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  1. Article ; Online: Function and Dysfunction of Complement Factor H During Formation of Lipid-Rich Deposits.

    Meri, Seppo / Haapasalo, Karita

    Frontiers in immunology

    2020  Volume 11, Page(s) 611830

    Abstract: Complement-mediated inflammation or dysregulation in lipid metabolism are associated with the pathogenesis of several diseases. These include age-related macular degeneration (AMD), C3 glomerulonephritis (C3GN), dense deposit disease (DDD), ... ...

    Abstract Complement-mediated inflammation or dysregulation in lipid metabolism are associated with the pathogenesis of several diseases. These include age-related macular degeneration (AMD), C3 glomerulonephritis (C3GN), dense deposit disease (DDD), atherosclerosis, and Alzheimer's disease (AD). In all these diseases, formation of characteristic lipid-rich deposits is evident. Here, we will discuss molecular mechanisms whereby dysfunction of complement, and especially of its key regulator factor H, could be involved in lipid accumulation and related inflammation. The genetic associations to factor H polymorphisms, the role of factor H in the resolution of inflammation in lipid-rich deposits, modification of macrophage functions, and complement-mediated clearance of apoptotic and damaged cells indicate that the function of factor H is crucial in limiting inflammation in these diseases.
    MeSH term(s) Alzheimer Disease/genetics ; Alzheimer Disease/immunology ; Alzheimer Disease/metabolism ; Animals ; Atherosclerosis/genetics ; Atherosclerosis/immunology ; Atherosclerosis/metabolism ; Complement Factor H/chemistry ; Complement Factor H/genetics ; Complement Factor H/metabolism ; Complement Pathway, Alternative ; Glomerulonephritis/genetics ; Glomerulonephritis/immunology ; Glomerulonephritis/metabolism ; Humans ; Inflammation/genetics ; Inflammation/immunology ; Inflammation/metabolism ; Lipid Metabolism ; Macular Degeneration/genetics ; Macular Degeneration/immunology ; Macular Degeneration/metabolism ; Polymorphism, Genetic ; Protein Conformation ; Signal Transduction ; Structure-Activity Relationship
    Chemical Substances CFH protein, human ; Complement Factor H (80295-65-4)
    Language English
    Publishing date 2020-12-08
    Publishing country Switzerland
    Document type Journal Article ; Research Support, Non-U.S. Gov't ; Review
    ZDB-ID 2606827-8
    ISSN 1664-3224 ; 1664-3224
    ISSN (online) 1664-3224
    ISSN 1664-3224
    DOI 10.3389/fimmu.2020.611830
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Regulation of the Complement System by Pentraxins.

    Haapasalo, Karita / Meri, Seppo

    Frontiers in immunology

    2019  Volume 10, Page(s) 1750

    Abstract: The functions of pentraxins, like C-reactive protein (CRP), serum amyloid protein P (SAP) and pentraxin-3 (PTX3), are to coordinate spatially and temporally targeted clearance of injured tissue components, to protect against infections and to regulate ... ...

