Duffy-Null Phenotype-Associated Neutropenia is the Most Common Etiology for Leukopenia/Neutropenia Referrals to a Tertiary Children's Hospital.

Duffy-null phenotype-associated neutropenia was present in 77.7% of leukopenia/neutropenia referrals to our center in Detroit with a high prevalence in Yemeni (96.6%), African American (91%), and non-Yemeni Middle Eastern (52.9%) patients. Greater availability of Duffy typing in patients with neutropenia but without recurrent/frequent/serious infections may lessen the need for additional consultations and investigations.

Ancestral reconstruction and correlation of the frequencies of the hemoglobin S allele and the Duffy blood group alleles in human populations.

OBJECTIVES: Malaria is an important selective force for human genetic adaptation due to the sustained, lethal impact it has had on populations worldwide. High frequencies of both hemoglobin S and the null allele FYBES of the Duffy blood group have been found in areas where this disease is endemic, attributed to the protective action of the carriers of these variants against malaria infection. The objective of this work was to perform ancestral reconstruction and analyze the correlation of the frequencies of these alleles throughout the phylogeny of 24 human populations. METHODS: A tree topology and the allelic frequencies reported in the literature for the 24 populations were used. The ancestral frequencies for the two alleles were reconstructed using the maximum likelihood method and the Brownian model of evolution (CI = 95%), and the correlation analysis was performed using phylogenetically independent contrasts (PICs). Statistical analyses were performed with the statistical software R version 3.4.1. RESULTS: For both alleles, a correspondence was found in the reconstruction of the ancestral frequencies, and a significant statistical correlation (p = .001) was observed between the S and FYBES alleles. CONCLUSIONS: These results provide evidence of an epistatic relationship between the two alleles, which may influence the fitness of the individuals who present with them when they are subjected to a selective force such as malaria.

Serological and Molecular Study of the Duffy Blood Group among Malarial Endemic Region Residents in Brazil.

BACKGROUND: The atypical chemokine receptor 1 (ACKR1) gene encodes the Duffy blood group antigens in two allelic forms: FY*A (FY*01) and FY*B (FY*02), which define the Fy(a+b-), Fy(a-b+), and Fy(a+b+) phenotypes. FY*BES (FY*02N.01) is a single T to C substitution at nucleotide -67 that prevents the FY*B from being expressed in red blood cells (RBCs). METHODS: We evaluated 250 residents from a Brazilian malarial endemic region (RsMR). All individuals were phenotyped for Fya and Fyb antigens and genotyped for FY*A, FY*B, FY*B SE , and FY*B weak alleles. RESULTS: Among the 250 individuals, 209 (83.6%) reported previous malaria infection, and 41 (16.4%) did not. The Fy(a+b+) phenotype was present in 97/250 (38.8%), while the Fy(a-b-) was present in 7/250 (2.8%). The FY*A/FY*B was found in 130/250 (52%) and the FY*A/FY*A in 45/250 (18%). The c.1-67>TC was present, in homozygosity, in 11/250 (4.4%). Among 34 individuals with the Fy(a+b-) and FYA*/FYB* mutations, 4/34 (11.8%) had homozygosity for the c.1-67T>C. One individual presented the Fy(a+b-), FY*A/FY*B, and c.1-67T>C in homozygosis, whereas the other presented the Fy(a+b-), FY*A/FY*A, and c.1-67T>C in heterozygosis. CONCLUSIONS: We reported a low prevalence of the Fy(a-b-) in persons who had previously been infected with Plasmodium vivax (67.5%). We observed that 102/141 (72.3%) individuals expressing the Fyb antigen had a P. vivax infection, indicating the importance of the Fyb antigen, silenced by a c.1-67T>C mutation in homozygosis, in preventing the P. vivax infection. We showed that the c.1-67T>C mutation in the FY*A did not silence the FY*A expression on RBCs.

Duffy blood system and G6PD genetic variants in vivax malaria patients from Manaus, Amazonas, Brazil.

