{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T09:29:33Z","timestamp":1785403773378,"version":"3.56.0"},"reference-count":25,"publisher":"MDPI AG","issue":"5","license":[{"start":{"date-parts":[[2026,5,20]],"date-time":"2026-05-20T00:00:00Z","timestamp":1779235200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100014101","name":"Novavax, Inc.","doi-asserted-by":"crossref","id":[{"id":"10.13039\/100014101","id-type":"DOI","asserted-by":"crossref"}]},{"id":[{"id":"https:\/\/ror.org\/05qa6yx98","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Microorganisms"],"abstract":"<jats:p>Mucosal immunity, including antibodies like immunoglobulin A (IgA), function as the body\u2019s first line of defense in the respiratory tract, particularly against viruses. An anti-rS protein IgA enzyme-linked immunosorbent assay (ELISA) was developed using the Omicron XBB.1.5 subvariant of SARS-CoV-2 and was validated to demonstrate the suitability of the method for testing saliva from SARS-CoV-2 vaccine clinical trials. This assay successfully met acceptance criteria for inter-\/intra-assay precision, specificity, selectivity, linearity, lower\/upper limits of quantitation, and assay robustness. The IgA in saliva was stable for up to 7 freeze\/thaw cycles, for up to 48 h at 24 \u00b0C, up to 7 days at 4 \u00b0C, up to 3 weeks at \u221220 \u00b0C, and up to 1 year at \u221280 \u00b0C. After validation using Omicron XBB.1.5 rS protein, cross-reactivity was demonstrated with the SARS-CoV-2 variant JN.1. This validated IgA assay can be a valuable tool to assess mucosal IgA levels in SARS-CoV-2 clinical trials.<\/jats:p>","DOI":"10.3390\/microorganisms14051154","type":"journal-article","created":{"date-parts":[[2026,5,20]],"date-time":"2026-05-20T09:12:41Z","timestamp":1779268361000},"page":"1154","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Validation of a Mucosal IgA Assay for SARS-CoV-2"],"prefix":"10.3390","volume":"14","author":[{"ORCID":"https:\/\/orcid.org\/0009-0005-1628-7442","authenticated-orcid":false,"given":"Mingzhu","family":"Zhu","sequence":"first","affiliation":[{"name":"Clinical Immunology, Novavax, Gaithersburg, MD 20878, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Edmond","family":"Massuda","sequence":"additional","affiliation":[{"name":"Clinical Immunology, Novavax, Gaithersburg, MD 20878, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Shane","family":"Cloney-Clark","sequence":"additional","affiliation":[{"name":"Clinical Immunology, Novavax, Gaithersburg, MD 20878, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2995-1515","authenticated-orcid":false,"given":"Urvashi","family":"Patel","sequence":"additional","affiliation":[{"name":"Clinical Immunology, Novavax, Gaithersburg, MD 20878, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Anand","family":"Parekh","sequence":"additional","affiliation":[{"name":"Clinical Immunology, Novavax, Gaithersburg, MD 20878, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Andrew","family":"Gorinson","sequence":"additional","affiliation":[{"name":"Clinical Immunology, Novavax, Gaithersburg, MD 20878, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Andrew","family":"Klindworth","sequence":"additional","affiliation":[{"name":"Clinical Immunology, Novavax, Gaithersburg, MD 20878, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ali","family":"Ahmadi","sequence":"additional","affiliation":[{"name":"Clinical Immunology, Novavax, Gaithersburg, MD 20878, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Miranda R.","family":"Cai","sequence":"additional","affiliation":[{"name":"Biostatistics, Novavax, Gaithersburg, MD 20878, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Chijioke","family":"Bennett","sequence":"additional","affiliation":[{"name":"Clinical Development, Novavax, Gaithersburg, MD 20878, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Raj","family":"Kalkeri","sequence":"additional","affiliation":[{"name":"Clinical Immunology, Novavax, Gaithersburg, MD 20878, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Joyce S.","family":"Plested","sequence":"additional","affiliation":[{"name":"Clinical