Cell and Tissue Interactions of Treponema pallidum in Primary and Secondary Syphilitic Skin Lesions: An Ultrastructural Study of Serial Sections

There are limited reports on the ultrastructure of syphilis skin lesions. The aim of this study has been to perform an electron microscopic investigation of the morphology and the tissue distribution of treponemes in primary and secondary cutaneous lesions. Three cases of primary syphilitic chancre and one case of secondary syphilis were included. Prominent epidermal abnormalities in the primary chancre and a perivascular inflammatory infiltrate in the secondary lesion were found by light microscopy. Ultrastructurally, spirochetes were located mainly in the blood vessel walls and dermal tissue of the chancre lesions. In the secondary syphilis case, spirochetes were more abundant between epidermal keratinocytes. Most of them adjusted to the intercellular spaces. Occasionally, the electron microscopy images were highly suggestive of an intracellular location. Both the ultrastructural and immunohistochemical examination of the primary and secondary syphilis lesions showed a paradoxical distribution of the causative microorganisms compared to the light microscopic changes. In addition, the ultrastructural findings strongly suggest that Treponema pallidum subspecies pallidum invades tissues, not only through an intercellular, but also through a transcellular pathway.     

Isolation and characterization of antigens from Treponema phagedenis biotype Reiter cross-reacting with Treponema pallidum

The specific aims of the studies reviewed here were to design a rational purification strategy for Reiter treponeme antigens using combinations of different chromatographic principles, to isolate and characterize the Reiter treponemal antigens, especially the antigens labelled TR-b, TR-c, TR-dl, TR-d2, and TR-e cross-reacting with antigens in Treponema pallidum, to develop and evaluate the use of these purified antigens in syphilis diagnostic enzyme-linked immunosorbent assays (ELISA), to investigate whether Reiter treponeme antigens can induce protective immunity against experimental syphilis in rabbits. By combining anion exchange chromatography, gel filtration, agarose gel electrophoresis, hydrophobic interaction chromatography, and affinity chromatography on Iminodiacetic acid-Sepharose CL 4B and Lysine Sepharose 4B we were able to isolate seven different water soluble Reiter antigens from one single Reiter sonicate supernatant (I, II, III, IV, V, VI). The applied chromatographic matrices were selected due to their efficiency for separation of the Reiter antigens in pilot experiments. In addition to the above mentioned Reiter antigens additional antigens labelled TR-o (V) and LPS (VI) were isolated. TR-b, TR-c, and TR-o were shown to be protein antigens (III, IV, V). The TR-c antigen of the Reiter treponeme cross-reacted not only with an antigen in T. pallidum but also with an antigen common to a wide range of bacteria (IX). The TR-d antigen composed of a ribonucleic acid component (TR-dl) (II) and a protein component (TR-d2). The TR-e antigen represented the flagellum of the bacterium (I), and the LPS antigen was a pure lipopolysaccharide antigen (VI).(ABSTRACT TRUNCATED AT 250 WORDS)     

Detection of Nonspecific Resistance to Listeria monocytogenes in Rabbits Infected with Treponema pallidum

Several lines of evidence suggest that cell-mediated immunity (CMI) is suppressed in the early stages of infection caused by Treponema pallidum and becomes activated at the time that latency is induced. In the studies reported in this paper, rabbits were infected intravenously with T. pallidum and subsequently challenged with Listeria monocytogenes. Enhanced ability to suppress the growth of Listeria was detected in their livers between 3 and 5 weeks after infection with T. pallidum, corresponding to the onset and regression of the generalized syphilitic eruption. A second infection of T. pallidum 4 weeks after the first, at a time when suppression was beginning to wane, prolonged the listericidal activity. These observations support the hypothesis that infection by T. pallidum stimulates CMI, which, in turn, may play a role in inducing latency.     

