Erythrocyte invasion by malaria parasites and cytoadherence of Plasmodium falciparum-infected erythrocytes to host capillaries are 2 key pathogenic mechanisms in malaria. The receptor-binding domains of erythrocyte-binding proteins (EBPs) such as Plasmodium falciparum EBA-175, which mediate invasion, and P falciparum erythrocyte membrane protein 1 (PfEMP-1) family members, which are encoded by var genes and mediate cytoadherence, have been mapped to conserved cysteine-rich domains referred to as Duffy-binding-like (DBL) domains. Here, we have mapped regions within DBL domains from EBPs and PfEMP-1 that contain receptor-binding residues. Using biochemical and molecular methods we demonstrate that the receptor-binding residues of parasite ligands that bind sialic acid on glycophorin A for invasion as well as complement receptor-1 and chondroitin sulfate A for cytoadherence map to central regions of DBL domains. In contrast, binding to intercellular adhesion molecule 1 (ICAM-1) requires both the central and terminal regions of DBLbetaC2 domains. Determination of functional regions within DBL domains is the first step toward understanding the structure-function bases for their interaction with diverse host receptors.

Cancer related anemia (CRA) adversely affects patient Quality of Life (QoL) and overall survival. We prospectively studied the prevalence, etiology and the impact of anemia on QoL in 218 Indian cancer patients attending a tertiary referral hospital. The study used the sTfR/log Ferritin index to detect iron deficiency anemia and assessed patient QoL using the Functional Assessment of Cancer Therapy-Anemia (FACT-An) tool, standardized for language. Mean patient age was 51±13 years and 60% were female. The prevalence of cancer related anemia in this setting was 64% (n = 139). As expected, plasma ferritin did not differ significantly between anemic (n = 121) and non-anemic cancer patients (n = 73). In contrast, plasma sTfR levels were significantly higher in anemic cancer patients compared to non-anemic cancer patients (31 nmol/L vs. 24 nmol/L, p = 0.002). Among anemic cancer patients, using the sTfR/log Ferritin index, we found that 60% (n = 83) had iron deficiency anemia (IDA). Interestingly, plasma sTfR levels were significantly higher in cancer patients with CRA+IDA (n = 83) compared with patients having CRA (n = 38) alone (39 nmol/L vs. 20 nmol/L, p<0.001). There was a significant linear correlation between Hb and QoL (Spearman ρ = 0.21; p = 0.001) and multivariate regression analysis revealed that every gram rise in Hb was accompanied by a 3.1 unit increase in the QoL score (95% CI = 0.19–5.33; p = 0.003). The high prevalence of anemia in cancer patients, a major portion of which is due to iron deficiency anemia, the availability of sensitive and specific biomarkers of iron status to detect IDA superimposed on anemia of inflammation, suggests an urgent need to diagnose and treat such patients. Despite the potential negative consequences of increasing metabolically available plasma iron in cancer, our clinical data suggest that detecting and treating IDA in anemic cancer patients will have important consequences to their QoL and overall survival. Clinical trials of iron therapy in these patients will be able to demonstrate the potential for benefit or harm.

The detection of iron deficiency anemia is challenged by the paucity of diagnostic tests demonstrating high sensitivity and specificity. Using two biomarkers, zinc-protoporphyrin/heme and hepcidin, we established the diagnostic cut-off values for iron deficiency anemia in preschool children and women. We randomly selected non-anemic individuals (n=190; women=90, children=100) and individuals with iron deficiency anemia (n=200; women=100, children=100) from a preexisting cohort of healthy preschool children and their mothers. The diagnostic performance of these biomarkers was estimated by analyzing receiver operating characteristic curves. Diagnostic cut-offs with a high predictive value for iron deficiency anemia were selected. Median zinc-protoporphyrin/heme and hepcidin values in non-anemic children were 49 μmol/mol heme and 42 ng/mL, respectively, and in non-anemic women these values were 66 μmol/mol heme and 17.7ng/mL, respectively. Children and women with iron deficiency anemia had higher zinc-protoporphyrin/heme ratios (children=151 μmol/mol heme and women=155 μmol/mol heme) and lower hepcidin levels (children=1.2ng/mL and women=0.6ng/mL). A zinc-protoporphyrin/heme ratio cut-off >90 μmole/mole heme in children and >107 μmole/mole heme in women was associated with a high diagnostic likelihood for iron deficiency anemia (children, likelihood ratio=20.2: women, likelihood ratio=10.8). Hepcidin cut-off values of ≤6.8ng/mL in children and ≤4.5ng/mL in women were associated with a high diagnostic likelihood for iron deficiency anemia (children, likelihood ratio=14.3: women, likelihood ratio=16.2). The reference ranges and cut-off values identified in this study provide clinicians with guidance for applying these tests to detect iron deficiency anemia. Erythrocyte zinc-protoporphyrin/heme ratio is a valid point-of-care biomarker to diagnose iron deficiency anemia.

