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

Treponema pallidum delays the apoptosis of human polymorphonuclear neutrophils through the intrinsic and extrinsic pathways

Treponema pallidum is a "stealth pathogen" responsible for infectious sexually transmitted diseases. Although neutrophils are usually present in skin lesions of early syphilis, the role of these cells in T. pallidum infection has barely been investigated. Neutrophils are short-lived cells that undergo constitutive apoptosis, and phagocytosis usually accelerates this process. Here, we demonstrated that human polymorphonuclear neutrophils (hPMNs) could phagocytose T. pallidum in vitro. An unexpected discovery was that T. pallidum inhibited hPMNs apoptosis markedly in an opsonin-independent manner. Furthermore, this phenomenon was not affected by bacterial viability, as detected by annexin V, morphology studies, and TUNEL staining. Exploration of the underlying mechanism showed that expression of the cleaved forms of caspase-3, -8, and -9 and effector caspase activity were diminished significantly in T. pallidum-infected hPMNs. T. pallidum also impaired staurosporine- and anti-Fas-induced signaling for neutrophil apoptosis. Of note, these effects were accompanied by inducing the autocrine production of the anti-apoptotic cytokine IL-8. Taken together, our data revealed that T. pallidum could inhibit the apoptosis of hPMNs through intrinsic and extrinsic pathways and provide new insights for understanding the pathogenicity mechanisms of T. pallidum.

A review of in vitro attempts to develop the axenic culture of Treponema pallidum and genomics-based suggestions to achieve this elusive goal

To date, the axenic culture of Treponema pallidum remains a challenge in the field of microbiology despite countless attempts. Here, we conducted a comprehensive bibliographic analysis using several databases and search engines, namely Pubmed, Google scholar, Google, Web of Science and Scopus. Numerous unsuccessful empiric studies have been conducted and evaluated using as criteria dark-field microscopic observation of motile spiral shaped cells in the culture and virulence of the culture through rabbit infectivity. All of these studies failed to induce rabbit infectivity, even when deemed positive after microscopic observation leading to the misnomer of avirulent T. pallidum. In fact, this criterion was improperly chosen because not all spiral shaped cells are T. pallidum. However, these studies led to the formulation of culture media particularly favourable to the growth of several species of Treponema, including Oral Microbiology and Immunology, Zürich medium (OMIZ), Oral Treponeme Enrichment Broth (OTEB) and T-Raoult, thus allowing the increase in the number of cultivable strains of Treponema. The predicted metabolic capacities of T. pallidum show limited metabolism, also exhibited by other non-cultured and pathogenic Treponema species, in contrast to cultured Treponema species. The advent of next generation sequencing represents a turning point in this field, as the knowledge inferred from the genome can finally lead to the axenic culture of T. pallidum.

Whole genome sequence of the Treponema pallidum subsp. pallidum strain Amoy: An Asian isolate highly similar to SS14

Treponema pallidum ssp. pallidum (T. pallidum), the causative agent of the sexually transmitted disease syphilis, is an uncultivatable human pathogen. The geographical differences in T. pallidum genomes leading to differences in pathogenicity are not yet understood. Presently, twelve T. pallidum genomes are available to the public, all of which are American in origin and often co-infect patients with human immunodeficiency virus (HIV). In this study, we examined the T. pallidum subsp. pallidum strain Amoy, a syphilis pathogen found in Xiamen, China. We sequenced its genome using Illumina next-generation sequencing technology and obtained a nearly (98.83%) complete genome of approximately 1.12 Mbps. The new genome shows good synteny with its five T. pallidum sibling strains (Nichols, SS14, Mexico A, DAL-1, and Chicago), among which SS14 is the strain closest to the Amoy strain. Compared with strain SS14, the Amoy strain possesses four uncharacterized strain-specific genes and is likely missing six genes, including a gene encoding the TPR domain protein, which may partially account for the comparatively low virulence and toxicity of the Amoy strain in animal infection. Notably, we did not detect the 23S rRNA A2058G/A2059G mutation in the Amoy strain, which likely explains the sensitivity of Amoy strain to macrolides. The results of this study will lead to a better understanding of the pathogenesis of syphilis and the geographical distribution of T. pallidum genotypes.

A Retrospective Study on Genetic Heterogeneity within Treponema Strains: Subpopulations Are Genetically Distinct in a Limited Number of Positions

BACKGROUND

Pathogenic uncultivable treponemes comprise human and animal pathogens including agents of syphilis, yaws, bejel, pinta, and venereal spirochetosis in rabbits and hares. A set of 10 treponemal genome sequences including those of 4 Treponema pallidum ssp. pallidum (TPA) strains (Nichols, DAL-1, Mexico A, SS14), 4 T. p. ssp. pertenue (TPE) strains (CDC-2, Gauthier, Samoa D, Fribourg-Blanc), 1 T. p. ssp. endemicum (TEN) strain (Bosnia A) and one strain (Cuniculi A) of Treponema paraluisleporidarum ecovar Cuniculus (TPLC) were examined with respect to the presence of nucleotide intrastrain heterogeneous sites.

