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

ACKR1 gene polymorphisms in Bombay blood group (Oh) individuals of Indian origin

BACKGROUND

ACKR1 blood group genes exhibit a high degree of polymorphisms with varying allele distribution seen among different populations and ethnic groups. The study aimed to genotype ACKR1 antigens and to establish FY allele frequency among the individuals with the Bombay (Oh) blood group phenotype.

MATERIALS AND METHODS

ACKR1 phenotype and genotype frequencies were estimated on 160 individuals typed as Oh and were compared with 100 non-oh blood donors from Mumbai, India by molecularly genotyping via PCR-RFLP.

RESULTS

The allelic and genotypic frequency of T(-67)C polymorphism showed the dominance of T allele and TT genotype [OR= 3.26 (0.59-17.99)] in both the study groups. The ACKR1 null (Fya-b-) phenotype was not found in the tested group. While the genotypic combination among the Oh group individuals was FYA/FYB (45.3 %), FYA/FYA (42.7 %), and FYB/FYB (12 %), in the non-Oh group donors, it was observed as FYA/FYB (53.3 %), FYA/FYA (39.1 %), and FYB/FYB (7.6 %). The haplotype TGGGC occurred in 38.4 % of the Oh group, but in non-Oh donors, it was found to be 50.9 % [OR = 1.820 (1.196-2.771)], and the difference was statistically significant (p = 0.005). Similarly, the TGGGT haplotype was found at a frequency of 12.7 % in non-Oh donors and 27.1 % in Oh group [OR= 0.411 (0.234-0.722)] (p = 0.001).

CONCLUSIONS

This study shows the prevalence of ACKR1 gene polymorphisms, including weak ACKR1 antigens in Oh individuals with a high frequency of haplotype TGGGC. The present study demonstrated for the first time the genotypes FyBweak, FyAweak and Fy Aweak/FyBESon RBC membranes in Indian subjects with Oh phenotype.

Polymorphisms in the human angiotensin converting enzyme gene (ACE) linked to susceptibility of COVID-19 and malaria infections in the Ghanaian population

Genetic variations in the human angiotensin converting enzyme gene (ACE) influence ACE enzyme expression levels in humans and subsequently influence both communicable and non-communicable disease outcomes. More recently, polymorphisms in this gene have been linked to susceptibility and outcomes of infectious diseases such as the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and malaria infections. This study is the first to investigate the genetic diversity of ACE and ACE2 polymorphisms in the Ghanaian population. Archived filter blood blot samples from malaria patients aged ≤9 years were used. Molecular analysis for the detection of ACE rs4646994 (I/D), ACE2 rs2106809 (C/T) and rs2285666 (G/A) alleles as well as ACE2 exons 1-4 polymorphisms was conducted on 300 samples. The D allele (54%,162/300) was the most dominant polymorphism observed in the ACE rs4646994 gene whilst the G (68%, 204/300) and T alleles (59.3%,178/300) were the most frequent ACE2 rs2285666 and rs2106809 polymorphisms observed. For the 300 samples sequenced for ACE2 exons 1-4, analyses were done on 268, 282 and 137 quality sequences for exons 1, 2 and 3-4 respectively. For exon 1, the mutation D38N (2.2%; 6/268) was the most prevalent. The S19P and E37K mutations previously reported to influence COVID-19 infections were observed at low frequencies (0.4%, 1/268 each). No mutations were observed in exon 2. The N121K/T variants were the most seen in exons 3-4 at frequencies of 5.1% (K121, 7/137) and 2.9% (T121, 4/137) respectively. Most of the variants observed in the exons were novel compared to those reported in other populations in the world. This is the first study to investigate the genetic diversity of ACE and ACE2 genes in Ghanaians. The observation of novel mutations in the ACE2 gene is suggesting selection pressure. The importance of the mutations for communicable and non-communicable diseases (malaria and COVID-19) are further discussed.

The highest Duffy (FYX) allele frequency ever reported for Scottish population: A cross-sectional study

Background and Aim

The Duffy (FY) blood group system has six known antigens among which the Fy^a and Fy^b are known as major antigens. Fy^x phenotype forms as a result of two point mutations in the FYB allele leading to instability of Duffy protein and so reduction of Duffy antigen expression in the cells. This study aimed to investigate the FYX allele frequency in the Scottish population.

