Isolation of the outer envelope from Borrelia burgdorferi

Borrelia burgdorferi consists of an inner protoplasmic cylinder, containing the genome and cytoplasmic elements, surrounded by a number of axial filaments, all completely encased within a multiple-layered outer envelope structure (OE). In this study, a sodium dodecyl sulfate-mediated technique was used to isolate the OE from Borrelia burgdorferi in an attempt to better understand this structure in terms of its antigenic reactivity to Lyme disease patient sera. Electron microscopic evidence suggested that the OE product was relatively free of other spirochete cellular components. SDS-PAGE analysis indicated that the electrophoretic pattern of the OE was consistent with that of the remaining protoplasmic cylinder (PC) and whole spirochete controls. Antigenic determinants in the OE were recognized by sera from Lyme disease patients in Western blots. Chemical analysis of the OE revealed a composition of 45.90% protein, 50.75% lipid and 3.33% carbohydrate. The OE comprised 16.5% by lyophilized dry weight of the whole spirochete. Antigenic determinants located within or associated with this structure are likely to play a significant role in the development of immunity in the infected host.