From Malaria to Chemokine Receptor: The Emerging Physiologic Role of the Duffy Blood Group Antigen

Association between FY*02N.01 and the severity of COVID-19: initial observations

Introduction

The pro-inflammatory immune response underlies severe cases of COVID-19. Antigens of the Duffy blood group systems are receptors for pro-inflammation chemokines. The ACKR1 c.-67T>C gene variation silences the expression of Duffy antigens on erythrocytes and individuals presenting this variant in homozygosity have impaired inflammatory response control. Our aim was to evaluate the association between the ACKR1 c.-67T>C and the severity of COVID-19.

Methods

This was a retrospective single-center case-control study, enrolling 164 participants who were divided into four groups: 1) Death: COVID-19 patients who died during hospitalization; 2) Hospital Discharge: COVID-19 patients who were discharged for home after hospitalizations; 3) Convalescent Plasma Donors: COVID-19 patients who were not hospitalized, and; 4) Controls: patients with diagnosis other than COVID-19. Patients were genotyped for the ACKR1 c.-67T>C (FY*02 N.01 allele) and the frequency of individuals presenting the altered allele was compared between the groups.

Results

The groups significantly differed in terms of the percentage of patients presenting at least one FY*02N.01 allele: 36.8% (Death group), 37% (Hospital Discharge group), 16.1% (Convalescent Plasma group) and 16.2% (Control group) (p = 0.027). The self-declared race (p < 0.001) and the occurrence of in hospital death (p = 0.058) were independently associated with the presence of the FY*02N.01 allele. Hypertension (p < 0.001), age (p < 0.001) and the presence of at least one FY*02N.01 allele (p = 0.009) were independently associated with the need for hospitalization.

Conclusion

There is a suggestive association between the presence of the FY*02N.01 and the severity of COVID-19. This may be a mechanism underlying the worse prognosis for Afro-descendants infected with SARS-CoV-2.

Cataloguing experimentally confirmed 80.7 kb-long ACKR1 haplotypes from the 1000 Genomes Project database

Background

Clinically effective and safe genotyping relies on correct reference sequences, often represented by haplotypes. The 1000 Genomes Project recorded individual genotypes across 26 different populations and, using computerized genotype phasing, reported haplotype data. In contrast, we identified long reference sequences by analyzing the homozygous genomic regions in this online database, a concept that has rarely been reported since next generation sequencing data became available.

Study design and methods

Phased genotype data for a 80.6 kb region of chromosome 1 was downloaded for all 2,504 unrelated individuals of the 1000 Genome Project Phase 3 cohort. The data was centered on the ACKR1 gene and bordered by the CADM3 and FCER1A genes. Individuals with heterozygosity at a single site or with complete homozygosity allowed unambiguous assignment of an ACKR1 haplotype. A computer algorithm was developed for extracting these haplotypes from the 1000 Genome Project in an automated fashion. A manual analysis validated the data extracted by the algorithm.

Results

We confirmed 902 ACKR1 haplotypes of varying lengths, the longest at 80,584 nucleotides and shortest at 1,901 nucleotides. The combined length of haplotype sequences comprised 19,895,388 nucleotides with a median of 16,014 nucleotides. Based on our approach, all haplotypes can be considered experimentally confirmed and not affected by the known errors of computerized genotype phasing.

Conclusions

Tracts of homozygosity can provide definitive reference sequences for any gene. They are particularly useful when observed in unrelated individuals of large scale sequence databases. As a proof of principle, we explored the 1000 Genomes Project database for ACKR1 gene data and mined long haplotypes. These haplotypes are useful for high throughput analysis with next generation sequencing. Our approach is scalable, using automated bioinformatics tools, and can be applied to any gene.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12859-021-04169-6.

Identifying adaptive alleles in the human genome: from selection mapping to functional validation

The suite of phenotypic diversity across geographically distributed human populations is the outcome of genetic drift, gene flow, and natural selection throughout human evolution. Human genetic variation underlying local biological adaptations to selective pressures is incompletely characterized. With the emergence of population genetics modeling of large-scale genomic data derived from diverse populations, scientists are able to map signatures of natural selection in the genome in a process known as selection mapping. Inferred selection signals further can be used to identify candidate functional alleles that underlie putative adaptive phenotypes. Phenotypic association, fine mapping, and functional experiments facilitate the identification of candidate adaptive alleles. Functional investigation of candidate adaptive variation using novel techniques in molecular biology is slowly beginning to unravel how selection signals translate to changes in biology that underlie the phenotypic spectrum of our species. In addition to informing evolutionary hypotheses of adaptation, the discovery and functional annotation of adaptive alleles also may be of clinical significance. While selection mapping efforts in non-European populations are growing, there remains a stark under-representation of diverse human populations in current public genomic databases, of both clinical and non-clinical cohorts. This lack of inclusion limits the study of human biological variation. Identifying and functionally validating candidate adaptive alleles in more global populations is necessary for understanding basic human biology and human disease.

Human genetics and malaria resistance

Malaria has been the pre-eminent cause of early mortality in many parts of the world throughout much of the last five thousand years and, as a result, it is the strongest force for selective pressure on the human genome yet described. Around one third of the variability in the risk of severe and complicated malaria is now explained by additive host genetic effects. Many individual variants have been identified that are associated with malaria protection, but the most important all relate to the structure or function of red blood cells. They include the classical polymorphisms that cause sickle cell trait, α-thalassaemia, G6PD deficiency, and the major red cell blood group variants. More recently however, with improving technology and experimental design, others have been identified that include the Dantu blood group variant, polymorphisms in the red cell membrane protein ATP2B4, and several variants related to the immune response. Characterising how these genes confer their effects could eventually inform novel therapeutic approaches to combat malaria. Nevertheless, all together, only a small proportion of the heritable component of malaria resistance can be explained by the variants described so far, underscoring its complex genetic architecture and the need for continued research.

The emerging role of red blood cells in cytokine signalling and modulating immune cells

For many years red blood cells have been described as inert bystanders rather than participants in intercellular signalling, immune function, and inflammatory processes. However, studies are now reporting that red blood cells from healthy individuals regulate immune cell activity and maturation, and red blood cells from disease cohorts are dysfunctional. These cells have now been shown to bind more than 50 cytokines and have been described as a sink for these molecules, and the loss of this activity has been correlated with disease progression. In this review, we summarise what is currently understood about the role of red blood cells in cytokine signalling and in modulating the activity of immune cells. We also discuss the implications of these findings for transfusion medicine and in furthering our understanding of anaemia of chronic inflammation. By bringing these disparate units of work together, we aim to shine a light on an area that requires significantly more investigation.

Characterization of a novel decellularized bone marrow scaffold as an inductive environment for hematopoietic stem cells

Due to the increasing demand for a bone marrow study model, we developed a natural scaffold from decellularized bovine bone marrow (DeBM). The obtained bioscaffold was analyzed after the decellularization process; histological staining, scanning and transmission electron microscopy confirmed the preservation of its native 3D-architecture; including blood vessels and cell niches as well as the integrity of important components of the extracellular matrix; Collagen III, IV and fibronectin. In addition to biochemical composition, physical properties of the bone marrow were also conserved. We evaluated the suitability of this bio-scaffold as a tridimensional culture platform. Seeding experiments with umbilical cord-derived hematopoietic stem cells and human bone marrow stromal cell line HS5 demonstrated that this scaffold is capable of supporting hematopoietic and stromal cell adhesion and proliferation without the need of exogenous factors. DeBM provided an inductive environment for the repopulation of the bone marrow inducing the expression of SDF-1, HGF and SCF by seeded stromal cells. The presence of these potent hematopoietic chemoattractants would be crucial for ex vivo long-term culture of HSCs, and for recreating the natural microenvironment of the bone marrow for bioengineering applications. We conclude that the decellularization process succeeded in preserving the 3D structure and mechanical properties of the bone marrow. The resulting scaffold is suitable for cell culture, representing an advantageous bone marrow experimental model, and potentially an effective platform for CD34+ HSC expansion and differentiation for clinical applications.

