CD7 and syphilis: Therefore, we can observe a sharp decrease in the total amount of T. pallidum on day 11 (Fig. 3B), while the transcriptional level of Tp40 mRNA/Tp0574 mRNA shows an increasing trend on day 25, which is consistent with the in vivo-induced antigenic property of T. pallidum and suggests that Tp40 may play an important role during the latent stage of syphilis.