BACKGROUND: Over a third of the world's population is at risk of 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 (RBC) variations that can confer protection against malaria. METHODS: Molecular genotyping of G6PD and Duffy variants was performed in 225 unrelated patients (97 with uncomplicated and 128 with severe vivax malaria) recruited at a Reference Centre for Infectious Diseases in Manaus. G6PD and Duffy variants characterizations were performed using Real Time PCR (qPCR) and PCR-RFLP, respectively. RESULTS: The Duffy blood group system showed a phenotypic distribution Fy(a + b-) of 70 (31.1%), Fy(a + b +) 96 (42.7%), Fy(a-b +) 56 (24.9%) and Fy(a-b-) 1 (0.44%.) The genotype FY*A/FY*B was predominant in both uncomplicated (45.3%) and severe malaria (39.2%). Only one Duffy phenotype Fy(a-b) was found and this involved uncomplicated vivax malaria. The G6PD c.202G > A variant was found in 11 (4.88%) females and 18 (8.0%) males, while c.376A > G was found in 20 females (8.88%) and 23 (10.22%) male patients. When combined GATA mutated and c.202G > A and c.376A > G mutated, was observed at a lower frequency in uncomplicated (3.7%) in comparison to severe malaria (37.9%). The phenotype Fy(a-b +) (p = 0.022) with FY*B/FY*B (p = 0.015) genotype correlated with higher parasitaemia. CONCLUSIONS: A high prevalence of G6PD c202G > A and c.376A > G and Duffy variants is observed in Manaus, an endemic area for vivax malaria. In addition, this study reports for the first time the Duffy null phenotype Fy(a-b-) in the population of the Amazonas state. Moreover, it is understood that the relationship between G6PD and Duffy variants can modify clinical symptoms in malaria caused by P. vivax and this deserves to be further investigated and explored among this population.

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

ABSTRACT 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.

Duffy phenotyping and FY*B-67T/C genotyping as screening test for benign constitutional neutropenia

ABSTRACT Objective: Low levels of neutrophils can be an intrinsic condition, with no clinical consequences or immunity impairment. This condition is the benign constitutional neutropenia (BCN), defined as an absolute neutrophils count (ANC) ≤2000 cells/mm. Diagnosis of BCN is of exclusion where patients are submitted to blood tests and possibly to invasive diagnostic search until secondary causes of neutropenia are ruled out. The natural history of the disease suggests benign evolution and Brazilian study showed an overall frequency of 2.59%. The main mechanisms include reduced neutrophil production, increased marginalization, extravasation to the tissues and immune destruction. Genetic studies showed strong association between the single nucleotide variant rs2814778 located on chromosome 1q23.2 in the promoter region of the atypical chemokine receptor 1 (Duffy blood group system) gene (ACKR1, also termed DARC) and BCN. The aim of this study is to evaluate FY phenotypes and genotypes including the analysis of the rs2814778 SNP in Brazilian patients with BCN in order to determine an effective diagnostic tool, allowing reassurance of the patient and cost reduction in their care. Methods: Case control study, with 94 individuals (18 patients and 76 controls). Phenotyping was performed by gel test and genotyping was performed by PCR-RFLP. Results: White blood cell (WBC) and absolute neutrophils (AN) counts showed lower levels in patients compared to controls. In the patient group 83.3% were genotyped as FY*B/FY*B. The SNP rs2814778 (-67T > C) was identified in 77.8% of the patients genotyped as FY*B-67C/FY*B-67C. In the control group, 72.7% were homozygous for the wild type and 23.3% were heterozygous. Conclusion: This study reinforces that FY phenotyping and genotyping can be used to detect most people with BCN, avoiding excessive diagnostic investigation. Besides, this procedure may reduce health costs and be reproductible in clinical practice.

Diversity of variant alleles encoding Kidd, Duffy, and Kell antigens in individuals with sickle cell disease using whole genome sequencing data from the NHLBI TOPMed Program.

