MEMBRANE-PROTEIN VARIATIONS ASSOCIATED WITH IN-VITRO PASSAGE OF BORRELIA-BURGDORFERI

Borrelia burgdorferi, the causative agent of Lyme disease, undergoes a loss in virulence with repeated passage in vitro. Defining the change s which occur after conversion to avirulence may assist in identifying virulence factors and mechanisms of pathogenesis. We have used a cros s-adsorption technique and two-dimensional nonequilibrium pH gradient electrophoresis to compare virulent (low-passage) and avirulent (high- passage) variants of B. burgdorferi B31. Using cross-adsorbed rabbit s era to probe immunoblots, we identified 10 low-passage-associated prot eins (relative molecular masses of 78, 58, 49, 34, 33, 28, 24, 20, and 16 kDa) unique to the virulent strain B31. Cross-adsorbed human serum detected five proteins of similar sizes (78, 58, 34, 28, and 20 kDa), suggesting that several of these proteins were expressed during human infection. By probing inner and outer membranes, two proteins (38 and 33 kDa) that localized specifically to the outer membrane were observ ed. An additional low-passage-associated protein (28 kDa) was identifi ed when outer membranes from low- and high-passage variants of strain B31 were compared by two-dimensional nonequilibrium pH gradient electr ophoresis.