METHODOLOGY/PRINCIPAL FINDINGS

The number of identified intrastrain heterogeneous sites in individual genomes ranged between 0 and 7. Altogether, 23 intrastrain heterogeneous sites (in 17 genes) were found in 5 out of 10 investigated treponemal genomes including TPA strains Nichols (n = 5), DAL-1 (n = 4), and SS14 (n = 7), TPE strain Samoa D (n = 1), and TEN strain Bosnia A (n = 5). Although only one heterogeneous site was identified among 4 tested TPE strains, 16 such sites were identified among 4 TPA strains. Heterogeneous sites were mostly strain-specific and were identified in four tpr genes (tprC, GI, I, K), in genes involved in bacterial motility and chemotaxis (fliI, cheC-fliY), in genes involved in cell structure (murC), translation (prfA), general and DNA metabolism (putative SAM dependent methyltransferase, topA), and in seven hypothetical genes.

CONCLUSIONS/SIGNIFICANCE

Heterogeneous sites likely represent both the selection of adaptive changes during infection of the host as well as an ongoing diversifying evolutionary process.

Structure of rrn operons in pathogenic non-cultivable treponemes: sequence but not genomic position of intergenic spacers correlates with classification of Treponema pallidum and Treponema paraluiscuniculi strains

This study examined the sequences of the two rRNA (rrn) operons of pathogenic non-cultivable treponemes, comprising 11 strains of T. pallidum ssp. pallidum (TPA), five strains of T. pallidum ssp. pertenue (TPE), two strains of T. pallidum ssp. endemicum (TEN), a simian Fribourg-Blanc strain and a rabbit T. paraluiscuniculi (TPc) strain. PCR was used to determine the type of 16S–23S ribosomal intergenic spacers in the rrn operons from 30 clinical samples belonging to five different genotypes. When compared with the TPA strains, TPc Cuniculi A strain had a 17 bp deletion, and the TPE, TEN and Fribourg-Blanc isolates had a deletion of 33 bp. Other than these deletions, only 17 heterogeneous sites were found within the entire region (excluding the 16S–23S intergenic spacer region encoding tRNA-Ile or tRNA-Ala). The pattern of nucleotide changes in the rrn operons corresponded to the classification of treponemal strains, whilst two different rrn spacer patterns (Ile/Ala and Ala/Ile) appeared to be distributed randomly across species/subspecies classification, time and geographical source of the treponemal strains. It is suggested that the random distribution of tRNA genes is caused by reciprocal translocation between repetitive sequences mediated by a recBCD-like system.

Complete genome sequence of Treponema pallidum strain DAL-1

Treponema pallidum strain DAL-1 is a human uncultivable pathogen causing the sexually transmitted disease syphilis. Strain DAL-1 was isolated from the amniotic fluid of a pregnant woman in the secondary stage of syphilis. Here we describe the 1,139,971 bp long genome of T. pallidum strain DAL-1 which was sequenced using two independent sequencing methods (454 pyrosequencing and Illumina). In rabbits, strain DAL-1 replicated better than the T. pallidum strain Nichols. The comparison of the complete DAL-1 genome sequence with the Nichols sequence revealed a list of genetic differences that are potentially responsible for the increased rabbit virulence of the DAL-1 strain.

Whole genome sequences of three Treponema pallidum ssp. pertenue strains: yaws and syphilis treponemes differ in less than 0.2% of the genome sequence

Background

The yaws treponemes, Treponema pallidum ssp. pertenue (TPE) strains, are closely related to syphilis causing strains of Treponema pallidum ssp. pallidum (TPA). Both yaws and syphilis are distinguished on the basis of epidemiological characteristics, clinical symptoms, and several genetic signatures of the corresponding causative agents.

Methodology/Principal Findings

To precisely define genetic differences between TPA and TPE, high-quality whole genome sequences of three TPE strains (Samoa D, CDC-2, Gauthier) were determined using next-generation sequencing techniques. TPE genome sequences were compared to four genomes of TPA strains (Nichols, DAL-1, SS14, Chicago). The genome structure was identical in all three TPE strains with similar length ranging between 1,139,330 bp and 1,139,744 bp. No major genome rearrangements were found when compared to the four TPA genomes. The whole genome nucleotide divergence (d_A) between TPA and TPE subspecies was 4.7 and 4.8 times higher than the observed nucleotide diversity (π) among TPA and TPE strains, respectively, corresponding to 99.8% identity between TPA and TPE genomes. A set of 97 (9.9%) TPE genes encoded proteins containing two or more amino acid replacements or other major sequence changes. The TPE divergent genes were mostly from the group encoding potential virulence factors and genes encoding proteins with unknown function.

