Joann M. Moulds

P. falciparum rosetting mediated by a parasite-variant erythrocyte membrane protein and complement-receptor 1

The factors determining disease severity in malaria are complex and include host polymorphisms, acquired immunity and parasite virulence. Studies in Africa have shown that severe malaria is associated with the ability of erythrocytes infected with the parasite Plasmodium falciparum to bind uninfected erythrocytes and form rosettes. The molecular basis of rosetting is not well understood, although a group of low-molecular-mass proteins called rosettins have been described as potential parasite ligands. Infected erythrocytes also bind to endothelial cells, and this interaction is mediated by the parasite-derived variant erythrocyte membrane protein PfEMP1 (refs 7, 8), which is encoded by the var gene family. Here we report that the parasite ligand for rosetting in a P. falciparum clone is PfEMP1, encoded by a specific var gene. We also report that complement-receptor 1 (CR1) on erythrocytes plays a role in the formation of rosettes and that erythrocytes with a common African CR1 polymorphism (Sl(a−)) have reduced adhesion to the domain of PfEMP1 that binds normal erythrocytes. Thus we describe a new adhesive function for PfEMP1 and raise the possibility that CR1 polymorphisms in Africans that influence the interaction between erythrocytes and PfEMP1 may protect against severe malaria.

Blood group O protects against severe Plasmodium falciparum malaria through the mechanism of reduced rosetting

Malaria has been a major selective force on the human population, and several erythrocyte polymorphisms have evolved that confer resistance to severe malaria. Plasmodium falciparum rosetting, a parasite virulence phenotype associated with severe malaria, is reduced in blood group O erythrocytes compared with groups A, B, and AB, but the contribution of the ABO blood group system to protection against severe malaria has received little attention. We hypothesized that blood group O may confer resistance to severe falciparum malaria through the mechanism of reduced rosetting. In a matched case-control study of 567 Malian children, we found that group O was present in only 21% of severe malaria cases compared with 44–45% of uncomplicated malaria controls and healthy controls. Group O was associated with a 66% reduction in the odds of developing severe malaria compared with the non-O blood groups (odds ratio 0.34, 95% confidence interval 0.19–0.61, P < 0.0005, severe cases versus uncomplicated malaria controls). In the same sample set, P. falciparum rosetting was reduced in parasite isolates from group O children compared with isolates from the non-O blood groups (P = 0.003, Kruskal–Wallis test). Statistical analysis indicated a significant interaction between host ABO blood group and parasite rosette frequency that supports the hypothesis that the protective effect of group O operates through the mechanism of reduced P. falciparum rosetting. This work provides insights into malaria pathogenesis and suggests that the selective pressure imposed by malaria may contribute to the variable global distribution of ABO blood groups in the human population.

Systemic lupus erythematosus in three ethnic groups: III A comparison of characteristics early in the natural history of the LUMINA cohort

Aim: To determine and contrast the socioeconomic-demographic and clinical features of patients with recent onset (5 y) systemic lupus erythematosus (SLE) from three ethnic groups, Hispanic, African-American and Caucasian (H, AA, C). Subjects and methods: SLE cases (American College of Rheumatology criteria) (incident (n ‘ 56), prevalent (n ‘ 173)), were enrolled in a longitudinal study at The University of Alabama at Birmingham, The University of Texas-Houston Health Science Center and The University of Texas Medical Branch at Galveston. Socioeconomic-demographic, clinical, immunological, behavioral and psychological data were obtained using validated instruments and standard laboratory techniques, and compared. Results: 70 H, 88 AA and 71 C SLE patients constitutethis cohort. H and AA patients were younger and of lower socioeconomic-demographic status. They also had evidence of more frequent organ system involvement (renal, cardiovascular), more auto-antibodies, more active disease (after adjusting for discrepant socioeconomic-demographic features), lower levels of social support and more abnormal illness-related behaviors (more in H than in AA). H also were more likely to have an abrupt disease onset; C were more likely to be on antimalarials but less likely to be on corticosteroids. H, AA, and C used health care resources comparably. They had similar levels of pain and physical and mental functioning after adjusting for age, disease duration, income, education, social support, illness-related behaviors, and Systemic Lupus Activity Measure or SLAM scores. Conclusions: H and AA patients have more active SLE, at an earlier age of onset, and a less favorable socioeconomic-demographic structure (worse among the H than AA) which predispose them to a less favorable natural history.