Primary Immunodeficiency and Cancer Predisposition Revisited: Embedding Two Closely Related Concepts Into an Integrative Conceptual Framework

Common understanding suggests that the normal function of a "healthy" immune system safe-guards and protects against the development of malignancies, whereas a genetically impaired one might increase the likelihood of their manifestation. This view is primarily based on and apparently supported by an increased incidence of such diseases in patients with specific forms of immunodeficiencies that are caused by high penetrant gene defects. As I will review and discuss herein, such constellations merely represent the tip of an iceberg. The overall situation is by far more varied and complex, especially if one takes into account the growing difficulties to define what actually constitutes an immunodeficiency and what defines a cancer predisposition. The enormous advances in genome sequencing, in bioinformatic analyses and in the functional in vitro and in vivo assessment of novel findings together with the availability of large databases provide us with a wealth of information that steadily increases the number of sequence variants that concur with clinically more or less recognizable immunological problems and their consequences. Since many of the newly identified hard-core defects are exceedingly rare, their tumor predisposing effect is difficult to ascertain. The analyses of large data sets, on the other hand, continuously supply us with low penetrant variants that, at least in statistical terms, are clearly tumor predisposing, although their specific relevance for the respective carriers still needs to be carefully assessed on an individual basis. Finally, defects and variants that affect the same gene families and pathways in both a constitutional and somatic setting underscore the fact that immunodeficiencies and cancer predisposition can be viewed as two closely related errors of development. Depending on the particular genetic and/or environmental context as well as the respective stage of development, the same changes can have either a neutral, predisposing and, in some instances, even a protective effect. To understand the interaction between the immune system, be it "normal" or "deficient" and tumor predisposition and development on a systemic level, one therefore needs to focus on the structure and dynamic functional organization of the entire immune system rather than on its isolated individual components alone.

Unpacking the Pathogen Box-An Open Source Tool for Fighting Neglected Tropical Disease

The Pathogen Box is a 400-strong collection of drug-like compounds, selected for their potential against several of the world's most important neglected tropical diseases, including trypanosomiasis, leishmaniasis, cryptosporidiosis, toxoplasmosis, filariasis, schistosomiasis, dengue virus and trichuriasis, in addition to malaria and tuberculosis. This library represents an ensemble of numerous successful drug discovery programmes from around the globe, aimed at providing a powerful resource to stimulate open source drug discovery for diseases threatening the most vulnerable communities in the world. This review seeks to provide an in-depth analysis of the literature pertaining to the compounds in the Pathogen Box, including structure-activity relationship highlights, mechanisms of action, related compounds with reported activity against different diseases, and, where appropriate, discussion on the known and putative targets of compounds, thereby providing context and increasing the accessibility of the Pathogen Box to the drug discovery community.

The Duffy antigen receptor for chemokines, ACKR1,- 'Jeanne DARC' of benign neutropenia

Benign neutropenia, observed in different ethnic groups, is the most common form of neutropenia worldwide. A specific single nucleotide polymorphism, rs2814778, located at the promoter of the ACKR1 (previously termed DARC) gene, which disrupts a binding site for the GATA1 erythroid transcription factor, resulting in a ACKR1-null phenotype, was found to serve as a predictor of low white blood cell and neutrophil counts in African-Americans and Yemenite Jews. Individuals with benign neutropenia due to the ACKR1-null allele have been found to have an increased susceptibility to human immunodeficiency virus infection and, on the other hand, a protective effect against malaria. The associated protective effect may explain the spread of the ACKR1-null allele by natural selection. The reviewed relationships between ACKR1 polymorphism and various pathological states may have important clinical implications to individuals with and without benign neutropenia. Potential mechanisms for ACKR1 (previously termed DARC) modulation during neutrophil recruitment to inflammation, and chemokine bioavailability in the circulation and in local tissue are reviewed and discussed.

Effect of functional genetic variants in chemokine decoy receptors on the recurrence risk of breast cancer

Duffy antigen receptor for chemokine (DARC) and CCBP2, the two members of chemokine decoy receptor family, restrain cell proliferation and invasion through sequestrating cytotoxic chemokines. Our previous research clarified two functional nonsynonymous single nucleotide polymorphisms (SNPs): rs12075 in DARC and rs2228468 in CCBP2 were significantly correlated with lymph node metastasis. However, the role of their genetic variations on survival of breast cancer remains unclear. In the present study, rs12075 in DARC and rs2228468 in CCBP2 were genotyped in 806 patients with primary breast cancer. The endpoint was recurrence‐free survival (RFS). Cox regression model was used to explore the association between SNPs and patients’ survival. The results revealed that participants with GG genotype in rs12075 appeared a higher recurrence risk compared with AG/AA genotype after adjustment with clinical parameters including lymph node status (AG+AA vs GG: hazard ratio [HR] = 0.54, 95% confidence interval [CI], 0.31‐0.93, P = 0.027). Furthermore, subgroup analysis revealed that GG genotype frequency of rs12075 had a positive correlation with RFS compared with AG/AA genotype (AG+AA vs GG: HR = 0.22, 95% CI, 0.05‐0.91, P = 0.021) in triple‐negative breast cancer (TNBC) subtype but not in other subtypes. No significant association between the genotypic variants and relapse risk was found in rs2228468 (AC+AA vs CC: HR = 0.80, 95% CI, 0.56‐1.14, P = 0.222). There was also no significant difference in survival among rs2228468 polymorphism in any subtypes. Our study suggested that rs12075 could be served as a key predictive factor of recurrence risk in breast cancer, especially for TNBC subtype. Further researches to monitor SNPs will provide further opportunities to determine clinical prognosis.

Molecular genotyping of G6PD mutations and Duffy blood group in Afro-descendant communities from Brazilian Amazon

Glucose-6-phosphate dehydrogenase deficiency (G6PDd) and Duffy-negative blood group are two red blood cells variants that confer protection against malaria. In this study, the distribution of the most common G6PD variants (G6PD*A-, GGPD*A and G6PD Mediterranean) and the major alleles of the Duffy blood group (FY*A, FY*B and FY*BES) were investigated in an Afro-descendant population from state of Pará, Brazilian Amazon. G6PD variants and Duffy blood group alleles were determined by TaqMan SNP genotyping assay. Overall, molecular genotyping revealed the presence of G6PD variants in 126 (24%) of the individuals studied (5% male and 19% female), and frequencies of the G6PD*A- and G6PD*A alleles were 0.061 and 0.104, respectively. Duffy blood group genotyping showed that 24.3% of people were Duffy-negative and 41.3% were heterozygous for FY*BES. The frequency of allele FY*BES was 41.0%. The results emphasize the need to monitor G6PD deficiency for the use of primaquine in the routine care of the Afro-descendant communities of the Trombetas, Erepecuru and Cumná rivers, evaluating the risks of hemolytic crisis in case of recurrence of malaria in the region. In addition, the possible greater protection against malaria conferred by these erythrocyte polymorphisms deserves to be better investigated and explored among these Afro-descendants.

Long-range haplotype analysis of the malaria parasite receptor gene ACKR1 in an East-African population

The human ACKR1 gene encodes a glycoprotein expressing the Duffy blood group antigens (Fy). The Duffy protein acts as a receptor for distinct pro-inflammatory cytokines and malaria parasites. We determined the haplotypes of the ACKR1 gene in a population inhabiting a malaria-endemic area. We collected blood samples from 60 healthy volunteers in Ethiopia’s southwestern low-altitude tropical region. An assay was devised to amplify the ACKR1 gene as a single amplicon and determine its genomic sequence. All haplotypes were resolved at 5178 nucleotides each, covering the coding sequence (CDS) of the ACKR1 gene and including the 5′- and 3′-untranslated regions (UTR), intron 1, and the 5′- and 3′-flanking regions. When necessary, allele-specific PCR with nucleotide sequencing or length polymorphism analysis was applied. Among the 120 chromosomes analyzed, 18 ACKR1 alleles were confirmed without ambiguity. We found 18 single-nucleotide polymorphisms (SNPs); only one SNP was novel. The non-coding sequences harbored 14 SNPs. No SNP, other than c.-67T>C, indicative of a non-functional allele, was detected. We described haplotypes of the ACKR1 gene in an autochthonous East-African population and found 18 distinct ACKR1 alleles. These long-range alleles are useful as templates to phase and analyze next-generation sequencing data, thus enhancing the reliability of clinical diagnostics.

