{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,17]],"date-time":"2026-06-17T17:21:40Z","timestamp":1781716900835,"version":"3.54.5"},"reference-count":58,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2025,8,21]],"date-time":"2025-08-21T00:00:00Z","timestamp":1755734400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Immunol."],"abstract":"<jats:p>Hemolytic uremic syndrome caused by an invasive <jats:italic>Streptococcus pneumoniae<\/jats:italic> infection (SP-HUS) is a rare and severe disease that primarily affects children under two years of age. The pathophysiology of SP-HUS remains poorly understood, and treatment is largely supportive. Complement factor H (FH) is a key regulator of the alternative pathway of the complement system. It has been hypothesized that loss of sialic acids from FH\u2019s N-glycans may impair its regulatory functions, thereby potentially leading to complement-mediated endothelial cell damage in SP-HUS. In this study, we investigated the N-glycosylation patterns of FH across three N-glycosylation sites for four SP-HUS patients and compared it to healthy controls using LC-MS\/MS-based glycopeptide profiling. We identified significant changes in FH glycosylation during the acute phase of SP-HUS, including an increased presence of N-glycans lacking sialic acids, galactose and N-acetylglucosamine (GlcNAc) relative to the controls. This abnormal glycosylation was most prominent during the acute phase in all patients and showed partial or complete normalization during remission. Interestingly, despite these major glycosylation changes, functional assays revealed no significant impairment in the complement regulatory activity of FH, as measured by its ability to facilitate C3b degradation and to prevent complement-mediated hemolysis of sheep erythrocytes. In conclusion, our findings show that FH\u2019s N-glycosylation is severely altered in the acute phase in SP-HUS patients, comprising more than just the loss of sialic acids. However, these changes do not directly affect FH\u2019s complement regulatory function. These results highlight the complex yet poorly understood role of N-glycosylation during infection, and the contribution of FH\u2019s N-glycans to complement (dys)regulation and disease pathogenesis.<\/jats:p>","DOI":"10.3389\/fimmu.2025.1645196","type":"journal-article","created":{"date-parts":[[2025,8,21]],"date-time":"2025-08-21T05:29:02Z","timestamp":1755754142000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":2,"title":["Glycoproteomics analysis of complement factor H and its complement-regulatory function during Streptococcus pneumoniae-associated hemolytic uremic syndrome"],"prefix":"10.3389","volume":"16","author":[{"given":"Laura M.","family":"Baas","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kioa L.","family":"Wijnsma","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Fokje","family":"Zijlstra","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nicole C. A. J.","family":"van de Kar","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lieke","family":"ter Steeg","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Antonia H. M.","family":"Bouts","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Marloes A. H. M.","family":"Michels","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jeroen D.","family":"Langereis","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Dirk","family":"Lefeber","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hans J. C. T.","family":"Wessels","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lambertus P.","family":"van den Heuvel","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2025,8,21]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","DOI":"10.1097\/INF.0000000000002368","article-title":"Pneumococcal-related hemolytic uremic syndrome in the United Kingdom: national surveillance, 2006-2016","volume":"38","author":"Makwana","year":"2019","journal-title":"Pediatr Infect Dis J"},{"key":"B2","doi-asserted-by":"publisher","DOI":"10.1016\/S0140-6736(17)30062-4","article-title":"Haemolytic