Methods

The Duffy blood group system was serologically and molecularly investigated in 222 samples collected from donors of Aberdeen Regional Blood Transfusion Center (BTC). The haemagglutination and BeadChip microarray chemistry methods were used for phenotyping and genotyping. Confirmatory tests were also used to check the discrepant results.

Results

In this study, the frequency of Duffy blood group phenotypes including Fy^a+, Fy^a+b+, and Fy^b+ were 17.57%, 42.79%, and 39.64%, respectively. Furthermore, the frequency of FYA/FYA, FYA/FYB, and FYB/FYB genotypes was estimated to be 14.41%, 45.95%, and 39.64%, respectively, using the Bioarray method. In the present study, based on Duffy DNA sequencing results, 12 samples (5.41%) had just one FYX allele.

Conclusion

The frequency of the FYX allele in this study was estimated to be 0.0270% which is more than the results reported so far.

Differential transmissibility to Anopheles arabiensis of Plasmodium vivax gametocytes in patients with diverse Duffy blood group genotypes

BACKGROUND

Measuring risk of malaria transmission is complex, especially in case of Plasmodium vivax. This may be overcome using membrane feeding assays in the field where P. vivax is endemic. However, mosquito-feeding assays are affected by a number of human, parasite and mosquito factors. Here, this study identified the contributions of Duffy blood group status of P. vivax-infected patients as a risk of parasite transmission to mosquitoes.

METHODS

A membrane feeding assay was conducted on a total of 44 conveniently recruited P. vivax infected patients in Adama city and its surroundings in East Shewa Zone, Oromia region, Ethiopia from October, 2019 to January, 2021. The assay was performed in Adama City administration. Mosquito infection rates were determined by midgut dissections at seven to 8 days post-infection. Duffy genotyping was defined for each of the 44 P. vivax infected patients.

RESULTS

The infection rate of Anopheles mosquitoes was 32.6% (296/907) with 77.3% proportion of infectious participants (34/44). Infectiousness of participants to Anopheles mosquitoes appeared to be higher among individuals with homozygous Duffy positive blood group (TCT/TCT) than heterozygous (TCT/CCT), but the difference was not statistically significant. The mean oocyst density was significantly higher among mosquitoes fed on blood of participants with FY*B/FY*BES than other genotypes (P = 0.001).

CONCLUSION

Duffy antigen polymorphisms appears to contribute to transmissibility difference of P. vivax gametocytes to Anopheles mosquitoes, but further studies are required.

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 Fy^a and Fy^b 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 Fy^b antigen had a P. vivax infection, indicating the importance of the Fy^b 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.

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.

The Duffy T-33C is an insightful marker of human history and admixture

A contrasting genotype and allele frequency pattern between Africans and non-Africans in the Duffy (T-33C) locus is reported. Its near fixation in various populations suggest is no longer under natural selection, and that current distribution is possibly a relic of distant extreme selection combined with genetic drift during the out of Africa. We put this difference into the utility to infer the ancestral state of ambiguous loci in different populations.

ACKR1 Alleles at 5.6 kb in a Well-Characterized Renewable US Food and Drug Administration (FDA) Reference Panel for Standardization of Blood Group Genotyping

The glycoprotein encoded by the ACKR1 gene expresses the Duffy blood group antigens and is a receptor for malaria parasites. We recently described 18 long-range ACKR1 alleles in an autochthonous population of a malaria endemic region. Extending this work, we sequenced the gene in a 53-sample repository established by the US Food and Drug Administration (FDA) as reference reagents for blood group genotyping. The FDA samples have been characterized for 19 genes; however, long-range haplotype information for these genes, including ACKR1, was lacking. We used a hybrid approach, novel for this type of gene, to characterize ACKR1 by combining two next-generation sequencing technologies, the short-read massively parallel sequencing and the long-read nanopore sequencing. The expedient integration of data from both next-generation sequencing systems were necessary and sufficient to allow determination of all 25 long-range ACKR1 alleles found in the 53 samples accurately. All 25 alleles identified in our current FDA cohort were novel and, unexpectedly, none had been observed among the 18 alleles in our previous study. The alleles will be useful for validation, calibration, and proficiency testing of red cell genotyping. The lack of any overlap between the ACKR1 alleles in the two studies documents differences in mutation rate and recombination frequency among populations. The exact haplotype and their interethnic or interpopulation dissimilarities can influence disease susceptibility and therapy.

