CHARACTERIZATION OF FINNISH BORRELIA-BURGDORFERI SENSU LATO ISOLATES BY SODIUM DODECYL SULFATE-POLYACRYLAMIDE GEL-ELECTROPHORESIS AND WITH MONOCLONAL-ANTIBODIES

Thirty-seven Borrelia burgdorferi strains, isolated in 1992 from Ixode s ricinus in Finland, were investigated by sodium dodecyl sulfate-poly acrylamide gel electrophoresis (SDS-PAGE) and by immunoblotting and in direct immunofluorescence assay (IFA) with five to nine monoclonal ant ibodies (MAbs). By SDS-PAGE results and reactivities to MAbs H3TS, J 8 .3, I 17.3, and D6, the 37 isolates were assigned to the species B. bu rgdorferi sensu stricto (n = 7), Borrelia afzelii (rt = 17), or Borrel ia garinii (n = 13). Twenty more isolates examined only by IFA and wit h part of the MAbs were distributed as follows: 9 B. burgdorferi sensu stricto and 11 other species. Among 16 of 37 isolates displaying a SD S-PAGE patterns considered typical of that of B. garinii, 3 were negat ive by the test,vith MAb D6; the rest were positive. The three MAb D6- negative isolates reacted with MAb J 8.3 but not with MAb I 17.3. It i s suggested that these isolates of a previously undescribed type repre sent atypical B. afzelii strains deficient in the expression of OspB p roteins. The misleading species designation by the SDS-PAGE result is described. The IFA results were generally consistent with those obtain ed by immunoblotting. The exception was for 3 of 29 isolates that were positive with MAb H5332 by immunoblotting but that were IFA negative. In the present material of 57 strains, all 16 B. burgdorferi sensu st ricto isolates originated from the Angstrom land Islands. B. afzelii a nd B. garinii were isolated from ail three regions where ticks were co llected. The distributive difference seems to offer a basis for compar ative clinico-epidemiological studies of Lyme borreliosis.