Cell-mediated immunity during syphilis

Novelty in the gut: a review of the gastrointestinal manifestations of syphilis

Syphilis is a systemic infection caused by the spirochete Treponema pallidum. It is transmitted during pregnancy or through sexual contact. Signs and symptoms vary depending on the clinical stage of the disease. Syphilis has been well-studied, and the introduction of penicillin has resulted in a decline in the number of new cases and deaths. Recently, however, there has been a surge in new cases in young people, especially those with human immunodeficiency virus (HIV). This epidemiological shift has been attributed to increased sexual activity, risky sexual behaviors, and immunodeficiency. There is a paucity of data on gastrointestinal (GI) manifestations of syphilis owing to its rarity and lack of physician awareness. T. pallidum can seed to any part of the GI tract, resulting in esophagitis, gastritis, hepatitis, pancreatitis, or proctocolitis. Depending on the affected part of the GI tract, syphilis can present with nausea, vomiting, painless esophageal ulcers, dysphagia, abdominal pain, weight loss due to early satiety, diarrhea, melena, hematochezia, dyschezia, or anorectal ulcers. Given its indolent clinical course and vague presentation, GI syphilis can mimic other GI disorders, which can delay diagnosis and treatment. A detailed medical history, physical examination, serological tests, and endoscopy can provide a definitive diagnosis. Syphilis and its GI complications are usually treated with long-acting intramuscular penicillin benzathine, and rarely with a 14-day course of intravenous penicillin. Herein, we describe the clinical features, etiopathogenesis, diagnosis, and treatment of GI syphilis. This primer should aid clinicians in timely diagnosis and treatment of various presentations of GI syphilis.

Investigation of the immune escape mechanism of Treponema pallidum

BACKGROUND

Syphilis is a chronic sexually transmitted disease caused by Treponema pallidum subspecies pallidum (T. pallidum), which is a public health problem that seriously affects human health worldwide. T. pallidum is characterized by early transmission and immune escape and is therefore termed an "invisible pathogen".

METHODS

This review systematically summarizes the host's innate and adaptive immune responses to T. pallidum infection as well as the escape mechanisms of T. pallidum.

PURPOSE

To lay the foundation for assessing the pathogenic mechanism and the systematic prevention and treatment of syphilis.

CONCLUSION

The immune escape mechanism of T. pallidum plays an important role in its survival. Exploring the occurrence and development of these mechanisms has laid the foundation for the development of syphilis vaccine.

Syphilis incidence in men who have sex with men with human immunodeficiency virus comorbidity and the importance of integrating sexually transmitted infection prevention into HIV care

INTRODUCTION

Syphilis continues to be a growing epidemic among men who have sex with men (MSM), particularly for those living with the human immunodeficiency virus (HIV). In 2016, MSM accounted for 80% of primary and secondary syphilis diagnoses in men in the United States; almost half of who were also HIV-infected. The synergistic relationship between HIV and syphilis has significant implications not only for HIV patient management, but also for sexually transmitted infection (STI) control among MSM. Areas covered: We review the literature on STI screening and treatment barriers at the patient-, provider-, and health system-levels, and present strategies to incorporate STI prevention into HIV care settings. Expert commentary: Integration of STI prevention into HIV care is paramount to stop the epidemic of not only syphilis, but also other curable STIs like gonorrhea and chlamydia. Although guidelines have been established for STI testing in HIV-infected MSM, screening rates continue to be lower than desired. Gonorrhea and chlamydia screening is below 50% in HIV-infected MSM; interventions that improve testing of those two infections must be implemented. For syphilis control, other additional strategies such as chemoprophylaxis should be considered given syphilis screening is above 50% in HIV-infected MSM.

Evolution of the syphilis epidemic among men who have sex with men

Syphilis has existed for millenni, but its epidemiology was only recently linked to men who have sex with men (MSM) after the introduction of penicillin in the 1940s; the syphilis epidemic became concentrated within the MSM community in subsequent decades. The HIV/AIDS epidemic in the 1980s led to a surge of new syphilis cases and revealed the potentiation between HIV and syphilis, as evidenced by a shift in the natural history of neurosyphilis. In response, MSM revolutionised their sexual behaviour by implementing community-driven seroadaptive strategies to stem HIV transmission. The Centers for Disease Control in the US called for the elimination of syphilis in the late 1990s since the rates had fallen sharply but this effort was overtaken by a resurgence of global outbreaks among MSM in the 2000s, many of which were linked to methamphetamine use and sexual networking websites. Syphilis remains highly prevalent today, especially among MSM and individuals infected with HIV, and it continues to present a significant public health conundrum. Innovative syphilis prevention strategies are warranted. MSM engaging in high-risk behaviour such as condomless anal receptive intercourse, sex with multiple partners or recreational drug use should be routinely screened for syphilis infection; they should also be counselled about the limits of seroadaptive behaviours and HIV pre-exposure prophylaxis as they relate to syphilis transmission.