Immunology, Novavax, Gaithersburg, MD 20878, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,5,20]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"de Sousa-Pereira, P., and Woof, J.M. (2019). IgA: Structure, Function, and Developability. Antibodies, 8.","DOI":"10.3390\/antib8040057"},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Quinti, I., Mortari, E.P., Fernandez Salinas, A., Milito, C., and Carsetti, R. (2021). IgA Antibodies and IgA Deficiency in SARS-CoV-2 Infection. Front. Cell. Infect. Microbiol., 11.","DOI":"10.3389\/fcimb.2021.655896"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"eabd2223","DOI":"10.1126\/scitranslmed.abd2223","article-title":"IgA dominates the early neutralizing antibody response to SARS-CoV-2","volume":"13","author":"Sterlin","year":"2021","journal-title":"Sci. Transl. Med."},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Tyagi, R., Basu, S., Dhar, A., Gupta, S., Gupta, S.L., and Jaiswal, R.K. (2023). Role of Immunoglobulin A in COVID-19 and Influenza Infections. Vaccines, 11.","DOI":"10.3390\/vaccines11111647"},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Amellal, H., Assaid, N., Charoute, H., Akarid, K., Maaroufi, A., Ezzikouri, S., and Sarih, M. (2023). Kinetics of specific anti-SARS-CoV-2 IgM, IgA, and IgG responses during the first 12 months after SARS-CoV-2 infection: A prospective longitudinal study. PLoS ONE, 18.","DOI":"10.1371\/journal.pone.0288557"},{"key":"ref_6","first-page":"665","article-title":"Longitudinal profile of immunoglobulin G (IgG), IgM, and IgA antibodies against the severe acute respiratory syndrome (SARS) coronavirus nucleocapsid protein in patients with pneumonia due to the SARS coronavirus","volume":"11","author":"Woo","year":"2004","journal-title":"Clin. Diagn. Lab. Immunol."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"799","DOI":"10.1038\/s41385-022-00511-0","article-title":"Systemic and mucosal IgA responses are variably induced in response to SARS-CoV-2 mRNA vaccination and are associated with protection against subsequent infection","volume":"15","author":"Isho","year":"2022","journal-title":"Mucosal Immunol."},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Brackett, C., Zhang, L., Do, B.T.N., Baral, S., Fisher, L.H., Hahn, W.O., Carnacchi, A.J., Hilliard, S.T., Li, S.S., and Premkumar, L. (2026). Early rise in nasal secretory IgA associated with shorter duration of SARS-CoV-2 virus shedding in an acute infection cohort. Front. Immunol., 17.","DOI":"10.3389\/fimmu.2026.1722585"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"121","DOI":"10.1093\/infdis\/jiae447","article-title":"Early, Robust Mucosal Secretory Immunoglobulin A but not Immunoglobulin G Response to Severe Acute Respiratory Syndrome Coronavirus 2 Spike in Oral Fluid Is Associated with Faster Viral Clearance and Coronavirus Disease 2019 Symptom Resolution","volume":"231","author":"Pisanic","year":"2025","journal-title":"J. Infect. Dis."},{"key":"ref_10","first-page":"e55","article-title":"Mucosal IgA against SARS-CoV-2 Omicron Infection","volume":"387","author":"Zuo","year":"2022","journal-title":"N. Engl. J. Med."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"106428","DOI":"10.1016\/j.jinf.2025.106428","article-title":"Safety and immunogenicity of Omicron protein vaccines in mRNA-vaccinated adolescents: A phase 3, randomised trial","volume":"90","author":"Bennett","year":"2025","journal-title":"J. Infect."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"e70645","DOI":"10.1002\/jmv.70645","article-title":"Detection of Anti-SARS-CoV-2 Mucosal Immunoglobulin A in Clinical Saliva Samples After a Dose of Novavax COVID-19 Vaccine","volume":"97","author":"Zhu","year":"2025","journal-title":"J. Med. Virol."