BACKGROUND: Genetic variants in the SLC14A1, ACKR1, and KEL genes, which encode Kidd, Duffy, and Kell red blood cell antigens, respectively, may result in weakened expression of antigens or a null phenotype. These variants are of particular interest to individuals with sickle cell disease (SCD), who frequently undergo chronic transfusion therapy with antigen-matched units. The goal was to describe the diversity and the frequency of variants in SLC14A1, ACKR1, and KEL genes among individuals with SCD using whole genome sequencing (WGS) data. STUDY DESIGN AND METHODS: Two large SCD cohorts were studied: the Recipient Epidemiology and Donor Evaluation Study III (REDS-III) (n = 2634) and the Outcome Modifying Gene in SCD (OMG) (n = 640). Most of the studied individuals were of mixed origin. WGS was performed as part of the National Heart, Lung, and Blood Institute's Trans-Omics for Precision Medicine (TOPMed) program. RESULTS: In SLC14A1, variants included four encoding a weak Jka phenotype and five null alleles (JKnull ). JKA*01N.09 was the most common JKnull . One possible JKnull mutation was novel: c.812G>T. In ACKR1, identified variants included two that predicted Fyx (FY*X) and one corresponding to the c.-67T>C GATA mutation. The c.-67T>C mutation was associated with FY*A (FY*01N.01) in four participants. FY*X was identified in 49 individuals. In KEL, identified variants included three null alleles (KEL*02N.17, KEL*02N.26, and KEL*02N.04) and one allele predicting Kmod phenotype, all in heterozygosity. CONCLUSIONS: We described the diversity and distribution of SLC14A1, ACKR1, and KEL variants in two large SCD cohorts, comprising mostly individuals of mixed ancestry. This information may be useful for planning the transfusion support of patients with SCD.

Estimated prevalence of the Duffy null phenotype Fy (a-b-) among black blood-donors in Southwestern Colombia.

INTRODUCTION: Hemolytic reactions are adverse complications associated with red blood cell transfusion. These reactions are associated with clinically important erythrocyte antigens, such as those of Duffy blood Meny (2010). Individuals with the Duffy null phenotype Fy (a-b-) are more likely to develop an alloimmunization reaction, resulting in an incompatibility with all available red blood cell units, thus increasing the risk of complications from their underlying disease Höher et al. (2018). Hence, it is important to determine the prevalence of the Fy (a-b-) phenotype in blood donors in our population and to create a database to ensure safe transfusion in patients with this phenotype. Moreover, we intend to establish whether there is any relationship between individuals with this phenotype and the sickle cell trait. We conducted this study to measure the prevalence of the Fy (a-b-) phenotype in our blood donors. MATERIALS AND METHODS: This prospective, descriptive study included black blood donors visiting the blood bank of a tertiary care university hospital between January 2019 and July 2019. We used Fitzpatrick classification phototype VI and self-identification to select donors in the study. The presence of the Duffy antigens Fya and Fyb was determined by the Coombs test using monoclonal antibodies. To establish the presence of hemoglobin S (HbS) and sickle cell traits, a hemoglobin electrophoresis test was performed. RESULTS: We included 166 patients in the study. Seventy-nine donors were identified as having Fy (a-b-). The prevalence of the Fy (a-b-) phenotype was 48 %. Sickle cell trait hemoglobinopathy was found in 6 blood donors (8%). CONCLUSION: This information is relevant for the implementation of a database of blood donors to guarantee the safety of transfusion in patients with a Fitzpatrick skin type 6at our institution. Moreover, it may provide information of interest to other blood banks in case donors with this phenotype are needed. No significant association was found between the donor Fy (a-b-) phenotype and the sickle cell trait.

Hotspots in Plasmodium and RBC Receptor-Ligand Interactions: Key Pieces for Inhibiting Malarial Parasite Invasion.

Protein-protein interactions (IPP) play an essential role in practically all biological processes, including those related to microorganism invasion of their host cells. It has been found that a broad repertoire of receptor-ligand interactions takes place in the binding interphase with host cells in malaria, these being vital interactions for successful parasite invasion. Several trials have been conducted for elucidating the molecular interface of interactions between some Plasmodium falciparum and Plasmodium vivax antigens with receptors on erythrocytes and/or reticulocytes. Structural information concerning these complexes is available; however, deeper analysis is required for correlating structural, functional (binding, invasion, and inhibition), and polymorphism data for elucidating new interaction hotspots to which malaria control methods can be directed. This review describes and discusses recent structural and functional details regarding three relevant interactions during erythrocyte invasion: Duffy-binding protein 1 (DBP1)-Duffy antigen receptor for chemokines (DARC); reticulocyte-binding protein homolog 5 (PfRh5)-basigin, and erythrocyte binding antigen 175 (EBA175)-glycophorin A (GPA).