[Bilateral panuveitis with papillary swelling]

Lues (syphilis) is a chronic cyclic infectious disease which can continue for decades if untreated. A simultaneous HIV infection can result in false negative results in serological tests for lues. The occurrence of neurolues has frequently been described in HIV positive patients. In the differential diagnosis an early ocular manifestion of lues should be considered. A 40-year-old homosexual patient presented in our hospital with bilateral pain-free increasing loss of vision. The ophthalmological examination revealed an intermediately expressed panuveitis with streaky opacity of the vitreous body and pronounced bilateral papillary swelling. Following systemic anti-inflammatory therapy with cortisone the situation worsened after initial improvement. The serological investigations revealed both HIV and lues infections. Intravenous therapy with mega units of penicillin led to a slow improvement of clinical symptoms and also vision. In cases of uveitis of unclear origin together with a HIV infection and suspected lues, regular serological testing should be carried out because the occurrence of late complications of lues can be avoided by the diagnosis of lues and adequate treatment.

Treponema pallidum elicits innate and adaptive cellular immune responses in skin and blood during secondary syphilis: a flow-cytometric analysis

BACKGROUND

Syphilis is caused by the spirochetal pathogen Treponema pallidum. The local and systemic cellular immune responses elicited by the bacterium have not been well studied in humans.

METHODS

We used multiparameter flow cytometry to characterize leukocyte immunophenotypes in skin and peripheral blood from 23 patients with secondary syphilis and 5 healthy control subjects recruited in Cali, Colombia. Dermal leukocytes were obtained from fluid aspirated from epidermal suction blisters raised over secondary syphilis skin lesions.

RESULTS

Compared with peripheral blood (PB), blister fluids (BFs) were enriched for CD4(+) and CD8(+) T cells, activated monocytes/macrophages, and CD11c(+) monocytoid and CD11c(-) plasmacytoid dendritic cells (mDCs and pDCs, respectively). Nearly all mDCs in BFs expressed the human immunodeficiency virus (HIV) coreceptors CCR5 and DC-specific intercellular adhesion molecule 3-grabbing nonintegrin (DC-SIGN) and high levels of human leukocyte antigen (HLA)-DR. Dermal pDCs expressed both HIV coreceptors without increases in HLA-DR intensity. Compared with normal blood, circulating mDCs in patients with syphilis expressed higher levels of both CCR5 and DC-SIGN, whereas circulating pDCs in patients expressed only higher levels of DC-SIGN. Most dermal T cells were CCR5(+) and displayed a memory (CD27(+)/CD45RO(+)) or memory/effector (CD27(-)/CD45RO(+)) immunophenotype. A corresponding shift toward memory and memory/effector immunophenotype was clearly discernible among circulating CD4(+) T cells. Compared with PB from control subjects, a larger percentage of CD4(+) T cells in PB from patients with syphilis expressed the activation markers CD69 and CD38.

CONCLUSIONS

During secondary syphilis, T. pallidum simultaneously elicits local and systemic innate and adaptive immune responses that may set the stage for the bidirectional transmission of HIV.

Syphilis and human immunodeficiency virus co-infection

Co-infection of syphilis and AIDS has profound implications for the African American community. The purpose of this review is to: evaluate the historical background of HIV and syphilis and their similarities in pathogenesis; review the epidemiology of syphilis and HIV co-infection, and implications for continued prevention efforts; examine the effect of syphilis on HIV transmission and acquisition; and, to examine the effects of HIV infection on syphilis transmission, diagnostic and serologic changes, clinical course, and treatment. The prevalence of HIV is higher in those with syphilis; moreover, the prevalence of HIV and syphilis co-infection is highest in African Americans. There may be humoral and cellular immune similarities. HIV may affect the transmission of syphilis, alter its serologic diagnosis, and accelerate and change the clinical course and response to treatment. In conclusion, combined infection of HIV and syphilis may alter the clinical presentation and course of either disease. There are historical and immunologic similarities and the high prevalence in African Americans compared to other groups is of great importance for prevention efforts.

Role of L3T4+ and 38+ T-cell subsets in resistance against infection with Treponema pallidum subsp. pertenue in hamsters

The protective immunity conferred by T-cell subsets against infection with Treponema pallidum subsp. pertenue was studied. We demonstrated that hamster T cells can be separated into two subsets by monoclonal antibody (MAb) GK 1.5 (anti-L3T4) and MAb 38. Eighty-five percent of hamster thymocytes were L3T4+ and 87% were 38+ cells; 84% were dual positive for MAbs anti-L3T4 and 38. In the peripheral lymph nodes, however, the L3T4+ and 38+ T cells were mutually exclusive according to two-color immunofluorescence analysis. The two T-cell subsets were found to be functionally distinct according to their secretion of interleukin 2 (IL-2) when stimulated with concanavalin A. The L3T4+ cells secreted IL-2 and had characteristics of T helper cells, while the 38+ cells did not secrete IL-2 and appeared to be T cytotoxic-suppressor cells. Transfer of 4 x 10(6) helper or cytotoxic-suppressor T lymphocytes from T. pallidum subsp. pertenue-immune hamsters protected irradiated naive hamsters against challenge with this subspecies. IL-2 production could still be detected in the irradiated recipients 12 days after irradiation of naive recipients, although at a low level. This suggests that the remaining lymph node cells could support the survival and expansion of the infused cytotoxic-suppressor T cells. No accumulation of macrophages was observed in regional lymph nodes of immune T-cell recipients within 10 days of infection. Instead, there was an influx of polymorphonuclear neutrophils in all animals injected with T. pallidum subsp. pertenue. This report demonstrates that hamster T cells can be separated into two phenotypically and functionally distinct subsets and that both T-cell subsets confer protection against challenge with T. pallidum subsp. pertenue.