uraemic syndrome","volume":"390","author":"Fakhouri","year":"2017","journal-title":"Lancet"},{"key":"B3","doi-asserted-by":"publisher","DOI":"10.12688\/f1000research.19957.1","article-title":"Haemolytic uremic syndrome: diagnosis and management","volume":"8","author":"Sheerin","year":"2019","journal-title":"F1000Res"},{"key":"B4","doi-asserted-by":"publisher","DOI":"10.1097\/INF.0b013e31828b31c8","article-title":"Trends in US hospital stays for Streptococcus pneumoniae-associated hemolytic uremic syndrome","volume":"32","author":"Veesenmeyer","year":"2013","journal-title":"Pediatr Infect Dis J"},{"key":"B5","doi-asserted-by":"publisher","DOI":"10.1097\/INF.0b013e3181db03a7","article-title":"Epidemiology of Streptococcus pneumoniae-induced hemolytic uremic syndrome in Utah children","volume":"29","author":"Bender","year":"2010","journal-title":"Pediatr Infect Dis J"},{"key":"B6","doi-asserted-by":"publisher","DOI":"10.1007\/s00467-007-0518-y","article-title":"Streptococcus pneumoniae-associated hemolytic uremic syndrome","volume":"23","author":"Copelovitch","year":"2008","journal-title":"Pediatr Nephrol"},{"key":"B7","doi-asserted-by":"publisher","DOI":"10.1016\/j.pcl.2018.09.011","article-title":"Hemolytic uremic syndrome","volume":"66","author":"Cody","year":"2019","journal-title":"Pediatr Clinics North A"},{"key":"B8","doi-asserted-by":"publisher","DOI":"10.1111\/trf.12981","article-title":"Red blood cell Thomsen-Friedenreich antigen expression and galectin-3 plasma concentrations in Streptococcus pneumoniae-associated hemolytic uremic syndrome and hemolytic anemia","volume":"55","author":"Burin des Roziers","year":"2015","journal-title":"Transfusion"},{"key":"B9","doi-asserted-by":"publisher","DOI":"10.1016\/j.micpath.2011.02.010","article-title":"Exposure of Thomsen-Friedenreich antigen in Streptococcus pneumoniae infection is dependent on pneumococcal neuraminidase A","volume":"50","author":"Coats","year":"2011","journal-title":"Microb Pathog"},{"key":"B10","doi-asserted-by":"publisher","DOI":"10.1016\/S0140-6736(77)92915-4","article-title":"Thomsen-Friedenreich antigen in haemolytic-uraemic syndrome","volume":"2","author":"Klein","year":"1977","journal-title":"Lancet"},{"key":"B11","doi-asserted-by":"publisher","DOI":"10.1182\/blood-2016-04-708172","article-title":"Sweeteners for factor H","volume":"127","author":"Conway","year":"2016","journal-title":"Blood"},{"key":"B12","doi-asserted-by":"publisher","first-page":"46","DOI":"10.3390\/biom2010046","article-title":"Factor h: a complement regulator in health and disease, and a mediator of cellular interactions","volume":"2","author":"Kopp","year":"2012","journal-title":"Biomolecules"},{"key":"B13","doi-asserted-by":"publisher","DOI":"10.1016\/j.molimm.2010.05.007","article-title":"Complement control protein factor H: the good, the bad, and the inadequate","volume":"47","author":"Ferreira","year":"2010","journal-title":"Mol Immunol"},{"key":"B14","doi-asserted-by":"publisher","DOI":"10.1093\/glycob\/cwy061","article-title":"Biophysical analysis of sialic acid recognition by the complement regulator Factor H","volume":"28","author":"Schmidt","year":"2018","journal-title":"Glycobiology"},{"key":"B15","doi-asserted-by":"publisher","DOI":"10.3389\/fcimb.2019.00218","article-title":"Role of pneumococcal nanA neuraminidase activity in peripheral blood","volume":"9","author":"Syed","year":"2019","journal-title":"Front Cell Infection Microbiol"},{"key":"B16","doi-asserted-by":"publisher","DOI":"10.3389\/fimmu.2021.641656","article-title":"Complement genetic variants and FH desialylation in S. pneumoniae-haemolytic uraemic syndrome","volume":"12","author":"Gomez Delgado","year":"2021","journal-title":"Front Immunol"},{"key":"B17","doi-asserted-by":"publisher","DOI":"10.1093\/glycob\/cwm060","article-title":"Site-specific N-glycan characterization of human complement factor H","volume":"17","author":"Fenaille","year":"2007","journal-title":"Glycobiology"},{"key":"B18","doi-asserted-by":"publisher","DOI":"10.4049\/jimmunol.133.6.3250","article-title":"Lysine