Children with Plasmodium vivax infection previously observed in Namibia, were Duffy negative and carried a c.136G > A mutation

Background In a previous study, using a molecular approach, we reported the presence of P. vivax in Namibia. Here, we have extended our investigation to the Duffy antigen genetic profile of individuals of the same cohort with and without Plasmodium infections. Methods Participants with P. vivax (n = 3), P. falciparum (n = 23) mono-infections and co-infections of P. vivax/P. falciparum (n = 4), and P. falciparum/P. ovale (n = 3) were selected from seven regions. Participants with similar age but without any Plasmodium infections (n = 47) were also selected from all the regions. Duffy allelic profile was examined using standard PCR followed by sequencing of amplified products. Sequenced samples were also examined for the presence or absence of G125A mutation in codon 42, exon 2. Results All individuals tested carried the − 67 T > C mutation. However, while all P. vivax infected participants carried the c.G125A mutation, 7/28 P. falciparum infected participants and 9/41 of uninfected participants did not have the c.G125A mutation. The exon 2 region surrounding codon 42, had a c.136G > A mutation that was present in all P. vivax infections. The odds ratio for lack of this mutation with P. vivax infections was (OR 0.015, 95% CI 0.001–0.176; p = 0.001). Conclusion We conclude that P. vivax infections previously reported in Namibia, occurred in Duffy negative participants, carrying the G125A mutation in codon 42. The role of the additional mutation c.136 G > A in exon 2 in P. vivax infections, will require further investigations.

The dimeric form of CXCL12 binds to atypical chemokine receptor 1

The pleiotropic chemokine CXCL12 is involved in diverse physiological and pathophysiological processes, including embryogenesis, hematopoiesis, leukocyte migration, and tumor metastasis. It is known to engage the classical receptor CXCR4 and the atypical receptor ACKR3. Differential receptor engagement can transduce distinct cellular signals and effects as well as alter the amount of free, extracellular chemokine. CXCR4 binds both monomeric and the more commonly found dimeric forms of CXCL12, whereas ACKR3 binds monomeric forms. Here, we found that CXCL12 also bound to the atypical receptor ACKR1 (previously known as Duffy antigen/receptor for chemokines or DARC). In vitro nuclear magnetic resonance spectroscopy and isothermal titration calorimetry revealed that dimeric CXCL12 bound to the extracellular N terminus of ACKR1 with low nanomolar affinity, whereas the binding affinity of monomeric CXCL12 was orders of magnitude lower. In transfected MDCK cells and primary human Duffy-positive erythrocytes, a dimeric, but not a monomeric, construct of CXCL12 efficiently bound to and internalized with ACKR1. This interaction between CXCL12 and ACKR1 provides another layer of regulation of the multiple biological functions of CXCL12. The findings also raise the possibility that ACKR1 can bind other dimeric chemokines, thus potentially further expanding the role of ACKR1 in chemokine retention and presentation.

Duffy Blood System and G6PD Genetic Variants In P. Vivax Malaria Patients From Manaus, Amazonas, Brazil

Over a third of the world’s population lives at risk of potentially severe Plasmodium vivax induced malaria. The unique aspect of the parasite’s biology and interactions with the human host make it harder to control and eliminate the disease. Glucose-6-phosphate dehydrogenase (G6PD) deficiency and Duffy-negative blood groups are two red blood cell variations that confer protection against malaria. Molecular genotyping of G6PD and Duffy was performed in 225 patients with severe and non-severe malaria. Of the 225 patients, 29 (12.94%) and 43 (19.19%) were carriers of the G6PD c.202G>A and c.376A>G, respectively. For the Duffy genotype (c.-67T>C in the GATA promoter region), 70 (31.11%) were phenotyped as Fy(a+b-), 98 (43.55%) Fy(a+b+), 56 (24.9%) Fy(a-b+) and 1 (0.44%) Fy(a-b-). The FY*01/FY*02 genotype was prevalent in both non-severe and severe malaria. However, the frequency increased when SNP c.376A>G was also present. In women, the FY*01/FY*02 allele occurred concomitantly with c.376A>G more frequently in non-severe malaria, while in men, this combination is revealed predominantly in severe malaria. G202A and A376G G6PD variants were higher in severe malaria, with c.202G>A (RR= 4.76 – p=.009) and c.376A>G (RR: 6.47 – p<0.001) strongly associated with the trials malaria (p<0.001). Duffy phenotype Fy(a-b+) (p=0.003) and genotype FY*02/ FY*02 (p=0.007) presented the highest values parasitemia density of the vivax malaria. Research on G6PD and Duffy antigen deficiencies has been valuable, particularly when focused on densely populated areas. Altogether, c.202G>A and c.376A>G SNPs seem to be risk factors for the development of severe vivax malaria. Molecular diagnosis before treatment may be necessary in the Amazonian population and uncomplicated malaria showed a greater frequency of variation for GATA and G6PD variants than severe malaria.

