Transcript levels of the Treponema pallidum protein Tp0751 in skin lesions of a rabbit model of early syphilis / 中华皮肤科杂志

ABSTRACT

Objective To trace changes in the transcript level of the Treponema pallidum(Tp)protein Tp0751 in skin lesions of a rabbit model of early syphilis. Methods Three New Zealand white rabbits were intracutaneously injected with 0.1 ml of Tp (Nichols Seattle strains)suspensions (107 treponemes/ml)at 10 sites on the shaved back to establish a model of early syphilis. All the rabbits received a single injection with the total amount of treponemes being 107. Then, skin changes at injection sites were observed, and the size of skin rashes was recorded on a daily basis. Skin specimens sized 0.4 cm × 0.4 cm were excised from an injection site and a non-injection site(negative control)separately every 3 days for the detection of Tp0751 and Tp0574 mRNAs. The whole experiment lasted 30 days, and a total of 11 skin biopsies were carried out. Fluorescence-based quantitative PCR was performed to measure the mRNA expressions of Tp0751 and Tp0574 continuously and dynamically during the development of chancre. Results After intracutaneous injection of Tp suspensions, red papules occurred on the back of rabbits on day 6, and reached maximum size on day 19 with the formation of ulcer and chancre. On day 25, disseminated secondary syphilides gradually appeared all over the body surface of the rabbits. The mRNA expression levels of Tp0574 and Tp0751 increased at the early stage, peaked onday 15 (compared with the other time points, all P < 0.05), thereafter rapidly declined, but rose slightly on day 27. The standardized expression level of Tp0751 mRNA increased gradually after day 15, and peaked on day 24 (compared with the other time points, all P < 0.05). Conclusion The transcript level of Tp0751 was high in rabbits at the late stage of Tp clearance when generalized disseminated secondary syphilides had not appeared, suggesting that Tp0751 may be involved in the systemic spread of Tp.