Duffy blood group system and ocular toxoplasmosis.

Duffy blood group phenotypes [Fy(a + b-), Fy(a-b+), Fy(a + b+), Fy(a-b-)], characterized by the expression of Fya, and Fyb antigens, are present in red blood cells. Therefore, we hypothesize that the non-hematopoietic expression of these antigens might influence cell invasion by T. gondii. 576 consecutive patients from both genders were enrolled. The presumed OT clinical diagnosis was performed. Duffy phenotyping was performed by hemagglutination in gel columns and for the correct molecular characterization Fy(a-b-) phenotype, using PCR-RFLP. Anti-T. gondii IgG antibodies were detected by ELISA. Chi-square, Fisher's exact tests were used to compare the proportions. OT was present in 22.9% (n = 132) and absent in 77.1% (n = 444) of patients. The frequencies of anti-T. gondii IgG antibodies were higher in OT (127/132, 96.2%) than those without this disease (321/444, 72.3%) (p < .0001). None of the Duffy antigens or phenotypes were associated with T. gondii infection (χ2: 2.222, GL: 3, p = .5276) as well as the risk of OT (χ2: 0.771, GL: 3, p = .8566). Duffy blood group system phenotypes and their antigens do not constitute risk factors for infection by T. gondii infection and the development of OT.

Identification of ACKR1 variants associated with altered Duffy phenotype expression in blood donors from southern Brazil.

The atypical chemokine receptor 1 gene (ACKR1) is responsible for the clinically significant Duffy blood group. The main antigens of this system, Fya and Fyb, can be related to a null or weak expression of the DARC protein. In the present work, we aimed to identify ACKR1 gene variants in blood donors from southern Brazil based on discrepancies between their serological and molecular typing results. Then, we analyzed the association of these variants with the expression of the Duffy phenotype. The Fy antigen types were determined via hemagglutination and real-time PCR (c.125 G > A, c.265C > T and c.-67T > C SNPs) tests in a sample composed of 382 regular repetitive voluntary blood donors to the Blood Bank of Hospital de Clínicas de Porto Alegre. An inconclusive correlation between phenotype-genotype analyses was found in 11 (2.88 %) donors, and the entire ACKR1 gene was sequenced in these samples. Our investigation found 11 genetic variants, four of which (c.-541C > T, c.21 + 150C > T, c.22-58A > G, and c.298 G > A SNPs) seem to have putative functional effects on the structure and expression of DARC undertaken for in silico analysis (SIFT, PolyPhen-2 and RegulomeDB). Molecular events can result in apparent discrepancies between red cell genotypes and phenotypes. Our findings provided insight into the molecular background of FY antigens to improve technical approaches for red cell genotyping.

Joint selection for two malaria resistance mutations in a south-west Colombian population.

In regions with an Afro-descendant population and where malaria is endemic, high frequencies of polymorphisms have been found that confer resistance to this disease, such as the haemoglobin S (HbS) and Duffy genes, which provide resistance to P. falciparum and P. vivax infection, respectively. The objective of this study was to evaluate the individual and joint selection actions of these two genes in an Afro-descendant Colombian population. A total of 819 individuals were analysed using stratified random sampling. PCR-RFLP and Hardy-Weinberg equilibrium deviation analysis (H-W eq.), linkage disequilibrium (LD), D'IS2 and D'ST2 indexes, neutrality tests, correlations and fitness were performed using Arlequin 3.5.2.2 and R 3.4.1 software. In general, the population showed neutrality and H-W eq. for the HbS gene but not for the Duffy gene (FYA/FYB, FYA/FYBES and FYB/FYBES genotypes were responsible for this deviation). LD between the HbS locus and the promoter region of the Duffy gene, a value D'IS2 = 0.001 and D'ST2 = 0.020 was found, an increase in fitness of the AS*FYBES/FYBES genotype combination (marked in adolescents and adults), and a strong correlation between these genotypes (Rho = 90%, p = .001) were found, evidencing a possible joint selection action for these two alleles. This work presents evidence of the action of natural selection, both individually and jointly, on malaria resistance genes, HbS and Duffy, in the Buenaventura population.