Conclusions/Significance

Hypothetical genes, with genetic differences, consistently found between TPE and TPA strains are candidates for syphilitic treponemes virulence factors. Seventeen TPE genes were predicted under positive selection, and eleven of them coded either for predicted exported proteins or membrane proteins suggesting their possible association with the cell surface. Sequence changes between TPE and TPA strains and changes specific to individual strains represent suitable targets for subspecies- and strain-specific molecular diagnostics.

Spirochete Treponema pallidum ssp. pertenue (TPE) is the causative agent of yaws while strains of Treponema pallidum ssp. pallidum (TPA) cause syphilis. Both yaws and syphilis are distinguished on the basis of epidemiological characteristics and clinical symptoms. Neither treponeme can reproduce outside the host organism, which precludes the use of standard molecular biology techniques used to study cultivable pathogens. In this study, we determined high quality whole genome sequences of TPE strains and compared them to known genetic information for T. pallidum ssp. pallidum strains. The genome structure was identical in all three TPE strains and also between TPA and TPE strains. The TPE genome length ranged between 1,139,330 bp and 1,139,744 bp. The overall sequence identity between TPA and TPE genomes was 99.8%, indicating that the two pathogens are extremely closely related. A set of 34 TPE genes (3.5%) encoded proteins containing six or more amino acid replacements or other major sequence changes. These genes more often belonged to the group of genes with predicted virulence and unknown functions suggesting their involvement in infection differences between yaws and syphilis.

Complete genome sequence of Treponema paraluiscuniculi, strain Cuniculi A: the loss of infectivity to humans is associated with genome decay

Treponema paraluiscuniculi is the causative agent of rabbit venereal spirochetosis. It is not infectious to humans, although its genome structure is very closely related to other pathogenic Treponema species including Treponema pallidum subspecies pallidum, the etiological agent of syphilis. In this study, the genome sequence of Treponema paraluiscuniculi, strain Cuniculi A, was determined by a combination of several high-throughput sequencing strategies. Whereas the overall size (1,133,390 bp), arrangement, and gene content of the Cuniculi A genome closely resembled those of the T. pallidum genome, the T. paraluiscuniculi genome contained a markedly higher number of pseudogenes and gene fragments (51). In addition to pseudogenes, 33 divergent genes were also found in the T. paraluiscuniculi genome. A set of 32 (out of 84) affected genes encoded proteins of known or predicted function in the Nichols genome. These proteins included virulence factors, gene regulators and components of DNA repair and recombination. The majority (52 or 61.9%) of the Cuniculi A pseudogenes and divergent genes were of unknown function. Our results indicate that T. paraluiscuniculi has evolved from a T. pallidum-like ancestor and adapted to a specialized host-associated niche (rabbits) during loss of infectivity to humans. The genes that are inactivated or altered in T. paraluiscuniculi are candidates for virulence factors important in the infectivity and pathogenesis of T. pallidum subspecies.

Genome analysis of Treponema pallidum subsp. pallidum and subsp. pertenue strains: most of the genetic differences are localized in six regions

The genomes of eight treponemes including T. p. pallidum strains (Nichols, SS14, DAL-1 and Mexico A), T. p. pertenue strains (Samoa D, CDC-2 and Gauthier), and the Fribourg-Blanc isolate, were amplified in 133 overlapping amplicons, and the restriction patterns of these fragments were compared. The approximate sizes of the genomes investigated based on this whole genome fingerprinting (WGF) analysis ranged from 1139.3-1140.4 kb, with the estimated genome sequence identity of 99.57-99.98% in the homologous genome regions. Restriction target site analysis, detecting the presence of 1773 individual restriction sites found in the reference Nichols genome, revealed a high genome structure similarity of all strains. The unclassified simian Fribourg-Blanc isolate was more closely related to T. p. pertenue than to T. p. pallidum strains. Most of the genetic differences between T. p. pallidum and T. p. pertenue strains were accumulated in six genomic regions. These genome differences likely contribute to the observed differences in pathogenicity between T. p. pallidum and T. p. pertenue strains. These regions of sequence divergence could be used for the molecular detection and discrimination of syphilis and yaws strains.

Complete genome sequence of Treponema pallidum ssp. pallidum strain SS14 determined with oligonucleotide arrays

Background

Syphilis spirochete Treponema pallidum ssp. pallidum remains the enigmatic pathogen, since no virulence factors have been identified and the pathogenesis of the disease is poorly understood. Increasing rates of new syphilis cases per year have been observed recently.