Purification of Treponema pallidum from Infected Rabbit Tissue: Resolution into Two Treponemal Populations

Virulent Treponema pallidum organisms, extracted from infected rabbit testes, were subjected to velocity sedimentation in discontinuous gradients of Hypaque, a high density, low viscosity material. After centrifugation of extracts at 20 C for 45 min at 100,000 x g, treponemes separated into two distinct bands based upon their relative velocities, although some variation was observed in the densities of the two bands and the number of treponemes per band. Rabbit tissue components sedimented more rapidly. Dark field and electron microscopy of preparations after velocity sedimentation indicated that treponemes retained general structural characteristics and no tissue contamination occurred in the treponemal fractions. Purification of treponemes in Hypaque resulted in their loss of motility and infectivity based upon animal inoculation. Antigenicity with respect to reactivity with antibody was preserved as shown by the high fluorescence intensity of treponemes in the fluorescent treponemal antibody adsorption test.     

Isolation of a Heat-stable Antigen from Treponema Reiter, Using an Immunoadsorbent with Antibodies from Syphilitic Patients

It was attempted to isolate antigens from Treponema Reiter, relevant to syphilis serology, by immunoadsorption with patients' antibodies coupled to CNBr-Sepharose 4B. One antigen was desorbed by 2 m KSCN in 0.05 m Tris barbital buffer, pH 8.6. The recovery was 3% and 7% in two experiments. A small amount of human antibodies in the isolate was removed on an immunoadsorbant column with insolubilized rabbit antibodies against normal human serum proteins. The antigen thus obtained was immunologically pure when analysed by crossed immunoelectrophoresis. By electron microscopy of immunoprecipitates and by tandem crossed immunoelectrophoresis it was shown that the antigen differed from the flagellar antigen of T. Reiter, but was identical to antigen d previously described in T. Reiter, Antigen d could also be isolated from supernatant of T. Reiter cultures, The d antigen was not denatured at pH 2.8, by 8 m urea or by 3 m KSCN, and it resisted heating to 100°C for 30 min. No protein could be detected in a concentrated preparation, and the antigen might be B polysaccharide. Antigen d is probably present in the sorbent used in the fluorescence treponemal antibody absorption (FTA-ABS) test and may constitute the active substance of this reagent.     

Mucopolysaccharidase of Treponema pallidum

Treponema pallidum (Nichols strain) exhibited mucopolysaccharidase activity. Acidic mucopolysaccharides were broken down more rapidly by viable treponemes than by heat-inactivated treponemes or membrane filtrates of treponemal suspensions. Ouchterlony immunodiffusion demonstrated the occurrence of antibodies to the hyaluronidase-like enzyme within syphilitic sera. After intratesticular inoculation of 2 x 10(7) to 6 x 10(7) treponemes, these anti-mucopolysaccharidase antibodies were detected between 9 and 35 days postinoculation. In addition, acidic mucopolysaccharides were present in the serum of infected animals 9 and 16 days postinoculation. Immune serum that contained antibodies to the mucopolysaccharidase restricted treponemal breakdown of acidic mucopolysaccharides. It has been previously demonstrated that immune rabbit serum contains a factor that blocks attachment of T. pallidum (Nichols strain) to cultured mammalian cells. This factor was effectively absorbed by prior incubation with bovine hyaluronidase. It is postulated that T. pallidum attaches to acidic mucopolysaccharides on the surface of cultured cells through the mucopolysaccharidase enzyme at the surface of the organisms. These findings are discussed in terms of the histopathogenesis of T. pallidum with applications to the healing immune response.     

Isolation and characterization of low molecular weight antibodies for Treponema pallidum.

A low molecular weight antibody which coated Treponema pallidum without producing any apparent reaction was isolated from human syphilitic serum. Its electrophoretic mobility was that of IgG immunoglobulins, and molecular weight was between 115,000 and 120,000.     

