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Salanti A, Dahlbäck M, Turner L, Nielsen MA, Barfod L, Magistrado P, Jensen ATR, Lavstsen T, Ofori MF, Marsh K, Hviid L, Theander TG. Evidence for the involvement of VAR2CSA in pregnancy-associated malaria. ACTA ACUST UNITED AC 2005; 200:1197-203. [PMID: 15520249 PMCID: PMC2211857 DOI: 10.1084/jem.20041579] [Citation(s) in RCA: 445] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In Plasmodium falciparum–endemic areas, pregnancy-associated malaria (PAM) is an important health problem. The condition is precipitated by accumulation of parasite-infected erythrocytes (IEs) in the placenta, and this process is mediated by parasite-encoded variant surface antigens (VSA) binding to chondroitin sulfate A (CSA). Parasites causing PAM express unique VSA types, VSAPAM, which can be serologically classified as sex specific and parity dependent. It is sex specific because men from malaria-endemic areas do not develop VSAPAM antibodies; it is parity dependent because women acquire anti-VSAPAM immunoglobulin (Ig) G as a function of parity. Previously, it was shown that transcription of var2csa is up-regulated in placental parasites and parasites selected for CSA binding. Here, we show the following: (a) that VAR2CSA is expressed on the surface of CSA-selected IEs; (b) that VAR2CSA is recognized by endemic plasma in a sex-specific and parity-dependent manner; (c) that high anti-VAR2CSA IgG levels can be found in pregnant women from both West and East Africa; and (d) that women with high plasma levels of anti-VAR2CSA IgG give birth to markedly heavier babies and have a much lower risk of delivering low birth weight children than women with low levels.
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Affiliation(s)
- Ali Salanti
- Centre for Medical Parasitology, Dept. of Medical Microbiology and Immunology, Panum Institute 24-2, Blegdamsvej 3, 2200 Copenhagen, Denmark.
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202
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Smith JD, Deitsch KW. Pregnancy-associated malaria and the prospects for syndrome-specific antimalaria vaccines. ACTA ACUST UNITED AC 2005; 200:1093-7. [PMID: 15520241 PMCID: PMC2211864 DOI: 10.1084/jem.20041974] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Aided by the Plasmodium falciparum genome project, recent discoveries regarding the molecular basis of malaria pathogenesis have led to a better understanding of the interactions between host and parasite. Although vaccines that prevent infection by malaria parasites remain only hopes for the future, there are now more immediate prospects for vaccines that protect against specific disease syndromes. Here, we discuss the latest advances in the development of a vaccine that specifically targets pregnancy-associated malaria (PAM).
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Affiliation(s)
- Joseph D Smith
- Seattle Biomedical Research Institute, 307 Westlake Ave. N., Ste. 500, Seattle, WA 98109-5219, USA.
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203
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Deitsch KW, Hviid L. Variant surface antigens, virulence genes and the pathogenesis of malaria. Trends Parasitol 2004; 20:562-6. [PMID: 15522665 DOI: 10.1016/j.pt.2004.09.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The first Molecular Approaches to Malaria meeting was held 2-5 February 2000 in Lorne, Australia. Following the meeting, Brian Cooke, Mats Wahlgren and Ross Coppel predicted that research into the molecular details of the mechanisms behind sequestration of parasitized erythrocytes would "become increasingly more complicated, with further interactions, receptors, ligands and functional domains". Furthermore, they cautioned that "the challenge will be not to lose ourselves in the molecular detail, but remain focused on the role of [the var genes and other multigene families] in pathogenesis of malaria". We contemplate on these statements, following the recent second Molecular Approaches to Malaria meeting, which was held at the same venue on 2-5 February 2004.