Results

The genome of the SS14 strain was sequenced to high accuracy by an oligonucleotide array strategy requiring hybridization to only three arrays (Comparative Genome Sequencing, CGS). Gaps in the resulting sequence were filled with targeted dideoxy-terminators (DDT) sequencing and the sequence was confirmed by whole genome fingerprinting (WGF). When compared to the Nichols strain, 327 single nucleotide substitutions (224 transitions, 103 transversions), 14 deletions, and 18 insertions were found. On the proteome level, the highest frequency of amino acid-altering substitution polymorphisms was in novel genes, while the lowest was in housekeeping genes, as expected by their evolutionary conservation. Evidence was also found for hypervariable regions and multiple regions showing intrastrain heterogeneity in the T. pallidum chromosome.

Conclusion

The observed genetic changes do not have influence on the ability of Treponema pallidum to cause syphilitic infection, since both SS14 and Nichols are virulent in rabbit. However, this is the first assessment of the degree of variation between the two syphilis pathogens and paves the way for phylogenetic studies of this fascinating organism.

A novel Treponema pallidum antigen, TP0136, is an outer membrane protein that binds human fibronectin

The antigenicity, structural location, and function of the predicted lipoprotein TP0136 of Treponema pallidum subsp. pallidum were investigated based on previous screening studies indicating that anti-TP0136 antibodies are present in the sera of syphilis patients and experimentally infected rabbits. Recombinant TP0136 (rTP0136) protein was purified and shown to be strongly antigenic during human and experimental rabbit infection. The TP0136 protein was exposed on the surface of the bacterial outer membrane and bound to the host extracellular matrix glycoproteins fibronectin and laminin. In addition, the TP0136 open reading frame was shown to be highly polymorphic among T. pallidum subspecies and strains at the nucleotide and amino acid levels. Finally, the ability of rTP0136 protein to act as a protective antigen to subsequent challenge with infectious T. pallidum in the rabbit model of infection was assessed. Immunization with rTP0136 delayed ulceration but did not prevent infection or the formation of lesions. These results demonstrate that TP0136 is expressed on the outer membrane of the treponeme during infection and may be involved in attachment to host extracellular matrix components.

Genome differences between Treponema pallidum subsp. pallidum strain Nichols and T. paraluiscuniculi strain Cuniculi A

The genome of Treponema paraluiscuniculi strain Cuniculi A was compared to the genome of the syphilis spirochete Treponema pallidum subsp. pallidum strain Nichols using DNA microarray hybridization, whole-genome fingerprinting, and DNA sequencing. A DNA microarray of T. pallidum subsp. pallidum Nichols containing all 1,039 predicted open reading frame PCR products was used to identify deletions and major sequence changes in the Cuniculi A genome. Using these approaches, deletions, insertions, and prominent sequence changes were found in 38 gene homologs and six intergenic regions of the Cuniculi A genome when it was compared to the genome of T. pallidum subsp. pallidum Nichols. Most of the observed differences were localized in tpr loci and the vicinity of these loci. In addition, 14 other genes were found to contain frameshift mutations resulting in major changes in protein sequences. Analysis of restriction target sites representing 0.34% of the total genome length and DNA sequencing of three PCR products (0.46% of the total genome length) amplified from Cuniculi A chromosomal regions and comparison to the Nichols genome revealed a sequence similarity of 98.6 to 99.3%. These results are consistent with a close genetic relationship among the T. pallidum strains and subspecies and a strong, but relatively divergent connection between the human and rabbit pathogens.

Transcriptome of Treponema pallidum: gene expression profile during experimental rabbit infection

RNA transcript levels in the syphilis spirochete Treponema pallidum subsp. pallidum (Nichols) isolated from experimentally infected rabbits were determined by the use of DNA microarray technology. This characterization of the T. pallidum transcriptome during experimental infection provides further insight into the importance of gene expression levels for the survival and pathogenesis of this bacterium.

Complete genome sequence of Treponema pallidum, the syphilis spirochete

The complete genome sequence of Treponema pallidum was determined and shown to be 1,138,006 base pairs containing 1041 predicted coding sequences (open reading frames). Systems for DNA replication, transcription, translation, and repair are intact, but catabolic and biosynthetic activities are minimized. The number of identifiable transporters is small, and no phosphoenolpyruvate:phosphotransferase carbohydrate transporters were found. Potential virulence factors include a family of 12 potential membrane proteins and several putative hemolysins. Comparison of the T. pallidum genome sequence with that of another pathogenic spirochete, Borrelia burgdorferi, the agent of Lyme disease, identified unique and common genes and substantiates the considerable diversity observed among pathogenic spirochetes.

Identification, sequences, and expression of Treponema pallidum chemotaxis genes

Treponema pallidum, the agent of syphilis, is a pathogenic spirochete that has no known mechanisms of genetic exchange and cannot be continuously cultivated in vitro. A probe based on the nucleotide sequence of the T. pallidum cheA gene was used to screen a T. pallidum genomic DNA library. A treponemal DNA region containing four open reading frames (orfs) was identified. The proteins encoded by these orfs have significant homology with proteins involved in bacterial chemotaxis. The orfs have been designated cheA, cheW, cheX, and cheY. The cheA, cheW, and cheY genes were individually-cloned and expressed in vitro. The observed molecular mass of each protein correlated well with its predicted molecular mass. Reverse transcriptase-PCR data indicate that cheA through cheY are co-transcribed. The organization of these genes suggests that they comprise an operon. We hypothesize that the ability to sense and respond to nutrient gradients is important for the survival and dissemination of T. pallidum in vivo. The presence of a putative che operon strongly suggests that T. pallidum has the potential for a chemotactic response.

