Fig 2. Study design for sample acquisition from (A) immunosuppressed vs. immunocompetent rabbits and (B) in vitro propagated treponemes vs. control.

(A) Five immunocompetent rabbits and five immunosuppressed rabbits were infected with inoculum at Week 0. Harvesting of punch biopsies from each rabbit was done weekly for 5 weeks. Samples were analyzed for treponemal load by qPCR and tprK sequence by next-generation sequencing. (B) Glycerol stock of T. pallidum Chicago C was thawed at Week -2, passaged in vitro at Week -1 and again at Week 0, at which point treponemes were 1) inoculated intradermally into a control rabbit, and 2) seeded into two sets of weekly-passaged cultured samples for 7 weeks. Samples were collected weekly from punch biopsies of the rabbit and from cell culture, then analyzed for treponemal load and tprK sequence.