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.

Objective To isolate and culture a clinical strain (GDI) of Treponema pallidum (Tp) in Guangdong province,and to investigate the difference in nonsynonymous single nucleotide polymorphisms (nsSNPs) between the GD1 strain and Tp Nichols strain.Methods The GD1 strain was isolated from the hard chancre in a patient with primary syphilis in Guangdong province,and continuously subcultured in the testes of New Zealand white rabbit.The serial subcultivation of GD1 was multi-verified by dark-field microscopy,polymerase chain reaction (PCR) for TP0548 gene,DNA sequencing and genotyping.Meglumine diatrizoate density gradient centrifugation was performed to isolate rabbit tissues and concentrate GD1,and DNA sequencing was used to verify the nsSNPs in the TP0443 and TP0584 genes.Results The GD1 strain was successfully isolated from the lesions of the patient with syphilis,and classified as a subtype f of TP0548.Compared with the American Tp (Nichols strain),there were nsSNP mutations in the GD1 strain.One mutation was located in the TP0443 gene,leading to the the substitution of threonine by alanine at amino acid position 120,and another one was located in the TP0584 gene,which caused a change from alanine to threonine at amino acid position 314.Conclusion The GD1 strain was successfully isolated firstly from the lesions in a patient with syphilis in Guangdong province,and nsSNP mutations were confirmed in the GD 1 strain on the etiology.

Objective:To establish a new molecular typing method for Treponema pallidum (TP) based on TP0136 protein sequence heterogeneity. Methods:The amino acid sequences of TP0136 open reading frame (ORF) of 9 strains of Treponema pallidum ssp. Pallidum (TPA) , 3 strains of Treponema pallidum ssp. Pertenue (TPE) , 1 unclassified simian strain of Treponema Fribourg-Blanc (FB) and 1 strain of Treponema pallidum ssp. Endemicum (TEN) were searched from Genbank, and multiple sequence comparisons were performed to obtain the molecular typing results of TP0136 protein. The TP0136 protein-based molecular typing method was used to classify 23 TPA clinical isolates, which were collected from Dermatology Hospital of Southern Medical University from January 2015 to December 2018, and the typing results were compared with those by the traditional typing method based on the tp0548/Arp/Tpr genes. Results:TP0136 protein was highly heterogeneous in different TP strains. According to the amino acid sequence of TP0136, TPE, FB and TEN strains were divided into 4 subtypes of Ⅰ- Ⅳ, TPA strains were divided into 6 subtypes of Ⅴ-Ⅹ, and TPA clinical strains were classified into 4 subtypes of Ⅶ, Ⅸ, Ⅹ, Ⅺ. Through the traditional typing method described above, 23 TPA clinical strains could be divided into 5 types (13D/d, 14D/f, 14D/g, 15D/f, 16A/e) . By using the TP0136 protein-based typing method combined with traditional typing method, the above clinical strains could be further subdivided into 10 types, and the 14D/f type could be further divided into 3 subtypes by using the TP0136 protein-based typing method.Conclusion:The TP0136 protein-based molecular typing method can be used to distinguish TP species, which is helpful for further improvement of traditional TPA molecular typing.