Distribution of Duffy Phenotypes among Plasmodium vivax Infections in Sudan

Negative Duffy expression on the surface of human red blood cells was believed to be a barrier for Plasmodium vivax infection in most Africans. However, P. vivax has been demonstrated to infect Duffy-negative individuals in several Central and East African countries. In this study, we investigated the distribution of Duffy blood group phenotypes with regard to P. vivax infection and parasitemia in Sudan. Out of 992 microscopic-positive malaria samples, 190 were identified as P. vivax positive infections. Among them, 186 were P. vivax mono-infections and 4 were mixed P. vivax and Plasmodium falciparum infections. A subset of 77 samples was estimated with parasitemia by quantitative real-time PCR. Duffy codons were sequenced from the 190 P. vivax positive samples. We found that the Duffy Fy(a-b+) phenotype was the most prevalent, accounting for 67.9% of all P. vivax infections, while homozygous Duffy-negative Fy(a-b-) accounted for 17.9% of the P. vivax infections. The prevalence of infection in Fy(a-b+) and Fy(a+b-)were significantly higher than Fy(a-b-) phenotypes (p = 0.01 and p < 0.01, respectively). A significantly low proportion of P. vivax infection was observed in Duffy negative individuals Fy(a-b-). This study highlights the prevalence of P. vivax in Duffy-negatives in Sudan and indicates low parasitemia among the Duffy-negative individuals.

Duffy blood group system - the frequency of Duffy antigen polymorphisms and novel mutations in the Polish population

Duffy blood group genes are highly polymorphic with the distribution of alleles varying between different populations and ethnic groups. The aim of this study was to genotype Duffy blood group antigens and to establish FY alleles frequency in the Polish population and screen for novel FY gene mutations. Duffy phenotype and genotype frequencies analysis was based on studies of 596 persons. All these subjects were genotyped by high-resolution melting (HRM) method. It was shown that phenotype Fy(a+b+), defined by genotypes FY*A/FY*B (33%), FY*A/FY*B298A (13%), and FY*A/FY*02W.01 (2.8%) was the most common in Polish population (˜49%), followed by Fy(a-b+), ˜29%, determined by genotypes arising from FY*B allele and all its variants. Fy(a+b-) phenotype occurred with a frequency of 21.3% and was defined by the following genotypes: FY*A/A (21%), and FY*A/02N.01 (0.3%). Among the Polish population the frequencies of FY*A, FY*B, and FY*B298A alleles were 45.7%, 36% and 15.5%, respectively. The alleles FY*B298A and FY*B combined together, represented higher frequency (51%) than FY*A. Alleles FY*02W.01 and FY*02N.01 had frequencies 2.51% and 0.25%, respectively. The distribution of Duffy genotypes in the Polish population was in accordance with Hardy-Weinberg equilibrium (p = 0.9682). Alleles in the genotypes are independent from each other (r = 0.0278, R² = 0.00077). New mutations identified in the promoter region (c.-79T > C) and the coding region of the FY gene (c.147C > A and c.175 G > A) did not affect the Duffy antigen expression on erythrocyte. Although FY alleles frequency is known in different populations, no data for Polish population is available.

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.

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 Fy^a and Fy^b 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 Fy^b 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 Fy^b 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.

Transmission of Plasmodium vivax in Duffy-negative individuals in central Sudan

BACKGROUND

Due to the recently observed rise in Plasmodium vivax incidence in Sudan and reported transmission in Duffy-negative individuals; we aimed to assess the possibility of P. vivax transmission in Duffy-negative individuals in Gezira state, central Sudan.

METHOD

A total of 126 suspected malaria patients were diagnosed with P. vivax infection using microscopy, RDT and PCR. PCR-RFLP was used to genotype participants Duffy status.

RESULTS

Forty eight (38%) were positive for P. vivax infection by PCR. Four patients (8.3%) were homozygous Duffy-negative.

CONCLUSION

These results confirm that P. vivax can infect Duffy-negative individuals, suggesting alternative mechanisms to bind and invade erythrocytes.