    Abstract The functions of pentraxins, like C-reactive protein (CRP), serum amyloid protein P (SAP) and pentraxin-3 (PTX3), are to coordinate spatially and temporally targeted clearance of injured tissue components, to protect against infections and to regulate related inflammation together with the complement system. For this, pentraxins have a dual relationship with the complement system. Initially, after a focused binding to their targets, e.g., exposed phospholipids or cholesterol in the injured tissue area, or microbial components, the pentraxins activate complement by binding its first component C1q. However, the emerging inflammation needs to be limited to the target area. Therefore, pentraxins inhibit complement at the C3b stage to prevent excessive damage. The complement inhibitory functions of pentraxins are based on their ability to interact with complement inhibitors C4bp or factor H (FH). C4bp binds to SAP, while FH binds to both CRP and PTX3. FH promotes opsonophagocytosis through inactivation of C3b to iC3b, and inhibits AP activity thus preventing formation of the C5a anaphylatoxin and the complement membrane attack complex (MAC). Monitoring CRP levels gives important clinical information about the extent of tissue damage and severity of infections. CRP is a valuable marker for distinguishing bacterial infections from viral infections. Disturbances in the functions and interactions of pentraxins and complement are also involved in a number of human diseases. This review will summarize what is currently known about the FH family proteins and pentraxins that interact with FH. Furthermore, we will discuss diseases, where interactions between these molecules may play a role.
    MeSH term(s) Animals ; C-Reactive Protein/immunology ; Complement Activation/immunology ; Complement Factor H/immunology ; Complement Membrane Attack Complex/immunology ; Complement System Proteins/immunology ; Humans ; Serum Amyloid P-Component/immunology
    Chemical Substances Complement Membrane Attack Complex ; Serum Amyloid P-Component ; PTX3 protein (148591-49-5) ; Complement Factor H (80295-65-4) ; Complement System Proteins (9007-36-7) ; C-Reactive Protein (9007-41-4)
    Language English
    Publishing date 2019-08-02
    Publishing country Switzerland
    Document type Journal Article ; Research Support, Non-U.S. Gov't ; Review
    ZDB-ID 2606827-8
    ISSN 1664-3224 ; 1664-3224
    ISSN (online) 1664-3224
    ISSN 1664-3224
    DOI 10.3389/fimmu.2019.01750
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Mechanism of Borrelia immune evasion by FhbA-related proteins.

    Kogan, Konstantin / Haapasalo, Karita / Kotila, Tommi / Moore, Robin / Lappalainen, Pekka / Goldman, Adrian / Meri, Taru

    PLoS pathogens

    2022  Volume 18, Issue 3, Page(s) e1010338

    Abstract: Immune evasion facilitates survival of Borrelia, leading to infections like relapsing fever and Lyme disease. Important mechanism for complement evasion is acquisition of the main host complement inhibitor, factor H (FH). By determining the 2.2 Å crystal ...

    Abstract Immune evasion facilitates survival of Borrelia, leading to infections like relapsing fever and Lyme disease. Important mechanism for complement evasion is acquisition of the main host complement inhibitor, factor H (FH). By determining the 2.2 Å crystal structure of Factor H binding protein A (FhbA) from Borrelia hermsii in complex with FH domains 19-20, combined with extensive mutagenesis, we identified the structural mechanism by which B. hermsii utilizes FhbA in immune evasion. Moreover, structure-guided sequence database analysis identified a new family of FhbA-related immune evasion molecules from Lyme disease and relapsing fever Borrelia. Conserved FH-binding mechanism within the FhbA-family was verified by analysis of a novel FH-binding protein from B. duttonii. By sequence analysis, we were able to group FH-binding proteins of Borrelia into four distinct phyletic types and identified novel putative FH-binding proteins. The conserved FH-binding mechanism of the FhbA-related proteins could aid in developing new approaches to inhibit virulence and complement resistance in Borrelia.
    MeSH term(s) Borrelia/metabolism ; Carrier Proteins/metabolism ; Humans ; Immune Evasion ; Lyme Disease ; Relapsing Fever/metabolism
    Chemical Substances Carrier Proteins
    Language English
    Publishing date 2022-03-18
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2205412-1
    ISSN 1553-7374 ; 1553-7374
    ISSN (online) 1553-7374
    ISSN 1553-7374
    DOI 10.1371/journal.ppat.1010338
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: Mechanism of Borrelia immune evasion by FhbA-related proteins.

    Konstantin Kogan / Karita Haapasalo / Tommi Kotila / Robin Moore / Pekka Lappalainen / Adrian Goldman / Taru Meri

    PLoS Pathogens, Vol 18, Iss 3, p e

    2022  Volume 1010338

    Abstract: Immune evasion facilitates survival of Borrelia, leading to infections like relapsing fever and Lyme disease. Important mechanism for complement evasion is acquisition of the main host complement inhibitor, factor H (FH). By determining the 2.2 Å crystal ...

