primary and secondary outcomes with adjusted odds ratios as the measures of effect. The prevalence of placental malaria was 38.4%. Among the participants with positive placenta malaria parasitemia, 49.6%, 36.5%, and 13.9% had chronic, acute, and past placental malaria infections, respectively. Only Plasmodium falciparum was found in the placenta. According to the bivariate analysis, unbooked status (p = 0.001), non-use of intermittent preventive therapy for malaria (p < 0.001), and village dwelling (p = 0.020) were significantly associated with placental malaria. However, on multivariable logistic regression, only non-uptake of intermittent preventive therapy for malaria was independently associated with placental malaria (adjusted odds ratio, 2.2, 95% confidence interval: 1.20, 4.1, p = 0.011). There was a significant difference in the mean birth weight between those with placental malaria and those without placental malaria (2.8 ± 0.5 kg vs. 3.2 ± 0.4 kg, p = 0.001). Additionally, placental malaria was significantly associated with low birth weight among the primigravidae (p < 0.001). In Nigeria, there is a strong correlation between low birth weight and placental malaria in Primidravidae. Placental malaria was found to be independently correlated with non-uptake of intermittent preventive therapy for malaria.

Cish knockout mice exhibit similar outcomes to malaria infection despite altered hematopoietic responses.

The Cytokine-inducible Src homology 2 domain-containing (CISH) protein is a negative feedback regulator induced by cytokines that play key roles in immunity and erythropoiesis. Single nucleotide polymorphisms (SNPs) in the human CISH gene have been associated with increased susceptibility to severe malaria disease. To directly assess how CISH might influence outcomes in the BALB/c model of malaria anemia, CISH knockout (Cish-/-) mice on this background were infected with Plasmodium berghei and their hematopoietic responses, cytokine production and ability to succumb to severe malaria disease evaluated. Despite basal erythrocytic disruption, upon P. berghei infection, the Cish -/- mice were better able to maintain peripheral blood cell counts, hemoglobin levels and a steady-state pattern of erythroid differentiation compared to wild-type (Cish+/+) mice. Ablation of CISH, however, did not influence the outcome of acute malaria infections in either the BALB/c model or the alternative C57BL/6 model of experimental cerebral malaria, with the kinetics of infection, parasite load, weight loss and cytokine responses being similar between Cish+/+ and Cish-/- mice, and both genotypes succumbed to experimental cerebral malaria within a comparable timeframe.

IL‐27 produced during acute malaria infection regulates Plasmodium‐specific memory CD4+ T cells

Malaria infection elicits both protective and pathogenic immune responses, and IL‐27 is a critical cytokine that regulate effector responses during infection. Here, we identified a critical window of CD4+ T cell responses that is targeted by IL‐27. Neutralization of IL‐27 during acute infection with Plasmodium chabaudi expanded specific CD4+ T cells, which were maintained at high levels thereafter. In the chronic phase, Plasmodium‐specific CD4+ T cells in IL‐27‐neutralized mice consisted mainly of CD127+KLRG1− and CD127−KLRG1+ subpopulations that displayed distinct cytokine production, proliferative capacity, and are maintained in a manner independent of active infection. Single‐cell RNA‐seq analysis revealed that these CD4+ T cell subsets formed independent clusters that express unique Th1‐type genes. These IL‐27‐neutralized mice exhibited enhanced cellular and humoral immune responses and protection. These findings demonstrate that IL‐27, which is produced during the acute phase of malaria infection, inhibits the development of unique Th1 memory precursor CD4+ T cells, suggesting potential implications for the development of vaccines and other strategic interventions.