Gummatous lesions in men infected with human immunodeficiency virus and syphilis

Two HIV-infected men are reported who developed gummatous lesions more than 12 months after appropriate treatment of presumptive syphilis. In one patient the lesions developed without any change in the VDRL titre. The most likely explanation for these lesions is reactivation of syphilis in the context of HIV infection. As these lesions respond to penicillin, the possible reactivation of appropriately treated syphilis, or even yaws, should now be considered in any ulcerative lesion in HIV infected individuals at risk from treponemal infection.

Immune studies in infants with congenital syphilis

Seventeen neonates with congenital syphilis were studied to determine the immune response of the fetus following intra-uterine infection with Treponema pallidum. The results were compared with those from healthy controls matched for gestational age, birth weight and sex. B cells, IgM, and circulating immune complexes were significantly elevated in the infected newborns. There were no differences in lymphocyte transformation to phytohaemagglutinin (PHA) and in the CD3, CD4, and CD8 lymphocytes between infants with congenital syphilis and controls. Newborns with congenital syphilis have a heightened humoral response but no quantitative abnormality in cell-mediated immunity. Speculation on the role of the circulating immune complexes is presented.

Immune T cells sorted by flow cytometry confer protection against infection with Treponema pallidum subsp. pertenue in hamsters

The role of cell-mediated immunity against infection with Treponema pallidum subsp. pertenue in humans or experimental animals is unclear. Hamsters injected subcutaneously in the hind paws with 4 x 10(6) unfractionated lymph node cells or enriched lymph node T cells (immunoglobulin negative, Ia negative) from T. pallidum subsp. pertenue-immune hamsters were resistant to challenge with T. pallidum subsp. pertenue. The popliteal lymph nodes of hamsters that received immune cells weighed less and had significantly fewer treponemes than did lymph nodes from hamsters infused with cells from nonimmune donors. Furthermore, recipients of immune T cells failed to develop antitreponemal antibodies 21 days after challenge. Enriched T cells were obtained by flow cytometric separation by using monoclonal anti-Ia antibody 14-4-4s, which identified hamster B cells. Flow cytometric analysis by two-color immunofluorescent staining with anti-hamster-immunoglobulin and monoclonal anti-Ia antibody 14-4-4s confirmed that monoclonal anti-Ia antibody 14-4-4s recognized B cells. In addition, lymph node cells obtained after treatment with anti-Ia monoclonal antibody 14-4-4s and complement were 97% T cells, as determined by monoclonal antibody 20, a hamster T-cell marker. These results demonstrated that highly enriched T cells (immunoglobulin negative, Ia negative) from T. pallidum subsp. pertenue-immune hamsters conferred partial protection on hamsters against infection with T. pallidum subsp. pertenue.

Infiltrate of syphilitic lesions before and after treatment

An immunohistological study of skin biopsy specimens from patients with early syphilis was undertaken before and after treatment (one day after intramuscular administration of 2.4 MIU benzathine penicillin and eight days later, after a total administration of 3.6 MIU. In chancres from seronegative patients treatment with 3.6 MIU usually resulted in fewer immunocompetent cells in the infiltrate. In lesions of secondary syphilis treatment with 2.4 MIU benzathine penicillin produced a significant decrease in immunocompetent cells. After treatment with 3.6 MIU there was no further decrease. It was worth noticing that even eight to nine days after the initial pretreatment biopsy, when 3.6 MIU had been administered, the overall lymphohistiocytic infiltrate was not substantially diminished. Significantly more suppressor (T8+) cells were found in lesions of primary syphilis than of secondary syphilis, and they showed remarkable exocytosis. Activated local T8+ cells may release immunosuppressive lymphokines.

Antigens of Borrelia burgdorferi recognized during Lyme disease. Appearance of a new immunoglobulin M response and expansion of the immunoglobulin G response late in the illness

Using immunoblots, we identified proteins of Borrelia burgdorferi bound by IgM and IgG antibodies during Lyme disease. In 12 patients with early disease alone, both the IgM and IgG responses were restricted primarily to a 41-kD antigen. This limited response disappeared within several months. In contrast, among six patients with prolonged illness, the IgM response to the 41-kD protein sometimes persisted for months to years, and late in the illness during arthritis, a new IgM response sometimes developed to a 34-kD component of the organism. The IgG response in these patients appeared in a characteristic sequential pattern over months to years to as many as 11 spirochetal antigens. The appearance of a new IgM response and the expansion of the IgG response late in the illness, and the lack of such responses in patients with early disease alone, suggest that B. burgdorferi remains alive throughout the illness.

