Fig 6.

BB0238 TPR-like/HTH motif supports initial infection in the mammalian host, contributing to evasion of the host cellular immune responses. (A) Disruption of the TPR-like/HTH motif attenuates B. burgdorferi transmission. Ticks (5 ticks/mouse) were infected via microinjection with Bb ^BB0238−, Bb ^BB0238+, Bb ^Y37A, or Bb ^P65A, and then allowed to feed on C3H/HeN mice (3 mice/group). Infection was assessed via RT-qPCR analysis of B. burgdorferi flaB transcripts normalized against mouse Actb levels. (B) Survival of spirochetes within the infected ticks. Microinjected ticks, as indicated in panel A, were examined for spirochete burden using RT-qPCR, by measuring copies of B. burgdorferi flaB transcripts normalized against tick Actb levels. (C) The TPR-like/HTH motif is important for establishing infection within the first 7 days of infection. C3H/HeN mice were subcutaneously injected with spirochetes and infection was assessed by RT-qPCR analysis at the injection dermal site 7 days post-infection (dpi). (D) The TPR-like/HTH motif point mutant, Bb ^P65A, can survive locally after a hyper-infection inoculum. C3H/HeN mice (3 mice per group) were subcutaneously injected with Bb ^BB0238+ (10⁵ spirochetes per mouse) or with Bb ^BB0238− and the Bb ^P65A point mutant (10⁷ spirochetes per mouse). Infection was assessed by RT-qPCR analysis of pathogen burden at two weeks post-infection. Bars and error bars represent means and standard error of means, respectively. ***P < 0.001; **P < 0.01.