Changes in hypothalamic–pituitary–adrenal axis function, immunity, and glucose during acute Plasmodium relictum infection in house sparrows (Passer domesticus)

Hosts of the same species vary in physiological responses to the same parasite, and some groups of individuals can disproportionately affect disease dynamics; however, the underlying pathophysiology of host-parasite interactions is poorly understood in wildlife. We tested the hypothesis that the hypothalamic–pituitary–adrenal (HPA) axis mediates host resistance and tolerance to avian malaria during the acute phase of infection by evaluating whether individual variation in circulating glucocorticoids predicted resistance to avian malaria in a songbird. We experimentally inoculated wild-caught house sparrows (Passer domesticus) with naturally sourced Plasmodium relictum and quantified baseline and restraint-induced circulating corticosterone, negative feedback ability, cellular and humoral immune function, and baseline and restraint-induced glycemia, prior to and during acute malaria infection. During peak parasitemia, we also evaluated the expression of several liver cytokines that are established pathological hallmarks of malaria in mammals: two pro-inflammatory (IFN-γ and TNF-α) and two anti-inflammatory (IL-10 and TGF-β). Although most of the host metrics we evaluated were not correlated with host resistance or tolerance to avian malaria, this experiment revealed novel relationships between malarial parasites and the avian immune system that further our understanding of the pathology of malaria infection in birds. Specifically, we found that: (1) TNF-α liver expression was positively correlated with parasitemia; (2) sparrows exhibited an anti-inflammatory profile during malaria infection; and (3) IFN-γ and circulating glucose were associated with several immune parameters, but only in infected sparrows. We also found that, during the acute phase of infection, sparrows increased the strength of corticosterone negative feedback at the level of the pituitary. In the context of our results, we discuss future methodological considerations and aspects of host physiology that may confer resistance to avian malaria, which can help inform conservation and rehabilitation strategies for avifauna at risk.

A CASE STUDY: THE AYURVEDIC MANAGEMENT OF SEVERE ACUTE MALNUTRION (KHUPOSHANAJANYA VYADHIS).

Childhood undernutrition is a fundamental cause of an estimated 45% of all deaths among under- 5 children. Such children frequently experience various complications of malnutrition like diarrhea, acute respiratory infec-tions, malaria, and skin infections if not managed well. In this case study, a 4-year-old child presented with se-vere to acute malnutrition (S.A.M.).The S.A.M. management protocol consists of early management of acute consequences, and the later part includes dietary management with a starter diet (F-75) &amp; catch-up diet (F-100). But generally, fewer efforts must be taken to improve hunger for appropriate digestion of heavy carbohydrates and protein-containing feeds. In Ayurveda, Samhitas, Karshya, Phakka, Balashosha, and Parigarbhika are dis-eases explained in detail which are resembling Malnutrition. The main causative factor in all these diseases is Agni. Agni, or digestive fire, is the main transforming unit of the body. Therefore, an imbalance of Agni leads to malnutrition. The treatment protocols for these diseases mainly include Deepana Pachana, Srotoshodhana, Bhrimhana. The case was managed with help of Ayurveda regimen which helps in Agni vardhan &amp; brimhana karya.

Evidence-based interventions for reducing sickle cell disease-associated morbidity and mortality in sub-Saharan Africa: A scoping review.

Sickle cell disease is a lifelong illness affecting millions of people globally, but predominantly burdensome in sub-Saharan Africa, where most affected children do not live to adulthood, despite available evidence-based interventions that reduce the disease burden in high-income countries. We reviewed studies evaluating evidence-based interventions that decrease sickle cell disease-related morbidity and mortality among children living in sub-Saharan Africa. We used the Joanna Briggs scoping review methodological framework and grouped identified evidence-based interventions into preventative pharmacotherapeutic agents, newborn screening and comprehensive healthcare, disease-modifying agents, nutritional supplementation, systemic treatment, supportive agents and patient/carer/population education. We included 36 studies: 18 randomized controlled trials, 11 observational studies, 5 before-and-after studies and 2 economic evaluation studies, with most of the studies performed in West African countries. Included studies suggest evidence-based interventions effectively to reduce the common morbidities associated with sickle cell disease such as stroke, vaso-occlusive crisis, acute chest syndrome, severe anaemia and malaria infection. Evidence-based interventions also improve survival among study participants. Specifically, our review shows hydroxyurea increases haemoglobin and foetal haemoglobin levels, a finding with practical implications given the challenges with blood transfusion in this setting. The feasibility of implementing individual interventions is hampered by challenges such as affordability, accessibility and the availability of financial and human resources. Our review suggests that regular use of low-dose hydroxyurea therapy, sulphadoxine-pyrimethamine chemoprophylaxis, L-arginine and Omega-3 fatty acid supplementation and establishment of specialist stand-alone sickle cell clinics could reduce the sickle cell disease-associated morbidity and mortality in sub-Saharan Africa countries.