Naturally Acquired Binding-Inhibitory Antibodies to Plasmodium vivax Duffy Binding Protein and Clinical Immunity to Malaria in Rural Amazonians

BACKGROUND

Antibodies to the cysteine-rich domain II of Plasmodium vivax Duffy binding protein (PvDBP) can inhibit binding of this parasite ligand to its receptor on red blood cells, the Duffy antigen/receptor for chemokines. These binding-inhibitory antibodies (BIAbs) also inhibit P. vivax invasion of reticulocytes in vitro.

METHODS

To investigate whether naturally acquired anti-PvDBP antibodies are associated with reduced risk of clinical malaria in a population exposed to low levels of P. vivax transmission, we measured total levels of immunoglobulin G antibodies to 5 PvDBP variants and used a functional in vitro assay to quantify their binding-inhibitory activity in a cohort of 466 rural Amazonians followed up for up to 37 months.

RESULTS

No association between total immunoglobulin G antibody responses to any PvDBP variant and risk of symptomatic, laboratory-confirmed vivax malaria was observed in this cohort. However, a Cox proportional hazards model, adjusted for age, sex, and genotype for the Duffy antigen/receptor for chemokines, showed a >40% decrease in the prospective risk of clinical vivax malaria in subjects with the strongest BIAb responses (upper and middle terciles). High BIAb responses were mostly PvDBP variant transcending and stable over time.

CONCLUSIONS

Strong naturally acquired BIAb responses are associated with a reduced risk of clinical P. vivax malaria in rural Amazonians.

FY*A silencing by the GATA-motif variant FY*A(-69C) in a Caucasian family

BACKGROUND

The c.1-67C variant polymorphism in a GATA motif of the FY promoter is known to result in erythroid-specific FY silencing, that is, in Fy(a-) and Fy(b-) phenotypes. A Caucasian donor presented with the very rare Fy(a-b-) phenotype and was further investigated.

STUDY DESIGN AND METHODS

Genomic DNA was analyzed by sequencing to identify the cause of the Fy(a-b-) phenotype. Samples were collected from some of his relatives to establish a correlation between the serology and genotyping results. Red blood cells were analyzed by gel column agglutination and flow cytometry. Genomic DNA was analyzed on genotyping microarrays, by DNA sequencing and by allele-specific PCR.

RESULTS

In the donor, a single-nucleotide polymorphism T>C within the GATA motif was found at Position c.1-69 of the FY promoter and shown to occur in the FY*A allele. His genotype was found to be FY*A(-69C), FY*BW.01. In six FY*A/FY*B heterozygous members of the family, a perfect correlation was found between the presence vs. absence of the FY*A(-69C) variant allele and a Fy(a-) vs. Fy(a+) phenotype.

CONCLUSION

The location of the c.1-69C polymorphism in a GATA motif whose disruption is known to result in a Fy null phenotype, together with the perfect correlation between the presence of the FY*A(-69C) allele and the Fy(a-) phenotype support a cause-effect relationship between the two.

Epidemiology of disappearing Plasmodium vivax malaria: a case study in rural Amazonia

Background

New frontier settlements across the Amazon Basin pose a major challenge for malaria elimination in Brazil. Here we describe the epidemiology of malaria during the early phases of occupation of farming settlements in Remansinho area, Brazilian Amazonia. We examine the relative contribution of low-density and asymptomatic parasitemias to the overall Plasmodium vivax burden over a period of declining transmission and discuss potential hurdles for malaria elimination in Remansinho and similar settings.

Methods

Eight community-wide cross-sectional surveys, involving 584 subjects, were carried out in Remansinho over 3 years and complemented by active and passive surveillance of febrile illnesses between the surveys. We used quantitative PCR to detect low-density asexual parasitemias and gametocytemias missed by conventional microscopy. Mixed-effects multiple logistic regression models were used to characterize independent risk factors for P. vivax infection and disease.

