Evaluation of treatment responses in late Lyme borreliosis on the basis of antibody decrease during the follow-up period

The purpose of this study was to identify a serological marker of successful treatment as distinct from treatment failure in late Lyme borreliosis, Consecutive serum samples from 68 treated patients with late Lyme borreliosis were analyzed during a 1-2 year follow-up period after the start of treatment. End-point enzyme immunoassay titres of IgG1, IgG2, IgG3, and combined IgG1+3 subclasses against a sonicate antigen of Borrelia burgdorferi were determined and compared to the IgG antibody response against Borrelia burgdorferi flagella, Individual half-lives of the antibody levels were calculated for each patient. The half-life values were compared to the patients' clinical outcome in order to find a serological marker of remaining disease activity or relapse. The levels of combined IgG1+3 subclass antibodies against the sonicate antigen and the individual levels of IgG1, IgG2, and IgG3 antibodies did not change significantly after treatment, In contrast, antibodies to flagella decreased markedly after successful treatment, with a half-life of 112+/-92 days (arithmetic mean value +/-SD). This was significantly shorter than the half-life after unsuccessful treatment (271+/-151 days), (P<0.0001), The decrease was observed mainly in IgG1 and IgG4 responses to flagella, less so for IgG2 or IgG3. The results suggest that a rapid decrease in flagella antibodies can serve as a marker for a successful treatment of Lyme borreliosis.