Plasmodium infection is associated with cross-reactive antibodies to carbohydrate epitopes on the SARS-CoV-2 Spike protein

Sero-surveillance can monitor and project disease burden and risk. However, SARS-CoV-2 antibody test results can produce false positive results, limiting their efficacy as a sero-surveillance tool. False positive SARS-CoV-2 antibody results are associated with malaria exposure, and understanding this association is essential to interpret sero-surveillance results from malaria-endemic countries. Here, pre-pandemic samples from eight malaria endemic and non-endemic countries and four continents were tested by ELISA to measure SARS-CoV-2 Spike S1 subunit reactivity. Individuals with acute malaria infection generated substantial SARS-CoV-2 reactivity. Cross-reactivity was not associated with reactivity to other human coronaviruses or other SARS-CoV-2 proteins, as measured by peptide and protein arrays. ELISAs with deglycosylated and desialated Spike S1 subunits revealed that cross-reactive antibodies target sialic acid on N-linked glycans of the Spike protein. The functional activity of cross-reactive antibodies measured by neutralization assays showed that cross-reactive antibodies did not neutralize SARS-CoV-2 in vitro. Since routine use of glycosylated or sialated assays could result in false positive SARS-CoV-2 antibody results in malaria endemic regions, which could overestimate exposure and population-level immunity, we explored methods to increase specificity by reducing cross-reactivity. Overestimating population-level exposure to SARS-CoV-2 could lead to underestimates of risk of continued COVID-19 transmission in sub-Saharan Africa.

Interventions for High-Burden Infectious Diseases in Children and Adolescents: A Meta-analysis.

Approximately 2.2 million deaths were reported among school-age children and young people in 2019, and infectious diseases remain the leading causes of morbidity and mortality, especially in low and middle-income countries. We aim to synthesize evidence on interventions for high-burden infectious diseases among children and adolescents aged 5 to 19 years. We conducted a comprehensive literature search until December 31, 2020. Two review authors independently screened studies for relevance, extracted data, and assessed risk of bias. We included a total of 31 studies, including 81 596 participants. Sixteen studies focused on diarrhea; 6 on tuberculosis; 2 on human immunodeficiency virus; 2 on measles; 1 study each on acute respiratory infections, malaria, and urinary tract infections; and 2 studies targeted multiple diseases. We did not find any study on other high burden infectious diseases among this age group. We could not perform meta-analysis for most outcomes because of variances in interventions and outcomes. Findings suggests that for diarrhea, water treatment, water filtration, and zinc supplementation have some protective effect. For tuberculosis, peer counseling, contingency contract, and training of health care workers led to improvements in tuberculosis detection and treatment completion. Continuation of cotrimoxazole therapy reduced the risk of tuberculosis and hospitalizations among human immunodeficiency virus-infected children and reduced measles complications and pneumonia cases among measles-infected children. Zinc supplementation led to a faster recovery in urinary tract infections with a positive effect in reducing symptoms. There is scarcity of data on the effectiveness of interventions for high-burden infectious diseases among school-aged children and adolescents.

The RELATIONSHIP BETWEEN TYPES OF PLASMODIUM FALCIPARUM AND PLASMODIUM VIVAX WITH THE DEGREE OF THROMBOCYTOPENIA IN MALARIA PATIENTS AT RSUD RATU AJI PUTRI BOTUNG PENAJAM PASER UTARA