Principal Findings/Conclusions

P. vivax prevalence decreased from 23.8% (March–April 2010) to 3.0% (April–May 2013), with no P. falciparum infections diagnosed after March–April 2011. Although migrants from malaria-free areas were at increased risk of malaria, their odds of having P. vivax infection and disease decreased by 2–3% with each year of residence in Amazonia. Several findings indicate that low-density and asymptomatic P. vivax parasitemias may complicate residual malaria elimination in Remansinho: (a) the proportion of subpatent infections (i.e. missed by microscopy) increased from 43.8% to 73.1% as P. vivax transmission declined; (b) most (56.6%) P. vivax infections were asymptomatic and 32.8% of them were both subpatent and asymptomatic; (c) asymptomatic parasite carriers accounted for 54.4% of the total P. vivax biomass in the host population; (d) over 90% subpatent and asymptomatic P. vivax had PCR-detectable gametocytemias; and (e) few (17.0%) asymptomatic and subpatent P. vivax infections that were left untreated progressed to clinical disease over 6 weeks of follow-up and became detectable by routine malaria surveillance.

Despite decades of control efforts, malaria remains a major public health concern in Brazil. A large proportion of the 243,000 cases diagnosed per year originate from areas of recent colonization in the densely forested Amazon Basin. This population-based longitudinal study addresses the epidemiology of malaria during the early stages of colonization of frontier settlements in Remansinho area, rural Amazonia. We documented a major decline in the prevalence of P. vivax infection, from 23.8% to 3.0%, between March–April 2010 and April–May 2013. Up to 73.1% of the P. vivax infections were missed by microscopy as malaria transmission declined and most (56.6%) of these infections caused no clinical signs or symptoms. Few (17.0%) asymptomatic P. vivax infections that were left untreated eventually progressed to clinical disease, becoming detectable by routine malaria surveillance, over 6 weeks of follow-up. Moreover, nearly all P. vivax infections that were undetected by microscopy had gametocytes, the parasite's blood stages responsible for malaria transmission to mosquito vectors, detected by molecular methods. These findings indicate that apparently healthy carriers of low-density parasitemias, who are often missed by conventional microscopy, contribute significantly to ongoing P. vivax transmission and may further complicate residual malaria elimination in Remansinho and similar endemic settings.

A novel FY*A allele with the 265T and 298A SNPs formerly associated exclusively with the FY*B allele and weak Fy(b) antigen expression: implication for genotyping interpretative algorithms

BACKGROUND AND OBJECTIVES

An Australian Caucasian blood donor consistently presented a serology profile for the Duffy blood group as Fy(a+b+) with Fy(a) antigen expression weaker than other examples of Fy(a+b+) red cells. Molecular typing studies were performed to investigate the reason for the observed serology profile.

MATERIAL AND METHODS

Blood group genotyping was performed using a commercial SNP microarray platform. Sanger sequencing was performed using primer sets to amplify across exons 1 and 2 of the FY gene and using allele-specific primers.

RESULTS

The propositus was genotyped as FY*A/B, FY*X heterozygote that predicted the Fy(a+b+(w) ) phenotype. Sequencing identified the 265T and 298A variants on the FY*A allele. This link between FY*A allele and 265T was confirmed by allele-specific PCR.

CONCLUSION

The reduced Fy(a) antigen reactivity is attributed to a FY*A allele-carrying 265T and 298A variants previously defined in combination only with the FY*B allele and associated with weak Fy(b) antigen expression. This novel allele should be considered in genotyping interpretative algorithms for generating a predicted phenotype.

Frequencies of Duffy blood group alleles in Northern Pakistani donors

OBJECTIVE

Find the allele frequencies of Duffy blood group antigens in donor population from northern Pakistan.

DESIGN

Cross sectional study.

PLACE AND DURATION OF STUDY

Armed Forces Institute of Transfusion (AFIT), Rawalpindi in year 2012.

PATIENTS AND METHODS

A total of 1000 healthy, adult blood donors were included in the study. Blood samples were collected in ethylenediamine tetra aceticacid (EDTA) tube and then tested with anti sera Fy(a) and Fy(b) by the tube method.

RESULTS

The allele frequencies of Duffy blood group antigens were calculated. The most common phenotype was Fy(a+b+) which was present in 552 (55.2%) donors followed by the Fy(a+b-) phenotype in 228 (22.8%) donors, while 178 (17.8%) were Fy(a-b+) and the least prevalent phenotype was Fy(a-b-) which was present in 42 (4.2%) of donors.

CONCLUSION

The majority of our population is heterozygous for Duffy antigens a and b.

