{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"institution":[{"name":"medRxiv"}],"indexed":{"date-parts":[[2026,8,7]],"date-time":"2026-08-07T15:27:22Z","timestamp":1786116442994,"version":"build-2736575974"},"posted":{"date-parts":[[2026,8,4]]},"group-title":"Infectious Diseases (except HIV\/AIDS)","reference-count":35,"publisher":"openRxiv","license":[{"start":{"date-parts":[[2026,8,4]],"date-time":"2026-08-04T00:00:00Z","timestamp":1785801600000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"accepted":{"date-parts":[[2026,8,4]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                <jats:sec>\n                  <jats:title>Background<\/jats:title>\n                  <jats:p>\n                    <jats:italic>Shigella<\/jats:italic>\n                    causes an estimated 200 million infections annually, disproportionately affecting children in low- and middle-income countries. Accurate incidence measurement is hindered by brief pathogen shedding and limited diagnostics. Serological approaches can detect infections missed by clinical surveillance but require well-characterized post-infection antibody kinetics.\n                  <\/jats:p>\n                <\/jats:sec>\n                <jats:sec>\n                  <jats:title>Methodology\/Principal findings<\/jats:title>\n                  <jats:p>\n                    We analyzed archived sera from the Study of Shigella Antibody Responses (SOSAR), a longitudinal cohort of 48 individuals with culture- or molecular-confirmed\n                    <jats:italic>Shigella<\/jats:italic>\n                    infection in Dhaka, Bangladesh (2021\u20132022). IgG and IgA responses to five antigens (IpaB and the O-specific polysaccharides [OSP] of\n                    <jats:italic>S. flexneri<\/jats:italic>\n                    2a, 3a, and 6, and\n                    <jats:italic>S. sonnei<\/jats:italic>\n                    ) were measured at baseline and approximately 7, 30, 90, and 180 days post-infection by multiplex bead-based immunoassay, and modeled with a two-phase rise-peak-decay model in a Bayesian hierarchical framework. We compared three estimation approaches: pooled (all infections), serotype-specific (serotype-matched only), and combined\n                    <jats:italic>S. flexneri<\/jats:italic>\n                    (2a and 3a, leveraging cross-reactivity). IgA rose rapidly and returned toward baseline within 2\u2013 3 months across all antigens, whereas IgG remained elevated above baseline throughout 200 days. Children under five showed lower baselines and higher peaks (primary infection); older children showed higher baselines and lower peaks (prior exposure). IpaB responses were elevated across all serotypes, whereas OSP responses were serotype-restricted, with cross-reactivity between\n                    <jats:italic>S. flexneri<\/jats:italic>\n                    2a and 3a.\n                  <\/jats:p>\n                <\/jats:sec>\n                <jats:sec>\n                  <jats:title>Conclusions\/Significance<\/jats:title>\n                  <jats:p>\n                    <jats:italic>Shigella<\/jats:italic>\n                    antibody kinetics are isotype-, antigen-, serotype-, and age-dependent. IgA marks recent infection; IgG reflects longer-term exposure. Pooling antigenically distinct serotypes (\n                    <jats:italic>S. sonnei<\/jats:italic>\n                    ) caused convergence failures, whereas serotype-matched estimation recovered biologically plausible decay. These parameters provide foundational inputs for seroepidemiologic tools and seroincidence estimation in\n                    <jats:italic>Shigella<\/jats:italic>\n                    -endemic settings.\n                  <\/jats:p>\n                <\/jats:sec>\n                <jats:sec>\n                  <jats:title>Author summary<\/jats:title>\n                  <jats:p>\n                    <jats:italic>Shigella<\/jats:italic>\n                    is a leading cause of diarrhea and death in young children, especially in low- resource settings where laboratory diagnosis is limited. Because the bacteria are difficult to detect directly, measuring antibodies in the blood is a promising way to identify people who have recently been infected \u2014 but this requires knowing how antibody levels rise and fall after infection. We followed 48 people with confirmed\n                    <jats:italic>Shigella<\/jats:italic>\n                    infection in Dhaka, Bangladesh, for up to 200 days and tracked their IgG and IgA antibody responses to several\n                    <jats:italic>Shigella<\/jats:italic>\n                    antigens. We found that IgA rose quickly and faded within a few months, whereas IgG remained elevated much longer, and that responses depended on the infecting serotype. These antibody kinetics provide the foundation for tools to estimate how often\n                    <jats:italic>Shigella<\/jats:italic>\n                    infections occur in a community \u2014 information that can guide surveillance, vaccine evaluation, and public-health decisions where the burden is greatest.