Physical map of the genome of Treponema pallidum subsp. pallidum (Nichols)

A physical map of the chromosome of Treponema pallidum subsp. pallidum (Nichols), the causative agent of syphilis, was constructed from restriction fragments produced by NotI, SfiI, and SrfI. These rare-cutting restriction endonucleases cleaved the T. pallidum genome into 16, 8, and 15 fragments, respectively. Summation of the physical lengths of the fragments indicates that the chromosome of T. pallidum subsp. pallidum is approximately 1,030 to 1,080 kbp in size. The physical map was constructed by hybridizing a variety of probes to Southern blots of single and double digests of T. pallidum genomic DNA separated by contour-clamped homogeneous electric field electrophoresis. Probes included cosmid clones constructed from T. pallidum subsp. pallidum genomic DNA, restriction fragments excised from gels, and selected genes. Physical mapping confirmed that the chromosome of T. pallidum subsp. pallidum is circular, as the SfiI and SrfI maps formed complete circles. A total of 13 genes, including those encoding five membrane lipoproteins (tpn47, tpn41, tpn29-35, tpn17, and tpn15), a putative outer membrane porin (tpn50), the flagellar sheath and hook proteins (flaA and flgE), the cytoplasmic filament protein (cfpA), 16S rRNA (rrnA), a major sigma factor (rpoD), and a homolog of cysteinyl-tRNA synthetase (cysS), have been localized in the physical map as a first step toward studying the genetic organization of this noncultivable pathogen.

Development and evaluation of a monoclonal antibody inhibition enzyme linked immunosorbent assay to diagnose syphilis

A highly specific inhibition enzyme linked immunosorbent assay (ELISA) using murine monoclonal antibodies to treponemes has been developed to diagnose syphilis. The monoclonal antibodies used in this study were reactive to antigens of both Treponema pallidum and Treponema pertenue and not to antigens of non-pathogenic treponemes. Inhibition of the binding of monoclonal antibody to the treponemal antigens was successful with serum antibodies of patients with syphilis in an inhibition ELISA using monoclonal antibodies raised against T pallidum antigens with molecular weights of 42 and 47 kilodaltons. In contrast, the binding of monoclonal antibodies obtained by immunising mice with treponemal membrane protein TmpB, derived from recombinant DNA was not inhibited by serum antibodies from patients with syphilis. The sensitivity of the inhibition ELISA using monoclonal antibody against the 47 kilodalton T pallidum antigen was 93% in 58 serum samples from patients with untreated syphilis. The sensitivity was 79% if the monoclonal antibody against the 42 kilodalton T pallidum antigen was used. By a combination of the test results obtained in these two inhibition assays a sensitivity of 97% in the 58 serum samples from untreated patients and 64% in 64 from treated patients was obtained. The specificity of the inhibition ELISA performed with either monoclonal antibody was 100% in 500 serum samples from non-infected people. The specificity in 432 non-infected patients attending a sexually transmitted disease clinic was 98.8% for the monoclonal antibody against the 42 kilodalton antigen, 99.5% for the monoclonal antibody against the 47 kilodalton antigen, and 98.4% for the combined antibodies. The sensitivity and specificity of the inhibition ELISA using the combination of test results obtained by the application of the monoclonal antibodies against the 42 kilodalton treponemal membrane protein, TmpA, and against the 47 kilodalton T pallidum antigen were comparable with those of the Treponema pallidum haemagglutination assay (TPHA) and the fluorescent treponemal antibody absorption (FTA-ABS) test for diagnosing early untreated disease. The inhibition ELISA offers the potential for additional confirmation of early untreated syphilis. Its use for confirming late untreated syphilis is still under investigation. The test is highly specific for pathogenic treponemes and does not need sorbens.

Enzyme-linked immunofiltration assay for rapid serodiagnosis of syphilis

A new rapid technique for detection of serum treponemal antibodies is described which is based on an enzyme-linked immunoassay using nitrocellulose as solid phase. With this technique antigen-antibody binding is accelerated by the filtration of the antibody solution through the antigen-coated nitrocellulose filter instead of its remaining over the solid phase for incubation. Test results are available in less than 15 min. Serum specimens from 255 syphilitics and 829 non-infected subjects were investigated. The sensitivity and specificity of the Treponema pallidum enzyme-linked immunofiltration assay were comparable to those of the Treponema pallidum haemagglutination assay and the fluorescent treponemal antibody absorption test.

