| 41. |
- Ribacke, Ulf, et al.
(författare)
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Genome wide gene amplifications and deletions in Plasmodium falciparum
- 2007
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Ingår i: Molecular and biochemical parasitology (Print). - : Elsevier BV. - 0166-6851 .- 1872-9428. ; 155:1, s. 33-44
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Tidskriftsartikel (refereegranskat)abstract
- The extent to which duplications and deletions occur in the Plasmodium falciparum genome, outside of the subtelomeres, and their contribution to the virulence of the malaria parasite is not known. Here we show the presence of multiple genome wide copy number polymorphisms (CNPs) covering 82 genes, the most extensive spanning a cumulative size of 110 kilobases. CNPs were identified in both laboratory strains and fresh clinical isolates using a 70-mer oligonucleotide microarray in conjunction with fluorescent in situ hybridizations and real-time quantitative PCR. The CNPs were found on all chromosomes except on chromosomes 6 and 8 and involved a total of 50 genes with increased copy numbers and 32 genes with decreased copy numbers relative to the 3D7 parasite. The genes, amplified in up to six copies, encode molecules involved in cell cycle regulation. cell division, drug resistance, erythrocyte invasion, sexual differentiation and unknown functions. These together with previous findings, suggest that the malaria parasite employs gene duplications and deletions as general strategies to enhance its survival and spread. Further analysis of the impact of discovered genetic differences and the underlying mechanisms is likely to generate a better understanding of the biology and the virulence of the malaria parasite.
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| 42. |
- Ribacke, Ulf, et al.
(författare)
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Improved in vitro culture of plasmodium falciparum permits establishment of clinical isolates with preserved multiplication, invasion and rosetting phenotypes
- 2013
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Ingår i: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 8:7
-
Tidskriftsartikel (refereegranskat)abstract
- To be able to robustly propagate P. falciparum at optimal conditions in vitro is of fundamental importance for genotypic and phenotypic studies of both established and fresh clinical isolates. Cryo-preserved P. falciparum isolates from Ugandan children with severe or uncomplicated malaria were investigated for parasite phenotypes under different in vitro growth conditions or studied directly from the peripheral blood. The parasite cultures showed a minimal loss of parasite-mass and preserved percentage of multiple infected pRBCs to that in peripheral blood, maintained adhesive phenotypes and good outgrowth and multiplication rates when grown in suspension and supplemented with gas. In contrast, abnormal and greatly fluctuating levels of multiple infections were observed during static growth conditions and outgrowth and multiplication rates were inferior. Serum, as compared to Albumax, was found necessary for optimal presentation of PfEMP1 at the pRBC surface and/or for binding of serum proteins (immunoglobulins). Optimal in vitro growth conditions of P. falciparum therefore include orbital shaking (50 rev/min), human serum (10%) and a fixed gas composition (5% O2, 5% CO2, 90% N2). We subsequently established 100% of 76 frozen patient isolates and found rosetting with schizont pRBCs in every isolate (>26% schizont rosetting rate). Rosetting during schizogony was often followed by invasion of the bound RBC as seen by regular and time-lapse microscopy as well as transmission electron microscopy. The peripheral parasitemia, the level of rosetting and the rate of multiplication correlated positively to one another for individual isolates. Rosetting was also more frequent with trophozoite and schizont pRBCs of children with severe versus uncomplicated malaria (p<0.002; p<0.004). The associations suggest that rosetting enhances the ability of the parasite to multiply within the human host.
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| 43. |
- Simone, Olivia, et al.
(författare)
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TLRs innate immunereceptors and Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) CIDR1α-driven human polyclonal B-cell activation.
- 2011
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Ingår i: Acta Tropica. - : Elsevier BV. - 0001-706X .- 1873-6254. ; 119:2-3, s. 144-150
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Tidskriftsartikel (refereegranskat)abstract
- Chronic malaria severely affects the immune system and causes polyclonal B-cell activation, as evidenced by the presence of hypergammaglobulinemia, elevated levels of autoantibodies, loss of B-cell memory and the frequent occurrence of Burkitt's lymphomas (BL) in children living in malaria endemic areas. Previous studies have shown that the cysteine-rich interdomain region 1α (CIDR1α) of the Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) of the FCR3S1.2 strain, subsequently named CIDR1α, interacts with B cells partially through the binding to the B-cell receptor (BCR). This interaction leads to an activated phenotype, increased survival, and a low degree of proliferation. CIDR1α preferentially activates the memory B-cell compartment, therefore PfEMP1 is considered to act as a polyclonal B-cell activator and its role in memory maintenance has been suggested. In this report, we extend the analysis of the PfEMP1-CIDR1α B-cell interaction and demonstrate that PfEMP1-CIDR1α increases the expression of TLR7 and TLR10 mRNA transcripts and sensitizes B cells to TLR9 signalling via the MyD88 adaptor molecule. Furthermore, despite its ability to bind to surface Igs, PfEMP1-CIDR1α-induced B-cell activation does not seem to proceed through the BCR, since it does not induce Lyn and/or phospho-tyrosine mediated signalling pathways. Rather PfEMP1-CIDR1α induces the phosphorylation of downstream kinases, such as ERK1/2, p38 and IKBα, in human B cells. These findings indicate that PfEMP1-CIDR1α induces a persistent activation of B cells, which in turn can contribute to the exhaustion and impairment of B-cell functions during chronic malaria infection.
