{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,27]],"date-time":"2026-10-27T20:32:07Z","timestamp":1793133127043,"version":"4.5.0"},"reference-count":18,"publisher":"American Society for Microbiology","issue":"9","license":[{"start":{"date-parts":[[2026,9,22]],"date-time":"2026-09-22T00:00:00Z","timestamp":1790035200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"},{"start":{"date-parts":[[2026,9,22]],"date-time":"2026-09-22T00:00:00Z","timestamp":1790035200000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/journals.asm.org\/non-commercial-tdm-license"}],"content-domain":{"domain":["journals.asm.org"],"crossmark-restriction":true},"short-container-title":["J Virol"],"published-print":{"date-parts":[[2026,9,22]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                  <jats:sec>\n                    <jats:title\/>\n                    <jats:p>\n                      SARS-CoV-2 antibody neutralization is a correlate of protection for COVID-19 and has been used to guide public health decisions. However, there is no standard neutralization assay, and absolute titers differ between assays. To investigate mechanisms causing these absolute titer differences, we compared 28 samples with three assays: a live virus cytopathic effect (CPE)-based microneutralization assay, a live virus focus reduction (immunospot, IS) assay, and a pseudotyped virus luciferase expression reduction (pseudovirus, PV) assay. We found significant correlations between all assays (\u03c1 &gt; 0.95 and\n                      <jats:italic toggle=\"yes\">P<\/jats:italic>\n                      &lt; 0.0001 for all pairwise comparisons), but also significant differences in absolute titers by assay (paired\n                      <jats:italic toggle=\"yes\">t<\/jats:italic>\n                      -tests\n                      <jats:italic toggle=\"yes\">P<\/jats:italic>\n                      &lt; 0.001). IS and PV assays that assess neutralization as the titer required to reduce foci\/luminescence by 50% had the smallest difference, with 1.2-fold higher IS assay titers (95% confidence interval, CI: 1.2\u20131.2). CPE assay titers were 5.5-fold lower (95% CI: 5.4\u20135.5) than in the IS assay. We show that these differences can be explained (i) by accounting for the size of inoculum being neutralized (half the infectious virions in the IS and PV assays, \u201cper virion,\u201d and the entire inoculum half the time in the CPE assay, \u201cper well\u201d) and (ii) by removing serum during the 5-day culture in the CPE assay (so serum can only neutralize the inoculum, rather than acting on the inoculum and slowing viral growth during culture). These findings highlight areas for more precise and harmonized terminology and particular assay elements that must be considered in efforts to harmonize neutralization assays.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>IMPORTANCE<\/jats:title>\n                    <jats:p>Protection against COVID-19 is related to how well serum antibodies neutralize SARS-CoV-2. This neutralization can be assessed using different assays, which often provide significantly different estimates. To better understand why assay results vary, we compared three commonly used types of neutralization assay. We found both strong correlations and significant differences in measured neutralization between the different assays. Differences in the type of virus (live SARS-CoV-2 virus compared to a pseudotyped virus with SARS-CoV-2 spike protein), how long cells, virus, and antibody were allowed to interact, and whether neutralization of a batch of virions (\u201cper well\u201d neutralization) or individual infectious virions (\u201cper virion\u201d) was measured, all impacted virus neutralization. Understanding which factors have the largest impact on the differences between neutralization assays is an important first step toward harmonization of neutralization assays across the field.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1128\/jvi.00823-26","type":"journal-article","created":{"date-parts":[[2026,8,27]],"date-time":"2026-08-27T13:00:44Z","timestamp":1787835644000},"update-policy":"https:\/\/doi.org\/10.1128\/asmj-crossmark-policy-page","source":"Crossref","is-referenced-by-count":0,"title":["Reconciliation of titer differences between SARS-CoV-2 neutralizing antibody assays"],"prefix":"10.1128","volume":"100","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-5129-8180","authenticated-orcid":true,"given":"Eva","family":"Stadler","sequence":"first","affiliation":[{"id":[{"id":"https:\/\/ror.org\/03r8z3t63","id-type":"ROR","asserted-by":"publisher"}],"name":"Infection Analytics Program, Kirby Institute, UNSW Sydney","place":["Sydney, Australia"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3754-2642","authenticated-orcid":true,"given":"Francesca","family":"Mordant","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/01ej9dk98","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Microbiology and Immunology, University of Melbourne, at the Peter Doherty Institute for Infection and Immunity, Parkville","place":["Melbourne, Australia"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Matthew","family":"Gartner","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/01ej9dk98","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Microbiology and Immunology, University of Melbourne, at the Peter Doherty Institute for Infection and Immunity, Parkville","place":["Melbourne, Australia"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3771-5504","authenticated-orcid":true,"given":"Steffen S.","family":"Docken","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/03r8z3t63","id-type":"ROR","asserted-by":"publisher"}],"name":"Infection Analytics Program, Kirby Institute, UNSW