Enzyme linked immunosorbent assays with Treponema pallidum or axial filament of T phagedenis biotype Reiter as antigen: evaluation as screening tests for syphilis

Enzyme linked immunosorbent assays with an ultrasonicate of Treponema pallidum (TP-ELISA) or axial filament of Treponema phagedenis biotype Reiter (AF-ELISA) were developed to detect treponemal antibody. TP-ELISA and AF-ELISA were compared with the T pallidum haemagglutination assay (TPHA), the fluorescent treponemal antibody-absorbed (FTA-ABS) test, and the Venereal Disease Research Laboratory (VDRL) test for sensitivity and specificity of serodiagnosis of syphilis. A total of 1423 serum samples, 253 from patients with various stages of syphilis, 500 from patients attending a sexually transmitted disease (STD) clinic, and 670 from people without syphilis, were investigated. At all stages of syphilis the sensitivity of the TP-ELISA, the AF-ELISA, the TPHA, and the FTA-ABS test did not differ significantly, except that the AF-ELISA was less sensitive than the TPHA (p less than 0.05) for treated syphilis. In primary syphilis, neurosyphilis, and treated syphilis the TP-ELISA and AF-ELISA were significantly more sensitive than the VDRL test (p less than 0.05). The specificity of all tests was comparable (p greater than 0.05). The TP-ELISA and AF-ELISA appear to be good alternatives to the TPHA as screening tests for syphilis. Because of the easy availability of a well defined antigen the AF-ELISA seems to be better suited for large scale testing.

Antigenic evidence for host origin of exudative fluids in lesions of Treponema pallidum-infected rabbits

Mucoid fluid accumulating within syphilitic lesions has been considered to be of Treponema pallidum origin. To test this assumption, we examined testicular exudative fluids from T. pallidum-infected rabbits for the presence of T. pallidum antigens by various sensitive immunochemical methods, including Western blot analysis. Antigenic analysis of these fluids revealed host components but not treponemal antigens. Prolonged immunization of rabbits, guinea pigs, and a goat with this material in complete Freund adjuvant elicited low titers (fluorescent-treponemal-antibody test titer, less than or equal to 10) of antitreponemal antibodies in the rabbits and guinea pigs but not in the goat. The data suggest that these mucoid fluids are of host origin. The presence of mucopolysaccharides in these fluids may be related to the infective process. The possible mechanism by which mucopolysaccharides protect T. pallidum from immune mechanisms and its potential relationship to the pathogenesis of the disease are discussed.

Molecular cloning and expression of Treponema pallidum DNA in Escherichia coli K-12

A gene bank of Treponema pallidum DNA in Escherichia coli K-12 was constructed by cloning SauI-cleaved T. pallidum DNA into the cosmid pHC79. Sixteen of 800 clones investigated produced one or more antigens that reacted with antibodies from syphilitic patients. According to the separation pattern of the antigens produced on sodium dodecyl sulfate-polyacrylamide gels, six different phenotypes were distinguished among these 16 clones. These antigens reacted also with anti-T. pallidum rabbit serum. No antibodies against the cloned antigens were found in normal rabbit serum and in nonsyphilitic human serum. The antigens produced by the E. coli K-12 recombinant DNA clones comigrated in sodium dodecyl sulfate-polyacrylamide gels with antigens extracted from T. pallidum bacteria, suggesting that the treponemal DNA is well expressed in E. coli K-12. Several of the cosmid recombinant plasmids have been subcloned, resulting in smaller T. pallidum recombinant plasmids which are more stably maintained in the cell and produce more treponemal antigen. Monoclonal antibodies were raised against T. pallidum, and one hybridoma produced antibodies that reacted not only with an antigen from T. pallidum but also with the antigen produced by one of the E. coli clones.

Identification and preliminary characterization of Treponema pallidum protein antigens expressed in Escherichia coli

We have previously described the construction in Escherichia coli K-12 of a hybrid plasmid colony bank of Treponema pallidum (Nichols strain) genomic DNA. By screening a portion of this bank with an in situ immunoassay, we identified six E. coli clones that express T. pallidum antigens. In this study, the recombinant plasmids from each of these clones have been analyzed in E. coli maxicells and have been found to encode a number of proteins that are not of vector pBR322 origin and are, therefore, of treponemal origin. In each case, several of these proteins can be specifically precipitated from solubilized maxicell extracts by high-titer experimental rabbit syphilitic serum. Certain of these proteins are also precipitated by high-titer latent human syphilitic sera (HSS). The T. pallidum DNA inserts in these plasmids range in size from 6.2 to 14 kilobase pairs, and from the restriction patterns of the inserts and the protein profiles generated by each plasmid in maxicells, it is apparent that we have recovered a total of four unique clones from our colony bank. Recombinant plasmids pLVS3 and pLVS5 were of particular interest. Plasmid pLVS3 encodes three major protein antigens with molecular weights of 39,000, 35,000, and 25,000. These three proteins, which were not recognized by pooled normal human sera, were efficiently precipitated by most secondary HSS, latent HSS, and late HSS tested. These proteins were also precipitated, although somewhat inefficiently, by most primary HSS tested. Plasmid pLVS5 encodes a major protein antigen with a molecular weight of 32,000 and several minor protein antigens that, although efficiently precipitated by experimental rabbit syphilitic serum, were generally not recognized by the various HSS tested. Evidence is presented indicating that the protein antigens encoded by plasmids pLVS3 and pLVS5 are specific for pathogenic treponemal species. We have also demonstrated that immunoglobulin G antibodies directed against these protein antigens can be detected in rabbits experimentally infected with T. pallidum Nichols as early as 11 days postinfection.

