{ "abstract": "Background: Treponema pallidum subsp. endemicum (TEN), the causative agent of bejel, is a nonvenereal treponematosis that occurs mainly in arid regions such as Africa and the Middle East. Recently, sexually transmitted TEN infections have been reported outside endemic regions, but their serological characteristics and treatment responses remain unclear. Methodology/principal findings: We analyzed 6 genetically confirmed bejel patients and 9 syphilis patients in Japan. Serum treponemal (TP) and non-treponemal (RPR) antibody titers were quantified at baseline and post-treatment using latex agglutination test (LA). The analysis of antibody profiles was performed with an immunoblot assay detecting IgM and IgG antibodies against Tp47, TmpA, Tp17, and Tp15. Phylogenetic analysis based on concatenated tp0548 and tp0856 sequences identified 6 bejel cases (TEN). Changes in TP and RPR antibody titers following treatment showed no apparent difference between bejel and syphilis groups. In both groups, some IgM antibodies decreased following treatment, while some IgG antibodies increased. Conclusions/significance: The serological profiles and post-treatment changes in antibody titers were similar between bejel patients and syphilis patients. These findings suggest that conventional serological assays developed for syphilis may also be useful for clinical management of bejel, including evaluation of treatment response. This study provides new insight into the diagnosis and serological monitoring of sexually transmitted bejel cases outside endemic areas. Author summary: Bejel, caused by Treponema pallidum subsp. endemicum (TEN), is one of the endemic treponematoses transmitted mainly through nonsexual contact in arid regions such as the Middle East and the Sahel region of Africa. However, recent reports have identified sexually transmitted TEN infections outside endemic areas. In Japan, we investigated 6 genetically confirmed bejel cases and compared them with 9 cases of Treponema pallidum subsp. pallidum (TPA) infection, which causes syphilis. Serological testing demonstrated that both bejel and syphilis patients showed similar patterns of treponemal (TP) and non-treponemal (RPR) antibody responses at baseline and post-treatment. Treponemal antibody profiles were comparable between bejel and syphilis patients. These findings suggest that existing serological assays for syphilis may be useful for the clinical management of bejel patients, providing valuable insights into the diagnosis and monitoring of this neglected treponemal disease.", "abstract_shown": true, "affiliations": [ "Customer Support Center, Diagnostics Division, Sekisui Medical Co., Ltd., Tokyo, Japan", "Diagnostic Product Development Department, Research & Development, Sekisui Medical Co., Ltd., Tokyo, Japan", "Division of Microbiology, Osaka Institute of Public Health, Osaka, Japan", "Sonezaki Furubayashi Clinic, Osaka, Japan" ], "article_type": "Research Article", "arxiv": null, "author_total": 7, "authors": [ { "affs": [ 0 ], "name": "Yu-ki Deno" }, { "affs": [ 1 ], "name": "Keiyu Yamamoto" }, { "affs": [ 2 ], "name": "Mie Matsumoto" }, { "affs": [ 3 ], "name": "Toshihiko Fujikawa" }, { "name": "Fumiya Banno" }, { "name": "Takuya Kawahata" }, { "name": "Keiichi Furubayashi" } ], "bibtex": "https://research.draconitic.com/paper/et80qdp9x78dh.bib", "cited_by": 0, "doi": "10.1371/journal.pntd.0014756", "fulltext_url": "https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0014756", "id": "et80qdp9x78dh", "issns": [ "1935-2735", "1935-2727" ], "landing_url": "https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0014756", "language": "eng", "licence": "CC-BY", "licence_label": "CC BY", "licence_source": "article", "licence_url": "https://creativecommons.org/licenses/by/4.0/", "metadata_licence": null, "native_subjects": [ [ "openalex", "2737|Syphilis Diagnosis and Treatment" ], [ "plos", "/Biology and life sciences/Evolutionary biology/Evolutionary systematics/Phylogenetics/Phylogenetic analysis" ], [ "plos", "/Biology and life sciences/Immunology/Clinical immunology/Antibody therapy" ], [ "plos", "/Biology and life sciences/Microbiology/Medical microbiology/Microbial pathogens/Bacterial pathogens/Treponema pallidum" ], [ "plos", "/Biology and life sciences/Taxonomy/Evolutionary systematics/Phylogenetics/Phylogenetic analysis" ], [ "plos", "/Computer and information sciences/Data management/Taxonomy/Evolutionary systematics/Phylogenetics/Phylogenetic analysis" ], [ "plos", "/Medicine and health sciences/Clinical medicine/Clinical immunology/Antibody therapy" ], [ "plos", "/Medicine and health sciences/Clinical medicine/Signs and symptoms/Ulcers" ], [ "plos", "/Medicine and health sciences/Immunology/Clinical immunology/Antibody therapy" ], [ "plos", "/Medicine and health sciences/Medical conditions/Infectious diseases/Bacterial diseases/Treponematoses/Bejel" ], [ "plos", "/Medicine and health sciences/Medical conditions/Infectious diseases/Bacterial diseases/Treponematoses/Syphilis" ], [ "plos", "/Medicine and health sciences/Medical conditions/Infectious diseases/Sexually transmitted diseases" ], [ "plos", "/Medicine and health sciences/Medical conditions/Infectious diseases/Sexually transmitted diseases/Syphilis" ], [ "plos", "/Medicine and health sciences/Medical conditions/Tropical diseases/Neglected tropical diseases/Treponematoses/Bejel" ], [ "plos", "/Medicine and health sciences/Medical conditions/Tropical diseases/Neglected tropical diseases/Treponematoses/Syphilis" ], [ "plos", "/Medicine and health sciences/Oncology/Cancer treatment/Antibody therapy" ], [ "plos", "/Medicine and health sciences/Pathology and laboratory medicine/Pathogens/Microbial pathogens/Bacterial pathogens/Treponema pallidum" ], [ "plos", "/Medicine and health sciences/Pathology and laboratory medicine/Serology" ], [ "plos", "/Medicine and health sciences/Urology/Genitourinary infections/Syphilis" ] ], "openalex": "W7222317507", "pdf_url": "https://journals.plos.org/plosntds/article/file?id=10.1371/journal.pntd.0014756&type=printable", "pmcid": "PMC13671511", "pmid": null, "published": "2026-10-01", "publisher": "Public Library of Science", "ris": "https://research.draconitic.com/paper/et80qdp9x78dh.ris", "sources": [ { "first_seen": "2026-10-30T12:17:23Z", "native_id": "10.1371/journal.pntd.0014756", "source": "plos", "url": "https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0014756" }, { "first_seen": "2026-10-30T12:18:29Z", "native_id": "PMC:PMC13671511", "source": "europepmc", "url": "https://europepmc.org/article/PMC/PMC13671511" } ], "subjects": [ { "field": "biology", "origin": "plos:immunology", "subfield": "immunology" }, { "field": "medicine", "origin": "plos:infectious diseases", "subfield": "infectious-disease" } ], "title": "Evaluation of treatment-related serological changes in Treponema pallidum subsp. endemicum infection using latex-based immunoassays, with comparison to Treponema pallidum subsp. pallidum", "title_text": "Evaluation of treatment-related serological changes in Treponema pallidum subsp. endemicum infection using latex-based immunoassays, with comparison to Treponema pallidum subsp. pallidum", "type": "peer-reviewed", "updated_at": "2026-10-30T12:18:29Z", "url": "https://research.draconitic.com/paper/et80qdp9x78dh", "venue": "PLOS Neglected Tropical Diseases", "versions": [] }