Researchers have surveyed genetic diversity related to malaria resistance in a region of Ethiopia where malaria is endemic. Duffy antigens, a component of blood type, are encoded by the ACKR1 gene, and individuals with the Duffy-negative blood type are resistant to malaria. Although the genes encoding resistant types have been identified, they have not been fully surveyed in malaria-endemic regions, where novel types are most likely to be found. Willy Flegel at the National Institutes of Health, Bethesda, USA, and co-workers sequenced ACKR1 in 60 people from Gambela, Ethiopia, where malaria is endemic. They detected 18 variants, including one never before documented. Almost all (16 of 18) of the variants encoded the Duffy-negative blood type. The authors plan to compare the genetic diversity in this region with a nearby region where malaria is not endemic.

Duffy blood group system: New genotyping method and distribution in a Brazilian extra-Amazonian population

Duffy blood group system is of interest in several fields of science including transfusion medicine, immunology and malariology. Although some methods have been developed for Duffy polymorphism genotyping, not all of them have been sufficiently described and validated, and all present limitations. At the same time, the frequency of Duffy alleles and antigens in some densely populated regions of the world are still missing. In this study we present new tests for genotyping the major alleles of the Duffy blood system and describe Duffy alleles and antigens in blood donors and transfusion-dependent patients in Minas Gerais, Brazil. A simple and reproducible strategy was devised for Duffy genotyping based on real-time PCR that included SNPs rs12075 and rs2814778. No significant differences between the allele frequencies were observed comparing blood donors and patients. Among the blood donors, the phenotype Fy(a-b+) was the most common and the Fy(a-b-) phenotype, associated with populations of African descent, was remarkably less common among subjects who self-identified as black in comparison to other ethnoracial categories. However, the African ancestry estimated by molecular markers was significantly higher in individuals with the allele associated to the Duffy null phenotype. The genotyping method presented may be useful to study Duffy genotypes accurately in different contexts and populations. The results suggest a reduced risk of alloimmunization for Duffy antigens and increased susceptibility for malaria in Minas Gerais, considering the high frequency of Duffy-positive individuals.

Duffy antigen receptor for chemokines (DARC) expressing in cancer cells inhibits tumor progression by suppressing CXCR2 signaling in human pancreatic ductal adenocarcinoma

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) has a dismal prognosis. Chemokines play important roles in the progression of many malignancies; however, the role of chemokine receptor expression in clinical cases of PDAC is unclear. Moreover, little is known about DARC, a decoy receptor of CXC chemokines, in the regulation of tumor progression.

METHODS

Functions of chemokine receptors were evaluated using surgical specimens collected from PDAC patients, and PDAC cell lines.

RESULTS

CXCR2 expression had no impacts on predicting prognosis, but low DARC expression in cancer cells was an independent risk factor for poor prognosis. In PDAC with low DARC expression, tumor sizes were larger and vascular invasion was increased. High CXCR2 expression was a significant predictor for poor prognosis, only in PDAC patients with low DARC expression. CXCR2 signaling induced STAT3 activation in PDAC, resulting in promoting cell cycle progression, inhibiting apoptosis, inducing angiogenesis, and enhancing invasiveness. DARC inhibited STAT3 activation by down-regulating CXCR2 signaling. These effects were confirmed by EMSA in vitro. DARC knockdown significantly increased cell proliferation in CFPAC-1 cells with high DARC expression, by activating STAT3. In contrast, CXCR2 knockdown inhibited the proliferative effects of IL-8 in MIA PaCa-2 cells with low DARC expression. Moreover, the inhibitory effect of CXCR2 antagonist on PDAC cell proliferation was more powerful in MIA PaCa-2 cells than CFPAC-1 cells.

CONCLUSIONS

DARC expressing in cancer cells inhibits PDAC progression by suppressing STAT3 activation through the inhibition of CXCR2 signaling. Therefore, DARC is a novel prognostic predictor and a potential therapeutic target for PDAC.

Erythrogene: a database for in-depth analysis of the extensive variation in 36 blood group systems in the 1000 Genomes Project

Blood group genotyping has recently developed into a clinical tool to improve compatibility of blood transfusions and management of pregnancies. Next-generation sequencing (NGS) is rapidly moving toward routine practice for patient and donor typing and has the potential to remedy some of the limitations of currently used platforms. However, a large-scale investigation into the blood group genotypes obtained by NGS in a multiethnic cohort is lacking. The 1000 Genomes Project provides information on genome variation among 2504 individuals representing 26 populations worldwide. We extracted their NGS data for all 36 blood group systems to a custom-designed database. In total, 210 412 alleles from 43 blood group-related genes were imported and curated. Matching algorithms were developed to compare them to blood group variants identified to date. Of the 1241 non-synonymous variants identified in the coding regions, 241 are known blood group polymorphisms. Interestingly, 357 of the remaining 1000 variants are predicted to occur on extracellular portions of 31 different blood group-carrying proteins and some may represent undiscovered antigens. Of the alleles analyzed, 1504 were not previously described. The ABO/GBGT1/FUT2/FUT3 and GYPB/GYPC genes showed the highest degree of variation per kilobase coding sequence, and ACKR1 variants had the most skewed distribution across 5 continental superpopulations in the dataset. Results were exported to an online search engine, www.erythrogene.com, which presents data according to the allele nomenclature developed for clinical reporting by the International Society of Blood Transfusion. The established database deepens our knowledge on blood group polymorphism globally and provides a long-sought platform for future research.

Chemokine and chemokine receptors in autoimmunity: the case of primary biliary cholangitis

Chemokines represent a major mediator of innate immunity and play a key role in the selective recruitment of cells during localized inflammatory responses. Beyond critical extracellular mediators of leukocyte trafficking, chemokines and their cognate receptors are expressed by a variety of resident and infiltrating cells (monocytes, lymphocytes, NK cells, mast cells, and NKT cells). Chemokines represent ideal candidates for mechanistic studies (particularly in murine models) to better understand the pathogenesis of chronic inflammation and possibly become biomarkers of disease. Nonetheless, therapeutic approaches targeting chemokines have led to unsatisfactory results in rheumatoid arthritis, while biologics against pro-inflammatory cytokines are being used worldwide with success. In this comprehensive review we will discuss the evidence supporting the involvement of chemokines and their specific receptors in mediating the effector cell response, utilizing the autoimmune/primary biliary cholangitis setting as a paradigm.

Blood Group Antigens C, Lub and P1 May Have a Role in HIV Infection in Africans

BACKGROUND

Botswana is among the world's countries with the highest rates of HIV infection. It is not known whether or not this susceptibility to infection is due to genetic factors in the population. Accumulating evidence, however, points to the role of erythrocytes as potential mediators of infection. We therefore sought to establish the role, if any, of some erythrocyte antigens in HIV infection in a cross-section of the population.

METHODS

348 (346 HIV-negative and 2 HIV-positive) samples were obtained from the National Blood Transfusion Service as residual samples, while 194 HIV-positive samples were obtained from the Botswana-Harvard HIV Reference Laboratory. Samples were grouped for twenty three antigens. Chi-square or Fischer Exact analyses were used to compare the frequencies of the antigens in the two groups. A stepwise, binary logistic regression was used to study the interaction of the various antigens in the light of HIV-status.

RESULTS

The Rh antigens C and E were associated with HIV-negative status, while blood group Jka, P1 and Lub were associated with HIV-positive status. A stepwise binary logistic regression analysis yielded group C as the most significant protective blood group while Lub and P1 were associated with significantly higher odds ratio in favor of HIV-infection. The lower-risk-associated group C was significantly lower in Africans compared to published data for Caucasians and might partially explain the difference in susceptibility to HIV-1.