Development of monoclonal antibodies that recognize Treponema pallidum

We developed a panel of monoclonal antibodies to Treponema pallidum (Nichols) antigens, some of which recognize treponemal antigens on T. pallidum (Nichols), T. pallidum strain 14, and Treponema phagedenis biotype Reiter. The antibodies were detected by either an enzyme-linked immunosorbent assay or a radioimmunoassay.

Molecular characterization of common treponemal antigens

A molecular characterization of cross-reactive antigens of Treponema pallidum Nichols and Treponema phagedenis biotype Reiter that are reactive with normal and syphilitic human sera is described. At least 8 common polypeptides, 14 T. pallidum-specific antigens, and 2 T. phagedenis biotype Reiter-specific antigens were identified.

Cloning and expression of Treponema pallidum protein antigens in Escherichia coli

Difficulties in culturing the bacterium Treponema pallidum have greatly hindered syphilis research. Recently, several laboratories have accomplished the expression of T. pallidum antigens in Escherichia coli. It is anticipated that treponemal antigens produced by recombinant DNA technology will provide new tools for investigating the pathogenesis and immunobiology of T. pallidum infection.

Concanavalin A-mediated affinity film for Treponema pallidum

Freshly extracted Treponema pallidum bound to glass cover slips preexposed to specific lectins, permitting biological testing in the absence of complex tissue fluids.

Cell-mediated immunity in Treponema pallidum infected rabbits: in vitro response of splenic and lymph node lymphocytes to mitogens and specific antigens

Peripheral blood lymphocytes from Treponema pallidum infected rabbits respond poorly to mitogen and specific antigens when cultured in the presence of autologous serum. Reactivity of lymphocytes from the spleen and popliteal lymph nodes of T. pallidum infected rabbits have therefore been examined by lymphocyte transformation using the mitogens phytohaemagglutinin (PHA) and concanavalin A (Con A) and extracts of T. pallidum. Spleen cell populations, both T cell enriched (by nylon wool elution) and non-nylon wool treated, which respond to T. pallidum as early as ten days post infection in normal serum, were suppressed in responses to T. pallidum when cultured in autologous serum. The same lymphocytes responded normally to PHA and Con A. Lymph node cells from infected rabbits responded normally to both T. pallidum antigen and mitogens in either autologous or normal rabbit serum. These data indicate that splenic lymphocytes are sensitive to regulatory factors in autologous serum during the early stages of T. pallidum infection whereas lymph node cells are not.

Surface-associated host proteins on virulent Treponema pallidum

A surface coat of host serum proteins was detected on virulent Treponema pallidum by sodium dodecyl sulfate-gel electrophoresis. The loosely associated serum proteins could be removed by repeated washings in a protein-free medium. Washed T. pallidum retained the ability to readsorb numerous host proteins from rabbit serum as well as iodinated rabbit or human albumin. In addition, various avidly associated host serum proteins including albumin, alpha(2)-macroglobulin, transferrin, ceruloplasmin, immunoglobulin G, immunoglobulin M, and C3 were identified on the outer envelope of washed treponemes by an immunoadsorbent technique with protein A-bearing staphylococcus. Hyaluronidase treatment did not remove the avidly associated host proteins from the surface of washed treponemes, whereas trypsin treatment resulted in decreased levels of agglutination. Electrophoretic patterns of trypsin-treated treponemes showed that treponemal proteins as well as adsorbed host proteins were released concurrently by protease digestion. Reacquisition studies involving alpha(2)-macroglobulin and transferrin suggested the presence of noncompetitive binding sites for serum proteins on the treponemal outer envelope. Finally, differences among the T. pallidum preparations from individual rabbits with respect to incorporation of [(35)S]methionine, extent of agglutination with antisera, and length of time required for removal of avidly associated host proteins by trypsin treatment indicated biological variability among the treponemal populations.

