{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,1]],"date-time":"2026-10-01T19:28:09Z","timestamp":1790882889494,"version":"4.1.0"},"reference-count":34,"publisher":"MDPI AG","issue":"22","license":[{"start":{"date-parts":[[2025,11,12]],"date-time":"2025-11-12T00:00:00Z","timestamp":1762905600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100015829","name":"Polish Ministry of Health","doi-asserted-by":"crossref","award":["SUBZ.D270.24.072"],"award-info":[{"award-number":["SUBZ.D270.24.072"]}],"id":[{"id":"10.13039\/501100015829","id-type":"DOI","asserted-by":"crossref"}]},{"DOI":"10.13039\/501100015829","name":"Polish Ministry of Health","doi-asserted-by":"crossref","award":["B.SUB.25.323"],"award-info":[{"award-number":["B.SUB.25.323"]}],"id":[{"id":"10.13039\/501100015829","id-type":"DOI","asserted-by":"crossref"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJMS"],"abstract":"<jats:p>In COVID-19 (coronavirus disease 2019), multi-organ complications depend on the immune system\u2019s activity. \u03b11-Acid glycoprotein (AGP) is a highly glycosylated positive acute-phase protein having multifaceted immunomodulatory and protective effects. We were interested in changes in serum AGP concentrations, expression of its glycans, and oxidation-reduction potential (ORP) between severe COVID-19 patients, convalescents, and healthy controls, and whether any of the analyzed parameters could serve as an additional diagnostic biomarker of severe COVID-19 and\/or help monitor recovery. We were also interested in associations between the examined parameters. AGP concentrations were measured using an immunoturbidimetric method. The profile and degree of AGP glycosylation were analyzed using lectin-ELISA with lectins: sialo-specific from Sambucus nigra (SNA) and Maackia amurensis (MAA), fucose-specific from Lotus tetragonolobus (LTA) and Aleuria aurantia (AAL). The static and capacitive ORP (sORP and cORP, respectively) were measured using MiOXSYS C+\u00ae device (Caerus Biotechnologies, Vilnius, Lithuania). Statistica13.3PL software was used for statistical analysis. AGP concentrations increased in COVID-19 patients, showing high clinical usefulness in distinguishing them from convalescents and controls. AGP \u03b12,6-sialylation (reactivity with SNA) was reduced in COVID-19 vs. other study groups, while \u03b12,3-sialylation (reactivity with MAA) was reduced in convalescents vs. controls. The expression of LTA-reactive fucose (Lewisx structures, Lex) was reduced in COVID-19 patients compared to controls and convalescents, but AGP reactivity with AAL did not differ between the study groups. The sORP was reduced, and the cORP was increased in COVID-19. The observed negative correlations between sORP and AGP levels may suggest the antioxidant effect of AGP during severe COVID-19. Higher levels of serum AGP in severe COVID-19, together with low expression of sialic acid \u03b12,6-linked and Lex structures, accompanied by reduced sORP, constitute a characteristic pattern of biomarker expression during severe COVID-19. The increased expression of SNA-reactive sialic acid and Lex structures may reflect the recovery process after SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) infection. The observed negative correlations between AGP and sORP levels may suggest that serum AGP in COVID-19 also plays a role as an antioxidative molecule.<\/jats:p>","DOI":"10.3390\/ijms262210946","type":"journal-article","created":{"date-parts":[[2025,11,12]],"date-time":"2025-11-12T10:56:47Z","timestamp":1762945007000},"page":"10946","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Glycosylation Variability of Serum \u03b11-Acid Glycoprotein in the Context of Developing Inflammation and Oxidative Stress in Patients with Severe COVID-19"],"prefix":"10.3390","volume":"26","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-2948-4574","authenticated-orcid":false,"given":"Ewa Maria","family":"Kratz","sequence":"first","affiliation":[{"name":"Division of Laboratory Diagnostics, Department of Laboratory Diagnostics, Wroclaw Medical University, Borowska Street 211A, 50-556 Wroclaw, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Patrycja","family":"Kossakowska","sequence":"additional","affiliation":[{"name":"Division of Laboratory Diagnostics, Department of Laboratory Diagnostics, Wroclaw Medical University, Borowska Street 211A, 50-556 Wroclaw, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3711-8614","authenticated-orcid":false,"given":"Izabela","family":"Kokot","sequence":"additional","affiliation":[{"name":"Division of Laboratory Diagnostics, Department of Laboratory Diagnostics, Wroclaw Medical University, Borowska Street 211A, 50-556 Wroclaw, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Violetta","family":"Dymicka-Piekarska","sequence":"additional","affiliation":[{"name":"Department of Clinical Laboratory Diagnostics, Medical University of Bialystok, Waszyngtona Street 15A, 15-269 Bialystok, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,11,12]]},"reference":[{"key":"ref_1","unstructured":"World Health Organization (WHO) (2023, September 14). 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