residues, but not carbohydrates, are required for the regulatory function of H on the amplification C3 convertase of complement","volume":"133","author":"Jouvin","year":"1984","journal-title":"J Immunol"},{"key":"B19","doi-asserted-by":"publisher","DOI":"10.3389\/fimmu.2024.1383123","article-title":"Moss-produced human complement factor H with modified glycans has an extended half-life and improved biological activity","volume":"15","author":"Tschongov","year":"2024","journal-title":"Front Immunol"},{"key":"B20","doi-asserted-by":"publisher","DOI":"10.1001\/jama.2013.281053","article-title":"World Medical Association Declaration of Helsinki: ethical principles for medical research involving human subjects","volume":"310","year":"2013","journal-title":"JAMA"},{"key":"B21","doi-asserted-by":"publisher","DOI":"10.3389\/fimmu.2019.01350","article-title":"Novel assays to distinguish between properdin-dependent and properdin-independent C3 nephritic factors provide insight into properdin-inhibiting therapy","volume":"10","author":"Michels","year":"2019","journal-title":"Front Immunol"},{"key":"B22","doi-asserted-by":"publisher","DOI":"10.3389\/fimmu.2018.00612","article-title":"Overactivity of alternative pathway convertases in patients with complement-mediated renal diseases","volume":"9","author":"Michels","year":"2018","journal-title":"Front Immunol"},{"key":"B23","doi-asserted-by":"publisher","DOI":"10.1101\/2022.05.31.494121","article-title":"Plasma glycoproteomics delivers high-specificity disease biomarkers by detecting site-specific glycosylation abnormalities","volume":"61","author":"Wessels","year":"2023","journal-title":"J Advanced Res"},{"key":"B24","doi-asserted-by":"publisher","DOI":"10.1021\/acs.analchem.3c05874","article-title":"Maximizing glycoproteomics results through an integrated parallel accumulation serial fragmentation workflow","volume":"96","author":"Baerenfaenger","year":"2024","journal-title":"Anal Chem"},{"key":"B25","doi-asserted-by":"publisher","DOI":"10.1038\/s41592-020-0967-9","article-title":"Fast and comprehensive N- and O-glycoproteomics analysis with MSFragger-Glyco","volume":"17","author":"Polasky","year":"2020","journal-title":"Nat Methods"},{"key":"B26","doi-asserted-by":"publisher","DOI":"10.1093\/nar\/gkae1010","article-title":"UniProt: the universal protein knowledgebase in 2025","volume":"53","year":"2025","journal-title":"Nucleic Acids Res"},{"key":"B27","doi-asserted-by":"publisher","DOI":"10.1093\/glycob\/cwz080","article-title":"GlyGen: computational and informatics resources for glycoscience","volume":"30","author":"York","year":"2020","journal-title":"Glycobiology"},{"key":"B28","doi-asserted-by":"publisher","DOI":"10.1515\/cclm-2023-1189","article-title":"N-linked glycosylation of the M-protein variable region: glycoproteogenomics reveals a new layer of personalized complexity in multiple myeloma","volume":"62","author":"Langerhorst","year":"2024","journal-title":"Clin Chem Lab Med"},{"key":"B29","doi-asserted-by":"publisher","DOI":"10.3389\/fimmu.2023.1279612","article-title":"Functional evaluation of complement factor I variants by immunoassays and SDS-PAGE","volume":"14","author":"Gerogianni","year":"2023","journal-title":"Front Immunol"},{"key":"B30","doi-asserted-by":"publisher","DOI":"10.1016\/j.molimm.2004.01.003","article-title":"Functional analysis in serum from atypical Hemolytic Uremic Syndrome patients reveals impaired protection of host cells associated with mutations in factor H","volume":"41","author":"S\u00e1nchez-Corral","year":"2004","journal-title":"Mol Immunol"},{"key":"B31","doi-asserted-by":"publisher","DOI":"10.1093\/nar\/gkae253","article-title":"MetaboAnalyst 6.0: towards a unified platform for metabolomics data processing, analysis and interpretation","volume":"52","author":"Pang","year":"2024","journal-title":"Nucleic Acids Res"},{"key":"B32","doi-asserted-by":"publisher","DOI":"10.1016\/j.pep.2010.12.002","article-title":"Production