ABSTRACT&#x0D; Malaria is a tropical infectious disease with high morbidity and mortality rates. In malaria, various kinds of haematological complications can arise, one of which is thrombocytopenia. Thrombocytopenia is most commonly encountered during acute malaria infection with varying degrees observed in both Plasmodium falciparum and Plasmodium vivax infections. The purpose of this study was to determine the relationship between the types of Plasmodium falciparum and Plasmodium vivax with the degree of thrombocytopenia in malaria patients at the Ratu Aji Putri Botung Penajam Paser Utara Hospital. This research is an observasional analytic study with cross sectional method. The data was taken by using purposive sampling method from the medical records of malaria patients hospitalized in Ratu Aji Putri Botung Penajam Paser Utara Hospital in the period of January 2013 - August 2018. Data analysis used the Chi-square test. Of the 310 malaria patients who were study subjects, 60,3% (n = 187) were infected with Plasmodium falciparum and 39,7% (n = 123) were infected with Plasmodium vivax. Most of the research subjects were male (95,8%) who were dominated by adults (56,5%). As many as 90% of malaria patients experienced thrombocytopenia with mild, moderate, and severe thrombocytopenia respectively 29,4% ; 56,6% ; 14,0%. Severe thrombocytopenia was more common in falciparum malaria patients (16,4%). The statistical test result for the type of Plasmodium with the degree of thrombocytopenia were p = 0,139. It was concluded that there was no relationship between the types of Plasmodium falciparum and Plasmodium vivax with the degree of thrombocytopenia in malaria patients.&#x0D; Keywords: Malaria, Plasmodium, Degree of Thrombocytopenia

Transcriptional analysis identifies potential biomarkers and molecular regulators in acute malaria infection

AimsMalaria is a serious health threat in tropical countries. The causative parasite of Malaria tropica, the severe form, is the protozoan Plasmodium falciparum. In humans, it infects red blood cells, compromising blood flow and tissue perfusion. This study aims to identify potential biomarkers and RNA networks in leukocyte transcriptomes from patients suffering from Malaria tropica. Materials and methodsWe identified differentially regulated mRNAs and microRNAs in peripheral blood leukocytes of healthy donors and Malaria patients. Genes whose expression changes were not attributable to changes in leukocyte composition were used for bioinformatics analysis and network construction. Using a previously published cohort of community-acquired pneumonia (CAP) patients, we established discriminating transcriptomic features versus Malaria. We aimed to establish differences between the patient groups by principal component (PCA) and receiving operator characteristic (ROC) analyses and in silico cell type deconvolution. Key findingsWe found 870 genes that were significantly differentially expressed between healthy donors and Malaria patients. E2F1, BIRC5 and CCNB1 were identified to be primarily responsible for PCA separation of these two groups. We searched for biological function and found that cell cycle processes were strongly activated. By in silico cell type deconvolution, we attribute this to an expansion of γδ T cells. Additional discrimination between CAP and Malaria yielded 445 differentially expressed genes, among which immune proteasome transcripts PSMB8, PSMB9 and PSMB10 were significantly induced in Malaria. SignificanceWe identified transcripts from patient leukocytes that differentiate between healthy, Malaria and CAP, and indicate a biological context with potential pathophysiological relevance.

Opsonized antigen activates Vδ2+ T cells via CD16/FCγRIIIa in individuals with chronic malaria exposure.

Vγ9Vδ2 T cells rapidly respond to phosphoantigens produced by Plasmodium falciparum in an innate-like manner, without prior antigen exposure or processing. Vδ2 T cells have been shown to inhibit parasite replication in vitro and are associated with protection from P. falciparum parasitemia in vivo. Although a marked expansion of Vδ2 T cells is seen after acute malaria infection in naïve individuals, repeated malaria causes Vδ2 T cells to decline both in frequency and in malaria-responsiveness, and to exhibit numerous transcriptional and phenotypic changes, including upregulation of the Fc receptor CD16. Here we investigate the functional role of CD16 on Vδ2 T cells in the immune response to malaria. We show that CD16+ Vδ2 T cells possess more cytolytic potential than their CD16- counterparts, and bear many of the hallmarks of mature NK cells, including KIR expression. Furthermore, we demonstrate that Vδ2 T cells from heavily malaria-exposed individuals are able to respond to opsonized P.falciparum-infected red blood cells through CD16, representing a second, distinct pathway by which Vδ2 T cells may contribute to anti-parasite effector functions. This response was independent of TCR engagement, as demonstrated by blockade of the phosphoantigen presenting molecule Butyrophilin 3A1. Together these results indicate that Vδ2 T cells in heavily malaria-exposed individuals retain the capacity for antimalarial effector function, and demonstrate their activation by opsonized parasite antigen. This represents a new role both for Vδ2 T cells and for opsonizing antibodies in parasite clearance, emphasizing cooperation between the cellular and humoral arms of the immune system.