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1067","DOI":"10.1080\/17576180.2024.2411925","article-title":"Harmonization of Vaccine Ligand Binding Assays Validation","volume":"16","author":"Dessy","year":"2024","journal-title":"Bioanalysis"},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Gould, V.M.W., Francis, J.N., Anderson, K.J., Georges, B., Cope, A.V., and Tregoning, J.S. (2017). Nasal IgA Provides Protection against Human Influenza Challenge in Volunteers with Low Serum Influenza Antibody Titre. Front. Microbiol., 8.","DOI":"10.3389\/fmicb.2017.00900"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"2253598","DOI":"10.1080\/21645515.2023.2253598","article-title":"The SeroNet Clinical and Translational Serology Task Force (CTTF) SARS-CoV-2 mucosal immunity methodological considerations and best practices workshop","volume":"19","author":"Hempel","year":"2023","journal-title":"Hum. Vaccin. Immunother."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"75","DOI":"10.1111\/imr.13118","article-title":"Guardians of the oral and nasopharyngeal galaxy: IgA and protection against SARS-CoV-2 infection","volume":"309","author":"Sanders","year":"2022","journal-title":"Immunol. Rev."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"1913","DOI":"10.1038\/s41590-024-01951-5","article-title":"Mucosal adenovirus vaccine boosting elicits IgA and durably prevents XBB.1.16 infection in nonhuman primates","volume":"25","author":"Gagne","year":"2024","journal-title":"Nat. Immunol."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"17","DOI":"10.1038\/s41541-024-00806-2","article-title":"Three immunizations with Novavax\u2019s protein vaccines increase antibody breadth and provide durable protection from SARS-CoV-2","volume":"9","author":"Lenart","year":"2024","journal-title":"NPJ Vaccines"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"104468","DOI":"10.1016\/j.jcv.2020.104468","article-title":"Evaluation of the EUROIMMUN Anti-SARS-CoV-2 ELISA Assay for detection of IgA and IgG antibodies","volume":"129","author":"Beavis","year":"2020","journal-title":"J. Clin. Virol."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"10366","DOI":"10.1038\/s41598-022-14294-8","article-title":"On the caveats of a multiplex test for SARS-CoV-2 to detect seroconversion after infection or vaccination","volume":"12","author":"Ferreira","year":"2022","journal-title":"Sci. Rep."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"1500","DOI":"10.4049\/jimmunol.2100934","article-title":"Development and Validation of an Enzyme Immunoassay for Detection and Quantification of SARS-CoV-2 Salivary IgA and IgG","volume":"208","author":"Costantini","year":"2022","journal-title":"J. Immunol."},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Varadhachary, A., Chatterjee, D., Garza, J., Garr, R.P., Foley, C., Letkeman, A., Dean, J., Haug, D., Breeze, J., and Traylor, R. (2020). Salivary anti-SARS-CoV-2 IgA as an accessible biomarker of mucosal immunity against COVID-19. medRxiv.","DOI":"10.1101\/2020.08.07.20170258"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"63","DOI":"10.1080\/08998280.2020.1829261","article-title":"Antibody tests for COVID-19","volume":"34","author":"Kopel","year":"2020","journal-title":"Bayl. Univ. Med. Cent. Proc."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"e0106522","DOI":"10.1128\/jcm.01065-22","article-title":"Salivary IgAs and Their Role in Mucosal Neutralization of SARS-CoV-2 Variants of Concern","volume":"60","author":"Diem","year":"2022","journal-title":"J. Clin. Microbiol."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"RP88387","DOI":"10.7554\/eLife.88387","article-title":"Comprehensive analysis of nasal IgA antibodies induced by intranasal administration of the SARS-CoV-2 spike protein","volume":"12","author":"Waki","year":"2025","journal-title":"eLife"}],"container-title":["Microorganisms"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2076-2607\/14\/5\/1154\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,5,22]],"date-time":"2026-05-22T04:19:57Z","timestamp":1779423597000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2076-2607\/14\/5\/1154"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,5,20]]},"references-count":25,"journal-issue":{"issue":"5","published-online":{"date-parts":[[2026,5]]}},"alternative-id":["microorganisms14051154"],"URL":"https:\/\/doi.org\/10.3390\/microorganisms14051154","relation":{},"ISSN":["2076-2607"],"issn-type":[{"value":"2076-2607","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,5,20]]}}}