of biologically active complement factor H in therapeutically useful quantities","volume":"76","author":"Schmidt","year":"2011","journal-title":"Protein Expression Purification"},{"key":"B33","doi-asserted-by":"publisher","DOI":"10.1016\/0165-2478(81)90078-X","article-title":"Involvement of membrane-associated sialic acid in the resistance of sheep erythrocytes to lysis by mouse complement","volume":"3","author":"Rademaker","year":"1981","journal-title":"Immunol Letters"},{"key":"B34","doi-asserted-by":"publisher","DOI":"10.1542\/peds.110.2.371","article-title":"Invasive pneumococcal disease and hemolytic uremic syndrome","volume":"110","author":"Brandt","year":"2002","journal-title":"Pediatrics"},{"key":"B35","doi-asserted-by":"publisher","DOI":"10.1542\/peds.102.5.1087","article-title":"Three-year multicenter surveillance of pneumococcal meningitis in children: clinical characteristics, and outcome related to penicillin susceptibility and dexamethasone use","volume":"102","author":"Arditi","year":"1998","journal-title":"Pediatrics"},{"key":"B36","doi-asserted-by":"publisher","DOI":"10.1053\/j.ajkd.2004.10.018","article-title":"Successful plasma therapy for atypical hemolytic uremic syndrome caused by factor H deficiency owing to a novel mutation in the complement cofactor protein domain 15","volume":"45","author":"Licht","year":"2005","journal-title":"Am J Kidney Dis"},{"key":"B37","doi-asserted-by":"publisher","DOI":"10.1093\/clinchem\/48.5.781","article-title":"Hemolytic uremic syndrome attributable to Streptococcus pneumoniae infection: a novel cause for secondary protein N-glycan abnormalities","volume":"48","author":"de Loos","year":"2002","journal-title":"Clin Chem"},{"key":"B38","doi-asserted-by":"publisher","DOI":"10.1093\/ndt\/gft198","article-title":"The role of complement in Streptococcus pneumoniae-associated haemolytic uraemic syndrome","volume":"28","author":"Szil\u00e1gyi","year":"2013","journal-title":"Nephrol Dial Transpl"},{"key":"B39","doi-asserted-by":"publisher","DOI":"10.3389\/fcimb.2022.929483","article-title":"Streptococcus pneumoniae interactions with the complement system","volume":"12","author":"Gil","year":"2022","journal-title":"Front Cell Infection Microbiol"},{"key":"B40","doi-asserted-by":"publisher","DOI":"10.1128\/IAI.70.10.5604-5611.2002","article-title":"The human complement regulator factor H binds pneumococcal surface protein PspC via short consensus repeats 13 to 15","volume":"70","author":"Duthy","year":"2002","journal-title":"Infect Immun"},{"key":"B41","doi-asserted-by":"publisher","DOI":"10.3389\/fmicb.2017.00224","article-title":"Role of streptococcus pneumoniae proteins in evasion of complement-mediated immunity","volume":"8","author":"Andre","year":"2017","journal-title":"Front Microbiol"},{"key":"B42","doi-asserted-by":"publisher","DOI":"10.1002\/1873-3468.13045","article-title":"Glycan-metabolizing enzymes in microbe-host interactions: the Streptococcus pneumoniae paradigm","volume":"592","author":"Hobbs","year":"2018","journal-title":"FEBS Lett"},{"key":"B43","doi-asserted-by":"publisher","DOI":"10.1159\/000334775","article-title":"Bacterial hydrolysis of host glycoproteins - powerful protein modification and efficient nutrient acquisition","volume":"4","author":"Garbe","year":"2012","journal-title":"J Innate Immun"},{"key":"B44","doi-asserted-by":"publisher","DOI":"10.1111\/j.1365-2958.2005.04984.x","article-title":"Deglycosylation of human glycoconjugates by the sequential activities of exoglycosidases expressed by Streptococcus pneumoniae","volume":"59","author":"King","year":"2006","journal-title":"Mol Microbiol"},{"key":"B45","doi-asserted-by":"publisher","first-page":"107257","DOI":"10.1016\/j.isci.2023.107257","article-title":"Impact of infection on proteome-wide glycosylation revealed by distinct signatures for bacterial and viral pathogens","volume":"26","author":"Willems","year":"2023","journal-title":"iScience"},{"key":"B46","doi-asserted-by":"publisher","DOI":"10.1681\/ASN.2015070745","article-title":"Moss-produced, glycosylation-optimized