Impact of Duffy polymorphisms on parasite density in Brazilian Amazonian patients infected by Plasmodium vivax.

BACKGROUND: The Duffy glycoprotein acts as the entry point for merozoites of Plasmodium vivax in the invasion of red blood cells. The host-parasite relationship has revealed new perspectives regarding the association between Duffy polymorphisms that can impact both the parasite density of this Plasmodium and the symptoms of this type of malaria. This study investigates the impact of Duffy polymorphisms on parasite density in patients infected with P. vivax in the Brazilian Amazon region. METHODS: Genotypes and Duffy polymorphism allele frequencies were compared in 287 patients with malaria, presenting low, medium and high density of P. vivax. The diagnosis of malaria was performed using a specialized team with a standardized clinical-laboratory method, while the Duffy genotyping was performed through the Bead Chip BioArray system. Both teams are reference services in Brazil. RESULTS: The FY*01 and FY*02 alleles were found in all three parasite density classes: low, medium and high, but when these alleles form genotypes with FY*02N.01 and FY*02W.01 alleles, they are found only in patients with low parasite density and low symptomatology. Another interesting finding found in this study is the presence of the genotype FY*02N.01/FY*02W.01 in one of the patients, presenting a very low parasite density and malaria considered subclinical, a genotype which had not been previously described in the literature. CONCLUSION: The presence of FY*02N.01 and FY*02W.01 alleles may have an impact on the reduction of clinical manifestations in malaria, leading to the development of subclinical malaria, making the infected individual an undetected natural reservoir, which may hinder the eradication of malaria in the Amazon.

Tipificación del antígeno Duffy como método indirecto para identificar individuos asintomáticos de malaria / Duffy antigen typing as an indirect method to identify asymptomatic malaria individuals

En países considerados endémicos de malaria a pesar de las estrategias realizadas anualmente para el control y erradicación de esta enfermedad existen brotes aislados de malaria debido probablemente a portadores asintomáticos, presencia de individuos con fenotipo Duffy negativo o movimientos poblacionales. El sector "50 casas" de la provincia de Esmeraldas-Ecuador reúne todas estas características por lo que el objetivo de esta investigación fue determinar la presencia del fenotipo Fy(a-b-) y su relación con el Plasmodium vivax. Se realizó una encuesta a cada miembro de las familias participantes y luego de aceptado y firmado el consentimiento informado se tomaron muestras sanguíneas para la realización de pruebas serológicas en búsqueda de anticuerpos y antígenos de P. vivax, fenotipificación del sistema Duffy y pruebas de PCR en tiempo real para la determinación de ADN de Plasmodium vivax y P. falciparum. Los resultados demostraron que existe una asociación estadísticamente significativa entre el fenotipo Duffy y malaria por P. vivax (p<0,05). Ante esta situación los organismos de control deberán proponer nuevas estrategias para la detección de portadores asintomáticos y medidas preventivas para evitar nuevos brotes de malaria, así como determinar si P. vivax ha encontrado un nuevo mecanismo de invasión en individuos portadores del fenotipo Fy(a-b-).

Despite the strategies carried out annually for the control and eradication in countries considered endemic for malaria, there are isolated outbreaks probably due to asymptomatic carriers. These involve the presence of individuals with Duffy negative phenotype or population movements. The neighbourhood "50 casas" of the province of Esmeraldas-Ecuador has all these characteristics, so the purpose of this research was to determine the presence of the Fy(a-b-) phenotype and its relationship with the Plasmodium vivax. A survey was carried out into each member of the participating families and after accepting and signing the informed consent, blood samples were taken to perform serological tests in search of antibodies and antigens of P. vivax. The phenotyping of Duffy system and real-time PCR tests for DNA determination of Plasmodium vivax and falciparum was realized. The results showed that there is a statistically significant association between the Duffy phenotype and P. vivax malaria (p<0.05). In view of this situation, the control agencies should propose new strategies for the detection of asymptomatic carriers and preventive measures to hinder new outbreaks of malaria and determine if P. vivax has found a new invasion mechanism in individuals with the Fy(a-b-) phenotype.