Unique lipid composition of Treponema pallidum (Nichols virulent strain)

The lipid composition of Treponema pallidum (Nichols virulent strain) was determined after purification of the organisms from the infected testes of corticosteroid-treated rabbits by differential centrifugation, filtration through Nuclepore membranes, and sedimentation in Hypaque density gradients. The total lipids were comprised of 32.2% neutral lipids, mainly cholesterol, and 67.8% phospholipids consisting of phosphatidylcholine (32.1%), sphingomyelin (14.8%), cardiolipin (13.0%), phosphatidylethanolamine (6.2%), phosphatidylinositol-serine (1.2%), and lysophosphatidylcholine (0.4%). Monoglycosyldiglyceride, a glycolipid comprising 25 to 50% of thetotal lipid of all Treponema previously examined, was not detected. The fatty acid composition was similar but quntitatively distinct from that of the infected testes tissue.

Unsustained multiplication of treponema pallidum (nichols virulent strain) in vitro in the presence of oxygen

Treponema pallidum (Nichols virulent strain) was incubated with or without oxygen using a modified medium supplemented with reduced glutathione and a variety of nutrients (PRNF10-B). Two- to fourfold increases in treponemal numbers were observed in cultures without mammalian cells within 96 h of incubation under 5 to 6% oxygen. Treponemal motility and multiplication were maintained more satisfactorily in cultures that were diluted and transferred daily, using an equal volume of fresh medium. Treponemes incubated without oxygen did not significantly increase in number. Virulent microorganisms were detected for at least 96 h in the cell-free system. In the presence of 3 to 4% oxygen, two- to fivefold increases in treponemal numbers were observed in the supernatant fluids of cultures containing human prepuce cells after 48 to 120 h at 35 degrees C. Without oxygen, treponemal numbers rarely approached a threefold increase. Virulent treponemes were detected by the rabbit skin lesion test after at least 120 h in vitro. Regardless of the system of incubation, increases in treponemal numbers could not be sustained for longer than 120 h, and treponemal virulence decreased as a function of time in vitro.

Genetics of Treponema: relationship between Treponema pallidum and five cultivable treponemes

Three genetically distinct groups of treponemes have been identified by saturation reassociation assays using 125I-labeled treponemal DNAs. The three groups are (i) virulent Treponema pallidum (Nichols strain), (ii) T. phagedenis and its biotypes Reiter and Kazan 5, and (iii) T. refringens biotypes Nichols and Noguchi. There is no detectable DNA sequence homology (less than 5%) among the three groups. The groups have distinct guanine + cytosine contents: 52.4 to 53.7% for T. pallidum, 41.5% for T. refringens, and 38 to 39% for T. phagedenis.

Catabolism of glucose and fatty acids by virulent Treponema pallidum

We describe a procedure which permits essentially full recovery of physiologically active Treponema pallidum from rabbit testicular extracts and greatly reduces contaminating tissue material. Such preparations were employed for investigations of the ability of T. pallidum to catabolize glucose and fatty acids. Radiorespirometric studies revealed that glucose and pyruvate, but not oleate or palmitate, could be degraded to CO2. The use of differentially labeled glucose, in conjunction with enzymatic analyses, indicated that glucose was catabolized by a combination of the Embden-Meyerhoff-Parnas and hexose monophosphate pathways. Pyruvate was degraded to CO2 from only the carboxyl position, suggesting the absence of a functioning Krebs cycle; this was substantiated by additional enzyme analyses and radiorespirometric experiments. Oleate and palmitate were incorporated but not catabolized by beta-oxidation. Glucose, although catabolized, was not incorporated. The potential significance of these findings is discussed.

Virulent Treponema pallidum: aerobe or anaerobe

Substrate degradation and protein synthesis served as indicators of metabolism in virulent Treponema pallidum. Opitmal metabolic activity in these spirochetes was observed at 10 to 20% O2 concentrations, with markedly reduced activity at higher or lower O2 levels or under anaerobiosis; alternate functioning electron acceptors that might substitute for O2 were not found. Carbon monoxide and cyanide at concentrations that inactivate cytochrome oxidase were not effective metabolic poisons for T. pallidum, although Micrococcus lutea, a strict aerobe with cytochrome-dependent respiration, was inhibited under similar experimental conditions. Motility of virulent T. pallidum was vigorous in the presence of O2 and sluggish or inhibited in its absence, reinforcing the role of O2 in T. pallidum metabolism.

Isolation and purification of Treponema pallidum from syphilitic lesions in rabbits

Treponema pallidum were extracted from testicular syphilomas of corticosteroid-treated rabbits and purified by differential centrifugation. The steroid therapy allowed a longer holding time for infected rabbits, which produced greater treponeme yields, averaging 1.58 x 10(10) treponemes per rabbit. The treatment, which also diminished cellular infiltration and increased the extracellular mucoid material in lesions, produced much cleaner suspensions than preparations from nontreated animals. Most of the treponemes in the purified suspensions were still motile, and none carried demonstrable host immunoglobulin. The preparations were free of recognizable host tissue debris and they contained, on the average, 1.9 x 10(-7) mug of protein per treponeme.