Borrelia-specific antibodies are not detectable until several weeks after infection and even if they are present they are no proof of an active infection. 89 4 while the Pyroxamide (NSC 696085) specificity was 98 7 In 1480 patients with clinically suspected borreliosis results from serology and LTT were comparable in 79.8% of cases. 18% were serologically positive and LTT-negative. These were mainly patients with borreliosis after antibiotic therapy. 2.2% showed a negative serology and a positive LTT result. Half of them had an early erythema migrans. Following antibiotic Pyroxamide (NSC 696085) treatment the LTT became unfavorable or borderline in patients with early manifestations of borreliosis whereas in patients with late symptoms it showed a regression while still remaining positive. Therefore we propose the follow-up monitoring of dis-seminated Borrelia infections as the main indication for the Borrelia-LTT. investigations and re-evaluated patient data and analytical valuesof patients which were investigated routinely in our laboratory. A Borrelia-LTT with one recombinant antigen and lysate antigens of the IQGAP1 three relevant Borrelia species (B. sensu stricto B. afzelii and Pyroxamide (NSC 696085) B.garinii) was developed and tested. The results achieved thus allow us to answer the following questions: In patients with clinical borreliosis prior to the start of antibiotic therapy there is a high degree of correspondence between the results of Borrelia serology and Borrelia-LTT studies. The sensitivity of the Borrelia-LTT is usually 89.4% for clinically active borreliosis with a specificity of 98 7 The lysate antigens of the three species of Borrelia and the recombinant OspC cross-reacted in the Borrelia-LTT. Therefore it is not possible to determine the respective species involved. The unfavorable results in clinically healthy seropositive subjects and the studies before and after antibiotic treatment of patients with clinically active disease are a strong indication that this Borrelia-LTT with lymphocytes from peripheral blood is usually positive only when the immune system is currently being stimulated by Borrelia. The proof that the test responds only during an active Borrelia contamination could only be provided by the simultaneous detection of Borrelia by culture or Borrelia PCR (Borrelia DNA detection). In our patient cohort this was demonstrated in only 6 out of the 32 cases tested by Borrelia PCR. The results of our study differ in part from some published data which show a low specificity of the Borrelia-LTT [24 25 This is very likely due to methodology. The addition of interferon-α to the cell culture medium inhibits nonspecific proliferation of lymphocytes and promotes the function of antigen-presenting cells. This improves the discriminatory power of positive and negative LTT results even though the SI values of the positive reactions and the blank values are lower than in assays without interferon [23]. Another modification is the use of polymyxin B for the elimination of nonspecific activating lipid groups from the Borrelia lysates and traces of LPS from the rOspC expressed in E. coli. In this way common nonspecific borderline and poor positive LTT reactions were eliminated (data not shown). Of great importance are the selection and especially the dosage of the Borrelia test antigens. Lysate antigens kindly provided by Seramun (Heidesee) were specially purified for the ELISA test and showed no positive reactions with unfavorable control sera. Nevertheless the presence of Borrelia-nonspecific proteins in the lysates that may cross-react with other bacterial species may be unavoidable. Our own experience in the development of antigen-specific LTT applications show that this Pyroxamide (NSC 696085) “specific diagnostic width” of the test antigens is particularly important. For the Borrelia-LTT therefore it was necessary to consider whether those concentrations of Borrelia test antigens which cause barely any positive/borderline LTT reactions in 20 seronegative subjects are sufficient to detect Borrelia-specific helper cells in the blood of patients with clinical borreliosis. Obviously the advantage of the Borrelia-LTT presented here is the use of a mixture of Borrelia-specific Pyroxamide (NSC 696085) antigens in the Borrelia lysates. This is confirmed by the calculated sensitivity of 89 6 and specificity of about 98 7 for seropositive clinical borreliosis prior to antibiotic therapy. In contrast in preliminary assessments with all recombinant Borrelia proteins (p93 p39 p34 p25 p18) available to us only the rOspC (p25) was proven to be a suitable test antigen for the Borrelia-LTT. For all other proteins the “specific.