human factor H for therapeutic application in complement disorders","volume":"28","author":"Michelfelder","year":"2017","journal-title":"J Am Soc Nephrol"},{"key":"B47","doi-asserted-by":"publisher","DOI":"10.1128\/AEM.03440-13","article-title":"The sialidases of clostridium perfringens type D strain CN3718 differ in their properties and sensitivities to inhibitors","volume":"80","author":"Li","year":"2014","journal-title":"Appl Environ Microbiol"},{"key":"B48","doi-asserted-by":"publisher","DOI":"10.14202\/vetworld.","article-title":"Potency of bacterial sialidase Clostridium perfringens as antiviral of Newcastle disease infections using embryonated chicken egg in ovo model","volume":"15","author":"Kurnia","year":"2022","journal-title":"Veterinary World"},{"key":"B49","doi-asserted-by":"publisher","first-page":"101341","DOI":"10.1016\/j.smim.2019.101341","article-title":"Regulation of regulators: Role of the complement factor H-related proteins","volume":"45","author":"Cserhalmi","year":"2019","journal-title":"Semin Immunol"},{"key":"B50","doi-asserted-by":"publisher","first-page":"25","DOI":"10.1111\/imr.13166","article-title":"The Factor H protein family: The switchers of the complement alternative pathway","volume":"313","author":"Lucientes-Continente","year":"2023","journal-title":"Immunol Rev"},{"key":"B51","doi-asserted-by":"publisher","DOI":"10.1016\/j.semcdb.2017.12.018","article-title":"Complement factor H family proteins in their non-canonical role as modulators of cellular functions","volume":"85","author":"J\u00f3zsi","year":"2019","journal-title":"Semin Cell Dev Biol"},{"key":"B52","doi-asserted-by":"publisher","DOI":"10.1074\/jbc.R000004200","article-title":"The leukocyte integrins*","volume":"275","author":"Harris","year":"2000","journal-title":"J Biol Chem"},{"key":"B53","doi-asserted-by":"publisher","first-page":"49","DOI":"10.1016\/j.molimm.2012.11.006","article-title":"The molecular basis of leukocyte recruitment and its deficiencies","volume":"55","author":"Schmidt","year":"2013","journal-title":"Mol Immunol"},{"key":"B54","doi-asserted-by":"publisher","DOI":"10.1042\/BSR20110101","article-title":"The leucocyte \u03b22 (CD18) integrins: the structure, functional regulation and signalling properties","volume":"32","author":"Tan","year":"2012","journal-title":"Biosci Rep"},{"key":"B55","doi-asserted-by":"publisher","DOI":"10.1038\/s41581-019-0129-4","article-title":"Glycosylation in health and disease","volume":"15","author":"Reily","year":"2019","journal-title":"Nat Rev Nephrol"},{"key":"B56","doi-asserted-by":"publisher","DOI":"10.3389\/fimmu.2023.1188838","article-title":"The role of N-glycosylation in B-cell biology and IgG activity. The aspects of autoimmunity and anti-inflammatory therapy","volume":"14","author":"Trzos","year":"2023","journal-title":"Front Immunol"},{"key":"B57","doi-asserted-by":"publisher","DOI":"10.1021\/cr990294a","article-title":"Glycosylation and the complement system","volume":"102","author":"Ritchie","year":"2002","journal-title":"Chem Rev"},{"key":"B58","doi-asserted-by":"publisher","DOI":"10.1093\/nar\/gkae1011","article-title":"The PRIDE database at 20 years: 2025 update","volume":"53","author":"Perez-Riverol","year":"2025","journal-title":"Nucleic Acids Res"}],"container-title":["Frontiers in Immunology"],"original-title":[],"link":[{"URL":"https:\/\/www.frontiersin.org\/articles\/10.3389\/fimmu.2025.1645196\/full","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,8,21]],"date-time":"2025-08-21T05:29:02Z","timestamp":1755754142000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.frontiersin.org\/articles\/10.3389\/fimmu.2025.1645196\/full"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,8,21]]},"references-count":58,"alternative-id":["10.3389\/fimmu.2025.1645196"],"URL":"https:\/\/doi.org\/10.3389\/fimmu.2025.1645196","relation":{},"ISSN":["1664-3224"],"issn-type":[{"value":"1664-3224","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,8,21]]},"article-number":"1645196"}}