Nos países considerados endêmicos para malária, apesar das estratégias realizadas anualmente para o controle e erradicação desta doença existem surtos isolados de malária, resultantes provavelmente de portadores assintomáticos, presença de indivíduos com fenótipo Duffy negativo ou movimentos populacionais. O setor "50 casas" na província de Esmeraldas-Equador reúne todas essas características. Portanto o objetivo desta pesquisa foi determinar a presença de fenótipo Fy(a-b-) e sua relação com Plasmodium vivax. Foi realizada uma enquete para cada membro das famílias participantes e após a aceitação e assinatura do Consentimento informado, foram coletadas amostras de sangue para a realização de testes sorológicos em busca de anticorpos e antígenos do P. vivax. Além de testes de fenotipagem do sistema Duffy e PCR em tempo real para determinação de DNA de Plasmodium vivax e P. falciparum. Os resultados mostraram que existe uma associação estatisticamente significante entre o fenótipo Duffy e a malária por P. vivax (p<0,05). Perante está situação os órgãos de fiscalização terão que propor novas estratégias para a detecção de portadores assintomáticos e medidas preventivas para evitar novos surtos de medidas de malária bem como determinar se P. vivax tem encontrado um novo mecanismo de invasão em indivíduos portadores do fenótipo Fy(a-b-).

Susceptibility to Plasmodium vivax malaria associated with DARC (Duffy antigen) polymorphisms is influenced by the time of exposure to malaria.

Malaria has provided a major selective pressure and has modulated the genetic diversity of the human genome. The variants of the Duffy Antigen/Receptor for Chemokines (DARC) gene have probably been selected by malaria parasites, particularly the FY*O allele, which is fixed in sub-Saharan Africa and confers resistance to Plasmodium vivax infection. Here, we showed the influence of genomic ancestry on the distribution of DARC genotypes in a highly admixed Brazilian population and confirmed the decreased susceptibility of the FY*A/FY*O genotype to clinical P. vivax malaria. FY*B/FY*O individuals were associated with a greater risk of developing clinical malaria. A remarkable difference among DARC variants concerning the susceptibility to clinical malaria was more evident for individuals who were less exposed to malaria, as measured by the time of residence in the endemic area. Additionally, we found that DARC-negative and FY*A/FY*O individuals had a greater chance of acquiring high levels of antibodies against the 19-kDa C-terminal region of the P. vivax merozoite surface protein-1. Altogether, our results provide evidence that DARC polymorphisms modulate the susceptibility to clinical P. vivax malaria and influence the naturally-acquired humoral immune response to malaria blood antigens, which may interfere with the efficacy of a future vaccine against malaria.

Genetic Variants of Duffy and Hemoglobin S Genes in an Afrodescendant Population from Colombia.

Malaria is an endemic disease in a large part of Colombia, and the city of Buenaventura reports one of the highest malaria infection rates. Some genetic variants confer resistance to malaria, such as the heterozygote for hemoglobin S (HbS) and the homozygous variant FYBES/FYBES of the Duffy gene. The aim of this work was the molecular characterization of these genes in an Afrodescendant population from the urban area of Buenaventura. A total of 819 individuals from a stratified random sampling in each of the 12 communities of this city were analyzed. Molecular analysis was performed using PCR-RFLP, and data analysis was performed using Arlequin 3.5, SPSS 20.0, and R 3.4.1. Frequencies of 3.1% and 72.2% were obtained for the S and FYBES alleles, respectively, with 6.1% AS heterozygous and 55% FYBES/FYBES homozygous genotypes. The highest percentages of the resistant genotype (genotypic combination AA*FYBES/FYBES) were found for the 13-27-year age group (8.2%) and communities 1 and 3 (18% and 10.3%, respectively). Therefore, it would be pertinent to consider the remaining communities and age groups when performing epidemiological studies and preventive and health care campaigns on malaria in the urban areas of the city of Buenaventura.

