Polymorphism of outer surface proteins of Borrelia burgdorferi as a tool for classification

A total of 23 isolates of Borrelia burgdorferi were characterized by SDS-PAGE and immunoblot analysis. One isolate came from the CSF of a Lyme neuro-borreliosis patient in Valais (Switzerland) and 22 were tick isolates (2 from I. dammini of Shelter Island, USA and 20 from I. ricinus of Valais, Switzerland). Based on the electrophoretic mobility of outer surface proteins (OspA and OspB), four groups of B. burgdorferi could be defined. Group I isolates possess an OspA of 31 KD and an OspB of 34 KD. The group II isolate showed an OspA of 32 KD and OspB of 35 KD. Group III isolates have a 33 KD OspA and group IV a 33.5 KD OspA. This classification was confirmed by the reactivity of a monoclonal antibody (D6) to a 12 KD antigen that was recognized in group III only. A Lyme patient's serum showed a 2-band pattern (10 and 13 KD) for group I and a one-band pattern (12 KD) for the other 3 groups. Therefore OspA, OspB and other proteins of low molecular weight (10, 12, and 13 KD) seem to be important keys for the classification of B. burgdorferi isolates. This typing system correlates with genetic analysis.