Duffy Blood System and G6PD Genetic Variants In P. Vivax Malaria Patients From Manaus, Amazonas, Brazil

Over a third of the world’s population lives at risk of potentially severe Plasmodium vivax induced malaria. The unique aspect of the parasite’s biology and interactions with the human host make it harder to control and eliminate the disease. Glucose-6-phosphate dehydrogenase (G6PD) deficiency and Duffy-negative blood groups are two red blood cell variations that confer protection against malaria. Molecular genotyping of G6PD and Duffy was performed in 225 patients with severe and non-severe malaria. Of the 225 patients, 29 (12.94%) and 43 (19.19%) were carriers of the G6PD c.202G>A and c.376A>G, respectively. For the Duffy genotype (c.-67T>C in the GATA promoter region), 70 (31.11%) were phenotyped as Fy(a+b-), 98 (43.55%) Fy(a+b+), 56 (24.9%) Fy(a-b+) and 1 (0.44%) Fy(a-b-). The FY*01/FY*02 genotype was prevalent in both non-severe and severe malaria. However, the frequency increased when SNP c.376A>G was also present. In women, the FY*01/FY*02 allele occurred concomitantly with c.376A>G more frequently in non-severe malaria, while in men, this combination is revealed predominantly in severe malaria. G202A and A376G G6PD variants were higher in severe malaria, with c.202G>A (RR= 4.76 – p=.009) and c.376A>G (RR: 6.47 – p<0.001) strongly associated with the trials malaria (p<0.001). Duffy phenotype Fy(a-b+) (p=0.003) and genotype FY*02/ FY*02 (p=0.007) presented the highest values parasitemia density of the vivax malaria. Research on G6PD and Duffy antigen deficiencies has been valuable, particularly when focused on densely populated areas. Altogether, c.202G>A and c.376A>G SNPs seem to be risk factors for the development of severe vivax malaria. Molecular diagnosis before treatment may be necessary in the Amazonian population and uncomplicated malaria showed a greater frequency of variation for GATA and G6PD variants than severe malaria.

Relationship between Duffy Antigen Receptor for Chemokines and Clinical Characteristics in Han People with Chronic Hepatitis C Infection in Dalian, China

Background and Objectives: Most patients with untreated chronic hepatitis C virus (HCV) infection develop hepatic fibrosis. Hepatic disease progression is monitored with hematological markers (alanine aminotransferase [ALT], aspartate aminotransferase [AST], albumin and platelet [PLT] count, AST/ALT ratio, AST/PLT ratio index [APRI], and fibrosis 4 score [FIB-4]) and FibroScan. The present study aimed to investigate the association between Duffy antigen/chemokines receptor (DARC) polymorphisms and clinical parameters in the Han people with chronic hepatitis C infection in Dalian, China. Materials and Methods: This cohort study was performed on 245 Han people with chronic HCV at Dalian infectious hospital during April-December 2015. The participants of the research were selected using the consecutive sampling method. The DARC genotyping was performed using the TaqMan probe method and transient elastography was measured by FibroScan. Results: Based on the findings, DARC polymorphisms correlated with ALT concentrations (FY*A/FY*A vs. FY*A/FY*B, P=0.025). However, the DARC polymorphism did not have an association with HCV RNA titers (FY*A/FY*A vs. FY*A/FY*B, P=0.241) or hepatic fibrosis (FY*A/FY*A vs. FY*A/FY*B, P=0.325). Moreover, correlation analyses showed that APRI (P<0.001, rho=0.603) and FIB-4 (P<0.001, rho=0.698) were useful predictors of hepatic fibrosis in chronic HCV infection. Besides, HCV RNA titers (P=0.327) and hepatic injury markers (P=0.814, 0.198, 0.767, and 0.171 for ALT, AST, ALB, and AST/ALT, respectively) were not useful for the estimation of the fibrosis stage in patients with chronic hepatitis C. Conclusion: The FY*A allele is a potentially valuable protective factor against hepatocyte damage in chronic HCV-infected patients.

Identification of a domain critical for Staphylococcus aureus LukED receptor targeting and lysis of erythrocytes