    Abstract Immune evasion facilitates survival of Borrelia, leading to infections like relapsing fever and Lyme disease. Important mechanism for complement evasion is acquisition of the main host complement inhibitor, factor H (FH). By determining the 2.2 Å crystal structure of Factor H binding protein A (FhbA) from Borrelia hermsii in complex with FH domains 19-20, combined with extensive mutagenesis, we identified the structural mechanism by which B. hermsii utilizes FhbA in immune evasion. Moreover, structure-guided sequence database analysis identified a new family of FhbA-related immune evasion molecules from Lyme disease and relapsing fever Borrelia. Conserved FH-binding mechanism within the FhbA-family was verified by analysis of a novel FH-binding protein from B. duttonii. By sequence analysis, we were able to group FH-binding proteins of Borrelia into four distinct phyletic types and identified novel putative FH-binding proteins. The conserved FH-binding mechanism of the FhbA-related proteins could aid in developing new approaches to inhibit virulence and complement resistance in Borrelia.
    Keywords Immunologic diseases. Allergy ; RC581-607 ; Biology (General) ; QH301-705.5
    Language English
    Publishing date 2022-03-01T00:00:00Z
    Publisher Public Library of Science (PLoS)
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  5. Article ; Online: Streptococci and the complement system: interplay during infection, inflammation and autoimmunity.

    Syed, Shahan / Viazmina, Larisa / Mager, Riccardo / Meri, Seppo / Haapasalo, Karita

    FEBS letters

    2020  Volume 594, Issue 16, Page(s) 2570–2585

    Abstract: Streptococci are a broad group of Gram-positive bacteria. This genus includes various human pathogens causing significant morbidity and mortality. Two of the most important human pathogens are Streptococcus pneumoniae (pneumococcus) and Streptococcus ... ...

    Abstract Streptococci are a broad group of Gram-positive bacteria. This genus includes various human pathogens causing significant morbidity and mortality. Two of the most important human pathogens are Streptococcus pneumoniae (pneumococcus) and Streptococcus pyogenes (group A streptococcus or GAS). Streptococcal pathogens have evolved to express virulence factors that enable them to evade complement-mediated attack. These include factor H-binding M (S. pyogenes) and pneumococcal surface protein C (PspC) (S. pneumoniae) proteins. In addition, S. pyogenes and S. pneumoniae express cytolysins (streptolysin and pneumolysin), which are able to destroy host cells. Sometimes, the interplay between streptococci, the complement, and antistreptococcal immunity may lead to an excessive inflammatory response or autoimmune disease. Understanding the fundamental role of the complement system in microbial clearance and the bacterial escape mechanisms is of paramount importance for understanding microbial virulence, in general, and, the conversion of commensals to pathogens, more specifically. Such insights may help to identify novel antibiotic and vaccine targets in bacterial pathogens to counter their growing resistance to commonly used antibiotics.
    MeSH term(s) Animals ; Anti-Bacterial Agents/therapeutic use ; Autoimmunity ; Bacterial Proteins/immunology ; Complement System Proteins/immunology ; Humans ; Immune Evasion ; Inflammation/drug therapy ; Inflammation/immunology ; Inflammation/microbiology ; Inflammation/pathology ; Pneumococcal Infections/drug therapy ; Pneumococcal Infections/immunology ; Pneumococcal Infections/pathology ; Streptococcus pneumoniae/immunology ; Streptococcus pneumoniae/pathogenicity ; Streptococcus pyogenes/immunology ; Streptococcus pyogenes/pathogenicity
    Chemical Substances Anti-Bacterial Agents ; Bacterial Proteins ; Complement System Proteins (9007-36-7)
    Language English
    Publishing date 2020-08-19
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't ; Review
    ZDB-ID 212746-5
    ISSN 1873-3468 ; 0014-5793
    ISSN (online) 1873-3468
    ISSN 0014-5793
    DOI 10.1002/1873-3468.13872
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: Retrospective study of the epidemiological risk and serological diagnosis of human babesiosis in Asturias, Northwestern Spain.