Treponemal infection specifically enhances node T-cell regulation of macrophage activity

Hamsters experimentally inoculated in the inguinal region with Treponema pallidum subsp. endemicum develop considerable pathology at that site. We examined the cell populations from these inguinal lymph nodes to determine their intercellular responses to infection. In vitro, syphilitic-node T cells markedly suppressed C3b receptor-mediated ingestion (C3bMI) in syphilitic macrophages derived from sites both proximal and distal to the inoculation. This activity was more pronounced when node T cells rather than peritoneal T cells were used. When treponemal preparations or live treponemes were added to the coculture system, the suppression was specifically enhanced, whereas the addition of heterologous agents did not promote this effect. Syphilitic macrophages from either compartment cultured alone showed no significant inhibition of C3bMI. In parallel studies on syphilitic macrophages, we observed that the expression of Ia quickly became elevated and was sustained throughout the infection. Moreover, in vitro culturing of the syphilitic-node T cells with these macrophages did not alter this function. These observations suggest that the syphilitic node contains a subpopulation of T cells that can selectively suppress macrophage C3bMI activity and concurrently regulate their cellular response to treponemal infection.

Enhanced primary resistance to Treponema pallidum infection and increased susceptibility to toxoplasmosis in T-cell-depleted guinea pigs

Strain 2 guinea pigs made T-cell deficient by thymectomy and irradiation and protected with syngeneic bone-marrow cells (TXB guinea pigs) have a surprisingly high level of resistance to cutaneous syphilis and to the dissemination of treponemes to the draining lymph node. Compared with normal euthymic controls infected with Treponema pallidum Nichols, syphilitic TXB guinea pigs developed fewer and less severe skin lesions and their lymph nodes contained lower numbers of treponemes. Associated with this evidence for enhanced innate resistance was the ability of the TXB host to produce, during each test interval of a primary infection, more antitreponemal antibodies than that of their euthymic counterparts. Similar levels of partial protection against cutaneous and disseminated syphilitic infection and elevated antibody levels occurred in challenged normal guinea pigs passively immunized with lymphocytes from T. pallidum-infected TXB donors. In contrast, the capacity of the TXB host to be protected against a lethal infection with the unrelated intracellular protozoan parasite Toxoplasma gondii was greatly impaired unless it received an intravenous infusion of normal syngeneic thymocytes. These seemingly paradoxical results are explained primarily in terms of a residual T-helper-cell population in the TXB guinea pig which is large and competent enough to generate antisyphilis, but not anti-Toxoplasma, immunity.

Acquired resistance and expression of a protective humoral immune response in guinea pigs infected with Treponema pallidum Nichols

Resistance to cutaneous syphilitic reinfection in strain 2 and strain 13 guinea pigs developed gradually 3 to 7 months after primary infection and reached maximum levels at 6 to 7 months after the induction of primary cutaneous disease. Associated with this acquired resistance was the occurrence of Arthus reactions and anamnestic-type antibody responses. Passive transfer of immune serum containing high-titered treponemal antibody into normal strain 2 guinea pigs significantly delayed the appearance and markedly diminished the severity and duration of skin lesions that developed after these recipients were challenged with treponemes but did not prevent the dissemination of organisms to the draining lymph nodes. These findings provide direct evidence that syphilitic infection elicits the formation of serum factors that are, at least, partially protective against symptomatic disease.

Antibody-mediated protection of guinea-pigs against infection with Treponema pallidum

The results of this study demonstrate that passive transfer of immune serum containing high titres of treponemal antibody into normal guinea-pigs significantly lowered the percentage of animals developing chancre-like lesions, but did not prevent the dissemination of organisms into the draining lymph nodes after these recipients were challenged with virulent treponemes. Similar levels of partial protection against cutaneous syphilitic infection occurred in guinea-pigs receiving partially purified anti-treponemal immunoglobulins, while immune serum depleted of IgG by treatment with Protein A was totally unprotective. Western blotting analysis revealed the presence of several Treponema pallidum polypeptides detectable by immune guinea-pig IgG. These findings provide direct evidence to suggest that syphilitic infection induces the formation of serum factors, residing primarily in the IgG fraction of immune serum, that are capable of providing a limited form of resistance to symptomatic disease.

Monoclonal antibody with hemagglutination, immobilization, and neutralization activities defines an immunodominant, 47,000 mol wt, surface-exposed immunogen of Treponema pallidum (Nichols)