CONCLUSION

The most influential antigen C, which also appears to be protective, is significantly lower in Africans than published data for Caucasians or Asians. On the other hand, there appear to be multiple antigens associated with increased risk that may override the protective role of C. A study of the distribution of these antigens in other populations may shed light on their roles in the HIV pandemic.

Distribution of Duffy Antigen Receptor for Chemokines (DARC) and Risk of Prostate Cancer in Barbados, West Indies

Blood typing across different racial groups has revealed that Caucasians predominantly test positive for the Duffy antigen/receptor for chemokines (DARC), while 70-95% of African-origin populations lack expression of DARC on their erythrocytes. Since men of African descent are known to have higher rates of prostate cancer (PC) and some animal studies have indicated anti-angiogenic effects associated with Duffy-positive mice, DARC-negativity may help to explain some of the racial differences in prostate tumorigenesis. The Prostate Cancer in a Black Population (PCBP) Study, a large case-control investigation including 1,007 incident PC cases and 1,005 controls, performed DARC testing on a subset of 1,295 participants (641 cases, 654 controls). The relationship between DARC expressivity and PC risk was evaluated using logistic regression models and findings are presented as odds ratios and 95% confidence intervals. More than three-quarters (76.5%) of African-Barbadian men lacked DARC expression, whereas almost three-fifths (59.3%) of White participants tested positive for the Duffy a and b alleles. DARC-negativity was not found to be associated with PC risk in the present investigation [OR 1.04, 95% CI (0.78, 1.37)], regardless of tumor grade. Findings from the PCBP study indicate that the majority of African-Barbadian men do not express DARC on their erythrocytes, yet absence of expression does not appear to be associated with PC development in this population.

The Duffy blood group system in the Tunisian population

BACKGROUND

Tunisia was described to as genetically heterogenous. Besides the 1% native Berber, the genetically influence of the Europeans seems much larger than that of sub-Saharan populations. Due to their ethnic variability, blood group variants have the potential to support population analyses. The aim of this study was to estimate the Duffy blood group system in this mixed population with enhanced characterization of samples with aberrant expression.

MATERIALS AND METHODS

Standard serological testing for the Duffy antigen was done for 105 Tunisian blood donors. Samples with altered Fy expression underwent DNA sequencing of the DARC, RHD and RHCE genes.

RESULTS

The Fy(a-b+) was the most common phenotype identified in the Tunisian population (38.1%). Five samples with Fy(a-b-) phenotype were determined as FY*02N.01/FY*02N.01 by a homozygous occurrence of the FY*B-67C>T alteration. Another three individuals exhibited a Fy(b+(w))Fy(x) expression, confirmed by a FY*A/FY*02M.01 (n = 1) and a FY*02M.01/FY*02M.01 (n = 2) genotype. RHD and RHCE sequencing (n= 8) revealed altered alleles observed in black populations in 5 samples. One individual with FY*02M.01/FY*02M.01 have the silent 165C>T nucleotide substitution each in the RHD and RHCE gene.

DISCUSSION

The composition of blood group variants determined in this study confirms the genetically proximity of Tunisia to Europe. The small sub-Saharan genetic influence was approved by a limited number of variant samples associated with the black population.

Studies of a murine monoclonal antibody directed against DARC: reappraisal of its specificity

Duffy Antigen Receptor for Chemokines (DARC) plays multiple roles in human health as a blood group antigen, a receptor for chemokines and the only known receptor for Plasmodium vivax merozoites. It is the target of the murine anti-Fy6 monoclonal antibody 2C3 which binds to the first extracellular domain (ECD1), but exact nature of the recognized epitope was a subject of contradictory reports. Here, using a set of complex experiments which include expression of DARC with amino acid substitutions within the Fy6 epitope in E. coli and K562 cells, ELISA, surface plasmon resonance (SPR) and flow cytometry, we have resolved discrepancies between previously published reports and show that the basic epitope recognized by 2C3 antibody is ²²FEDVW²⁶, with ²²F and ²⁶W being the most important residues. In addition, we demonstrated that ³⁰Y plays an auxiliary role in binding, particularly when the residue is sulfated. The STD-NMR studies performed using 2C3-derived Fab and synthetic peptide corroborated most of these results, and together with the molecular modelling suggested that ²⁵V is not involved in direct interactions with the antibody, but determines folding of the epitope backbone.

Duffy antigen receptor genetic variant and the association with Interleukin 8 levels

The aim of this study is to identify loci associated with circulating levels of Interleukin 8 (IL8). We investigated the associations of 121,445 single nucleotide polymorphisms (SNPs) from the Illumina 200K CardioMetabochip with IL8 levels in 1077 controls from the Stockholm Heart Epidemiology Program (SHEEP) study, using linear regression under an additive model of inheritance. Five SNPs (rs12075A/G, rs13179413C/T, rs6907989T/A, rs9352745A/C, rs1779553T/C) reached the pre-defined threshold of genome-wide significance (p<1.0×10(-5)) and were tested for in silico replication in three independent populations, derived from the PIVUS, MDC-CC and SCARF studies. IL8 was measured in serum (SHEEP, PIVUS) and plasma (MDC-CC, SCARF). The strongest association was found with the SNP rs12075 A/G, Asp42Gly (p=1.6×10(-6)), mapping to the Duffy antigen receptor for chemokines (DARC) gene on chromosome 1. The minor allele G was associated with 15.6% and 10.4% reduction in serum IL8 per copy of the allele in SHEEP and PIVUS studies respectively. No association was observed between rs12075 and plasma IL8.

CONCLUSION

rs12075 was associated with serum levels but not with plasma levels of IL8. It is likely that serum IL8 represents the combination of levels of circulating plasma IL8 and additional chemokine liberated from the erythrocyte DARC reservoir due to clotting. These findings highlight the importance of understanding IL8 as a biomarker in cardiometabolic diseases.

Chemokines responses to Plasmodium falciparum malaria and co-infections among rural Cameroonians

Malaria remains the major cause of disease morbidity and mortality in sub-Saharan Africa with complex immune responses associated with disease outcomes. Symptoms associated with severe malaria have generally shown chemokine upregulation but little is known of responses to uncomplicated malaria. Eight villages in central Cameroon of 1045 volunteers were screened. Among these, malaria-positive individuals with some healthy controls were selected for chemokine analysis using Enzyme-Linked Immunosorbent Assay (ELISA) kits. Depressed serum levels of CXCL5 and raised CCL28 were observed in malarial positives when compared with healthy controls. The mean concentration of CXCL11 was higher in symptomatic than asymptomatic group, while CCL28 was lower in symptomatic individuals. Lower chemokine levels were associated with symptoms of uncomplicated malaria except for CXCL11 which was upregulated among fever-positive group. The mean CXCL5 level was higher in malaria sole infection than co-infections with HIV and Loa loa. Also, there was a raised mean level of malaria+HIV co-infection for CXCL9. This study hypothesises a situation where depressed chemokines in the face of clinical presentations could indicate an attempt by the immune system in preventing a progression process from uncomplicated to complicated outcomes with CXCL11 being identified as possible biomarker for malarial fever.

Antibody-mediated immune suppression of erythrocyte alloimmunization can occur independently from red cell clearance or epitope masking in a murine model

Anti-D can prevent immunization to the RhD Ag on RBCs, a phenomenon commonly termed Ab-mediated immune suppression (AMIS). The most accepted theory to explain this effect has been the rapid clearance of RBCs. In mouse models using SRBC, these xenogeneic cells are always rapidly cleared even without Ab, and involvement of epitope masking of the SRBC Ags by the AMIS-inducing Ab (anti-SRBC) has been suggested. To address these hypotheses, we immunized mice with murine transgenic RBCs expressing the HOD Ag (hen egg lysozyme [HEL], in sequence with ovalbumin, and the human Duffy transmembrane protein) in the presence of polyclonal Abs or mAbs to the HOD molecule. The isotype, specificity, and ability to induce AMIS of these Abs were compared with accelerated clearance as well as steric hindrance of the HOD Ag. Mice made IgM and IgG reactive with the HEL portion of the molecule only. All six of the mAbs could inhibit the response. The HEL-specific Abs (4B7, IgG1; GD7, IgG2b; 2F4, IgG1) did not accelerate clearance of the HOD-RBCs and displayed partial epitope masking. The Duffy-specific Abs (MIMA 29, IgG2a; CBC-512, IgG1; K6, IgG1) all caused rapid clearance of HOD RBCs without steric hindrance. To our knowledge, this is the first demonstration of AMIS to erythrocytes in an all-murine model and shows that AMIS can occur in the absence of RBC clearance or epitope masking. The AMIS effect was also independent of IgG isotype and epitope specificity of the AMIS-inducing Ab.