    Montero, Estrella / Folgueras, María / Rodriguez-Pérez, Mercedes / Pérez-Ls, Laura / Díaz-Arias, Javier / Meana, Maria / Revuelta, Belén / Haapasalo, Karita / Collazos, Julio / Asensi, Víctor / Gonzalez, Luis Miguel

    Parasites & vectors

    2023  Volume 16, Issue 1, Page(s) 195

    Abstract: Background: Babesiosis is a globally growing tick-borne disease in humans. Severe babesiosis caused by Babesia divergens has been reported in two patients from Asturias (Northwestern Spain), suggesting an undetected risk for the disease. To analyze this ...

    Abstract Background: Babesiosis is a globally growing tick-borne disease in humans. Severe babesiosis caused by Babesia divergens has been reported in two patients from Asturias (Northwestern Spain), suggesting an undetected risk for the disease. To analyze this risk, we retrospectively evaluated the seroprevalence of babesiosis in the Asturian population from 2015 through 2017, a period covering the intermediate years in which these two severe cases occurred.
    Methods: Indirect fluorescent assay (IFA) and Western blot (WB) were performed to detect B. divergens IgG antibodies in 120 serum samples from Asturian patients infected with the tick-transmitted spirochete Borrelia burgdorferi sensu lato, a condition that indicates exposure to tick bites.
    Results: This retrospective study confirmed a B. divergens seroprevalence rate of 39.2% according to IFA results. B. divergens incidence was 7.14 cases/100,000 population, exceeding previously reported seroprevalence rates. No differences in epidemiology and risk factors were found between patients infected solely with B. burgdorferi s.l. and those infected with B. burgdorferi s.l. and with IgG antibodies against B. divergens. This last group of patients lived in Central Asturias, had a milder clinical course and, according to WB results, developed different humoral responses against B. divergens.
    Conclusions: Babesia divergens parasites have circulated for several years in Asturias. Epidemiological evidence of babesiosis makes Asturias an emerging risk area for this zoonosis. Human babesiosis could also be relevant in other Spanish and European regions affected by borreliosis. Hence, the potential risk of babesiosis on human health in Asturias and other European forest regions needs to be addressed by the health authorities.
    MeSH term(s) Animals ; Humans ; Babesiosis/diagnosis ; Babesiosis/epidemiology ; Babesiosis/parasitology ; Retrospective Studies ; Spain/epidemiology ; Seroepidemiologic Studies ; Babesia ; Immunoglobulin G
    Chemical Substances Immunoglobulin G
    Language English
    Publishing date 2023-06-09
    Publishing country England
    Document type Journal Article
    ZDB-ID 2409480-8
    ISSN 1756-3305 ; 1756-3305
    ISSN (online) 1756-3305
    ISSN 1756-3305
    DOI 10.1186/s13071-023-05817-x
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  7. Article: Streptococci and the complement system: interplay during infection, inflammation and autoimmunity

    Syed, Shahan / Viazmina, Larisa / Mager, Riccardo / Meri, Seppo / Haapasalo, Karita

    FEBS letters. 2020 Aug., v. 594, no. 16

    2020  

    Abstract: Streptococci are a broad group of Gram‐positive bacteria. This genus includes various human pathogens causing significant morbidity and mortality. Two of the most important human pathogens are Streptococcus pneumoniae (pneumococcus) and Streptococcus ... ...

