VIRULENT-STRAIN ASSOCIATED OUTER-MEMBRANE PROTEINS OF BORRELIA-BURGDORFERI

We have isolated and purified outer membrane vesicles (OMV) from Borre lia burgdorferi strain B31 based on methods developed for isolation of Treponema pallidum OMV. Purified OMV exhibited distinct porin activit ies with conductances of 0.6 and 12.6 nano-Siemen and had no detectabl e beta-NADH oxidase activity indicating their outer membrane origin an d their lack of inner membrane contamination, respectively. Hydrophobi c proteins were identified by phase partitioning with Triton X-114. Mo st of these hydrophobic membrane proteins were not acylated, suggestin g that they are outer membrane-spanning proteins. Identification of pa mitate-labeled lipoproteins revealed that several were enriched in the OMV, several were enriched in the protoplasmic cylinder inner membran e fraction, and others were found exclusively associated with the inne r membrane. The protein composition of OMV changed significantly with successive in vitro cultivation of strain B31, Using antiserum with sp ecificity for virulent strain B31, we identified OMV antigens on the s urface of the spirochete and identified proteins whose presence in OMV could be correlated with virulence and protective immunity in the rab bit Lyme disease model. These virulent strain associated outer membran e-spanning proteins may provide new insight into the pathogenesis of L yme disease.