Molecular basis of the Duffy blood group system.

ACKR1, located on chromosome 1q23.2, is the gene that encodes a glycoprotein expressing the Duffy blood group antigens. This gene is transcribed in two mRNA variants yielding two isoforms, encoding proteins with 338 and 336 amino acids. This review provides a general overview of the Duffy blood group to characterise and elucidate the genetic basis of this system. The Fya and Fyb antigens are encoded by co-dominant FY*A (FY*01) and FY*B (FY*02) alleles, which differ by c.125G>A (rs12075), defining the Fy(a+b-), Fy(a-b+) and Fy(a+b+) phenotypes. The Fy(a-b-) phenotype that occurs in Africans provides an explanation for the apparent absence of Plasmodium vivax in this region: this phenotype arises from homozygosity for the FY*B allele carrying a point mutation c.1-67T>C (rs2814778), which prevents Fyb antigen expression only in red blood cells. The same mutation has also been found on the FY*A allele, but it is very rare. The Fy(a-b-) phenotype in Europeans and Asians arises from mutations in the coding region of the FY*A or FY*B allele, preventing Duffy antigen expression on any cell in the body and thus are true Duffy null phenotypes. According to the International Society for Blood Transfusion, ten alleles are associated with the null expression of the Fy antigens. Furthermore, different allelic forms of FY*B modify Fyb antigen expression, which may result in very weak or equivocal serology results. The mostly common found variants, c.265C>T (rs34599082) and c.298G>A (rs13962) -previously defined in combination only with the FY*B allele - have already been observed in the FY*A allele. Thus, six alleles have been recognised and associated with weak expression of the Fy antigens. Considering the importance of the Duffy blood group system in clinical medicine, additional studies via molecular biology approaches must be performed to resolve and clarify the discrepant results that are present in the erythrocyte phenotyping.

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.

MNS, Duffy, and Kell blood groups among the Uygur population of Xinjiang, China.

Human blood groups are a significant resource for patients, leading to a fierce international competition in the screening of rare blood groups. Some rare blood group screening programs have been implemented in western countries and Japan, but not particularly in China. Recently, the genetic background of ABO and Rh blood groups for different ethnic groups or regions in China has been focused on increasingly. However, rare blood groups such as MN, Duffy, Kidd, MNS, and Diego are largely unexplored. No systematic reports exist concerning the polymorphisms and allele frequencies of rare blood groups in China's ethnic minorities such as Uygur and Kazak populations of Xinjiang, unlike those on the Han population. Therefore, this study aimed to investigate the allele frequencies of rare blood groups, namely, MNS, Duffy, Kell, Dombrock, Diego, Kidd, Scianna, Colton, and Lutheran in the Uygur population of Xinjiang Single specific primer-polymerase chain reaction was performed for genotyping and statistical analysis of 9 rare blood groups in 158 Uygur individuals. Allele frequencies were compared with distribution among other ethnic groups. Observed and expected values of genotype frequencies were compared using the chi-square test. Genotype frequencies obeyed the Hardy-Weinberg equilibrium (P > 0.5) and allele frequencies were stable. Of all subjects detected, 4 cases carried the rare phenotype S-s- of MNS blood group (frequency of 0.0253), and 1 case carried the phenotype Jka-b- (frequency of 0.0063). Frequencies of the four groups, MNS, Duffy, Dombrock, and Diego, in the Uygur population differed from those in other ethnic groups. Gene distribution of the Kell, Kidd, and Colton was similar to that in Tibetan and Han populations, though there were some discrepancies. Gene distribution of Scianna and Lutheran groups showed monomorphism similar to that in Tibetan and Han populations. These findings could contribute to the investigation of the origin, evolution, and hematology of Uygur population of Xinjiang and assist in screening of rare blood groups in ethnic minorities, meeting of clinical blood supply demands, and building of the national rare blood group library.