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Affiliation(s)
- Kirk W Deitsch
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, 1300 York Avenue, W-704, Box 62, New York, NY 10021, USA
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204
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Hviid L. The immuno-epidemiology of pregnancy-associated Plasmodium falciparum malaria: a variant surface antigen-specific perspective. Parasite Immunol 2004; 26:477-86. [PMID: 15771683 DOI: 10.1111/j.0141-9838.2004.00733.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Women living in areas of intense P. falciparum transmission have acquired substantial protective immunity to malaria when they reach childbearing age. Nevertheless, pregnancies in such areas are associated with substantial malaria-related morbidity and mortality, particularly among women of low parity. The parity-dependency of susceptibility to malaria in pregnant women suggests that protective immunity to this type of malaria can be developed. However, until recently it has been poorly understood why the clinical protection against malaria, which young women in endemic areas acquire well before their first pregnancy, is suddenly rendered inadequate when they become pregnant, only to be regained during the course of a few pregnancies. In this article, I discuss some recent immuno-epidemiological studies of pregnancy-associated malaria, which, in combination with the generally improved understanding of how protective immunity to P. falciparum malaria operates and is acquired, have provided important insights into this enigma.
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Affiliation(s)
- L Hviid
- Centre for Medical Parasitology at Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet) and Institute for Medical Microbiology and Immunology, University of Copenhagen, Copenhagen Ø, Denmark.
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205
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Staalsoe T, Shulman CE, Dorman EK, Kawuondo K, Marsh K, Hviid L. Intermittent preventive sulfadoxine-pyrimethamine treatment of primigravidae reduces levels of plasma immunoglobulin G, which protects against pregnancy-associated Plasmodium falciparum malaria. Infect Immun 2004; 72:5027-30. [PMID: 15321995 PMCID: PMC517429 DOI: 10.1128/iai.72.9.5027-5030.2004] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pregnancy-associated malaria (PAM) is an important cause of maternal and neonatal suffering. It is caused by Plasmodium falciparum capable of inhabiting the placenta through expression of particular variant surface antigens (VSA) with affinity for proteoglycans such as chondroitin sulfate A. Protective immunity to PAM develops following exposure to parasites inhabiting the placenta, and primigravidae are therefore particularly susceptible to PAM. The adverse consequences of PAM in primigravidae are preventable by intermittent preventive treatment (IPTp), where women are given antimalarials at specified intervals during pregnancy, but this may interfere with acquisition of protective PAM immunity. We found that Kenyan primigravidae receiving sulfadoxine-pyrimethamine IPTp had significantly lower levels of immunoglobulin G (IgG) with specificity for the type of parasite-encoded VSA-called VSA(PAM)-that specifically mediate protection against PAM than did women receiving a placebo. VSA(PAM)-specific IgG levels depended on the number of IPTp doses received and were sufficiently low to be of clinical concern among multidose recipients. Our data suggest that IPTp should be extended to women of all parities, in line with current World Health Organization recommendations.
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Affiliation(s)
- Trine Staalsoe
- Centre for Medical Parasitology, Department of Infectious Diseases, Copenhagen University Hospital, Rigshospitalet, Institute for Medical Microbiology and Immunology, University of Copenhagen, Denmark
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206
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Sharling L, Enevold A, Sowa KMP, Staalsoe T, Arnot DE. Antibodies from malaria-exposed pregnant women recognize trypsin resistant epitopes on the surface of Plasmodium falciparum-infected erythrocytes selected for adhesion to chondroitin sulphate A. Malar J 2004; 3:31. [PMID: 15350207 PMCID: PMC517943 DOI: 10.1186/1475-2875-3-31] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2004] [Accepted: 09/06/2004] [Indexed: 11/17/2022] Open
Abstract
Background The ability of Plasmodium falciparum-infected erythrocytes to adhere to the microvasculature endothelium is thought to play a causal role in malaria pathogenesis. Cytoadhesion to endothelial receptors is generally found to be highly sensitive to trypsinization of the infected erythrocyte surface. However, several studies have found that parasite adhesion to placental receptors can be markedly less sensitive to trypsin. This study investigates whether chondroitin sulphate A (CSA) binding parasites express trypsin-resistant variant surface antigens (VSA) that bind female-specific antibodies induced as a result of pregnancy associated malaria (PAM). Methods Fluorescence activated cell sorting (FACS) was used to measure the levels of adult Scottish and Ghanaian male, and Ghanaian pregnant female plasma immunoglobulin G (IgG) that bind to the surface of infected erythrocytes. P. falciparum clone FCR3 cultures were used to assay surface IgG binding before and after selection of the parasite for adhesion to CSA. The effect of proteolytic digestion of parasite erythrocyte surface antigens on surface IgG binding and adhesion to CSA and hyaluronic acid (HA) was also studied. Results P. falciparum infected erythrocytes selected for adhesion to CSA were found to express trypsin-resistant VSA that are the target of naturally acquired antibodies from pregnant women living in a malaria endemic region of Ghana. However in vitro adhesion to CSA and HA was relatively trypsin sensitive. An improved labelling technique for the detection of VSA expressed by CSA binding isolates has also been described. Conclusion The VSA expressed by CSA binding P. falciparum isolates are currently considered potential targets for a vaccine against PAM. This study identifies discordance between the trypsin sensitivity of CSA binding and surface recognition of CSA selected parasites by serum IgG from malaria exposed pregnant women. Thus, the complete molecular definition of an antigenic P. falciparum erythrocyte surface protein that can be used as a malaria in pregnancy vaccine has not yet been achieved.