    Abstract Streptococci are a broad group of Gram‐positive bacteria. This genus includes various human pathogens causing significant morbidity and mortality. Two of the most important human pathogens are Streptococcus pneumoniae (pneumococcus) and Streptococcus pyogenes (group A streptococcus or GAS). Streptococcal pathogens have evolved to express virulence factors that enable them to evade complement‐mediated attack. These include factor H‐binding M (S. pyogenes) and pneumococcal surface protein C (PspC) (S. pneumoniae) proteins. In addition, S. pyogenes and S. pneumoniae express cytolysins (streptolysin and pneumolysin), which are able to destroy host cells. Sometimes, the interplay between streptococci, the complement, and antistreptococcal immunity may lead to an excessive inflammatory response or autoimmune disease. Understanding the fundamental role of the complement system in microbial clearance and the bacterial escape mechanisms is of paramount importance for understanding microbial virulence, in general, and, the conversion of commensals to pathogens, more specifically. Such insights may help to identify novel antibiotic and vaccine targets in bacterial pathogens to counter their growing resistance to commonly used antibiotics.
    Keywords Streptococcus pneumoniae ; Streptococcus pyogenes ; antibiotics ; autoimmune diseases ; autoimmunity ; complement ; humans ; inflammation ; morbidity ; mortality ; pneumolysin ; streptolysin ; surface proteins ; vaccines ; virulence
    Language English
    Dates of publication 2020-08
    Size p. 2570-2585.
    Publishing place John Wiley & Sons, Ltd
    Document type Article
    Note REVIEW
    ZDB-ID 212746-5
    ISSN 1873-3468 ; 0014-5793
    ISSN (online) 1873-3468
    ISSN 0014-5793
    DOI 10.1002/1873-3468.13872
    Database NAL-Catalogue (AGRICOLA)

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  8. Article ; Online: Reduced binding of apoE4 to complement factor H promotes amyloid-β oligomerization and neuroinflammation.

    Chernyaeva, Larisa / Ratti, Giorgio / Teirilä, Laura / Fudo, Satoshi / Rankka, Uni / Pelkonen, Anssi / Korhonen, Paula / Leskinen, Katarzyna / Keskitalo, Salla / Salokas, Kari / Gkolfinopoulou, Christina / Crompton, Katrina E / Javanainen, Matti / Happonen, Lotta / Varjosalo, Markku / Malm, Tarja / Leinonen, Ville / Chroni, Angeliki / Saavalainen, Päivi /
    Meri, Seppo / Kajander, Tommi / Wollman, Adam Jm / Nissilä, Eija / Haapasalo, Karita

    EMBO reports

    2023  Volume 24, Issue 7, Page(s) e56467

    Abstract: The APOE4 variant of apolipoprotein E (apoE) is the most prevalent genetic risk allele associated with late-onset Alzheimer's disease (AD). ApoE interacts with complement regulator factor H (FH), but the role of this interaction in AD pathogenesis is ... ...

    Abstract The APOE4 variant of apolipoprotein E (apoE) is the most prevalent genetic risk allele associated with late-onset Alzheimer's disease (AD). ApoE interacts with complement regulator factor H (FH), but the role of this interaction in AD pathogenesis is unknown. Here we elucidate the mechanism by which isoform-specific binding of apoE to FH alters Aβ1-42-mediated neurotoxicity and clearance. Flow cytometry and transcriptomic analysis reveal that apoE and FH reduce binding of Aβ1-42 to complement receptor 3 (CR3) and subsequent phagocytosis by microglia which alters expression of genes involved in AD. Moreover, FH forms complement-resistant oligomers with apoE/Aβ1-42 complexes and the formation of these complexes is isoform specific with apoE2 and apoE3 showing higher affinity to FH than apoE4. These FH/apoE complexes reduce Aβ1-42 oligomerization and toxicity, and colocalize with complement activator C1q deposited on Aβ plaques in the brain. These findings provide an important mechanistic insight into AD pathogenesis and explain how the strongest genetic risk factor for AD predisposes for neuroinflammation in the early stages of the disease pathology.
    MeSH term(s) Humans ; Apolipoprotein E4/genetics ; Apolipoprotein E4/metabolism ; Complement Factor H/genetics ; Alzheimer Disease/genetics ; Alzheimer Disease/metabolism ; Neuroinflammatory Diseases ; Apolipoproteins E/chemistry ; Apolipoproteins E/genetics ; Apolipoproteins E/metabolism ; Amyloid beta-Peptides/metabolism ; Protein Isoforms/genetics ; Protein Isoforms/metabolism
    Chemical Substances Apolipoprotein E4 ; Complement Factor H (80295-65-4) ; Apolipoproteins E ; Amyloid beta-Peptides ; Protein Isoforms
    Language English
    Publishing date 2023-05-08
    Publishing country England
    Document type Journal Article
    ZDB-ID 2020896-0
    ISSN 1469-3178 ; 1469-221X
    ISSN (online) 1469-3178
    ISSN 1469-221X
    DOI 10.15252/embr.202256467
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  9. Article ; Online: Role of Pneumococcal NanA Neuraminidase Activity in Peripheral Blood.