Surface Mucopolysaccharides of Treponema pallidum

The viscous mucoid fluid that accumulates within syphilitic lesions may be due to breakdown of host tissue during infection, or may be synthesized by Treponema pallidum. Experiments were performed to investigate the acidic mucopolysaccharides that occur at the surface of T. pallidum (Nichols strain). These mucopolysaccharides were demonstrated by reaction with acidified bovine serum albumin and by agglutination with wheat germ agglutinin and soybean agglutinin. The polycations ruthenium red and toluidine blue influenced treponemal survival. Concentrations of both compounds at 200 mug/ml inhibited survival, whereas concentrations at 0.1mug/ml enhanced survival. The mucopolysaccharide concentration within the mucoid fluid that accumulates during intratesticular infection was determined by reaction with acidified bovine serum albumin; it ranged from 10,000 mug/ml to less than 8 mug/ml. The addition of this mucoid fluid to treponemal suspensions resulted in differing effects on T. pallidum survival. Some preparations were inhibitory, and others were stimulatory. Commercial preparations of hyaluronic acid and chondroitin sulfate at 400, 200, 100, and 50 mug/ml were detrimental to treponemal survival. The organisms exhibited pronounced clumping in the presence of the higher concentrations of hyaluronic acid. These clumps of treponemes were comprised of mucopolysaccharides as shown by acidified bovine serum albumin and toluidine blue reactions and by hyaluronidase degradation. Results are discussed in terms of the derivation and potential role of acidic mucopolysaccharides at the surface of T. pallidum.     

Molecular subtyping of Treponema pallidum from North and South Carolina

Patients from five clinics in North and South Carolina who had lesions suggestive of primary or secondary syphilis were evaluated using molecular techniques that allow the differentiation of Treponema pallidum strains on the basis of two variable genes, tpr and arp. Lesion samples were screened for the presence of T. pallidum DNA using PCR for polA, which represents a segment of the polymerase I gene that is unique to the spirochete. Twenty-seven of 154 lesion samples were found to contain T. pallidum, 23 of which had typeable DNA. Seven molecular subtypes were found (10f, 12f, 13f, 14f, 14g, 15f, and 16f); one to four subtypes were identified at each clinic. Subtype 14f was found in 52% of the typeable specimens and was distributed in four of the five clinics. Subtype 16f was found in 22% of specimens and was concentrated at one clinic. Further data are needed to define the role of this technique in examining the epidemiology of syphilis.     

Respiration and Oxidative Phosphorylation in Treponema pallidum

Exogenous and endogenously generated reduced pyridine nucleotides caused marked stimulation of O(2) uptake when added to treponemal cell-free extracts, which indicated that terminal electron transport was coupled to the consumption of O(2). Oxidation of reduced nicotinamide adenine dinucleotide (NADH) was shown to correlate stoichiometrically with O(2) reduction, suggesting that NADH was being oxidized through a mainstream respiratory chain dehydrogenase. Oxygen evolution in treponemal extracts was observed after the completion of O(2) uptake which was stimulated by exogenous NADH and endogenously generated reduced NAD phosphate. Oxygen evolution was inhibited by both cyanide and pyruvate, which was consistent with O(2) release from H(2)O(2) by catalase. The addition of exogenous H(2)O(2) to treponemal extracts caused rapid O(2) evolution characteristic of a catalase reaction. A spectrophotometric assay was used to measure ATP formation in T. pallidum cell-free extracts that were stimulated with NADH. P/O ratios from 0.5 to 1.1 were calculated from the amounts of ATP formed versus NADH oxidized. Phosphorylating activity was dependent on P(i) concentration and was sensitive to cyanide, N, N'-dicyclohexylcarbodiimide, and carbonyl cyanide m-chlorophenyl hydrazone. Adenine nucleotide pools of T. pallidum were measured by the firefly luciferin-luciferase assay. Shifts in adenine nucleotide levels upon the addition of NADH to cell-free extracts were impossible to evaluate due to the presence of NAD(+) nucleosidase. However, when whole cells, previously incubated under an atmosphere of 95% N(2)-5% CO(2), were sparged with air, ATP and ADP levels increased, while AMP levels decreased. The shift was attributed to both oxidative phosphorylation and to the presence of an adenylate kinase activity. T. pallidum was also found to possess an Mg(2+) - and Ca(2+) -stimulated ATPase activity which was sensitive to N, N' -dicyclohexylcarbodiimide. These data indicated a capability for oxidative phosphorylation by T. pallidum.     

Penicillin-binding proteins and peptidoglycan of Treponema pallidum subsp. pallidum.