Systemic lupus erythematosus in three ethnic groups: I. The effects of HLA class II, C4, and CR1 alleles, socioeconomic factors, and ethnicity at disease onset

Objective To study the relative impact of immunogenetic versus socioeconomic factors on systemic lupus erythematosus (SLE) at disease onset/presentation. Methods Medical records regarding SLE onset/presentation were abstracted on 229 SLE patients who were enrolled in a prospective lupus outcome study. Patients were grouped in equivalent proportions of Caucasians, African Americans, and Hispanics. HLA-DRB1, DQA1, and DQB1 oligotyping, as well as C4 and CR1 allotyping, were carried out by standard methods. In addition to these genetic factors, data on ethnicity, age at SLE onset, monthly income, level of education, and home ownership were entered into stepwise logistic or stepwise multiple linear regression models as independent variables, and each specific clinical feature (neurologic, renal, and cardiovascular disease due to SLE), as well as the total Systemic Lupus Activity Measure (SLAM) score and physicians global assessment of disease activity at disease onset, were entered as dependent variables. Results HLA-DRB1*0301 (DR3), DRB1*1503 (DR2), and DRB1*08 (DR8) alleles were more frequently found in Caucasians, African Americans, and Hispanics, respectively. Hispanics were more likely to have cardiac and renal disease, as well as a higher physicians global assessment of disease activity. African Americans were more likely to have neurologic disease, renal disease, and a higher SLAM score. Those with less education had a higher SLAM score. Patients with HLA-DRB1*01 had less renal disease and a lower SLAM score. Those with C4A*3 alleles had a higher SLAM score and a higher physicians global assessment of disease activity. Conclusion Both genetic and socioeconomic determinants, as well as other factors associated with Hispanic and African-American ethnicity, affect the presentation of SLE.

A human complement receptor 1 polymorphism that reduces Plasmodium falciparum rosetting confers protection against severe malaria

Parasitized red blood cells (RBCs) from children suffering from severe malaria often adhere to complement receptor 1 (CR1) on uninfected RBCs to form clumps of cells known as “rosettes.” Despite a well documented association between rosetting and severe malaria, it is controversial whether rosetting is a cause or a correlate of parasite virulence. CR1-deficient RBC show greatly reduced rosetting; therefore, we hypothesized that, if rosetting is a direct cause of malaria pathology, CR1-deficient individuals should be protected against severe disease. In this study, we show that RBC CR1 deficiency occurs in up to 80% of healthy individuals from the malaria-endemic regions of Papua New Guinea. This RBC CR1 deficiency is associated with polymorphisms in the CR1 gene and, unexpectedly, with α-thalassemia, a common genetic disorder in Melanesian populations. Analysis of a case-control study demonstrated that the CR1 polymorphisms and α-thalassemia independently confer protection against severe malaria. We have therefore identified CR1 as a new malaria resistance gene and provided compelling evidence that rosetting is an important parasite virulence phenotype that should be a target for drug and vaccine development.

Systemic lupus erythematosus in three ethnic groups. II. Features predictive of disease activity early in its course

Objective To determine the factors associated with disease activity in patients with recent-onset (≤5 years) systemic lupus erythematosus (SLE) who were of Hispanic, African-American, or Caucasian ethnicity. Methods Incident and prevalent cases of SLE, as defined by the American College of Rheumatology criteria for SLE, among the 3 ethnic groups were identified in Alabama (The University of Alabama at Birmingham) and Texas (The University of Texas-Houston Health Science Center and The University of Texas Medical Branch at Galveston). Variables from the sociodemographic, clinical, immunologic, immunogenetic, behavioral, and psychological domains were obtained using validated instruments. Disease activity was ascertained with the Systemic Lupus Activity Measure (SLAM). Stepwise domain regressions with SLAM score as the dependent variable were performed. Final ethnic-specific and overall regression models were obtained by entering variables that were retained in the domain regressions. Results SLAM scores at study entry were higher in the African Americans (mean ± SD 12.6 ± 6.9) and Hispanics (11.0 ± 6.2) than in the Caucasians (8.5 ± 3.7) (P ≤ 0.001). The final overall regression model (R2 = 28%) for higher SLAM score included the following variables: African-American ethnicity, lack of private health insurance, abrupt disease onset, presence of anti-Ro antibodies, absence of HLA-DRB1*0301, higher levels of helplessness, and abnormal illness-related behaviors. Conclusion Socioeconomic, immunologic, immunogenetic, behavioral, and psychological variables were all predictive of disease activity early in the course of SLE, irrespective of ethnic group. However, there remain ethnic group differences in disease activity that were not explained by these factors.

Characterization of the Gene Encoding the Human Kidd Blood Group/Urea Transporter Protein EVIDENCE FOR SPLICE SITE MUTATIONS IN JknullINDIVIDUALS