Plasmodium genetic loci linked to host cytokine and chemokine responses

Both host and parasite factors contribute to disease severity of malaria infection; however, the molecular mechanisms responsible for the disease and the host-parasite interactions involved remain largely unresolved. To investigate effects of parasite factors on host immune responses and pathogenesis, we measured levels of plasma cytokines/chemokines (CC) and growth rates in mice infected with two Plasmodium yoelii strains having different virulence phenotypes and in progeny from a genetic cross of the two parasites. Quantitative trait loci (QTL) analysis linked levels of many CCs, particularly IL-1β, IP-10, IFN-γ, MCP-1, and MIG, and early parasite growth rate to loci on multiple parasite chromosomes, including chromosomes 7, 9, 10, 12, and 13. Comparison of the genome sequences spanning the mapped loci revealed various candidate genes. The loci on chromosome 7 and 13 had significant (p < 0.005) additive effects on IL-1β, IL-5, and IP-10 responses, and the chromosome 9 and 12 loci had significant (p = 0.017) interaction. Infection of knockout mice showed critical roles of MCP-1 and IL-10 in parasitemia control and host mortality. These results provide important information for better understanding of malaria pathogenesis and can be used to examine the role of these factors in human malaria infection.

Strain-specific innate immune signaling pathways determine malaria parasitemia dynamics and host mortality

Malaria infection triggers vigorous host immune responses; however, the parasite ligands, host receptors, and the signaling pathways responsible for these reactions remain unknown or controversial. Malaria parasites primarily reside within RBCs, thereby hiding themselves from direct contact and recognition by host immune cells. Host responses to malaria infection are very different from those elicited by bacterial and viral infections and the host receptors recognizing parasite ligands have been elusive. Here we investigated mouse genome-wide transcriptional responses to infections with two strains of Plasmodium yoelii (N67 and N67C) and discovered differences in innate response pathways corresponding to strain-specific disease phenotypes. Using in vitro RNAi-based gene knockdown and KO mice, we demonstrated that a strong type I IFN (IFN-I) response triggered by RNA polymerase III and melanoma differentiation-associated protein 5, not Toll-like receptors (TLRs), binding of parasite DNA/RNA contributed to a decline of parasitemia in N67-infected mice. We showed that conventional dendritic cells were the major sources of early IFN-I, and that surface expression of phosphatidylserine on infected RBCs might promote their phagocytic uptake, leading to the release of parasite ligands and the IFN-I response in N67 infection. In contrast, an elevated inflammatory response mediated by CD14/TLR and p38 signaling played a role in disease severity and early host death in N67C-infected mice. In addition to identifying cytosolic DNA/RNA sensors and signaling pathways previously unrecognized in malaria infection, our study demonstrates the importance of parasite genetic backgrounds in malaria pathology and provides important information for studying human malaria pathogenesis.

Polymorphism of leukocyte and erythrocyte antigens in chronic kidney disease patients in southern Brazil

We investigated the polymorphism of human leukocyte antigens (HLA) and Duffy erythrocyte antigens in chronic kidney disease (CKD) patients in southern Brazil. One hundred and eighty-three CKD patients, over 18 years old, on hemodialysis, were included. HLA-A, -B and -DRB1 typing was performed using the LABType®SSO (One Lambda, Inc.). Duffy phenotypes were determined by gel column agglutination using anti-Fy^a and anti-Fy^b monoclonal anti-sera. The patients' predominant ages ranged between 51 and 70 years (43%) and the predominant gender, ethnic group and dialysis period were, respectively, male (62%), white (62%) and 1–3 years (40%). The highest and lowest frequencies of Duffy phenotypes were Fy(a+b+) and Fy(a−b−), respectively. Nineteen HLA-A, 30 HLA-B and 13 HLA-DRB1 allele groups were identified. The most frequent HLA allele groups were HLA-A*01, -A*02, -A*03, -A*11, -A*24; HLA-B*07, -B*15, -B*35, -B*44, -B*51; HLA-DRB1*03, -DRB1*04, -DRB1*07, -DRB1*11 and -DRB1*13. Statistically significant differences were observed in the Duffy and HLA polymorphisms compared between CKD patients and healthy subjects. The Fy(a+b−) phenotype (p<0.0001, OR = 2.56, 95% CI = 1.60–4.07) was the most frequent in the patients (p<0.05), and the Fy(a+b+) phenotype (p = 0.0039, OR = 1.71, 95% CI = 1.18–2.51) was the most frequent in the healthy subjects in the same region of Paraná state (p<0.05). Regarding HLA, the HLA-B*42, -B*45, -B*51 and -DRB1*03 allele groups were the most frequent in the patients (p<0.05), and the HLA-B*44 allele group was the most frequent in the healthy subjects in the same region of Brazil (p<0.05). The polymorphism of these two markers among CKD patients in southern Brazil and healthy subjects of other studies, suggests that these markers might be involved with CKD development. Further studies should be undertaken to analyze the markers' influence on CKD and the long-term results from kidney transplantation.

Association of duffy blood group gene polymorphisms with IL8 gene in chronic periodontitis

The antigens of the Duffy blood group system (DARC) act as a receptor for the interleukin IL-8. IL-8 plays an important role in the pathogenesis of chronic periodontitis due to its chemotactic properties on neutrophils. The aim of this study was to investigate a possible association of Duffy blood group gene polymorphisms with the -353T>A, -845T>C and -738T>A SNPs of the IL8 gene in chronic periodontitis. One hundred and twenty-four individuals with chronic periodontitis and 187 controls were enrolled. DNA was extracted using the salting-out method. The Duffy genotypes and IL8 gene promoter polymorphisms were investigated by PCR-RFLP. Statistical analyses were conducted using the Chi square test with Yates correction or Fisher's Exact Test, and the possibility of associations were evaluated by odds ratio with a 95% confidence interval. When analyzed separately, for the Duffy blood group system, differences in the genotype and allele frequencies were not observed between all the groups analyzed; and, in nonsmokers, the -845C allele (3.6% vs. 0.4%), -845TC genotype (7.3% vs. 0.7%) and the CTA haplotype (3.6% vs. 0.4%) were positively associated with chronic periodontitis. For the first time to our knowledge, the polymorphisms of erythroid DARC plus IL8 -353T>A SNPs were associated with chronic periodontitis in Brazilian individuals. In Afro-Brazilians patients, the FY*02N.01 with IL8 -353A SNP was associated with protection to chronic periodontitis.

The role of red blood cells in enhancing or preventing HIV infection and other diseases

Aim. To highlight the apparently neglected role of erythrocyte antigens in the epidemiology of infectious diseases, especially HIV, with the prime objective of stimulating research in this area. Method. A literature search was performed on the PubMed for relevant papers from 1984 to 2013, the era covering active HIV research. This was achieved by using the phrases “erythrocyte blood groups HIV” (81 papers) or “red cell antigen, blood groups, and HIV” (60 papers). A manual Google Scholar search was done and supplemented by original papers referenced by various authors. However, the review was limited by the relative scarcity of papers on the subject, and only papers written in English were reviewed during the period October 2012 to September 2013. Results. Many communicable and noncommunicable diseases are associated with specific blood groups. Examples of these diseases are discussed in detail. HIV has been shown to bind to erythrocytes, and candidate erythrocyte-binding molecules and mechanisms are also discussed. Moreover, erythrocyte-HIV binding is associated with increased viral infectivity, thus, underscoring the need to study this phenomenon and its implications for HIV epidemiology. Conclusion. Erythrocyte antigens may be important in the pathogenesis and epidemiology of many diseases, including HIV.

