{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,2]],"date-time":"2026-10-02T00:06:02Z","timestamp":1790899562188,"version":"4.1.0"},"reference-count":24,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2026,5,24]],"date-time":"2026-05-24T00:00:00Z","timestamp":1779580800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Western Norway University of Applied Science"},{"id":[{"id":"https:\/\/ror.org\/05phns765","id-type":"ROR","asserted-by":"publisher"}]},{"name":"The Influenza Centre, University of Bergen"},{"name":"Bioingeni\u00f8rfaglig institutt, Oslo"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Viruses"],"abstract":"<jats:p>Background: Lower respiratory tract infections remain a major cause of morbidity and mortality in infants worldwide. Newborns possess an immature immune system but acquire passive immunity through maternal antibodies transferred via the placenta (IgG) and breast milk (IgA). Maternal vaccination may enhance this protection. This study aimed to quantify antibody levels against respiratory viruses in serum and breast milk from lactating women. Methods: Serum and breast milk samples were collected from 26 lactating mothers. Antibody levels were measured using an indirect enzyme-linked immunosorbent assay (ELISA) targeting seven viral antigens: influenza A (A\/Thailand, A\/California), influenza B (B\/Phuket, B\/Austria), SARS-CoV-2 (Spike and receptor-binding domain, RBD) and RSV F pre-fusion protein. Antibody isotypes IgG, IgA and IgM were analysed. Results: Virus-specific IgG and IgA antibodies were detected in all samples. Breast milk showed the highest levels of IgA, whereas serum contained higher IgG levels. A moderate positive correlation was observed between serum and milk IgG. No correlation was found between serum IgG and milk IgA, but both levels were elevated. Conclusions: Breast milk and serum contain relatively high levels of antibodies against the tested respiratory viruses. The elevated levels of serum IgG and milk IgA indicate a coordinated defence between systemic and mucosal immunity in response to infections. The levels and correlation of specific isotypes point to the source of the antibodies: milk IgG probably originates from the blood, whereas milk IgA is produced locally.<\/jats:p>","DOI":"10.3390\/v18060593","type":"journal-article","created":{"date-parts":[[2026,5,25]],"date-time":"2026-05-25T02:32:28Z","timestamp":1779676348000},"page":"593","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Analysing Antibodies Against Respiratory Viruses in Breast Milk: A Pilot Study"],"prefix":"10.3390","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0009-0000-0147-7052","authenticated-orcid":false,"given":"Sindre H.","family":"Hauan","sequence":"first","affiliation":[{"name":"Department of Safety, Chemistry and Biomedical Laboratory Sciences, Western Norway University of Applied Science, Postboks 7030, 5020 Bergen, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0000-3752-1350","authenticated-orcid":false,"given":"Camilla H.","family":"Nundal","sequence":"additional","affiliation":[{"name":"Department of Safety, Chemistry and Biomedical Laboratory Sciences, Western Norway University of Applied Science, Postboks 7030, 5020 Bergen, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sarah","family":"Lartey Jalloh","sequence":"additional","affiliation":[{"name":"Influenza Centre, Department of Clinical Science, University of Bergen, 5020 Bergen, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"June","family":"Skudal","sequence":"additional","affiliation":[{"name":"Department of Safety, Chemistry and Biomedical Laboratory Sciences, Western Norway University of Applied Science, Postboks 7030, 5020 Bergen, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Elin Ekornes","family":"H\u00e5skjold","sequence":"additional","affiliation":[{"name":"Department of Safety, Chemistry and Biomedical Laboratory Sciences, Western Norway University of Applied Science, Postboks 7030, 5020 Bergen, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sigrid Christiansen","family":"B\u00f8e","sequence":"additional","affiliation":[{"name":"Department of Safety, Chemistry and Biomedical Laboratory Sciences, Western Norway University of Applied Science, Postboks 7030, 5020 Bergen, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Camilla","family":"T\u00f8ndel","sequence":"additional","affiliation":[{"name":"Department of Paediatrics, Haukeland University Hospital, 5020 Bergen, Norway"},{"name":"Department of Clinical Science, University of Bergen, 5020 Bergen, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3726-5198","authenticated-orcid":false,"given":"Linn Marie","family":"S\u00f8rbye","sequence":"additional","affiliation":[{"name":"Department of Obstetrics and Gynaecology, Haukeland University Hospital, 5020 Bergen, Norway"},{"name":"Faculty of Health and Social Sciences, Western Norway University of Applied Sciences, 5020 Bergen, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8341-4078","authenticated-orcid":false,"given":"Rebecca J.","family":"Cox","sequence":"additional","affiliation":[{"name":"Influenza Centre, Department of Clinical Science, University of Bergen, 5020 Bergen, Norway"},{"name":"Department of Microbiology, Haukeland University Hospital, 5020 Bergen, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Karl A.","family":"Brokstad","sequence":"additional","affiliation":[{"name":"Department of Safety, Chemistry and Biomedical Laboratory Sciences, Western Norway University of Applied Science, Postboks 7030, 5020 Bergen, Norway"},{"name":"Influenza Centre, Department of Clinical Science, University of Bergen, 5020 Bergen, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,5,24]]},"reference":[{"key":"ref_1","unstructured":"World Health Organization (2026, April 21). 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Nutr."}],"container-title":["Viruses"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1999-4915\/18\/6\/593\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,6,11]],"date-time":"2026-06-11T06:58:44Z","timestamp":1781161124000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1999-4915\/18\/6\/593"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,5,24]]},"references-count":24,"journal-issue":{"issue":"6","published-online":{"date-parts":[[2026,6]]}},"alternative-id":["v18060593"],"URL":"https:\/\/doi.org\/10.3390\/v18060593","relation":{},"ISSN":["1999-4915"],"issn-type":[{"value":"1999-4915","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,5,24]]}}}