The Kidd (JK) blood group is carried by an integral membrane glycoprotein which transports urea through the red cell membrane and is also present on endothelial cells of the vasa recta in the kidney. The exon-intron structure of the human blood group Kidd/urea transporter gene has been determined. It is organized into 11 exons distributed over 30 kilobase pairs. The mature protein is encoded by exons 4–11. The transcription initiation site was identified by 5′-rapid amplification of cDNA ends-polymerase chain reaction at 335 base pairs upstream of the translation start point located in exon 4. The 5′-flanking region, from nucleotide −837 to −336, contains TATA and inverted CAAT boxes as well as GATA-1/SP1 erythroid-specificcis-acting regulatory elements. Analysis of the 3′-untranslated region reveals that the two equally abundant erythroid transcripts of 4.4 and 2.0 kilobase pairs arise from usage of different alternative polyadenylation signals. No obvious abnormality of the Kidd/urea transporter gene, including the 5′- and 3′-untranslated regions, has been detected by Southern blot analysis of the blood of two unrelated Jknull individuals (B.S. and L.P.), which lacks all Jk antigens and Jk proteins on red cells, but was genotyped as homozygous for a “silent”Jk b allele. Further analysis indicated that different splice site mutations occurred in each variant. The first mutation affected the invariant G residue of the 3′-acceptor splice site of intron 5 (variant B.S.), while the second mutation affected the invariant G residue of the 5′-donor splice site of intron 7 (variant L.P.). These mutations caused the skipping of exon 6 and 7, respectively, as seen by sequence analysis of the Jk transcripts present in reticulocytes. Expression studies in Xenopusoocytes demonstrated that the truncated proteins encoded by the spliced transcripts did not mediate a facilitated urea transport compared with the wild type Kidd/urea transporter protein and were not expressed on the oocyte’s plasma membrane. These findings provide a rational explanation for the lack of Kidd/urea transporter protein and defect in urea transport of Jknull cells.

Blood group terminology 2004: from the International Society of Blood Transfusion committee on terminology for red cell surface antigens

1 Bristol Institute for Transfusion Sciences, Bristol, UK 2 Growing your Knowledge, Spit Junction, NSW, Australia 3 American Red Cross Blood Services, Los Angeles-Orange Counties Region, Los Angeles, CA, USA 4 Biotechnology Research Centre, Auckland University of Technology, Auckland, New Zealand 5 Regional Blood Transfusion Center, Department of Clinical Immunology, University Hospital, Arhus N, Denmark 6 Department of Pathology, University Hospitals UH-2G332, Ann Arbor, Michigan, USA 7 Reference Laboratory for Immunohematology and Blood Groups, National Blood Services Centre, Tel Hashomer, Israel 8 New York Blood Center, New York, NY, USA 9 Ortho-Clinical Diagnostics, Raritan, NJ, USA 10 Drexel University College of Medicine, Philadelphia, PA, USA 11 Gamma Biologicals Inc (subsidiary of Immunocor Inc), Houston, TX, USA 12 Central Laboratory of the Netherlands Red Cross Blood Transfusion Service, Amsterdam, the Netherlands 13 Centre national de Reference pour les Groupes sanguines (CNTS), Paris, France 14 International Blood Group Reference Laboratory, Bristol, UK 15 Finnish Red Cross Blood Transfusion Service, Helsinki, Finland 16 South African National Blood Service, East Coast Region, Pinetown, South Africa 17 Osaka Red Cross Blood Center, Osaka, Japan 18 Blood Bank, Hospital Sirio-Libanes, Sao Paulo, Brazil 19 Rh Laboratory, University of Manitoba, Winnipeg, Manitoba, Canada

Mapping of the Region of Complement Receptor (CR) 1 Required for Plasmodium falciparum Rosetting and Demonstration of the Importance of CR1 in Rosetting in Field Isolates

The malaria parasite Plasmodium falciparum induces a number of novel adhesion properties in the erythrocytes that it infects. One of these properties, the ability of infected erythrocytes to bind uninfected erythrocytes to form rosettes, is associated with severe malaria and may play a direct role in the pathogenesis of disease. Previous work has shown that erythrocytes deficient in complement receptor (CR) 1 (CR1, CD35; C3b/C4b receptor) have greatly reduced rosetting capacity, indicating an essential role for CR1 in rosette formation. Using deletion mutants and mAbs, we have localized the region of CR1 required for the formation of P. falciparum rosettes to the area of long homologous repeat regions B and C that also acts as the binding site for the activated complement component C3b. This result raises the possibility that C3b could be an intermediary in rosetting, bridging between the infected erythrocyte and CR1. We were able to exclude this hypothesis, however, as parasites grown in C3-deficient human serum formed rosettes normally. We have also shown in this report that rosettes can be reversed by mAb J3B11 that recognizes the C3b binding site of CR1. This rosette-reversing activity was demonstrated in a range of laboratory-adapted parasite strains and field isolates from Kenya and Malawi. Thus, we have mapped the region of CR1 required for rosetting and demonstrated that the CR1-dependent rosetting mechanism occurs commonly in P. falciparum isolates, and could therefore be a potential target for future therapeutic interventions to treat severe malaria.

International Society of Blood Transfusion Working Party on red cell immunogenetics and blood group terminology: Berlin report.

The International Society of Blood Transfusion Working Party on red cell immunogenetics and blood group terminology convened during the International congress in Cancun, July 2012. This report details the newly identified antigens in existing blood group systems and presents three new blood group systems.