INTRODUCTION: The etiology of HIV- associated anemia is multifactorial. We previously found a high prevalence of anaemia of inflammation and anemia due to micronutrient deficiencies in HIV patients (Eur J Pediatr 2012, 17:531). Inflammatory disease confounds the value of standard diagnostic markers, posing a challenge to the detection of iron deficient and iron-restricted erythropoiesis. Using serum hepcidin as a biomarker, we tested the hypothesis that total body iron stores like inflammatory signals would also influence serum hepcidin levels in patients with HIV infection. METHODS: Healthy subjects, patients with pure iron deficiency anemia (IDA) andpatients with HIV infection were prospectively enrolled after obtaining informed consent. Using sex adjusted WHO values for anemia diagnosis, ferritin <12µg/L, and CRP values, subjects were categorized into healthy and IDA groups (N Engl J Med 2015, 373:485). Using age adjusted WHO values for anemia, patients with HIV were divided into anemic and non-anemic groups. Using the soluble transferrin receptor (sTfR)/log ferritin (F) index, we defined those subjects with an sTfR-F index < 1.03 as having anemia of inflammation (AI) and those subjects with an sTfR-F index ≥1.03 as having IDA superimposed on AI (Am J Hematol. 2011, 86:923). All laboratory analytes were measured using standard commercial assays. RESULTS: The demographic characteristics of the different groups in the study population are shown in table 1. Compared with healthy controls, mean hemoglobin was significantly lower in patients with pure IDA, HIV patients with anemia, and HIV patients without anemia (p<0.001). The serum soluble transferin receptor (sTfR) levels and serum erythropoietin levels were significantly elevated in pure IDA patients (p<0.001) and HIV patients with anemia (p<0.001) compared with healthy controls, reflecting erythropoietic stress. Compared with healthy controls, serum hepcidin levels were markedly lower in pure IDA patients (p<0.01) and HIV patients with anemia suggesting that iron status influenced hepcidin levels more profoundly than inflammation in HIV infected patients. We also measured erythrocyte ZPP levels and found them to be significantly higher in pure IDA patients (p<0.001) and HIV patients with anemia (p<0.001) compared to healthy controls. All HIV patients with anemia had an sTfR-F index ≥1.03 suggesting the presence of IDA superimposed on AI. Interestingly, serum hepcidin levels correlated inversely with the sTfR-F index in both patients with pure IDA (ρ=-0.76; p<0.001) and in HIV patients with anemia (ρ=-0.4; p<0.02). Similarly, ZPP levels correlated linearly with the sTfR-F index in pure IDA patients (ρ=0.6; p<0.002) and in HIV patients with anemia (ρ=0.5; p<0.001). CONCLUSION: Our data shows significant differences in serum hepcidin and erythrocyte ZPP levels in healthy, IDA and HIV patients. These two biomarkers could be included in the panel of diagnostic tests used to detect iron deficiency anemia superimposed on anemia of inflammation. Further studies are needed to provide the appropriate cut-off values with which IDA can be detected with appropriate sensitivity and specificity in patients with anemia of inflammation. Such data may also be helpful in monitoring therapeutic responses to iron. Table 1. Haematological and biochemical parameters Healthy(n = 45) Pure IDA(n=33) HIV with anemia(n=46) HIV without anemia(n=46) Age ± SD 31±7.5 25±3.6 35±11.9 39±12 Hemoglobin ± SD(g/dl) 15.2±1.2 10.1±1.3a, c, d 11±1.1a, d 13.8±1.3a MCV ± SD 85±4.2 74±7.7 80±8.7 85±4.6 Biochemical parameters Serum Ferritin*(ng/mL) 57 (43, 83) 4.5a, c, d (3.1, 7) 14a, d (7, 34) 47 (32, 130) Serum sTfR*(mg/L) 1.7b, c (1.3, 2) 4.3 (3, 6.3) 2.5 (2, 3.7) 1.8b, c (1.3, 2.1) Serum Erythropoietin*(mU/mL) 6.5b, c (4.9, 9.8) 40 (28, 61) 20b (13, 32) 10b, c (5, 14) Biomarkers Serum Hepcidin*(ng/mL) 20.6 (14.2, 25.6) 0.5a (0.1, 3.3) 11.6b (2.9, 29.8) Erythrocyte ZPP*(μmol/mol heme) 50b, c (40, 58) 200 (117, 247) 101b (69, 131) 56b, c (42, 75) *All non Gaussian distributed data are presented as median (25th percentile, 75th percentile); ap < 0.05 compared with healthy subjects, bp < 0.05 compared with pure IDA patients, cp < 0.05 compared with HIV anemia patients, dp < 0.05 compared with HIV without anemia patients. Disclosures No relevant conflicts of interest to declare.