Characteristics of immune response and pathogen tissue dissemination during progressive Treponema pallidum infection: Insights from humanized mice.

Abstract

Characterizing the immune response and pathogen tissue dissemination during progressive Treponema pallidum (T. pallidum) infection in the human is crucial for comprehending syphilis but it remains poorly understood, due to the unethical nature of inoculating volunteers with T. pallidum. An urgent new model is needed to study this issue. A human haematopoietic stem cell (Hu-HSC) mice model of syphilis was constructed through inoculation with T. pallidum. Blood and tissue samples were collected at serial time points (0, 3, 7, 14, 28 and 42 days post-infection) to analyse changes in the immune response and the presence of T. pallidum polA DNA and mRNA in the Hu-HSC mice. Treponema pallidum increased the percentage of helper T cell (Th) 1 and Th2 cells and induced the expression of Th1 and Th2 cytokines in the Hu-HSC mice, with a pattern of increasing and then decreasing response. However, there were no significant changes in the percentage of Th17 and Treg cells. Treponema pallidum polA DNA was detected in various organs such as the liver and spleen, indicating the dissemination of T. pallidum in the tissues. Furthermore, these organs were found to maintain the activity of T. pallidum through the detection of T. pallidum polA mRNA. These results suggested that Treponema pallidum induced the Th1 and Th2 immune response and disseminated in tissues in Hu-HSC mice. This study can provide a basis for future in vivo research on syphilis using the Hu-HSC mouse model and offer new references for explaining the pathogenesis of human syphilis.