Evaluation of treatment-related serological changes in Treponema pallidum subsp. endemicum infection using latex-based immunoassays, with comparison to Treponema pallidum subsp. pallidum
4 affiliations
- 1Customer Support Center, Diagnostics Division, Sekisui Medical Co., Ltd., Tokyo, Japan
- 2Diagnostic Product Development Department, Research & Development, Sekisui Medical Co., Ltd., Tokyo, Japan
- 3Division of Microbiology, Osaka Institute of Public Health, Osaka, Japan
- 4Sonezaki Furubayashi Clinic, Osaka, Japan
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.
Related
- High transmission risk of Human Immunodeficiency Virus in blood transfusions: A critical evaluation of blood bank serological tests in Mozambique
- Multiplexed hormone immunoassays for women's health on a regenerable silicon photonic chip
- Bos indicus cattle resistant to digital dermatitis exhibit a balanced proinflammatory cytokine response upon exposure to Treponema phagedenis in contrast to Bos taurus cattle
- Neutrophil-derived oncostatin m contributes to endothelial cell dysfunction during Treponema denticola interaction
- Continental-scale survey of Treponema pallidum in African nonhuman primates: expanding the range to the Mediterranean basin
BibTeX
@article{deno2026evaluation,
title = {{Evaluation of treatment-related serological changes in Treponema pallidum subsp. endemicum infection using latex-based immunoassays, with comparison to Treponema pallidum subsp. pallidum}},
author = {Yu-ki Deno and Keiyu Yamamoto and Mie Matsumoto and Toshihiko Fujikawa and Fumiya Banno and Takuya Kawahata and Keiichi Furubayashi},
journal = {PLOS Neglected Tropical Diseases},
year = {2026},
month = oct,
doi = {10.1371/journal.pntd.0014756},
url = {https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0014756},
note = {CC BY},
}
RIS
TY - JOUR
TI - Evaluation of treatment-related serological changes in Treponema pallidum subsp. endemicum infection using latex-based immunoassays, with comparison to Treponema pallidum subsp. pallidum
AU - Yu-ki Deno
AU - Keiyu Yamamoto
AU - Mie Matsumoto
AU - Toshihiko Fujikawa
AU - Fumiya Banno
AU - Takuya Kawahata
AU - Keiichi Furubayashi
PY - 2026
DA - 2026/10/01
JO - PLOS Neglected Tropical Diseases
DO - 10.1371/journal.pntd.0014756
UR - https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0014756
AB - 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.
SN - 1935-2735
SN - 1935-2727
ER -