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| 44. |
- Stea, T. H., et al.
(författare)
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Mapping the Concept, Content, and Outcome of Family-Based Outdoor Therapy for Children and Adolescents with Mental Health Problems : A Scoping Review
- 2022
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Ingår i: International Journal of Environmental Research and Public Health. - : MDPI AG. - 1661-7827 .- 1660-4601. ; 19:10
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Forskningsöversikt (refereegranskat)abstract
- Outdoor therapy and family-based therapy are suggested to be promising interventions for the treatment of mental health problems. The aim of the present scoping review was to systematically map the concept, content, and outcome of combining family-and outdoor-based therapy for children and adolescents with mental health problems. The Joanna Briggs Institute methodology and PRISMA guidelines were applied. Eligible qualitative and quantitative studies were screened, included, and extracted for data. Seven studies were included. Findings from these studies indicated that family-based outdoor therapy programs have a positive impact on family-and peer relationships, adolescent behavior, mental health, self-perceptions (self-concept), school success, social engagement, and delinquency rates. However, participant characteristics, study design, and content and mode of delivery of the interventions varied substantially, hence preventing detailed comparison of outcomes across studies. In addition, most of the studies included few participants and lacked population diversity and comparable control groups. Although important ethical concerns were raised, such as non-voluntary participation in some of the programs, there was a lack of reporting on safety. This review indicates that a combination of family-and outdoor-based therapy may benefit mental health among children and adolescents, but due to the limited number of studies eligible for inclusion and high levels of heterogeneity, it was difficult to draw firm conclusions. Thus, future theory-based studies using robust designs are warranted.
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| 45. |
- Tijani, Muyideen K., et al.
(författare)
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Acquisition, maintenance and adaptation of invasion inhibitory antibodies against Plasmodium falciparum invasion ligands involved in immune evasion
- 2017
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 12:8
-
Tidskriftsartikel (refereegranskat)abstract
- Erythrocyte-binding antigens (EBAs) and P. falciparum reticulocyte-binding homologue proteins (PfRhs) are two important protein families that can vary in expression and utilization by P. falciparum to evade inhibitory antibodies. We evaluated antibodies at repeated time-points among individuals living in an endemic region in Nigeria over almost one year against these vaccine candidates. Antibody levels against EBA140, EBA175, EBA181, PfRh2, PfRh4, and MSP2, were measured by ELISA. We also used parasites with disrupted EBA140, EBA175 and EBA181 genes to show that all these were targets of invasion inhibitory antibodies. However, antigenic targets of inhibitory antibodies were not stable and changed substantially over time in most individuals, independent of age. Antibodies levels measured by ELISA also varied within and between individuals over time and the antibodies against EBA181, PfRh2 and MSP2 declined more rapidly in younger individuals (15 years) compared with older (>15). The breadth of high antibody responses over time was more influenced by age than by the frequency of infection. High antibody levels were associated with a more stable invasion inhibitory response, which could indicate that during the long process of formation of immunity, many changes not only in levels but also in functional responses are needed. This is an important finding in understanding natural immunity against malaria, which is essential for making an efficacious vaccine.
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| 46. |
- Vogt, Anna M, et al.
(författare)
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Heparan sulfate on endothelial cells mediates the binding of Plasmodium falciparum-infected erythrocytes via the DBL1alpha domain of PfEMP1
- 2003
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Ingår i: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 101:6, s. 2405-2411
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Tidskriftsartikel (refereegranskat)abstract
- Plasmodium falciparum may cause severe forms of malaria when excessive sequestration of infected and uninfected erythrocytes occurs in vital organs. The capacity of wild-type isolates of P falciparum-infected erythrocytes (parasitized red blood cells [pRBCs]) to bind glycosaminoglycans (GAGs) such as heparin has been identified as a marker for severe disease. Here we report that pRBCs of the parasite FCR3S1.2 and wild-type clinical isolates from Uganda adhere to heparan sulfate (HS) on endothelial cells. Binding to human umbilical vein endothelial cells (HUVECs) and to human lung endothelial cells (HLECs) was found to be inhibited by HS/heparin or enzymes that remove HS from cell surfaces. (35)S-labeled HS extracted from HUVECs bound directly to the pRBCs' membrane. Using recombinant proteins corresponding to the different domains of P falciparum erythrocyte membrane protein 1 (PfEMP1), we identified Duffy-binding-like domain-1alpha (DBL1alpha) as the ligand for HS. DBL1alpha bound in an HS-dependent way to endothelial cells and blocked the adherence of pRBCs in a dose-dependent manner. (35)S-labeled HS bound to DBL1alpha-columns and eluted as a distinct peak at 0.4 mM NaCl. (35)S-labeled chondroitin sulfate (CS) of HUVECs did not bind to PfEMP1 or to the pRBCs' membrane. Adhesion of pRBCs of FCR3S1.2 to platelet endothelial cell adhesion molecule-1 (PECAM-1)/CD31, mediated by the cysteine-rich interdomain region 1alpha (CIDR1alpha), was found be operative with, but independent of, the binding to HS. HS and the previously identified HS-like GAG on uninfected erythrocytes may act as coreceptors in endothelial and erythrocyte binding of rosetting parasites, causing excessive sequestration of both pRBCs and RBCs.