Aetiology of acute febrile illness in children in a high malaria transmission area in West Africa

ObjectivesAreas with declining malaria transmission in sub-Saharan Africa have recently witnessed important changes in the aetiology of childhood acute febrile illness (AFI). We describe the aetiology of AFI in a high malaria transmission area in rural Burkina Faso. MethodsIn a prospective hospital-based diagnostic study, children aged 3 months to 15 years with AFI were recruited and assessed using a systematic diagnostic protocol, including blood cultures, whole blood PCR on a selection of bacterial pathogens, malaria diagnostics and a multiplex PCR on nasopharyngeal swabs targeting 21 viral and 4 bacterial respiratory pathogens. ResultsA total of 589 children with AFI were enrolled from whom an infectious disease was considered in 575 cases. Acute respiratory tract infections, malaria and invasive bacterial infections (IBI) accounted for 179 (31.1%), 175 (30.4%) and 75 (13%) of AFI cases respectively; 16 (21.3%) of IBI cases also had malarial parasitaemia. A viral pathogen was demonstrated from the nasopharynx in 157 children (90.7%) with respiratory tract symptoms. Of all children with viral respiratory tract infections, 154 (92.4% received antibiotics, whereas no antibiotic was provided in 13 (17%) of IBI cases. ConclusionsViral respiratory infections are a common cause of childhood AFI in high malaria transmission areas, next to malaria and IBI. These findings highlight the importance of interventions to improve targeted treatment with antimicrobials. Most patients with viral infections received antibiotics unnecessarily, while a considerable number with IBI did not receive antibiotics.

Central Nervous System Virus Infection in African Children with Cerebral Malaria.

We aimed to identify the contribution of central nervous system (CNS) viral coinfection to illness in African children with retinopathy-negative or retinopathy-positive cerebral malaria (CM). We collected cerebrospinal fluid (CSF) from 272 children with retinopathy-negative or retinopathy-positive CM and selected CSF from 111 of these children (38 retinopathy positive, 71 retinopathy negative, 2 retinopathy unknown) for analysis by metagenomic next-generation sequencing. We found CSF viral coinfections in 7/38 (18.4%) retinopathy-positive children and in 18/71 (25.4%) retinopathy-negative children. Excluding HIV-1, human herpesviruses (HHV) represented 61% of viruses identified. Excluding HIV-1, CNS viral coinfection was equally likely in children who were retinopathy positive and retinopathy negative (P = 0.1431). Neither mortality nor neurological morbidity was associated with the presence of virus (odds ratio [OR] = 0.276, 95% CI: 0.056-1.363). Retinopathy-negative children with a higher temperature, lower white blood cell count, or being dehydrated were more likely to have viral coinfection. Level of consciousness at admission was not associated with CNS viral coinfection in retinopathy-negative children. Viral CNS coinfection is unlikely to contribute to coma in children with CM. The herpesviruses other than herpes simplex virus may represent incidental bystanders in CM, reactivating during acute malaria infection.