Penicillin-binding proteins (PBPs) of Treponema pallidum subsp. pallidum (T. pallidum) were characterized by using [3H]penicillin G and a conjugate consisting of ampicillin and 125I-labeled Bolton-Hunter reagent. Both antibiotics specifically radiolabeled proteins with molecular masses of 94, 80, 63, and 58 kilodaltons (kDa); 125I-labeled Bolton-Hunter reagent-ampicillin also radiolabeled several polypeptides with lower molecular masses. The 94- and 58-kDa proteins demonstrated the highest binding affinities for [3H]penicillin G and were radiolabeled at concentrations of 8 and 40 nM, respectively. Radiolabeling of PBPs was detectable after 1 min of incubation in 1 microM [3H]penicillin G and was nearly maximal within 10 min. The rapidity of penicillin binding contrasted with the observation that only 40% of virulent treponemes became immobilized during prolonged incubation in vitro with a much higher concentration (1 mM) of unlabeled penicillin. Two lines of evidence indicated that most, if not all, of the PBPs are integral cytoplasmic membrane proteins: (i) preincubation of organisms in 0.1% Triton X-100 solubilized nearly all of the outer membranes but did not affect radiolabeling of PBPs, and (ii) except for the 80-kDa protein, the PBPs partitioned into the detergent phase following extraction with the nonionic detergent Triton X-114. The presence of peptidoglycan in T. pallidum was confirmed by the detection of muramic acid in the sodium dodecyl sulfate-insoluble, proteinase K-resistant residue obtained from Triton X-114-extracted organisms.     

Molecular basis of immunological cross-reactivity between Treponema pallidum and Treponema pertenue

Protein antigens of Treponema pallidum, Nichols strain, and Treponema pertenue, Gauthier strain, were identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting techniques. Treponemal proteins were solubilized in 1% sodium dodecyl sulfate, electrophoresed on 12.5% polyacrylamide gels, and either stained with Coomassie brilliant blue or electrophoretically transferred to nitrocellulose paper. These antigen blots were incubated with sera from rabbits infected with either T. pallidum or T. pertenue and 125I-labeled staphylococcal protein A and exposed to X-ray film for visualization of antigenic molecules. Protein profiles of each organism separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and stained with Coomassie brilliant blue showed no distinguishable differences. Antigenic profiles as determined by Western blots were similar with two exceptions. A 39,500-dalton band was present on T. pertenue but absent from T. pallidum, and a 19,000-dalton band was present on T. pallidum but absent from T. pertenue (although two additional antigenic bands at 21,000 and 18,000 daltons were seen on T. pertenue). Because these differences were detected by using antisera raised against either T. pallidum or T. pertenue, these molecules must contain some antigenic determinants in common despite their differences in molecular weight.     

Activation of the classical and alternative pathways of complement by Treponema pallidum subsp. pallidum and Treponema vincentii

Both in vivo and in vitro studies have indicated that complement plays an important role in the syphilitic immune responses. Few quantitative data are available concerning activation of the classical pathway by Treponema pallidum subsp. pallidum, and no information is available on treponemal activation of the alternative pathway. Activation of both pathways was compared by using T. pallidum subsp. pallidum and the nonpathogen T. vincentii. With rabbit and human sources of complement, both organisms rapidly activated the classical pathway, as shown by hemolysis of sensitized sheep erythrocytes and by the generation of soluble C4a. With human sources of complement, both organisms also activated the alternative pathway, as shown by hemolysis of rabbit erythrocytes and by the generation of soluble C3a in the presence of magnesium ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA). During incubation, organisms remained actively mobile and did not lyse, indicating that activation was a function of complement reactivity with the intact outer treponemal surface. In addition, freshly harvested T. pallidum subsp. pallidum immediately activated both pathways of complement; preincubation of organisms did not enhance complement reactivity. T. vincentii was a more potent activator of this pathway. T. pallidum subsp. pallidum contained almost four times as much surface sialic acid as T. vincentii did. When sialic acid was enzymatically removed from T. pallidum subsp. pallidum, enhanced activation of the alternative pathway was detected. It is proposed that T. pallidum subsp. pallidum retards complement-mediated damage by the alternative pathway through surface-associated sialic acid. This may be an important virulence determinant that enables these organisms to readily disseminate through the bloodstream to infect other tissues.     

Outer Envelope of Virulent Treponema pallidum

Ultrathin sections of virulent Treponema pallidum (Nichols strain) were examined with the electron microscope, and the presence of an outer cell envelope was documented.     

