Persistent joint swelling and borrelia-specific antibodies in Borrelia garinii-infected mice after eradication of vegetative spirochetes with antibiotic treatment

We wanted to study the pathogenesis and the long-term manifestations of Borrelia garinii infection in SJL and C3H/He mice. We report here that B. garinii Å218 causes a persisting infection in these mouse strains. Mice infected with intracutaneous inoculation of B. garinii at 4–5 weeks of age developed a disseminated infection and joint swelling within 2 weeks of inoculation and remained infected with joint symptoms until the end of follow-ups of up to 52 weeks. Treatment with ceftriaxone or ampicillin at 18 or 44 weeks of infection did not affect the joint swelling during the follow-ups of 19 and 8 weeks, respectively. However, B. garinii could not be cultured from any of the post mortem tissue samples of the treated mice, whereas the spirochete grew from samples of all untreated infected animals. borrelia-specific IgG antibodies were detectable after 2 weeks of infection, and in late infection, all mice had high anti-borrelia IgG levels. Antibiotic treatment had no effect on antibody levels. Histology showed only slight changes in the joints of the infected mice with occasional lymphocyte infiltration, synovial proliferation and slight involvement of the Achilles' tendon. No difference was seen in the findings between ceftriaxone-treated and untreated mice. The results suggest that the presence of vegetative spirochetes is no prerequisite for persisting joint symptoms and elevated anti-borrelia IgG levels in these B. garinii-infected mice.