Effects of Hydroxyurea Treatment on Malaria Infections in Sub-Saharan Africa

Introduction. Realizing Effectiveness Across Continents with Hydroxyurea (REACH, NCT01966731) is a prospective multicenter open-label trial that has already demonstrated hydroxyurea treatment at maximum tolerated dose (MTD) is safe, feasible, and offers major benefits for children with sickle cell anemia living in sub-Saharan Africa (Tshilolo et al, NEJM 2019;380:121-131). One unexpected benefit was a significant reduction in the number of malaria infections, including those with Grade 3 severity or above, across four trial sites in varied epidemiological settings. The overall rate of symptomatic malaria infections decreased from 46.9 events per 100 patient-years during screening to 22.9 events per 100 patient-years on treatment, an incidence rate ratio of 0.49 (95% confidence intervals [CI] = 0.37-0.66). This decreased rate of malaria was observed during the first 12 months of treatment, but declined further between Months 12-36, after the children had dose escalation to achieve hydroxyurea MTD at 22.5 mg/kg/day. Potential mechanisms of malaria protection remain unknown at this time, but could relate to both patient characteristics as well as treatment-related laboratory changes in hemoglobin (Hb), mean corpuscular volume (MCV), absolute neutrophil count (ANC), or fetal hemoglobin (HbF). Methods. Malaria infections were recorded in the REACH REDCap electronic database. Using several methods for recurrent events, with time-varying predictors as well as landmark analysis, associations with infections recorded during study treatment were assessed for multiple variables including trial site, high or low malaria season, age, gender, spleen status, hydroxyurea dose, MTD status, latest laboratory values (Hb, MCV, ANC, and HbF, all measured at least 15 days prior to the onset of the infection), as well as genetic modifiers alpha-thalassemia and G6PD deficiency. Univariate relationships were assessed using the Anderson-Gill model, followed by multiple regression to estimate Hazard Ratios (HR) with 95% CI's. Additional analyses were performed using a gap-time model that resets the clock after each infection, as well as using only the first infection in each participant; the subset of 200 acute blood-smear proven malaria infections was also analyzed separately. Results. A total of 635 children were enrolled in REACH and eligible for analysis, of whom 606 started hydroxyurea treatment. There were 333 malaria infections recorded during 1580 patient-years of observation, including 50 during screening and 283 on treatment, of which 200 had documented positive blood smears at the clinical site. Significant associations for malaria risk were identified with higher ANC (HR = 1.06 per 1 x 109 neutrophils/L, CI = 1.02-1.10, P=0.005), higher MCV (HR = 1.01 per fL, CI = 1.00-1.02), and palpable splenomegaly (HR 1-4cm = 1.73, CI = 1.22-2.45, P= 0.002, HR ≥5cm = 1.52, CI = 1.04-2.21, P=0.03). In multiple regression, the latest ANC and MCV, as well as splenomegaly remained significant but higher HbF was also associated with more malaria (HR = 1.02 per %HbF, CI = 1.00-1.03, P=0.03). These trends were consistent when using the landmark, gap-time and first infection analytical approaches. Analysis of only documented blood-smear positive malaria infections again identified higher ANC, MCV, and splenomegaly as risk factors, but found no association with HbF. Achieving MTD was found to confer significant protection against documented malaria infections (HR = 0.62, CI=0.39-1.00, P=0.048). Conclusion. Hydroxyurea treatment in children with sickle cell anemia living in sub-Saharan Africa is associated with a decreased risk of malaria infections, particularly after achieving MTD. The mechanisms by which hydroxyurea protects against malaria are likely multi-factorial, but do not appear to be related to HbF induction, as higher HbF values were not protective and in some analyses were a risk factor. However, a higher ANC was significantly associated with malaria risk in all models and analyses; since hydroxyurea treatment lowers the ANC, dose escalation to MTD may confer protection against malaria infection by reducing inflammation. Spleen status is also crucial and the role of splenomegaly as a risk factor for malaria requires further investigation. Disclosures Ware: Novartis: Other: DSMB; Agios: Membership on an entity's Board of Directors or advisory committees; Nova Laboratories: Membership on an entity's Board of Directors or advisory committees; CSL Behring: Membership on an entity's Board of Directors or advisory committees; Addmedica: Other: Research Drug Donation; Bristol Myers Squibb: Other: Research Drug Donation; Global Blood Therapeutics: Membership on an entity's Board of Directors or advisory committees.