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MESH Headings
- Animals
- Antibodies, Protozoan/blood
- Antibodies, Protozoan/immunology
- Antigens, Protozoan/blood
- Antigens, Protozoan/drug effects
- Antigens, Protozoan/immunology
- Antigens, Surface/blood
- Antigens, Surface/drug effects
- Antigens, Surface/immunology
- Cattle
- Cell Adhesion
- Chondroitin Sulfates/metabolism
- Epitopes/blood
- Epitopes/drug effects
- Epitopes/immunology
- Erythrocytes/immunology
- Erythrocytes/parasitology
- Female
- Flow Cytometry
- Humans
- Hyaluronic Acid/metabolism
- Immunoglobulin G/blood
- Immunoglobulin G/immunology
- Malaria, Falciparum/blood
- Malaria, Falciparum/immunology
- Male
- Plasmodium falciparum/immunology
- Plasmodium falciparum/physiology
- Pregnancy
- Pregnancy Complications, Parasitic/blood
- Pregnancy Complications, Parasitic/immunology
- Protozoan Proteins/blood
- Protozoan Proteins/drug effects
- Protozoan Proteins/immunology
- Trypsin/pharmacology
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Affiliation(s)
- Lisa Sharling
- Institute of Cell, Animal and Population Biology, University of Edinburgh, King's Buildings, West Mains Road, Edinburgh, EH9 3JT, Scotland, UK
| | - Anders Enevold
- Centre for Medical Parasitology, Department of Infectious Diseases M7641. Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen Ø, Denmark
| | - Kordai MP Sowa
- Institute of Cell, Animal and Population Biology, University of Edinburgh, King's Buildings, West Mains Road, Edinburgh, EH9 3JT, Scotland, UK
| | - Trine Staalsoe
- Centre for Medical Parasitology, Department of Infectious Diseases M7641. Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen Ø, Denmark
| | - David E Arnot
- Institute of Cell, Animal and Population Biology, University of Edinburgh, King's Buildings, West Mains Road, Edinburgh, EH9 3JT, Scotland, UK
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207
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Abstract
Sequestration of Plasmodium falciparum-infected erythrocytes in the placenta is responsible for many of the harmful effects of malaria during pregnancy. Sequestration occurs as a result of parasite adhesion molecules expressed on the surface of infected erythrocytes binding to host receptors in the placenta such as chondroitin sulphate A (CSA). Identification of the parasite ligand(s) responsible for placental adhesion could lead to the development of a vaccine to induce antibodies to prevent placental sequestration. Such a vaccine would reduce the maternal anaemia and infant deaths that are associated with malaria in pregnancy. Current research indicates that the parasite ligands mediating placental adhesion may be members of the P. falciparum variant surface antigen family PfEMP1, encoded by var genes. Two relatively well-conserved subfamilies of var genes have been implicated in placental adhesion, however, their role remains controversial. This review examines the evidence for and against the involvement of var genes in placental adhesion, and considers whether the most appropriate vaccine candidates have yet been identified.