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| 47. |
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| 48. |
- Vogt, Anna M., et al.
(författare)
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Release of sequestered malaria parasites upon injection of a glycosaminoglycan
- 2006
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Ingår i: PLoS Pathogens. - : Public Library of Science (PLoS). - 1553-7366 .- 1553-7374. ; 2:9, s. 853-863
-
Tidskriftsartikel (refereegranskat)abstract
- Severe human malaria is attributable to an excessive sequestration of Plasmodium falciparum-infected and uninfected erythrocytes in vital organs. Strains of P. falciparum that form rosettes and employ heparan sulfate as a host receptor are associated with development of severe forms of malaria. Heparin, which is similar to heparan sulfate in that it is composed of the same building blocks, was previously used in the treatment of severe malaria, but it was discontinued due to the occurrence of serious side effects such as intracranial bleedings. Here we report to have depolymerized heparin by periodate treatment to generate novel glycans (dGAG) that lack anticoagulant-activity. The dGAGs disrupt rosettes, inhibit merozoite invasion of erythrocytes and endothelial binding of P. falciparum-infected erythrocytes in vitro, and reduce sequestration in in vivo models of severe malaria. An intravenous injection of dGAGs blocks up to 80% of infected erythrocytes from binding in the micro-vasculature of the rat and releases already sequestered parasites into circulation. P. falciparum-infected human erythrocytes that sequester in the non-human primate Macaca fascicularis were similarly found to be released in to the circulation upon a single injection of 500 mu g of dGAG. We suggest dGAGs to be promising candidates for adjunct therapy in severe malaria.
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| 49. |
- Västberg, Amanda, et al.
(författare)
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Investigating thermally induced aggregation of Somatropin- new insights using orthogonal techniques
- 2023
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Ingår i: International Journal of Pharmaceutics. - : Elsevier B.V.. - 0378-5173 .- 1873-3476. ; 637
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Tidskriftsartikel (refereegranskat)abstract
- Three orthogonal techniques were used to provide new insights into thermally induced aggregation of the therapeutic protein Somatropin at pH 5.8 and 7.0. The techniques were Dynamic Light Scattering (DLS), Asymmetric Flow-Field Flow-Fractionation (AF4), and the TEM-based analysis system MiniTEM™. In addition, Differential Scanning Calorimetry (DSC) was used to study the thermal unfolding and stability. DSC and DLS were used to explain the initial aggregation process and aggregation rate at the two pH values. The results suggest that less electrostatic stabilization seems to be the main reason for the faster initial aggregation at pH 5.8, i.e., closer to the isoelectric point of Somatropin. AF4 and MiniTEM were used to investigate the aggregation pathway further. Combining the results allowed us to demonstrate Somatropin's thermal aggregation pathway at pH 7.0. The growth of the aggregates appears to follow two steps. Smaller elongated aggregates are formed in the first step, possibly initiated by partly unfolded species. In the second step, occurring during longer heating, the smaller aggregates assemble into larger aggregates with more complex structures. © 2023 The Author(s)
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| 50. |
- Wahlgren, Mats
(författare)
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Antigens and antibodies involved in humoral immunity to plasmodium falciparum
- 1986
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Malaria plasmodiidae cause more death and disease than any other known human pathogen. The parasite still threatens half of the world population {2.5 billion) and 300 million people are considered to become infected every year. More than 1 million African children annually die from malaria and there are an estimated 80 million clinical cases/year in the world. How protection or immunity to the parasites is mounted in humans is still partially unknown, although both cellular and antibody mediated immunity has been implied. This thesis describes several aspects of the humoral immune response to Plasmodium falciparurn in humans. Sera from individuals with different degrees of exposure to the parasite or with clinical immunity were used to study antibodies to P. falciparum antigens by means of ELISA, indirect immunofluorescence, immunoprecipiation and immunoblotting. Antibodies of IgM and all four IgG isotypes were detected both in sera from immune donors and in those with their first infection. However, whereas high titered sera contained antibodies of IgM and IgG1-4 isotypes, IgG2 and IgG4 antibodies were frequently missing in low titered sera. This could indicate that the isotype expression, on the average, follows the downstreams order of the Igh-C genes and is correlated with the intensity of immunization as occurring in infection. Using the same methods for a detailed investigation of sera from children and adults living in a holoendemic area of Liberia, no (or weak) correlations between age-dependent acquisition of P.falciparum immunity and overall antibody activities or isotype expression were seen.
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