Lipids of Treponema pallidum Kazan 5

The lipid composition of Treponema pallidum Kazan 5 cultivated in a lipid-defined medium was investigated. Lipids comprised 18 to 20% of the dry weight of the treponeme. Glycolipid and phospholipids accounted for 90 to 95% of the total lipids and free fatty acids made up the remaining 5 to 10%. The major polar lipids were the glycolipid, 1-(O-alpha-d-galactopyranosyl)-2,3-diglyceride (45 to 55%), and phosphatidylcholine (30 to 40%). Phosphatidylethanolamine (5 to 10%), an unidentified compound (1 to 2%), and occasional trace amounts of diphosphatidylglycerol (cardiolipin) were also found. The monogalactosyldiglyceride was also a major component (50%) of the lipids of the Reiter, Noguchi, and Nichols strains of T. pallidum. The fatty acid composition of Kazan 5 usually consisted of saturated and unsaturated fatty acids ranging from 14 to 18 carbons depending upon the fatty acids added to the culture medium. When the cells were cultivated on elaidic acid (trans-9-octadecenoic acid), their lipids contained only elaidic acid.     

Treponema pallidum subsp. pertenue displays pathogenic properties different from those of T. pallidum subsp. pallidum

The present study described the susceptibility of C4D guinea pigs to cutaneous infection with Treponema pallidum subsp. pertenue Haiti B strain. The general manifestations of the disease in adults and neonates differ, to a certain degree, from those induced by T. pallidum subsp. pallidum Nichols strain. Noticeable differences between the infections were reflected in the character of the skin lesions, their onset and persistence, and the kinetics of the humoral response. The incidence and dissemination of cutaneous yaws lesions in very young guinea pigs were remarkably different from the low frequency observed in a similar age group of syphilis infection, 100 versus 17%, respectively. Moreover, as opposed to T. pallidum subsp. pallidum, T. pallidum subsp. pertenue does not cross the placenta. Offspring born to yaws-infected mothers did not produce immunoglobulin M antibodies and their organs, examined by PCR and rabbit infectivity test (RIT), were all negative. Examination of a large number of tissues and organs in adult, neonate, and maternal yaws by PCR and RIT clearly demonstrated that, unlike syphilis, there was a low incidence and short persistence of the yaws pathogen in internal organs. These findings stress the dermotropic rather than the organotropic character of yaws and provide further evidence of distinctive biological and pathological differences between yaws and venereal syphilis.     

Surface Characterization of Virulent Treponema pallidum

Characterization of the surface of Treponema pallidum was accomplished by [¹²⁵I]lactoperoxidase-catalyzed iodination of intact organisms and sensitive radioimmunoprecipitation and gel electrophoresis technology. At least 11 outer membrane proteins with molecular weights ranging from 89,000 (89K) to 20K were identified, and all elicited high titers of antibody in experimentally infected rabbits. Proteins of 89.5K, 29.5K, and 25.5K previously implicated as ligands involved in attachment (J. B. Baseman and E. C. Hayes, J. Exp. Med. 151:573-586, 1980) were found to reside on the treponemal surface. Low levels of the 89.5K treponemal protein were released by high salt concentrations, whereas the remaining comigrating material was neither radioiodinated nor released with selective detergents. Other lower-molecular-weight (60K, 45K, and 30K) surface proteins were extracted with octyl glucoside detergent, suggesting their hydrophobic interaction with the external membrane. The molecular organization of surface proteins was studied by employing the cross-linker dithiobis(succinimidyl)-propionate, and data suggested the presence of a highly fluid envelope resulting in random collisions by the surface proteins. The biological function of the treponemal outer envelope proteins was evaluated using, as the indicator system, adherence of T. pallidum to monolayer cultures of eucaryotic cells. Trypsin treatment of motile, freshly harvested organisms decreased the extent of surface parasitism to normal rabbit testicular cells, reinforcing the idea of the proteinaceous nature and role of treponemal ligands for attachment. Other data supported functional and antigenic relatedness among the implicated ligands. Finally, brief periodate treatment of human epithelial (HEp-2) and normal rat testicular cells as well as casein-elicited rabbit peritoneal macrophages significantly reduced the extent of treponemal parasitism, suggesting a role of specific host membrane molecules as mediators of attachment.