Radioimmunoprecipitation (RIP) analyses performed on 125I-surface-labeled Treponema pallidum cells using various immune sera revealed the presence of six major surface antigens (immunogens) with apparent molecular weights of 47 K, 36 K, 34 K, 32 K, 29 K, and 13 K. Among these, the 47 K surface antigen was most abundant. Radioimmunoprecipitation assays using 125I-labeled T. phagedenis biotype Reiter or immunoblot analyses using the same strain, failed to reveal the presence of the 47 K mol wt antigen in the representative nonpathogenic treponeme. Preabsorption of anti-T. pallidum immune rabbit serum (IRS) with the Reiter organism did not remove anti-T. pallidum antibodies from immune serum that reacted with the 47 K mol wt immunogen or other immunogens of T. pallidum present in the characteristic antigenic profile. Monoclonal antibodies (mAb) directed specifically against the 47 K mol wt immunogen of T. pallidum also failed to react with an analogous 47 K mol wt component in Treponema phagedenis biotype Reiter, further suggesting the unique presence of this antigen in pathogenic treponemes. The presence of the 47 K mol wt surface immunogen in pathogenic treponemes other than T. pallidum subspecies pallidum was also observed (43). Anti-47 K immunogen mAb was nonreactive against rabbit IgG or IgM. mAb directed specifically against the 47 K mol wt immunogen of T. pallidum was examined for strategic functional activities. It was found to be reactive in the microhemagglutination assay for T. pallidum antibodies, the T. pallidum immobilization test, and was found to be capable of significant blockage of attachment of virulent T. pallidum to host cells in tissue culture. Additional significant biological activity for the anti-47 K mol wt immunogen mAb was revealed through results of the in vitro-in vivo neutralization test of Bishop and Miller, in which a 99% or 100% neutralizing activity was demonstrated. The combined data of this study suggest that the 47 K mol wt immunogen of T. pallidum represents an abundant, immunodominant, surface-exposed immunogen possessing potential biological importance in the pathogenesis and immunology of T. pallidum infection. These studies serve to establish the first functionally defined immunogen for T. pallidum, which may represent the major immunogen of the organism.

Inhibitory effect of syphilitic rabbit serum on DNA synthesis in rabbit cells in vitro

A previously described toxic factor associated with Treponema pallidum (Nichols) and found in extracts of syphilitic rabbit testes has now also been detected in syphilitic rabbit serum. The toxic factor, which inhibits DNA synthesis in baby rabbit genital organ (BRGO) cells in vitro, is present in rabbit serum up to 30 days after infection with T pallidum.

Treponema pallidum receptor binding proteins interact with fibronectin

Analysis of plasma proteins avidly bound to T. pallidum surfaces revealed the ability of T. pallidum to acquire numerous host macromolecules. No acquisition was evident by the avirulent spirochete, T. phagedenis biotype Reiter. Western blotting technology using hyperimmune antifibronectin serum as a probe revealed the ability of virulent treponemes to avidly bind fibronectin from a complex medium such as plasma. The specificity of the tiplike adherence of motile T. pallidum to fibronectin-coated glass surfaces and to fibronectin on HEp-2 cells was reinforced by the observation that pretreatment of coverslips or cell monolayers with monospecific antiserum against fibronectin substantially reduced T. pallidum attachment. The stoichiometric binding of T. pallidum to fibronectin-coated coverslips and the inability of unlabeled or 35S-radiolabeled treponemes to interact with glass surfaces treated with other plasma proteins further established the specific nature of the interaction between virulent T. pallidum and fibronectin. The avid association between three outer envelope proteins of T. pallidum and fibronectin was also demonstrated. These treponemal surface proteins have been previously identified as putative receptor-binding proteins responsible for T. pallidum parasitism of host cells. The data suggest that surface fibronectin mediates tip-oriented attachment of T. pallidum to host cells via a receptor-ligand mechanism of recognition.

Failure to detect cell-mediated cytotoxicity against Chlamydia trachomatis-infected cells

Mice were infected with Chlamydia trachomatis (L2/434) and at various intervals after infection their lymphoid cells were tested directly for cytotoxic activity against Chlamydia-infected L929 cells. In a modified cell-mediated lympholysis assay, splenic, lymph node, and peritoneal exudate cells did not significantly cause the destruction of the infected targets, although infection did result in the formation of antichlamydial antibodies. Whereas chlamydial antigens are capable of activating cell-mediated immunity in other experimental models, our results show that either this chlamydial infection does not induce the generation of cytotoxic effector cells or chlamydial antigens are absent from the surface of infected cells.

Fluctuations in natural killer cell activity in early syphilis

The natural killer cell activity was studied in 25 patients with primary, secondary, or latent syphilis before and after treatment. In primary syphilis natural killer cell activity was increased, especially in patients lacking circulating lipoidal antibodies. In patients who had become seroreactive in the lipoidal tests it was depressed in those with secondary and latent syphilis. The natural killer cell activity thus becomes activated by the syphilitic infection but is significantly reduced during progression of the disease. The importance of the natural killer cell activity in controlling syphilitic infection is questionable.

Langerhans cells in granulomatous syphilis

In a case of granulomatous syphilis (transitional state between early and late syphilis), several Langerhans cells (LC) were present in the basal and medial part of the epidermis. Evidence of LC activation was given by the presence of many Langerhans granules, vesicles, a large Golgi apparatus and, sometimes, Golgi complexes. In some LC, signs of degeneration were visible. Langerhans granules surrounded by cytoplasmic material were present in the intercellular space of the epidermis. Apposition of lymphocytes to LC in the dermal space supports the role of LC in immunologic mechanisms. This was further confirmed by signs of phagocytosis in LC. The interaction of LC with intra-epidermal microorganisms (as, for instance, the Treponema pallidum) might be important in the development of the epidermotropic infiltration. This mainly consists of lymphocytes, which sometimes form a pseudolymphoma. A correlation between LC and granuloma formation is suggested.