Sydney","place":["Sydney, Australia"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Miles P.","family":"Davenport","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/03r8z3t63","id-type":"ROR","asserted-by":"publisher"}],"name":"Infection Analytics Program, Kirby Institute, UNSW Sydney","place":["Sydney, Australia"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2663-1551","authenticated-orcid":true,"given":"David S.","family":"Khoury","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/03r8z3t63","id-type":"ROR","asserted-by":"publisher"}],"name":"Infection Analytics Program, Kirby Institute, UNSW Sydney","place":["Sydney, Australia"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1713-3056","authenticated-orcid":true,"given":"Kanta","family":"Subbarao","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/01ej9dk98","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Microbiology and Immunology, University of Melbourne, at the Peter Doherty Institute for Infection and Immunity, Parkville","place":["Melbourne, Australia"]},{"name":"WHO Collaborating Centre for Reference and Research on Influenza, VIDRL at the Doherty Institute for Infection and Immunity","place":["Melbourne, Australia"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"235","reference":[{"key":"e_1_3_4_2_2","doi-asserted-by":"publisher","DOI":"10.1038\/s41591-021-01377-8"},{"key":"e_1_3_4_3_2","doi-asserted-by":"publisher","DOI":"10.1016\/S2666-5247(21)00267-6"},{"key":"e_1_3_4_4_2","doi-asserted-by":"publisher","DOI":"10.1016\/S2666-5247(23)00194-5"},{"key":"e_1_3_4_5_2","doi-asserted-by":"publisher","DOI":"10.1038\/s41467-022-35768-3"},{"key":"e_1_3_4_6_2","doi-asserted-by":"publisher","DOI":"10.1056\/NEJMc2404555"},{"key":"e_1_3_4_7_2","volume-title":"Vaccines and Related Biological Products Advisory Committee Meeting","author":"FDA","year":"2021","unstructured":"FDA. 2021. Licensure and emergeny use authorization of vaccines to prevent COVID-19 for use in pediatric populations (10\/06\/2021). Vaccines and Related Biological Products Advisory Committee Meeting. https:\/\/www.fda.gov\/media\/149935\/download."},{"key":"e_1_3_4_8_2","unstructured":"WHO. 2023. Good practice statement on the use of variant-containing COVID-19 vaccines (20\/02\/2023). Available from: https:\/\/iris.who.int\/server\/api\/core\/bitstreams\/41e46f17d\u201340b53\u201344e45b\u2013a530\u2013566dbbb259ab537\/content"},{"key":"e_1_3_4_9_2","unstructured":"Australian Technical Advisory Group on Immunisation (ATAGI). 2023. Recommendations on the use of a 3rd primary dose of COVID-19 vaccine in individuals who are severely immunocompromised (01\/03\/2023). Available from: https:\/\/www.eviq.org.au\/getmedia\/4c0f9f3f\u2013a290\u2013249a299\u2013a222a\u2013198fc294f254d247\/atagi\u2013recommendations\u2013on\u2013the\u2013use\u2013of\u2013a\u2013third\u2013primary\u2013dose\u2013of\u2013covid\u2013219\u2013vaccine\u2013in\u2013individuals\u2013who\u2013are\u2013severely\u2013immunocompromised.pdf"},{"key":"e_1_3_4_10_2","doi-asserted-by":"publisher","DOI":"10.3390\/v16121936"},{"key":"e_1_3_4_11_2","doi-asserted-by":"publisher","DOI":"10.1038\/s41392-023-01389-5"},{"key":"e_1_3_4_12_2","doi-asserted-by":"publisher","DOI":"10.1038\/s41577-020-00471-1"},{"key":"e_1_3_4_13_2","doi-asserted-by":"publisher","DOI":"10.1126\/scitranslmed.adl1722"},{"key":"e_1_3_4_14_2","volume-title":"Expert Committee on Biological Standardization","author":"World Health Organization (WHO)","year":"2020","unstructured":"World Health Organization (WHO). 2020. Establishment of the WHO international standard and reference panel for anti-SAR-CoV-2 antibody. Expert Committee on Biological Standardization; Geneva."},{"key":"e_1_3_4_15_2","doi-asserted-by":"publisher","DOI":"10.3201\/eid2902.221422"},{"key":"e_1_3_4_16_2","doi-asserted-by":"publisher","DOI":"10.1038\/s41591-020-0995-0"},{"key":"e_1_3_4_17_2","doi-asserted-by":"publisher","DOI":"10.1038\/s41596-021-00536-y"},{"key":"e_1_3_4_18_2","unstructured":"National Institute for Biological Standards and Control (NIBSC). 2022. 1st International Standard for antibodies to SARS-CoV-2 variants of concern (NIBSC code: 21\/338). https:\/\/nibsc.org\/documents\/ifu\/21\u2013338.pdf."},{"key":"e_1_3_4_19_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.vaccine.2022.03.064"}],"container-title":["Journal of Virology"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/journals.asm.org\/doi\/pdf\/10.1128\/jvi.00823-26","content-type":"application\/pdf","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/journals.asm.org\/doi\/pdf\/10.1128\/jvi.00823-26","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,10,27]],"date-time":"2026-10-27T19:32:46Z","timestamp":1793129566000},"score":1,"resource":{"primary":{"URL":"https:\/\/journals.asm.org\/doi\/10.1128\/jvi.00823-26"}},"subtitle":[],"editor":[{"given":"Stacey","family":"Schultz-Cherry","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"editor"}]}],"short-title":[],"issued":{"date-parts":[[2026,9,22]]},"references-count":18,"journal-issue":{"issue":"9","published-print":{"date-parts":[[2026,9,22]]}},"alternative-id":["10.1128\/jvi.00823-26"],"URL":"https:\/\/doi.org\/10.1128\/jvi.00823-26","relation":{},"ISSN":["0022-538X","1098-5514"],"issn-type":[{"value":"0022-538X","type":"print"},{"value":"1098-5514","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,9,22]]},"assertion":[{"value":"2026-05-26","order":0,"name":"received","label":"Received","group":{"name":"publication_history","label":"Publication History"}},{"value":"2026-07-29","order":2,"name":"accepted","label":"Accepted","group":{"name":"publication_history","label":"Publication History"}},{"value":"2026-08-27","order":3,"name":"published","label":"Published","group":{"name":"publication_history","label":"Publication History"}}],"article-number":"e00823-26"}}