The outer membranes from Treponema pallidum subsp. pa~idum and Treponema vincentii were isolated by a novel method. Purified outer membranes from T. palidum and T. vincentii following sucrose gradient centrifugation banded at 7 and 31% (wt/wt) sucrose, respectively. Freeze fracture electron microscopy of purified membrane vesicles from T. pallidum and T. vincentii revealed an extremel low density of protein particles; the particle density of T. pallidum was approximately six times less than that of T. vincentii. The great majority of T. vincentii lipopolysaccharide was found in the outer membrane preparation. The T. vincentii outer membrane also contained proteins of 55 and 65 kDa. 1251-penicillin V labeling demonstrated that T. pallidum penicillin-binding proteins were found exclusively with the protoplasmic cylinders and were not detectable with purified outer membrane material, indicating the absence of inner membrane contamination. Isolated T.pallidum outer membrane was devoid of the 19-kDa 4D protein and the normally abundant 47-kDa lipoprotein known to be associated with the cytoplasmic membrane; only trace amounts of the periplasmic endoflagella were detected. Proteins associated with the T. pallidum outer membrane were identified by one-and two-dimensional electrophoretic analysis using gold staining and immunoblotting. Small amounts of strongly antigenic 17-and 45-kDa proteins were detected and shown to correspond to previously identified lipoproteins which are found principally with the cytoplasmic membrane. Less antigenic proteins of 65, 31 (acidic pl), 31 (basic pl), and 28 kDa were identified. Compared with whole-organism preparations, the 65-and the more basic 31-kDa proteins were found to be highly enriched in the outer membrane preparation, indicating that they may represent the T. pallidum rare outer membrane proteins. Reconstitution of solubilized T. paUidum outer membrane into lipid bilayer membranes revealed porin activity with two estimated channel diameters of 0.35 and 0.68 nm based on the measured single-channel conductances in 1 M KCI of 0.40 and 0.76 nS, respectively.The outer membranes of spirochetes, including that of Treponema pallidum subsp. pallidum, the agent of syphilis, are fragile compared with those of typical gram-negative bacteria (17,22,24,39,42,49). Spirochetal outer membranes bleb from the underlying protoplasmic cylinder under relatively mild conditions, including dilute detergents and hypotonic environments (24). Freeze fracture electron microscopy has revealed that the outer membranes of pathogenic spirochetes contain amounts of integral membrane protein that are 1 to 2 orders of magnitude less than those of gram-negative bacteria (45,54,55). This striking feature has been suggested to be a key factor in the pathogenicity of these organisms by contributing to their ability to evade the host immune response and to establish chronic infection (11,15,38,45,54,55).The outer membrane of T. pallidum has an extremely low content of membrane-spanning protein (45, 55), a finding...

We describe 4 patients with encephalitis due to possible reactivation of human herpesvirus 6 (HHV-6) infection who were enrolled in the California Encephalitis Project. All were immunocompetent and had HHV-6 loads determined in cerebrospinal fluid specimens. Tests for detection of HHV-6 should be considered for individuals with encephalitis.

We have recently reported the isolation and purification of the

Helicobacter pylori is a causative agent of gastritis in humans and is correlated with gastric ulcer formation. Infections with this bacterium have proven difficult to treat with antimicrobial agents. To better understand how this bacterium transports compounds such as antimicrobial agents across its outer membrane, identification of porin proteins is important. We have recently identified a family of H. pylori porins (HopA to HopD) (M. M. Exner, P. Doig, T. J. Trust, and R. E. W. Hancock, Infect. Immun. 63:1567-1572, 1995). Here, we report on an unrelated porin species (HopE) from this bacterium. This protein had a apparent molecular mass of 31 kDa and was seen to form 50-and 90-kDa aggregates that were designated putative dimeric and trimeric forms, respectively. The protein was purified to homogeneity and, with a model planar lipid membrane system, was shown to act as a nonselective pore with a single channel conductance in 1.0 M KCl of 1.5 nS, similarly to other bacterial nonspecific porins. An internal peptide sequence of HopE shared homology with the P2 porin of Haemophilus influenzae. HopE was also shown to be antigenic in vivo as assessed by sera taken from H. pylori-infected individuals and was immunologically conserved with both patient sera and specific monoclonal antibodies. From these data, it appears that HopE is a major nonselective porin of H. pylori. The implications of these findings are discussed.