Murine monoclonal antibodies specific for virulent Treponema pallidum (Nichols)

Murine anti-Treponema pallidum (Nichols) lymphocyte hybridoma cell lines secreting monoclonal antibodies against a variety of treponemal antigens have been generated. Hybridomas isolated were of three major types: those that were directed specifically against T. pallidum antigens, those that were directed against treponemal group antigens (as evidenced by their cross-reactivity with T. phagedenis biotype Reiter antigens), and those that cross-reacted with both treponemal as well as rabbit host testicular tissue antigens. The majority (31 of 39 clones) of these anti-T. pallidum hybridomas, which produced monoclonal antibodies of mouse isotypes immunoglobulin G1 (IgG1), IgG2a, IgG2b, IgG3 or IgM, were directed specifically against T. pallidum and not other treponemal or rabbit antigens tested by radioimmunoassay. Four of these T. pallidum-specific hybridomas secreted monoclonal antibodies with greater binding affinity for "aged" rather than freshly isolated intact T. pallidum cells, suggesting a possible specificity for "unmasked" surface antigens of T. pallidum. Six anti-T. pallidum hybridomas produced complement-fixing monoclonal antibodies (IgG2a, IgG2b, or IgM) that were capable of immobilizing virulent treponemes in the T. pallidum immobilization (TPI) test; these may represent biologically active monoclonal antibodies against treponemal surface antigens. Three other hybridomas secreted monoclonal antibodies which bound to both T. pallidum and T. phagedenis biotype Reiter antigens, thus demonstrating a possible specificity for treponemal group antigens. Five hybridoma cell lines were also isolated which produced IgM monoclonal antibodies that cross-reacted with all treponemal and rabbit host testicular tissue antigens employed in the radioimmunoassays. This report describes the construction and characteristics of these hybridoma cell lines. The potential applications of the anti-T. pallidum monoclonal antibodies are discussed.

Purification of a Reiter treponemal protein antigen that is immunologically related to an antigen in Treponema pallidum

A protein antigen called TR-o was isolated from supernatant of a sonically treated Reiter treponeme. The isolation procedure included anion-exchange chromatography on Whatman DE-52, hydrophobic interaction chromatography on decyl agarose, and finally gel filtration on Ac-A-22 Ultrogel. The fractionations were monitored by immunoprecipitation techniques. The recovery was found to be 35%, and the isolated protein was enriched 220 times. The molecular weight of the native protein was estimated to be 550,000 by polyacrylamide gel electrophoresis and 450,000 by gel filtration. Only one 66,000-molecular-weight polypeptide was found by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified protein. The protein was immunologically pure when tested in crossed immunoelectrophoresis against polyspecific rabbit anti-Reiter immunoglobulin, detecting more than 40 treponemal antigens. A monospecific antiserum was raised in rabbits immunized with the purified protein. Monospecific rabbit anti-TR-o gave strong fluorescence with both the Reiter treponeme and Treponema pallidum. The corresponding antigen in T. pallidum could not be demonstrated directly in a crude T. pallidum sonic extract, but rabbit anti-T. pallidum immunoglobulin contained precipitating antibodies against the purified protein. No antibodies against TR-o were found in selected sera from patients with secondary syphilis reactive in traditional syphilis tests.

Analysis of serum IgG against Treponema pallidum protein antigens in experimentally infected rabbits

Sensitive and highly specific radioimmunoprecipitation and gel electrophoreses-fluorography were used to monitor the serum IgG response of experimentally infected rabbits against key protein antigens of Treponema pallidum. The sera from six rabbits challenged intradermally (ID) and six intratesticularly (IT) with T pallidum were examined over a period of four months. A specific antibody response to most treponemal surface proteins (including those ligands implicated as mediating host-cell-surface adherence) developed by about day 20 after inoculation. Maximum antibody concentrations against most of these immunogens were detected by day 50 in all animals irrespective of the route of inoculation. Differences as well as similarities in the IgG response to infection were observed among selected rabbits. Furthermore, the antibody reactivity of each animal was comparable to that of human sera from patients with secondary syphilis. Antibody directed against treponemal outer envelope proteins was detected by preferential agglutination of washed radiolabelled organisms with protein A-bearing Staphylococcus aureus in the presence of syphilitic rabbit sera.