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Affiliation(s)
- J A Rowe
- Institute of Cell, Animal and Population Biology, University of Edinburgh, West Mains Road, Edinburgh EH9 3JT, UK.
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208
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Abstract
Newborn infants in endemic areas are markedly resistant to Plasmodium falciparum malaria. Consequently, severe disease is rare during the first few months of life, and infections tend to be low density and relatively asymptomatic during this period. Although this is generally ascribed to passively transferred immunity, attempts to identify the targets and mechanisms of this protection have been unsuccessful. The implications of the hypothesis that the progression from resistance through susceptibility and back to resistance during infancy and early childhood reflects the gradual acquisition of IgG to variant surface antigens (VSAs), while protection from maternal VSA-specific IgG steadily fades, are discussed here.
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Affiliation(s)
- Lars Hviid
- Centre for Medical Parasitology, Department of Infectious Diseases, Rigshospitalet, 2100, Copenhagen Ø, Denmark.
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209
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Khattab A, Reinhardt C, Staalsoe T, Fievet N, Kremsner PG, Deloron P, Hviid L, Klinkert MQ. Analysis of IgG with specificity for variant surface antigens expressed by placental Plasmodium falciparum isolates. Malar J 2004; 3:21. [PMID: 15242514 PMCID: PMC479693 DOI: 10.1186/1475-2875-3-21] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2004] [Accepted: 07/08/2004] [Indexed: 11/29/2022] Open
Abstract
Background Pregnancy-associated malaria (PAM) is caused by Plasmodium falciparum-infected erythrocytes that can sequester in placental intervillous space by expressing particular variant surface antigens (VSA) that can mediate adhesion to chondroitin sulfate A (CSA) in vitro. IgG antibodies with specificity for the VSA expressed by these parasites (VSAPAM) are associated with protection from maternal anaemia, prematurity and low birth weight, which is the greatest risk factor for death in the first month of life. Methods In this study, the development of anti-VSAPAM antibodies in a group of 151 women who presented to the maternity ward of Albert Schweitzer Hospital in Lambaréné, Gabon for delivery was analysed using flow cytometry assays. Plasma samples from placenta infected primiparous women were also investigated for their capacity to inhibit parasite binding to CSA in vitro. Results In the study cohort, primiparous as well as secundiparous women had the greatest risk of infection at delivery as well as during pregnancy. Primiparous women with infected placentas at delivery showed higher levels of VSAPAM-specific IgG compared to women who had no malaria infections at delivery. Placental isolates of Gabonese and Senegalese origin tested on plasma samples from Gabon showed parity dependency and gender specificity patterns. There was a significant correlation of plasma reactivity as measured by flow cytometry between different placental isolates. In the plasma of infected primiparous women, VSAPAM-specific IgG measured by flow cytometry could be correlated with anti-adhesion antibodies measured by the inhibition of CSA binding. Conclusion Recognition of placental parasites shows a parity- and sex- dependent pattern, like that previously observed in laboratory strains selected to bind to CSA. Placental infections at delivery in primiparous women appear to be sufficient to induce functional antibodies which can both recognize the surface of the infected erythrocytes as well as block their binding to CSA. The correlation between serum reactivities of placental field isolates from different geographic locations and collected at different times is indicative of the conserved nature of the antigen(s) mediating PAM.
