INTERPRETATION CRITERIA FOR STANDARDIZED WESTERN BLOTS FOR 3 EUROPEANSPECIES OF BORRELIA-BURGDORFERI SENSU-LATO

Western blots (WBs; immunoblots) are a widely used tool for the serodi agnosis of Lyme borreliosis, but so far, no defined criteria for perfo rmance, analysis, and interpretation have been established in Europe. For the current study WBs were produced with strains PKa2 (Borrelia bu rgdorferi sensu stricto), PKo (Borrelia afzelii), and PBi (Borrelia ga rinii). To improve resolution we used gels of 17 cm in length. In a fi rst step, 13 immuno-dominant proteins were identified with monoclonal antibodies. Then, the apparent molecular masses of all visually distin guishable bands were determined densitometrically. Approximately 40 ba nds of between 14 and 100 kDa were differentiated for each strain. Fro m a study with 330 serum samples (from 189 patients with Lyme borrelio sis and 141 controls), all observed bands were documented. To establis h criteria for a positive WB result, the discriminating ability of a s eries of band combinations (interpretation rules) were evaluated separ ately for each strain (for immunoglobulin G [IgG] WB, >40 combinations ; for IgM WB, > 15 combinations). The following interpretation criteri a resulting in specificities of greater than 96% were recommended: for Ige WB, at least one band of p83/100, p58, p56, OspC, p21, and p17a f or PKa2; at least two bands of p83/100, p58, p43, p39, p30, OspC, p21, p17, and p14 for PKo; and at least one band of p83/100, p39, OspC, p2 1, and p17b for PBi; for IgM WB, at least one band of p39, OspC, and p 17a or a strong pll band for PKa2; at least one band of p39, OspC, and p17 or a strong p41 band for PKo; and at least one band of p39 and Os pC or a strong pill band for PBi. The overall sensitivity was the high est for PKo WB, followed by PBI and PKa2 WB, in decreasing order. Stan dardization of WB assays is necessary for comparison of results from d ifferent laboratories.