Sequential changes in susceptibility to Treponema pallidum of rabbits previously infected with Treponema paraluis-cuniculi

Rabbits immunised with virulent Treponema paraluis-cuniculi were challenged intradermally with graded doses of Treponema pallidum at three, five, seven, 12, and 30 months to ascertain the level of protection to T pallidum at various intervals after immunisation.Rabbits challenged at three months after immunisation showed no protection against T pallidum and developed syphilitic lesions significantly faster than the control rabbits, which suggests that the former rabbits were immunosuppressed. Some protection was evident at five and seven months after immunisation, as fewer inoculation sites developed syphilitic lesions with challenges of 10(3), 10(2), and 10 T pallidum and lesions developed significantly slower with 10(6) challenge. Two rabbits showed significant protection at 12 months after immunisation but a third, presumably still immunosuppressed, developed lesions significantly faster than the control rabbits after challenge. At 30 months after immunisation one rabbit was completely protected and developed no lesions after challenge; the other rabbit showed only partial protection against challenge with 10(4), 10(3), and 10(2) but complete protection against challenge with 10 T pallidum.T paraluis-cuniculi appeared to induce a state of immunosuppression by three months after infection; in one rabbit this may have been 12 months. In most immunised rabbits, however, limited cross-protection to low challenge doses of T pallidum developed by five months and was also detectable at seven and 12 months. Only one rabbit was completely resistant to challenge with 10(4)T pallidum after 30 months and another was only partly immune. Thus, T paraluis-cuniculi infection does not produce a rapid pronounced cross-immunity to T pallidum in rabbits, which may thus limit its usefulness as a vaccine against syphilis.

Experimental infection of man with rabbit-virulent Treponema paraluis-cuniculi

Virulent Treponema paraluis-cuniculi was inoculated intradermally into the arm of a human volunteer and into the shaved backs of 10 rabbits. An identical, but heat-killed, preparation was inoculated into the opposite arm of the volunteer as control. A superficial and transient infection developed in the volunteer, shown by a small zone of erythema that persisted for 24 days. The control preparation caused a smaller zone of erythema that disappeared after five days. A very poor immune response was detected by standard serological tests for syphilis. The inoculated rabbits developed lesions about six days after infection and seroconverted by 84 days. The poor antitreponemal antibody response to T paraluis-cuniculi infection in the volunteer suggests that this naturally attenuated treponeme may not be suitable as a vaccine against infection with t pallidum in humans.

Surface characterization of virulent Treponema pallidum

Characterization of the surface of Treponema pallidum was accomplished by [(125)I]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.

A histopathologic and immunologic study of the course of syphilis in the experimentally infected rabbit. Demonstration of long-lasting cellular immunity

Inoculation of the causative agent of syphilis, Treponema pallidum into the testes of rabbits initiated the following sequence of events: 1) a rapid proliferation of organisms in the interstitial tissues of the testes, reaching a maximum at about 10-11 days after infection; 2) systemic spread of organisms primarily in the lymphoid organs; 3) a prompt immune response manifested by hyperplasia of T cell domains in draining lymph nodes and spleen, blast transformation responses of lymphoid cells to sonicates of T pallidum, the appearance of serum antibody, and the marked infiltration of the infected areas of the testes by T cells; 4) essential clearing of organisms identified by immunofluorescence from the infected site 10-14 days after infection associated with evolution of the inflammatory response from primarily a T cell infiltrate to a larger mononuclear cell type, and the immunofluorescent identification of presumptive T pallidum antigen in macrophages; 5) interstitial fibrosis or resolution 17-21 days after infection so that examination of infected testes from 1 to 24 months later reveals foci of tubular atrophy and fibrosis of varying size, alternating with regenerated tubules, separated by interstitial areas with only minimal fibrosis. During the long period of latency there is no evidence of atrophy or hypoplasia of the lymphoid organs and long-lasting T cell memory with regard to T pallidum sonicates is demonstrable. Reinfection of previously inoculated rabbits indicates partial protection at 25 days after infection followed by essentially complete protection after 55 days. It is concluded that there is a prompt and long-lasting immune response to T pallidum in experimentally infected rabbits. The main mechanism for destruction of infecting organisms appears to be T-cell-initiated macrophage-mediated destruction, but a role for antibody dependent phagocytosis cannot be ruled out. The reason that some organisms may survive in various body organs remains unknown, but possible explanations are presented.

Uneven distribution of antitreponema antibody acitivity in differing immunoglobulin G fractions from patients with early syphilis

Three fractions, containing immunoglobulin G's (IgG's) of differing relative electrophoretic mobility, were isolated from sera of 33 male patients with untreated early syphilis. Serological testing, employing four different serodiagnostic procedures for these fractions at equal amounts of IgG, revealed a very constant reaction pattern for all patients. In the earliest stages of the disease, the most basic fraction was the first to show antibody activity. In progressive stages, antibody activity subsequently was also found in the two less basic fractions. However, in all stages of disease studied, the basic part of the IgG made the largest contribution of the total antibody activity within the IgG class, indicating an uneven distribution of antitreponema antibody activity over heterogeneous IgG. Several possible explanations of the observations are discussed.

