Complement component 3 mutations alter the longitudinal risk of pediatric malaria and severe malarial anemia

Severe malarial anemia (SMA) is a leading cause of childhood morbidity and mortality in holoendemic Plasmodium falciparum transmission regions. To gain enhanced understanding of predisposing factors for SMA, we explored the relationship between complement component 3 (C3) missense mutations [rs2230199 (2307C>G, Arg>Gly102) and rs11569534 (34420G>A, Gly>Asp1224)], malaria, and SMA in a cohort of children (n = 1617 children) over 36 months of follow-up. Variants were selected based on their ability to impart amino acid substitutions that can alter the structure and function of C3. The 2307C>G mutation results in a basic to a polar residue change (Arg to Gly) at position 102 (β-chain) in the macroglobulin-1 (MG1) domain, while 34420G>A elicits a polar to acidic residue change (Gly to Asp) at position 1224 (α-chain) in the thioester-containing domain. After adjusting for multiple comparisons, longitudinal analyses revealed that inheritance of the homozygous mutant (GG) at 2307 enhanced the risk of SMA (RR = 2.142, 95%CI: 1.229–3.735, P = 0.007). The haplotype containing both wild-type alleles (CG) decreased the incident risk ratio of both malaria (RR = 0.897, 95%CI: 0.828–0.972, P = 0.008) and SMA (RR = 0.617, 95%CI: 0.448–0.848, P = 0.003). Malaria incident risk ratio was also reduced in carriers of the GG (Gly102Gly1224) haplotype (RR = 0.941, 95%CI: 0.888–0.997, P = 0.040). Collectively, inheritance of the missense mutations in MG1 and thioester-containing domain influence the longitudinal risk of malaria and SMA in children exposed to intense Plasmodium falciparum transmission.

4148 Thrombocytopenia and whole blood transfusion in children with severe falciparum malaria

OBJECTIVES/GOALS: Severe malarial anemia due to Plasmodium falciparum is often accompanied by thrombocytopenia. Treatment includes transfusion of whole blood, which contains erythrocytes, platelets, and other blood components. The objective of the study was to assess the effect of whole blood transfusion on survival in children with severe falciparum malaria and to examine the potential interaction of thrombocytopenia with malaria mortality and transfusion response. METHODS/STUDY POPULATION: We analyzed a retrospective cohort of 842 hospitalized children in Zambia with severe malarial anemia (703 transfused, 139 not transfused due to stock-out or other reason). Severe malarial anemia was defined as a positive rapid diagnostic test or blood smear in combination with an admission hemoglobin concentration ≤5 g/dL. RESULTS/ANTICIPATED RESULTS: Mortality was 13% (94/703) in the transfused group and 24% (34/139) in the non-transfused group. Kaplan-Meier survival estimates stratified by transfusion status and thrombocytopenia (150,000/μL threshold) showed increased mortality in children with thrombocytopenia who did not undergo transfusion, with no differences in mortality among the other transfused and non-transfused groups (log-rank test P = 0.0001). Effect modification analysis by Cox proportional hazards regression adjusted for age, sex, hemoglobin concentration, blood group type, and eosinophilia showed a significant interaction between platelet count and transfusion status (P = 0.028). Children with thrombocytopenia who were transfused and died had little or no post-transfusion increase in platelets, in contrast to those who survived. Freshness of transfused whole blood, construed from expiration dates, correlated with greater platelet recovery and improved survival. DISCUSSION/SIGNIFICANCE OF IMPACT: The role of platelets in malaria pathophysiology is complex and incompletely understood; prior studies describe preferential binding of platelets to parasitized erythrocytes and direct parasitocidal activity, whereas others detailed deleterious effects in malaria involving the central nervous system vasculature. These findings point to a potential clinical role for platelet-directed transfusion strategies to improve survival in children with severe falciparum malaria, which should be further assessed in randomized interventional studies.