Splenomegaly in Children with Sickle Cell Anemia Receiving Hydroxyurea in Sub-Saharan Africa

Introduction. Children with sickle cell anemia enrolled in Realizing Effectiveness Across Continents with Hydroxyurea (REACH, NCT01966731) received open-label hydroxyurea at maximum tolerated dose (MTD) in four countries within sub-Saharan Africa (Tshilolo et al, NEJM 2019;380:121-131). Unlike children in the United States or Europe, a substantial proportion of REACH participants had splenomegaly at enrollment, and more developed splenomegaly while receiving hydroxyurea. Splenic enlargement in association with hydroxyurea treatment in sub-Saharan Africa is previously unrecognized, and its causes and consequences remain unclear. Methods. Palpable splenomegaly was evaluated at both the mid-clavicular and mid-axillary lines at each scheduled and unscheduled sick visit. The size of the spleen, defined as the greatest distance (cm) below the subcostal margin, was recorded in the REDCap trial database at all four clinical sites. Cross-sectional analysis was performed at baseline enrollment using four spleen categories (Not Palpable, 1-4 cm, ≥5 cm, or Splenectomy) with correlations for age, sex, site, growth parameters, alpha-thalassemia trait and G6PD deficiency. This analysis was repeated using the largest spleen size over the first two years on hydroxyurea, but examining two-year laboratory values and also the hydroxyurea dose at MTD, time to MTD, dose-limiting toxicities, and clinical outcomes including acute splenic sequestration, malaria infections, and sepsis. Results. A total of 606 children started hydroxyurea study treatment, including 6 (1.0%) with previous splenectomy, 59 (9.7%) with previous splenic sequestration, and 99 (16.3%) with palpable splenomegaly at enrollment (52 children with 1-4 cm and 47 with ≥5 cm). Large spleens (≥5 cm) were commonly observed at baseline at all clinical sites except Uganda, which identified only 1 child. Compared to those with no palpable spleen, children with large spleens at baseline had similar age and growth parameters, but were significantly more likely to have alpha-thalassemia (78.7% versus 56.2%, P=0.004) and also G6PD deficiency among males (28.0% versus 17.6%, P=0.32). Children with large spleens at enrollment also had a lower hemoglobin (Hb = 6.5 versus 7.3 g/dL, P&amp;lt;0.001) and lower platelet count (platelets = 227 versus 410 x 109/L, P&amp;lt;0.001), but equivalent fetal hemoglobin (HbF = 10.2 versus 9.4%, P=0.82). On hydroxyurea treatment with escalation to MTD, 262 children (43.7%) had palpable splenomegaly recorded, including 120 (20.0%) with spleens ≥5 cm. These large spleens were observed at all four clinical sites, with DRC having the most (52) and Uganda with the least (14). After 24 months of hydroxyurea treatment, laboratory differences were noted according to the cumulative occurrence of splenomegaly including a significantly lower hemoglobin and platelet count, higher absolute reticulocyte count, and lower hydroxyurea dose at MTD (Table). Large spleens were associated with a high cumulative incidence of laboratory dose-limiting toxicities, as well as a significantly higher risk of having clinically symptomatic malaria and receiving blood transfusions (Table). A total of 31 children (5.2%) on hydroxyurea treatment received elective splenectomy, including one partial splenectomy using arterial embolization. Conclusion. Children with sickle cell anemia living in sub-Saharan Africa have an increased risk of having palpable splenomegaly, which is further increased while receiving hydroxyurea treatment. Large spleen at baseline were associated with lower blood counts, consistent with hypersplenism. On hydroxyurea treatment, children with large spleens had significantly lower blood counts and more dose-limiting toxicities, which lowered their eventual hydroxyurea dose at MTD but still led to robust HbF responses. Children with large spleens were also at higher risk of developing malaria infections, receiving transfusions, and requiring surgical splenectomy. Splenic enlargement in association with hydroxyurea treatment was common in children with sickle cell anemia in the REACH trial; its cause remains unclear but the consequences include substantial laboratory toxicity and clinical morbidity. Investigating the etiologies and management of children with chronically enlarged spleens is crucial before expanding hydroxyurea access across Africa for sickle cell anemia. Disclosures Ware: Global Blood Therapeutics: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Other: Research Drug Donation; Nova Laboratories: Membership on an entity's Board of Directors or advisory committees; CSL Behring: Membership on an entity's Board of Directors or advisory committees; Novartis: Other: DSMB; Agios: Membership on an entity's Board of Directors or advisory committees; Addmedica: Other: Research Drug Donation.