Duffy blood group and malaria

Very important progress has been made over the last years in understanding the Duffy blood group system and its complexity. The Duffy blood group antigen serves not only as blood group antigen, but also as a receptor for a family of proinflammatory cytokines termed chemokines, and as a receptor for Plasmodium vivax malaria parasites. The Duffy antigen has been termed the "Duffy Antigen Receptor for Chemokines" (DARC) or the Duffy chemokine receptor. DARC might play a role as a scanvenger on the red blood cell surface to eliminate excess of toxic chemokines produced in some pathologic situations [48]. Plasmodium vivax (P. vivax) causes approximately between 70 and 80 million cases of malaria per year and is the most amply distributed human malaria in the world [51]. Individuals with the Duffy-negative phenotype are resistant to P. vivax invasion, and the molecular mechanism that gives rise to the phenotype Fy(a - b - ) in black individuals has been associated with a point mutation - 33TC expressed in homozigosity in the FYB allele [5]. Despite P. vivax be widespread throughout the tropical and subtropical world, it is absent from West Africa, where more than 95% of the population is Duffy negative. Recently, this point mutation has been described in heterozigosity in the FYA allele in others malaria endemic regions [7, 8], and until now we do not know if it confers a certain degree of protection against P. vivax infection.

Genome-wide and gene-centric analyses of circulating myeloperoxidase levels in the charge and care consortia

Increased systemic levels of myeloperoxidase (MPO) are associated with the risk of coronary artery disease (CAD). To identify the genetic factors that are associated with circulating MPO levels, we carried out a genome-wide association study (GWAS) and a gene-centric analysis in subjects of European ancestry and African Americans (AAs). A locus on chromosome 1q31.1 containing the complement factor H (CFH) gene was strongly associated with serum MPO levels in 9305 subjects of European ancestry (lead SNP rs800292; P = 4.89 × 10(-41)) and in 1690 AA subjects (rs505102; P = 1.05 × 10(-8)). Gene-centric analyses in 8335 subjects of European ancestry additionally identified two rare MPO coding sequence variants that were associated with serum MPO levels (rs28730837, P = 5.21 × 10(-12); rs35897051, P = 3.32 × 10(-8)). A GWAS for plasma MPO levels in 9260 European ancestry subjects identified a chromosome 17q22 region near MPO that was significantly associated (lead SNP rs6503905; P = 2.94 × 10(-12)), but the CFH locus did not exhibit evidence of association with plasma MPO levels. Functional analyses revealed that rs800292 was associated with levels of complement proteins in serum. Variants at chromosome 17q22 also had pleiotropic cis effects on gene expression. In a case-control analysis of ∼80 000 subjects from CARDIoGRAM, none of the identified single-nucleotide polymorphisms (SNPs) were associated with CAD. These results suggest that distinct genetic factors regulate serum and plasma MPO levels, which may have relevance for various acute and chronic inflammatory disorders. The clinical implications for CAD and a better understanding of the functional basis for the association of CFH and MPO variants with circulating MPO levels require further study.

Non-ABO blood group systems phenotyping in non-human primates for blood banking laboratory and xenotransplantation

Some biomedical research procedures, such as organ xenotransplantation, usually require intensive hemotherapy. Knowledge of the whole phenotype of blood donor and graft could be useful in the field of xenotransplantation. Human and simian-type categories of blood groups have been established and they can be tested by standard methods used for human blood grouping. The aim of this work was to study the incidence of non-ABO blood group systems in different species of non-human primates, which are employed in biomedical research. The phenotype of Rh, Lewis, Kidd, Kell, MNSs, Lutheran, P and Duffy antigens was investigated in olive baboon (n = 48), chacma baboon (n = 9), Guinea baboon (n = 14), Rhesus macaque (n = 38) and squirrel monkey (n = 30) by using commercial microtyping cards. Kell, Lutheran, Kidd and Duffy antigens have been detected in all species, Rh in squirrel monkey, MNSs in rhesus macaque and squirrel monkey, and Lewis in baboon and rhesus macaque. There were differences in frequency and haemagglutination scores between species regardless of their gender and age. The main differences were found in squirrel monkey when compared with baboons and macaques. This typing system provides a tool to assess the presence of antigens in animals used for experimental procedures, such as xenotransplantation and xenotransfusion.

Understanding the Dynamics of Gene Regulatory Systems; Characterisation and Clinical Relevance of cis-Regulatory Polymorphisms

Modern genetic analysis has shown that most polymorphisms associated with human disease are non-coding. Much of the functional information contained in the non-coding genome consists of cis-regulatory sequences (CRSs) that are required to respond to signal transduction cues that direct cell specific gene expression. It has been hypothesised that many diseases may be due to polymorphisms within CRSs that alter their responses to signal transduction cues. However, identification of CRSs, and the effects of allelic variation on their ability to respond to signal transduction cues, is still at an early stage. In the current review we describe the use of comparative genomics and experimental techniques that allow for the identification of CRSs building on recent advances by the ENCODE consortium. In addition we describe techniques that allow for the analysis of the effects of allelic variation and epigenetic modification on CRS responses to signal transduction cues. Using specific examples we show that the interactions driving these elements are highly complex and the effects of disease associated polymorphisms often subtle. It is clear that gaining an understanding of the functions of CRSs, and how they are affected by SNPs and epigenetic modification, is essential to understanding the genetic basis of human disease and stratification whilst providing novel directions for the development of personalised medicine.

The biochemistry and biology of the atypical chemokine receptors

A subset of chemokine receptors, initially called "silent" on the basis of their apparent failure to activate conventional signalling events, has recently attracted growing interest due to their ability to internalize, degrade, or transport ligands and thus modify gradients and create functional chemokine patterns in tissues. These receptors recognize distinct and complementary sets of ligands with high affinity, are strategically expressed in different cellular contexts, and lack structural determinants supporting Gα(i) activation, a key signalling event in cell migration. This is in keeping with the hypothesis that they have evolved to fulfil fundamentally different functions to the classical signalling chemokine receptors. Based on these considerations, these receptors (D6, Duffy antigen receptor for chemokines (DARC), CCX-CKR1 and CXCR7) are now collectively considered as an emerging class of 'atypical' chemokine receptors. In this article, we review the biochemistry and biology of this emerging chemokine receptor subfamily.

Analysis for genotyping Duffy blood group in inhabitants of Sudan, the fourth cataract of the Nile

Background

Genetic polymophisms of the Duffy antigen receptor for the chemokines (DARC) gene successfully protected against blood stage infection by Plasmodium vivax infection. The Fy (a-, b-) phenotype is predominant among African populations, particularly those originating from West Africa, and it is rare among non-African populations. The aim of this study was to analyse the frequency of four Duffy blood groups based on SNPs (T-33C, G125A, G298A and C5411T) in two local tribes of Sudanese Arabs, the Shagia and Manasir, which are both from the region of the Fourth Nile cataract in Sudan.

Methods

An analysis of polymorphisms was performed on 217 individuals (126 representatives of the Shagia tribe and 91 of the Manasir). Real-time PCR and TaqMan Genotyping Assays were used to study the prevalence of alleles and genotypes.

Results

The analysis of allelic and genotype frequency in the T-33C polymorphisms demonstrated a significant dominance of the C allele and CC genotype (OR = 0.53 [0.32-0.88]; p = 0.02) in both tribes. The G125A polymorphism is associated with phenotype Fy(a-, b-) and was identified in 83% of Shagia and 77% of Manasir. With regard to G298A polymorphisms, the genotype frequencies were different between the tribes (p = 0,002) and no single AA homozygote was found. Based on four SNPs examined, 20 combinations of genotypes for the Shagia and Manasir tribes were determined. The genotype CC/AA/GG/CT occurred most often in Shagia tribe (45.9%) but was rare in the Manasir tribe (6.6%) (p < 0.001 Shagia versus Manasir). The FY*A^ES allele was identified in both analysed tribes. The presence of individuals with the FY*A/FY*A genotype was demonstrated only in the Shagia tribe.