    Syed, Shahan / Hakala, Pipsa / Singh, Anirudh K / Lapatto, Helena A K / King, Samantha J / Meri, Seppo / Jokiranta, T Sakari / Haapasalo, Karita

    Frontiers in cellular and infection microbiology

    2019  Volume 9, Page(s) 218

    Abstract: The most frequent form of hemolytic-uremic syndrome (HUS) is associated with infections caused by Shiga-like toxin-producing ... ...

    Abstract The most frequent form of hemolytic-uremic syndrome (HUS) is associated with infections caused by Shiga-like toxin-producing Enterohaemorrhagic
    MeSH term(s) Bacterial Proteins/genetics ; Blood Platelets/metabolism ; Complement System Proteins/drug effects ; Erythrocytes ; HEK293 Cells ; Hemolysis ; Hemolytic-Uremic Syndrome/microbiology ; Humans ; Inflammation ; Neuraminidase/blood ; Neuraminidase/genetics ; Neuraminidase/metabolism ; Neuraminidase/pharmacology ; Pneumococcal Infections/microbiology ; Sequence Deletion ; Sialic Acids ; Streptococcus pneumoniae/enzymology ; Streptococcus pneumoniae/metabolism
    Chemical Substances Bacterial Proteins ; Sialic Acids ; Complement System Proteins (9007-36-7) ; Neuraminidase (EC 3.2.1.18)
    Language English
    Publishing date 2019-06-26
    Publishing country Switzerland
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2619676-1
    ISSN 2235-2988 ; 2235-2988
    ISSN (online) 2235-2988
    ISSN 2235-2988
    DOI 10.3389/fcimb.2019.00218
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  10. Article ; Online: Streptococcus pneumoniae

    Syed, Shahan / Nissilä, Eija / Ruhanen, Hanna / Fudo, Satoshi / Gaytán, Meztlli O / Sihvo, Sanna P / Lorey, Martina B / Metso, Jari / Öörni, Katariina / King, Samantha J / Oommen, Oommen P / Jauhiainen, Matti / Meri, Seppo / Käkelä, Reijo / Haapasalo, Karita

    iScience

    2021  Volume 24, Issue 6, Page(s) 102535

    Abstract: High-density lipoproteins (HDLs) are a group of different subpopulations of sialylated particles that have an essential role in the reverse cholesterol transport (RCT) pathway. Importantly, changes in the protein and lipid composition of HDLs may lead to ...

    Abstract High-density lipoproteins (HDLs) are a group of different subpopulations of sialylated particles that have an essential role in the reverse cholesterol transport (RCT) pathway. Importantly, changes in the protein and lipid composition of HDLs may lead to the formation of particles with reduced atheroprotective properties. Here, we show that
    Language English
    Publishing date 2021-05-12
    Publishing country United States
    Document type Journal Article
    ISSN 2589-0042
    ISSN (online) 2589-0042
    DOI 10.1016/j.isci.2021.102535
    Database MEDical Literature Analysis and Retrieval System OnLINE

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