\n                  <\/jats:p>\n                <\/jats:sec>","DOI":"10.64898\/2026.08.03.26359548","type":"posted-content","created":{"date-parts":[[2026,8,4]],"date-time":"2026-08-04T19:50:11Z","timestamp":1785873011000},"source":"Crossref","is-referenced-by-count":0,"title":["Antibody kinetics following confirmed\n                  <i>Shigella<\/i>\n                  infection: A longitudinal study in Dhaka, Bangladesh"],"prefix":"10.64898","author":[{"ORCID":"https:\/\/orcid.org\/0009-0004-9723-2007","authenticated-orcid":false,"given":"Kwan Ho","family":"Lee","sequence":"first","affiliation":[{"name":"Department of Public Health Sciences, School of Medicine, University of California Davis, Davis, California, United States of America"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Claire","family":"Munroe","sequence":"additional","affiliation":[{"name":"Division of Infectious Diseases, Massachusetts General Hospital, Boston, Massachusetts, United States of America"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ashraful I.","family":"Khan","sequence":"additional","affiliation":[{"name":"International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), Dhaka, Bangladesh"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Fahima","family":"Chowdhury","sequence":"additional","affiliation":[{"name":"International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), Dhaka, Bangladesh"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7139-1086","authenticated-orcid":false,"given":"Samuel","family":"Schildhauer","sequence":"additional","affiliation":[{"name":"Department of Public Health Sciences, School of Medicine, University of California Davis, Davis, California, United States of America"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0004-4326-2905","authenticated-orcid":false,"given":"Natalie","family":"Desilets","sequence":"additional","affiliation":[{"name":"Division of Infectious Diseases, Massachusetts General Hospital, Boston, Massachusetts, United States of America"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jessica C.","family":"Seidman","sequence":"additional","affiliation":[{"name":"Global Immunization, Sabin Vaccine Institute, Washington, DC, United States of America"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Edward T.","family":"Ryan","sequence":"additional","affiliation":[{"name":"Division of Infectious Diseases, Massachusetts General Hospital, Boston, Massachusetts, United States of America"},{"name":"Department of Medicine, Harvard Medical School, Boston, Massachusetts, United States of America"},{"name":"Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, United States of America"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Md. Taufiqur Rahman","family":"Bhuiyan","sequence":"additional","affiliation":[{"name":"International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), Dhaka, Bangladesh"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Firdausi","family":"Qadri","sequence":"additional","affiliation":[{"name":"International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), Dhaka, Bangladesh"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kristen","family":"Aiemjoy","sequence":"additional","affiliation":[{"name":"Department of Public Health Sciences, School of Medicine, University of California Davis, Davis, California, United States of America"},{"name":"Department of Microbiology and Immunology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7195-830X","authenticated-orcid":false,"given":"Douglas E.","family":"Morrison","sequence":"additional","affiliation":[{"name":"Department of Public Health Sciences, School of Medicine, University of California Davis, Davis, California, United States of America"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8881-1849","authenticated-orcid":false,"given":"Richelle C.","family":"Charles","sequence":"additional","affiliation":[{"name":"Division of Infectious Diseases, Massachusetts General Hospital, Boston, Massachusetts, United States of America"},{"name":"Department of Medicine, Harvard Medical School, Boston, Massachusetts, United States of America"},{"name":"Department of Immunology and Infectious Diseases, Harvard T.H. 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