Conclusion

This is probably the first report showing genotypically Duffy-negative people who carry both FY*B^ES and FY*A^ES. The identification of the FY*A^ES allele in both tribes may be due to admixture of the non-African genetic background. Taken as a whole, allele and genotype frequencies between the Shagia and the Manasir were statistically different. However, the presence of individuals with the FY*A/FY*A genotype was demonstrated only in the Shagia tribe.

One-step immunopurification and lectinochemical characterization of the Duffy atypical chemokine receptor from human erythrocytes

Duffy antigen/receptor for chemokines (DARC) is a glycosylated seven-transmembrane protein acting as a blood group antigen, a chemokine binding protein and a receptor for Plasmodium vivax malaria parasite. It is present on erythrocytes and endothelial cells of postcapillary venules. The N-terminal extracellular domain of the Duffy glycoprotein carries Fy(a)/Fy(b) blood group antigens and Fy6 linear epitope recognized by monoclonal antibodies. Previously, we have shown that recombinant Duffy protein expressed in K562 cells has three N-linked oligosaccharide chains, which are mainly of complex-type. Here we report a one-step purification method of Duffy protein from human erythrocytes. DARC was extracted from erythrocyte membranes in the presence of 1% n-dodecyl-β-D-maltoside (DDM) and 0.05% cholesteryl hemisuccinate (CHS) and purified by affinity chromatography using immobilized anti-Fy6 2C3 mouse monoclonal antibody. Duffy glycoprotein was eluted from the column with synthetic DFEDVWN peptide containing epitope for 2C3 monoclonal antibody. In this single-step immunoaffinity purification method we obtained highly purified DARC, which migrates in SDS-polyacrylamide gel as a major diffuse band corresponding to a molecular mass of 40-47 kDa. In ELISA purified Duffy glycoprotein binds anti-Duffy antibodies recognizing epitopes located on distinct regions of the molecule. Results of circular dichroism measurement indicate that purified DARC has a high content of α-helical secondary structure typical for chemokine receptors. Analysis of DARC glycans performed by means of lectin blotting and glycosidase digestion suggests that native Duffy N-glycans are mostly triantennary complex-type, terminated with α2-3- and α2-6-linked sialic acid residues with bisecting GlcNAc and α1-6-linked fucose at the core.

Refining the value of secretory phospholipase A2 as a predictor of acute chest syndrome in sickle cell disease: results of a feasibility study (PROACTIVE)

Acute chest syndrome (ACS) is defined as fever, respiratory symptoms and a new pulmonary infiltrate in an individual with sickle cell disease (SCD). Nearly half of ACS episodes occur in SCD patients already hospitalized, potentially permitting pre-emptive therapy in high-risk patients. Simple transfusion of red blood cells may abort ACS if given to patients hospitalized for pain who develop fever and elevated levels of secretory phospholipase A2 (sPLA2). In a feasibility study (PROACTIVE; ClinicalTrials.gov NCT00951808), patients hospitalized for pain who developed fever and elevated sPLA2 were eligible for randomization to transfusion or observation; all others were enrolled in an observational arm. Of 237 enrolled, only 10 were randomized; one of the four to receive transfusion had delayed treatment. Of 233 subjects receiving standard care, 22 developed ACS. A threshold level of sPLA2 ≥ 48 ng/ml gave optimal sensitivity (73%), specificity (71%) and accuracy (71%), but a positive predictive value of only 24%. The predictive value of sPLA2 was improved in adults and patients with chest or back pain, lower haemoglobin concentration and higher white blood cell counts, and in those receiving less than two-thirds maintenance fluids. The hurdles identified in PROACTIVE should facilitate design of a larger, definitive, phase 3 randomized controlled trial.

Molecular evolution of a malaria resistance gene (DARC) in primates

Genes involved in host-pathogen interactions are often strongly affected by positive natural selection. The Duffy antigen, coded by the Duffy antigen receptor for chemokines (DARC) gene, serves as a receptor for Plasmodium vivax in humans and for Plasmodium knowlesi in some nonhuman primates. In the majority of sub-Saharan Africans, a nucleic acid variant in GATA-1 of the gene promoter is responsible for the nonexpression of the Duffy antigen on red blood cells and consequently resistance to invasion by P. vivax. The Duffy antigen also acts as a receptor for chemokines and is expressed in red blood cells and many other tissues of the body. Because of this dual role, we sequenced a ~3,000-bp region encompassing the entire DARC gene as well as part of its 5' and 3' flanking regions in a phylogenetic sample of primates and used statistical methods to evaluate the nature of selection pressures acting on the gene during its evolution. We analyzed both coding and regulatory regions of the DARC gene. The regulatory analysis showed accelerated rates of substitution at several sites near known motifs. Our tests of positive selection in the coding region using maximum likelihood by branch sites and maximum likelihood by codon sites did not yield statistically significant evidence for the action of positive selection. However, the maximum likelihood test in which the gene was subdivided into different structural regions showed that the known binding region for P. vivax/P. knowlesi is under very different selective pressures than the remainder of the gene. In fact, most of the gene appears to be under strong purifying selection, but this is not evident in the binding region. We suggest that the binding region is under the influence of two opposing selective pressures, positive selection possibly exerted by the parasite and purifying selection exerted by chemokines.

Immune factors influencing ethnic disparities in kidney transplantation outcomes

An influence of ethnicity on the outcomes of kidney transplant recipients has been recognized for several decades. Both immune and nonimmune factors have been explored as potential explanations. Most studies have focused on the inferior outcomes of African-Americans. As a group, African-Americans differ from Caucasians with respect to a number of measurable components of the alloimmune response, including the T-cell repertoire and the expression and function of costimulatory molecules and various cytokines and chemokines. In general, these differences suggest that African-Americans may be high immune responders. However, no single difference in any of these components of alloimmunity satisfactorily explains the disparities in outcomes. It seems probable that some combination of immune factors interacts with nonimmune factors, such as socioeconomic resources, to influence transplant outcomes in a complex manner.

Duffy antigen receptor for chemokines mediates chemokine endocytosis through a macropinocytosis-like process in endothelial cells

Background

The Duffy antigen receptor for chemokines (DARC) shows high affinity binding to multiple inflammatory CC and CXC chemokines and is expressed by erythrocytes and endothelial cells. Recent evidence suggests that endothelial DARC facilitates chemokine transcytosis to promote neutrophil recruitment. However, the mechanism of chemokine endocytosis by DARC remains unclear.

Methodology/Principal Findings

We investigated the role of several endocytic pathways in DARC-mediated ligand internalization. Here we report that, although DARC co-localizes with caveolin-1 in endothelial cells, caveolin-1 is dispensable for DARC-mediated ¹²⁵I-CXCL1 endocytosis as knockdown of caveolin-1 failed to inhibit ligand internalization. ¹²⁵I-CXCL1 endocytosis by DARC was also independent of clathrin and flotillin-1 but required cholesterol and was, in part, inhibited by silencing Dynamin II expression.¹²⁵I-CXCL1 endocytosis was inhibited by amiloride, cytochalasin D, and the PKC inhibitor Gö6976 whereas Platelet Derived Growth Factor (PDGF) enhanced ligand internalization through DARC. The majority of DARC-ligand interactions occurred on the endothelial surface, with DARC identified along plasma membrane extensions with the appearance of ruffles, supporting the concept that DARC provides a high affinity scaffolding function for surface retention of chemokines on endothelial cells.

Conclusions/Significance

These results show DARC-mediated chemokine endocytosis occurs through a macropinocytosis-like process in endothelial cells and caveolin-1 is dispensable for CXCL1 internalization.