Immunoglobulin-bearing lymphoid cells in primary syphilis. Quantitative and elution studies

The delay in antibody production in response to infection with Treponema pallidum may be caused by a block in the differentiation of antigen-stimulated B (Bursa-dependent) lymphoid cells towards plasma cells. This hypothesis was tested by a study to detect clonal expansion of immunoglobulin-bearing B lymphoid cells by in-vitro immunofluorescence tests in patients with primary syphilis. In addition, antibodies eluted from circulating lymphoid cells were investigated for treponemal binding by the enzyme-linked immunosorbent assay, the T pallidum immobilisation test, and the immunoglobulin class-specific FTA-ABS test. Results indicated that the number of IgG-bearing lymphoid cells were increased in patients with primary syphilis. However, in only a few cases could antitreponemal antibodies be eluted from isolated lymphoid cells. For this reason, the original hypothesis was rejected.

Molecular characterization of receptor binding proteins and immunogens of virulent Treponema pallidum

Receptor binding proteins of Treponema pallidum were identified by incubation of [35S]methionine-labeled, soluble T. pallidum preparations with formaldehyde-fixed HEp-2 cells. Three major treponemal proteins (bands 1--3) that avidly bound to the eucaryotic cell surface were detected by sodium dodecylsulfate-polyacrylamide gel electrophoresis and fluorography. Brief trypsin treatment of HEp-2 cells before formaldehyde fixation reduced the extent of the interaction of these treponemal macromolecules, which implicated receptor-mediated attachment mechanisms. The presence of unlabeled T. pallidum preparations directly competed with radiolabeled T. pallidum samples for the available HEp-2 cells, which suggested a limiting number of membrane binding sites. Samples of unlabeled avirulent Reiter treponeme did not compete. T. Pallidum immunogens were examined by radioimmunoprecipitation with human and rabbit syphilitic sera. Of interest were the similarities and extent of the humoral response represented by the detection of antigen-antibody complexes against numberous treponemal proteins, including bands 1--3. T. pallidum portein band 1 appeared to be the major antigenic stimulus. Formation of antigen-antibody complexes between 35S-labeled T. pallidum proteins and human syphilitic sera was prevented by unlabeled T. pallidum but not by T. phagedenis preparations, which demonstrated specificity of the reaction. Gel profiles of radioimmunoprecipitation assays using radiolabeled T. pallidum antigens and human syphilitic and yaws sera delineated both the similarities and differences in the humoral response to these two spirochetes. The latter suggested both overlapping and distinguishing antigenic properties between T. pallidum and T. pertenue. Detection in yaws sera of specific antibody against T. pallidum protein bands 1--3 further incriminates the role of these three treponemal proteins as virulence determinants.

Antitreponemal IgE in early syphilis

Using a solid-phase radioimmunoassay technique, mean serum IgE concentrations were found to be raised in patients with early syphilis. Antitreponemal specificity of the IgE response was investigated by the fluorescent treponemal antibody absorption test using a fluorescein-isothiocyanate-labelled antiserum against the Fc-fragment of human IgE. Validity of this test procedure was assessed by blocking experiments. The results provide evidence of the antitreponemal specificity of the IgE response in syphilis and indicate a possible role for antitreponemal IgE in the pathogenesis of the Jarisch-Herxheimer reaction and in the immune-complex origin of some of the lesions of secondary syphilis.

Rate of clearance of virulent Treponema pallidum (Nichols) from the blood stream of normal, Mycobacterium bovis BCG-treated, and immune syphilitic rabbits

The rate of clearance of virulent Treponema pallidum (Nichols) from the blood stream of normal rabbits and rabbits previously treated with Mycobacterium bovis BCG was similar, there being treponemes still circulating 8 h after intravenous inoculation. In contrast, immune syphilitic rabbits cleared the virulent treponemes within 1 to 2 hours. Rabbits with passive humoral immunity to T. pallidum (after the transfer of 70 ml of immune serum) showed a similar clearance rate to that of the immune rabbits. Rabbits previously treated with BCG and with passive humoral immunity did not show a synergistic enhanced clearance rate, it being similar to that of immune rabbits.

Clinical application of serological tests for syphilis

This article differentiates and describes the serological tests for syphilis- antitreponemal antibody tests (TPI, FTA-ABS, TPHA), non-treponemal antigen test (VDRL)-their clinical and serological correlation, the responses to therapy and the biologically false positive syndrome.

Limited protection of rabbits against infection with Treponema pallidum by immune rabbit sera

After intradermal infection of rabbits with 3 x 10(6) Treponema pallidum (Melbourne 1 strain) samples of serum were taken at one, two, three, four, and six months after infection. Normal rabbits were passively immunised with these sera, challenged with intradermal doses (10(4), 10(3), 10(2), 10) of T. pallidum, and the latent periods of infection, lesion diameters, and the number of inoculation sites developing into lesions were observed. The sera taken at three, four, and six months reduced the number of intradermal inoculation sites that developed into syphilitic lesions after challenge with 10 T. pallidum. These same three sera also increased the latent period of infection after challenge with 10(4) T. pallidum. The transfer of 50 ml of immune serum per rabbit over a nine-day period before challenge had very little effect on the course of the challenge infection. Only a low level of immunity in rabbits to this strain of T. pallidum appears to be mediated by immune serum but this small degree of protection did increase with time after infection. Enhanced growth of T. pallidum in the serum-recipient rabbits did not occur, thus suggesting that none of the sera was immunosuppressive.