Circulating endothelial cells in severe Plasmodium falciparum infection

Plasmodium falciparum infection is associated with diffuse vascular dys-regulation. Levels of blood circulating endothelial cells (CECs; CD146+CD45−) are a marker of vascular injury. This study aimed to measure blood CECs by flow cytometery in patients with acute malaria infection before and after treatment and to evaluate the prognostic value of that measurement for that disease. The subjects were allocated into: Group I: uncomplicated malaria (UM, n = 32), Group II: severe malaria (SM, n = 12), Group III: the treated UM (TUM, n = 32), Group IV: the treated SM (TSM, n = 12) and Group V: healthy controls (HC, n = 25). Before treatment, SM patients showed the highest mean number of CECs (30,658.3 ± 2658.2/5 × 106 peripheral blood mononuclear cells (PBMCs)), followed by UM patients (19,481.56 ± 866.83/5x106PBMCs) and both groups were significantly higher than HC (2034 ± 300.59/5x106PBMCs, P < .001). The level of CECs decreased significantly in both infected groups after treatment; in TUM it became 5602.18 ± 509.72/5 × 106PBMCs and in TSM it reached 8457.5 ± 452.4/5 × 106 PBMCs (both values P < .001 in comparison with SM). By receiver operating characteristic curve analysis, the best cut-off count for CECs which enables prediction of the occurrence of severe malaria infection was 27,150/5 × 106 PBMCs or more, with 100% sensitivity, 100% specificity, and 100% accuracy. CECs had a significant positive correlation with parasitemia index and serum creatinine and a significant negative correlation with hemoglobin concentration in patients with acute malaria. In conclusion, the level of CECs could be used as a biomarker denoting endothelium damage during acute P. falciparum infection, and it correlated with infection severity and predicted its prognosis.

Malaria, anemia, and invasive bacterial disease: A neutrophil problem?

Invasive bacterial disease is well described in immunocompromised hosts, including those with malaria infection. One bacterial infection frequently observed in children with Plasmodium falciparum infection is nontyphoidal salmonella (NTS) infection, in which a typically intestinal infection becomes systemic with serious, often fatal, consequences. In this review, we consider the role of malaria‐induced immunoregulatory responses in tipping the balance from tissue homeostasis during malaria infection to risk of invasive NTS. Also, neutrophils are crucial in the clearance of NTS but their ability to mount an oxidative burst and kill intracellular Salmonella is severely compromised during, and for some time after, an acute malaria infection. Here, we summarize the evidence linking malaria and invasive NTS infections; describe the role of neutrophils in clearing NTS infections; review evidence for neutrophil dysfunction in malaria infections; and explore roles of heme oxygenase‐1, IL‐10, and complement in mediating this dysfunction. Finally, given the epidemiological evidence that low density, subclinical malaria infections pose a risk for invasive NTS infections, we consider whether the high prevalence of such infections might underlie the very high incidence of invasive bacterial disease across much of sub‐Saharan Africa.

Cellular aging dynamics after acute malaria infection: A 12-month longitudinal study.

SummaryAccelerated cellular aging and reduced lifespan have recently been shown in birds chronically infected with malaria parasites. Whether malaria infection also affects cellular aging in humans has not been reported. Here, we assessed the effect of a single acute Plasmodium falciparum malaria infection on cellular aging dynamics in travelers prospectively followed over one year in Sweden. DNA and RNA were extracted from venous blood collected at the time of admission and repeatedly up to one year. Telomere length was measured using real‐time quantitative PCR, while telomerase activity and CDKN2A expression were measured by reverse transcriptase (RT)–qPCR. Our results show that acute malaria infection affects cellular aging as reflected by elevated levels of CDKN2A expression, lower telomerase activity, and substantial telomere shortening during the first three months postinfection. After that CDKN2A expression declined, telomerase activity increased and telomere length was gradually restored over one year, reflecting that cellular aging was reversed. These findings demonstrate that malaria infection affects cellular aging and the underlying cellular mechanism by which pathogens can affect host cellular aging and longevity need to be elucidated. Our results urge the need to investigate whether repeated malaria infections have more pronounced and long‐lasting effects on cellular aging and lifespan (similarly to what was observed in birds) in populations living in malaria endemic areas.