DARC alleles and Duffy phenotypes in African Americans

BACKGROUND

The DARC (Duffy blood group, chemokine receptor) gene encodes for a transmembrane glycoprotein that functions as a chemokine transporter, is a receptor for Plasmodium vivax and P. knowlesi, and expresses the Duffy blood group antigens (Fy). The Fy(a-b-) phenotype found in people of African descent is typically associated with a -67t>c mutation in the 5'-untranslated region (UTR), which prevents red blood cells being invaded by P. vivax and P. knowlesi. The aim of this study was to establish DARC allele frequencies in an African American blood donor cohort, determine a phylogenetic tree for DARC, and compare human and Neandertal DARC genes.

STUDY DESIGN AND METHODS

The DARC nucleotide sequence of 54 African American blood donors was determined from genomic DNA. Heterozygous substitutions were resolved by sequencing of haplotype-specific amplifications. A phylogenetic tree for DARC was established using the neighbor-joining method with Pan troglodytes as root.

RESULTS

A total of 108 haplotypes of the DARC gene could be unambiguously determined from nucleotide position -300 in the 5' UTR to +300 in the 3' UTR. Eleven different alleles were found, including the clinically relevant FY*A, FY*B, FY*B-67C, FY*B298A, and FY*X alleles. All phenotype predictions based on genotypes matched the serologically determined phenotypes exactly: 52% Fy(a-b-), 28% Fy(a-b+), and 20% Fy(a+b-).

CONCLUSIONS

The nucleotide sequencing approach using one amplicon is a practical genotyping method for DARC and allows the determination of haplotypes even in heterozygous constellations. We developed a phylogenetic tree for DARC alleles and postulated a distinct FY*B allele as ancestral for the extant DARC alleles in humans.

Red blood cell storage lesions and related transfusion issues: a Canadian Blood Services research and development symposium

For centuries, man has been trying to figure out how to revive sick and traumatized individuals using fluids of various types, even from animals. In the 17th century, it was determined that blood was the best fluid to use and, in the early 1900s, after the discovery of the ABO blood groups, human blood was found to provide significant benefit for patients with shock and/or anemia. In the 1950s and 1960s, various ways to obtain, process, and store human blood were developed. It soon became apparent that storage of human blood for transfusion was problematic because red cells, as they aged in vitro, underwent a multitude of physicochemical changes that greatly affected their shelf life, the so-called storage lesion. More recently, the question has arisen as to the potential detrimental effects of the storage lesion and suggestions that older blood may induce increased morbidity and even mortality despite its acceptable in vivo survival. To address this issue of the efficacy and safety of transfusion of aged stored blood, a number of controlled clinical trials have been instituted to determine if older blood is significantly detrimental compared with fresher blood in transfusion recipients.

Malaria-related anaemia: a Latin American perspective

Malaria is the most important parasitic disease worldwide, responsible for an estimated 225 million clinical cases each year. It mainly affects children, pregnant women and non-immune adults who frequently die victims of cerebral manifestations and anaemia. Although the contribution of the American continent to the global malaria burden is only around 1.2 million clinical cases annually, there are 170 million inhabitants living at risk of malaria transmission in this region. On the African continent, where Plasmodium falciparum is the most prevalent human malaria parasite, anaemia is responsible for about half of the malaria-related deaths. Conversely, in Latin America (LA), malaria-related anaemia appears to be uncommon, though there is a limited knowledge about its real prevalence. This may be partially explained by several factors, including that the overall malaria burden in LA is significantly lower than that of Africa, that Plasmodium vivax, the predominant Plasmodium species in the region, appears to display a different clinical spectrus and most likely because better health services in LA prevent the development of severe malaria cases. With the aim of contributing to the understanding of the real importance of malaria-related anaemia in LA, we discuss here a revision of the available literature on the subject and the usefulness of experimental animal models, including New World monkeys, particularly for the study of the mechanisms involved in the pathogenesis of malaria.

Evidence that erythrocyte DARC-positive phenotype can affect the GVHD occurrence after HLA-identical sibling HSCT

Chemokine receptors are very important players in the pathogenesis of GVHD. The aim of this study is to test the hypothesis that the lack of expression of the DARC receptor on erythrocytes can affect the GVHD incidence. A total of 105 recipients and their 105 respective sibling donors of HSCs were enrolled in this study. All patients were evaluated for acute and chronic GVHD. The DARC genotyping assay was performed using the SSP-PCR method. The case-control analyses showed that the donor DARC 146G allele and T(-46)G(146) haplotype, coding for the FY2 version of DARC, are very significant in the GVHD paradigm because they are associated with the incidence of acute effects of this outcome in recipients (p=0.007, χ²=7.200). It seems that this version of DARC receptor is a powerful facilitator of chemokine transcytosis and subsequently leukocyte migration into GVHD target organs.

Duffy-null-associated low neutrophil counts influence HIV-1 susceptibility in high-risk South African black women

BACKGROUND

The Duffy-null trait and ethnic netropenia are both highly prevalent in Africa. The influence of pre-seroconversion levels of peripheral blood cell counts (PBCs) on the risk of acquiring human immunodeficiency virus (HIV)-1 infection among Africans is unknown.

METHODS

The triangular relationship among pre-seroconversion PBC counts, host genotypes, and risk of HIV acquisition was determined in a prospective cohort of black South African high-risk female sex workers. Twenty-seven women had seroconversion during follow-up, and 115 remained HIV negative for 2 years, despite engaging in high-risk activity.

RESULTS

Pre-seroconversion neutrophil counts in women who subsequently had seroconversion were significantly lower, whereas platelet counts were higher, compared with those who remained HIV negative. Comprising 27% of the cohort, subjects with pre-seroconversion neutrophil counts of <2500 cells/mm(3) had a ∼3-fold greater risk of acquiring HIV infection. In a genome-wide association analyses, an African-specific polymorphism (rs2814778) in the promoter of Duffy Antigen Receptor for Chemokines (DARC -46T > C) was significantly associated with neutrophil counts (P = 7.9 × 10(-11)). DARC -46C/C results in loss of DARC expression on erthyrocytes (Duffy-null) and resistance to Plasmodium vivax malaria, and in our cohort, only subjects with this genotype had pre-seroconversion neutrophil counts of <2500 cells/mm(3). The risk of acquiring HIV infection was ∼3-fold greater in those with the trait of Duffy-null-associated low neutrophil counts, compared with all other study participants.

CONCLUSIONS

Pre-seroconversion neutrophil and platelet counts influence risk of HIV infection. The trait of Duffy-null-associated low neutrophil counts influences HIV susceptibility. Because of the high prevalence of this trait among persons of African ancestry, it may contribute to the dynamics of the HIV epidemic in Africa.

Expression of blood group genes by mesenchymal stem cells

Incompatible blood group antigens are highly immunogenic and can cause graft rejections. Focusing on distinct carbohydrate- and protein-based membrane structures, defined by blood group antigens, we investigated human bone marrow-derived mesenchymal stem cells (MSCs) cultured in human serum. The presence of H (CD173), ABO, RhD, RhCE, RhAG, Kell, urea transporter type B (SLC14A1, previously known as JK), and Duffy antigen receptor of chemokines (DARC) was evaluated at the levels of genome, transcriptome and antigen. Fucosyltransferase-1 (FUT1), RHCE, KEL, SLC14A1 (JK) and DARC mRNA were transcribed in MSCs. FUT1 mRNA transcription was lost during differentiation. The mRNA transcription of SLC14A1 (JK) decreased during chondrogenic differentiation, while that of DARC increased during adipogenic differentiation. All MSCs synthesized SLC14A1 (JK) but no DARC protein. However, none of the protein antigens tested occurred on the surface, indicating a lack of associated protein function in the membrane. As A and B antigens are neither expressed nor adsorbed, concerns of ABO compatibility with human serum supplements during culture are alleviated. The H antigen expression by GD2dim+ MSCs identified two distinct MSC subpopulations and enabled their isolation. We hypothesize that GD2(dim+) H(+) MSCs retain a better 'stemness'. Because immunogenic blood group antigens are lacking, they cannot affect MSC engraftment in vivo, which is promising for clinical applications.