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Affiliation(s)
- Ayman Khattab
- Bernhard-Nocht Institute for Tropical Medicine, Hamburg, Germany
- Institute for Tropical Medicine, University of Tübingen, Tübingen, Germany
| | - Christina Reinhardt
- Institute for Tropical Medicine, University of Tübingen, Tübingen, Germany
- Medical Research Unit, Albert Schweitzer Hospital, Lambaréné, Gabon
| | - Trine Staalsoe
- Centre for Medical Parasitology at Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet) and at Institute for Medical Microbiology and Immunology, University of Copenhagen, Copenhagen, Denmark
| | - Nadine Fievet
- 1UR R010, Mother and Child Health in the Tropics, Institut de Recherche pour le Développement (IRD), Faculté de Pharmacie, Paris, France
| | - Peter G Kremsner
- Institute for Tropical Medicine, University of Tübingen, Tübingen, Germany
- Medical Research Unit, Albert Schweitzer Hospital, Lambaréné, Gabon
| | - Philippe Deloron
- 1UR R010, Mother and Child Health in the Tropics, Institut de Recherche pour le Développement (IRD), Faculté de Pharmacie, Paris, France
| | - Lars Hviid
- Centre for Medical Parasitology at Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet) and at Institute for Medical Microbiology and Immunology, University of Copenhagen, Copenhagen, Denmark
| | - Mo-Quen Klinkert
- Bernhard-Nocht Institute for Tropical Medicine, Hamburg, Germany
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210
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Staalsoe T, Shulman CE, Bulmer JN, Kawuondo K, Marsh K, Hviid L. Variant surface antigen-specific IgG and protection against clinical consequences of pregnancy-associated Plasmodium falciparum malaria. Lancet 2004; 363:283-9. [PMID: 14751701 DOI: 10.1016/s0140-6736(03)15386-x] [Citation(s) in RCA: 203] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Pregnancy-associated malaria caused by Plasmodium falciparum adherence to chondroitin sulfate A in the placental intervillous space is a major cause of low birthweight and maternal anaemia in areas of endemic P falciparum transmission. Adhesion-blocking antibodies that specifically recognise parasite-encoded variant surface antigens (VSA) are associated with resistance to pregnancy-associated malaria. We looked for a possible relation between VSA-specific antibody concentrations, placental infection, and protection from low birthweight and maternal anaemia. METHODS We used flow cytometry to measure VSA-specific IgG concentrations in plasma samples taken during child birth from 477 Kenyan women selected from a cohort of 910 women on the basis of HIV-1 status, gravidity, and placental histology. We measured VSA expressed by one placental P falciparum isolate and two isolates selected or not selected for chondroitin sulfate A adhesiveness in-vitro. FINDINGS Concentrations of plasma IgG specific for VSA, expressed by chondroitin sulfate A-adhering parasites (VSA in pregnancy-associated malaria or vsa-pam), increased with gravidity and were associated with placental histological findings. Women with chronic pregnancy-associated malaria and low or absent VSA-PAM-specific IgG had lower haemoglobin values (reduced by 17 g/L; 95% CI 8.1-25.2) and delivered smaller babies (birthweight reduced by 0.26 kg; 0.10-0.55) than did corresponding women with high VSA-PAM-specific IgG. No such relation was shown for concentrations of IgG with specificity for non-pregnancy-associated malaria VSA. INTERPRETATION VSA-PAM-specific IgG protects against low birthweight and maternal anaemia. Our data indicate an important mechanism of clinical protection against malaria and raise hope for the clinical effectiveness of a potential VSA-based vaccine against pregnancy-associated malaria.
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MESH Headings
- Animals
- Antibodies, Protozoan/immunology
- Antigens, Protozoan/immunology
- Antigens, Surface/immunology
- Cell Adhesion/immunology
- Chondroitin Sulfates/immunology
- Erythrocytes/immunology
- Erythrocytes/parasitology
- Female
- Flow Cytometry
- Humans
- Immunity, Innate/immunology
- Immunoglobulin G/blood
- Immunoglobulin G/immunology
- Infant, Low Birth Weight/immunology
- Infant, Newborn
- Malaria Vaccines
- Malaria, Falciparum/immunology
- Placenta Diseases/immunology
- Plasmodium falciparum/immunology
- Plasmodium falciparum/isolation & purification
- Pregnancy
- Pregnancy Complications, Parasitic/blood
- Pregnancy Complications, Parasitic/immunology
- Pregnancy Complications, Parasitic/parasitology
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Affiliation(s)
- Trine Staalsoe
- Centre for Medical Parasitology at Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet) and Institute for Medical Microbiology and Immunology, University of Copenhagen, Copenhagen, Denmark
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