An association between lactose intolerance and anthropometric variables in the Sudanese Shagia tribe (East Africa)

BACKGROUND

The culture of contemporary Sudanese tribes is not homogeneous. One of the three main tribes in northern Sudan is the Shagia tribe. This study is part of the large-scale research project to anthropologically and genetically describe the Shagia population, who inhabited three villages in an isolated region of the Fourth Nile Cataract. This population is extremely homogeneous as a result of geographical, genetic and cultural isolation.

AIM

The aim of the study was to analyse the frequency of two single nucleotide polymorphisms (SNPs), C/T-13910 and G/C-14010, within the isolated population. These SNPs are closely associated with lactase persistence. In addition, this study has correlated the SNPs with anthropometric measurements.

SUBJECTS AND METHODS

Buccal swabs were collected from 126 subjects. The DNA was extracted and the occurrence of the two alleles at each SNP was analysed using real-time PCR. An anthropometric examination of 64 adult individuals was used for an analysis of body measurements and proportions.

RESULTS

At the C/T-13910 SNP, the CT genotype frequency was 3.2%, whilst 96.8% of individuals were homozygous for the C allele. The presence of the T allele showed a strong association with body mass index (BMI) and waist circumference. At the G/C-14010 locus, all the examined subjects were homozygous for the G allele.

CONCLUSIONS

The C/T-13910 polymorphism correlated with anthropometric measurements. Identification of the T allele of C/T-13910, in this isolated tribe, may be linked to their previously nomadic lifestyle and could provide important information on the ancestry of the tribe and the admixture of European genes.

Malaria risk mapping for control in the republic of Sudan

Evidence shows that malaria risk maps are rarely tailored to address national control program ambitions. Here, we generate a malaria risk map adapted for malaria control in Sudan. Community Plasmodium falciparum parasite rate (PfPR) data from 2000 to 2010 were assembled and were standardized to 2-10 years of age (PfPR(2-10)). Space-time Bayesian geostatistical methods were used to generate a map of malaria risk for 2010. Surfaces of aridity, urbanization, irrigation schemes, and refugee camps were combined with the PfPR(2-10) map to tailor the epidemiological stratification for appropriate intervention design. In 2010, a majority of the geographical area of the Sudan had risk of < 1% PfPR(2-10). Areas of meso- and hyperendemic risk were located in the south. About 80% of Sudan's population in 2011 was in the areas in the desert, urban centers, or where risk was < 1% PfPR(2-10). Aggregated data suggest reducing risks in some high transmission areas since the 1960s.

Analysis of the genetic variants of glucose-6-phosphate dehydrogenase in inhabitants of the 4th Nile cataract region in Sudan

Malaria is one of the most common diseases in the African population. Genetic variance in glucose dehydrogenase 6-phosphate (G6PD) in humans determines the response to malaria exposure. In this study, we aimed to analyze the frequency of two single-nucleotide polymorphisms (G202A and A376G) present in two local tribes of Sudanese Arabs from the region of the 4th Nile cataract in Sudan, the Shagia and Manasir. The polymorphisms in G6PD were analyzed in 217 individuals (126 representatives of the Shagia tribe and 91 of the Manasir tribe). Real-time PCR and RFLP-PCR were utilized to analyze significant differences in the prevalence of alleles and genotypes. The 202A G6P allele frequency was 0.7%, whereas the G202 variant was found in 93.3% of cases. The AA, GA, and GG genotype frequencies for the A376G G6PD codon among the Shagia were 88, 11.1, and 0.9%, respectively; this is similar to the distribution among Manasir tribe representatives (94.5, 3.3, and 2.2%, respectively; OR 3.44 [0.85-16.17], p=0.6). Notably, in north-eastern Sudan the G6PD B (202G/376A) compound genotype frequency was 90.3%, whereas the G6PD A variant (202G/376G) was found in 1.4% of that population. Identification of the G6PD A- variant (202A/376G) in the isolated Shagia tribe provides important information regarding the tribal ancestry. Taken together, the data presented in this study suggest that the Shagia tribe was still nomadic between 4000 and 12,000 years ago. Moreover, the lack of G6PD A- genotype among ethnically diverse Monasir tribesmen indicates a separation of the Shagia from the other tribes in the region of the 4th Nile cataract in Sudan.