Delayed iron improves iron status without altering malaria risk in severe malarial anemia

ABSTRACT Background WHO guidelines recommend concurrent iron and antimalarial treatment in children with malaria and iron deficiency, but iron may not be well absorbed or utilized during a malaria episode. Objectives We aimed to determine whether starting iron 28 d after antimalarial treatment in children with severe malaria and iron deficiency would improve iron status and lower malaria risk. Methods We conducted a randomized clinical trial on the effect of immediate compared with delayed iron treatment in Ugandan children 18 mo–5 y of age with 2 forms of severe malaria: cerebral malaria (CM; n = 79) or severe malarial anemia (SMA; n = 77). Asymptomatic community children (CC; n = 83) were enrolled as a comparison group. Children with iron deficiency, defined as zinc protoporphyrin (ZPP) ≥ 80 µmol/mol heme, were randomly assigned to receive a 3-mo course of daily oral ferrous sulfate (2 mg · kg–1 · d–1) either concurrently with antimalarial treatment (immediate arm) or 28 d after receiving antimalarial treatment (delayed arm). Children were followed for 12 mo. Results All children with CM or SMA, and 35 (42.2%) CC, were iron-deficient and were randomly assigned to immediate or delayed iron treatment. Immediate compared with delayed iron had no effect in any of the 3 study groups on the primary study outcomes (hemoglobin concentration and prevalence of ZPP ≥ 80 µmol/mol heme at 6 mo, malaria incidence over 12 mo). However, after 12 mo, children with SMA in the delayed compared with the immediate arm had a lower prevalence of iron deficiency defined by ZPP (29.4% compared with 65.6%, P = 0.006), a lower mean concentration of soluble transferrin receptor (6.1 compared with 7.8 mg/L, P = 0.03), and showed a trend toward fewer episodes of severe malaria (incidence rate ratio: 0.39; 95% CI: 0.14, 1.12). Conclusions In children with SMA, delayed iron treatment did not increase hemoglobin concentration, but did improve long-term iron status over 12 mo without affecting malaria incidence. This trial was registered at clinicaltrials.gov as NCT01093989.

Profound Alteration of Host Response in Severe Malarial Anemia By Sickle Cell Disease: Reduction of Parasite Sequestration and Inflammation, Upregulation of Angiopoietin-2

Introduction. Plasmodium falciparum malaria is a major cause of morbidity in African children with sickle cell anemia (SCA). Factors associated with severe disease and mortality in malaria, including tumor necrosis factor (TNF)-alpha and components of the angiopoietin (Angpt)-Tie-2 system, have also been implicated in the pathogenesis and clinical severity of SCA. However, there is no data on how these factors are altered in children with SCA during severe malaria. Methods. A total of 232 children who presented with severe malarial anemia (hemoglobin < 5 g/dL with Plasmodium parasitemia on peripheral blood smear) were enrolled in a prospective study of severe malaria at Mulago National Referral Hospital in Kampala, Uganda. No child had known SCA at the time of severe malarial anemia diagnosis. Samples from enrolled children were subsequently tested by genotyping for the presence of hemoglobin S (HbS) using a TaqMan assay at rs334. Clinical and laboratory parameters, plasma markers of inflammation and endothelial activation, and the estimated total, sequestered, and circulating parasite biomass were compared in children with HbSS compared to HbAA. Results. The study cohort included 208 children with HbAA (90.4%), 22 children with HbSS (9.6%), and 2 with HbAS. Children with HbSS were older than children with HbAA (Table 1), so all comparisons were adjusted for age. Children with HbSS versus HbAA did not differ significantly in duration of symptoms, clinical signs, disease severity, or degree of peripheral P. falciparum parasitemia. However, children with HbSS had significantly lower concentrations of PfHRP2, a marker of total parasite biomass, and lower levels of estimated sequestered parasite biomass (Table 1). Children with HbSS had pronounced leukocytosis, a feature of chronic inflammation in SCA, but had significantly lower concentrations of the inflammatory biomarkers C-reactive protein and alpha-1-acid glycoprotein and the pro-inflammatory cytokine TNF-alpha than children with HbAA (Table 1). In contrast, concentrations of angiopoietin-2 (Angpt-2), a marker of endothelial dysregulation that has been associated with mortality in severe malaria, were 3-fold greater in children with HbSS than HbAA (Table 1), and were associated with an increased risk of post-discharge recurrent malaria in the cohort, after adjustment for age, sex, and hemoglobin S genotype (odds ratio per log-10 increase in Angpt-2 [95% confidence interval], 2.11 [1.01, 4.38]). Conclusion. In this population, undiagnosed SCA is common in children with severe malarial anemia. During episodes of severe malarial anemia, children with SCA suppress parasite sequestration and inflammation but upregulate Angpt-2, which may increase risk of recurrence of malaria. Disclosures Conroy: ALC: Patents & Royalties: angiopoietin-1, angiopoietin-2. Ware:Addmedica: Other: Research Drug Donation; Global Blood Therapeutics: Membership on an entity's Board of Directors or advisory committees; 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; Novartis: Other: DSMB; Bristol Myers Squibb: Other: Research Drug Donation.