Leukocidin ED (LukED) is a pore-forming toxin produced by Staphylococcus aureus, which lyses host cells and promotes virulence of the bacteria. LukED enables S. aureus to acquire iron by lysing erythrocytes, which depends on targeting the host receptor Duffy antigen receptor for chemokines (DARC). The toxin also targets DARC on the endothelium, contributing to the lethality observed during bloodstream infection in mice. LukED is comprised of two monomers: LukE and LukD. LukE binds to DARC and facilitates hemolysis, but the closely related Panton–Valentine leukocidin S (LukS-PV) does not bind to DARC and is not hemolytic. The interaction of LukE with DARC and the role this plays in hemolysis are incompletely characterized. To determine the domain(s) of LukE that are critical for DARC binding, we studied the hemolytic function of LukE–LukS-PV chimeras, in which areas of sequence divergence (divergence regions, or DRs) were swapped between the toxins. We found that two regions of LukE's rim domain contribute to hemolysis, namely residues 57–75 (DR1) and residues 182–196 (DR4). Interestingly, LukE DR1 is sufficient to render LukS-PV capable of DARC binding and hemolysis. Further, LukE, by binding DARC through DR1, promotes the recruitment of LukD to erythrocytes, likely by facilitating LukED oligomer formation. Finally, we show that LukE targets murine Darc through DR1 in vivo to cause host lethality. These findings expand our biochemical understanding of the LukE–DARC interaction and the role that this toxin-receptor pair plays in S. aureus pathophysiology.

Adaptation to Mediterranea

The Mediterranean region encompasses countries that surround Mediterranean Sea. Due to its position at the intersection of Eurasia and Africa it has often been a route of human migrations during history, which contributed to its high biodiversity. People living in this area had been exposed to the episodes of natural selection that led to the establishment of specific genetic variations, for which is thought to carry a certain adaptation. Some recent studies have shown that genetic adaptations are probably related to the immune defense against infectious pathogens. One of the most recognizable disease of the region is familial Mediterranean fever (FMF), a prototype of a monogenic autoinflammatory disease. FMF is predisposed by the mutations in the Mediterranean fever (MEFV) gene that encodes inflammasome regulatory protein - pyrin. Specific variations of several other genes have been proposed to confer a protection against Plasmodium malariae parasite. Some of these are hemoglobin S (HbS), thalassemia, glucose-6-phosphate dehydrogenase deficiency, ovalocytosis, and mutation in the Duffy antigen (FY). In this chapter we will summarize important genetics and pathogenesis features of diseases commonly encountered in the Mediterranean region with a short discussion of potential adaptations that they may carry.

Plasmodium vivax Strains Use Alternative Pathways for Invasion

Plasmodium vivax has 2 invasion ligand/host receptor pathways (P. vivax Duffy-binding protein/Duffy antigen receptor for chemokines [DARC] and P. vivax reticulocyte binding protein 2b/transferrin receptor [TfR1]) that are promising targets for therapeutic intervention. We optimized invasion assays with isogenic cultured reticulocytes. Using a receptor blockade approach with multiple P. vivax isolates, we found that all strains utilized both DARC and TfR1, but with significant variation in receptor usage. This suggests that P. vivax, like Plasmodium falciparum, uses alternative invasion pathways, with implications for pathogenesis and vaccine development.

Abstract MP154: Deletion of the Duffy Antigen Receptor for Chemokines (DARC) Confers Protection Against Abdominal Aortic Aneurysm (AAA) Formation

Introduction: Abdominal aortic aneurysms (AAA) are characterized by inflammation and matrix metalloproteinase (MMP)-mediated degradation of extra cellular matrix proteins leading to aortic dilation and potentially rupture. Inflammatory chemokines that promote AAA are modulated by binding to the Duffy antigen receptor for chemokines (DARC), a non-signaling receptor expressed primarily on erythrocytes. Interestingly, African Americans exhibit reduced frequency of AAA, and the majority of African descendent individuals do not express DARC on their erythrocytes. Here, we tested the hypothesis that DARC gene deletion protects against the development of AAA. Methods: The induction of AAA was performed using both angiotensin II (AngII) infusion and calcium chloride (CaCl 2 ) application models. Eight week old LDLR knockout (KO, control) and LDLR KO/DARC KO mice were infused with AngII via osmotic mini-pumps for four weeks. For the CaCl 2 application model, twelve week old DARC KO and WT control mice underwent laparotomy and 0.5 mol/L CaCl 2 was applied to the infrarenal aorta. Aortic dilation and AAA formation was assessed using ultrasound, mice were then euthanized and tissues were harvested for analysis. Results: The aortic diameter of LDLR KO/DARC KO mice was significantly lower relative to control mice after AngII infusion (P=0.02). There was no difference in the pressor response to AngII between groups. Furthermore, IL-6 levels were significantly reduced in the aortas of LDLR KO/DARC KO mice compared to control mice (P=0.001). Expression of MCP-1, which has strong affinity for DARC, tended to be higher in aortas from LDLR KO/DARC KO mice compared to control (P=0.063). In contrast, plasma IL-6 levels were similar in both LDLR KO/DARC KO and control mice, while MCP-1 tended to be lower in the plasma of LDLR KO/DARC KO (P=0.07). DARC KO mice likewise exhibited a trend toward reduced aortic dilation in the CaCl 2 application model compared to controls (P=0.09). Conclusions: DARC KO mice are protected against AAA formation, perhaps through differential regulation of aortic chemokine trafficking. Understanding the mechanisms by which loss of DARC confers protection from AAA formation may be relevant to ethnic differences in susceptibility to AAA.