CD4+ lymphocytes and gamma interferon predominate in local immune responses in early experimental syphilis

Jarisch-Herxheimer Reaction After Benzathine Penicillin G Treatment in Adults With Early Syphilis: Secondary Analysis of a Randomized Clinical Trial

Importance

Syphilis rates have been increasing in the US for the past decade. The incidence of the Jarisch-Herxheimer reaction (JHR) after penicillin treatment for early syphilis is reported to range from 8% to 56%.

Objectives

To prospectively assess the incidence of JHR signs and symptoms among adults with early syphilis treated with benzathine penicillin G and to document factors associated with JHR and benzathine penicillin G treatment response outcomes.

Design, Setting, and Participants

The main study was designed as a phase 4 randomized clinical trial to compare the treatment efficacy of 1 vs 3 doses of benzathine penicillin G in adults with early syphilis, measured as serologic response at 6 months. A total of 249 adults with or without HIV were screened and enrolled between October 31, 2018, and March 3, 2020. Participants were screened and enrolled at 10 US study sites in the Sexually Transmitted Infections Clinical Trials Group. Statistical analysis for this secondary analysis took place between March 2023 and August 2024.

Intervention

Participants received a first dose of benzathine penicillin G, 2.4 million units intramuscularly, at the enrollment visit. The JHR assessment window was day 1 to day 7 after the first dose of benzathine penicillin G.

Main Outcomes and Measures

Primary outcomes in this study were the incidence of symptoms consistent with JHR within 7 days after benzathine penicillin G treatment. Unelicited and elicited symptoms were assessed by participant self-report using a standardized checklist during contact made by a study clinician. Factors associated with JHR were collected at baseline, and serologic treatment response was assessed at 6 months. Posttreatment incident JHR symptoms were captured as safety outcomes for this trial. Analysis was performed on an intention-to-treat basis.

Results

Of 249 participants, the median age was 32 years (IQR, 27-41 years), 242 (97.2%) were men, and 153 (61.4%) were living with HIV. One or more JHR symptoms occurred in 59 participants (23.7%) treated for early syphilis, with a median symptom onset at 4.9 hours (IQR, 3.0-9.2 hours) and a median duration of 12.8 hours (IQR, 5.0-24.0 hours). Symptom onset was within 12 hours of treatment for 49 of 57 participants (86.0%). Among 59 symptomatic participants, myalgias (30 [50.8%]), chills (27 [45.8%]), weakness (23 [39.0%]), and feverishness (21 [35.6%]) were most common. In adjusted models, JHR was associated with secondary syphilis (adjusted odds ratio [AOR], 2.91 [95% CI, 1.51-5.61]) and the absence of HIV (AOR for living with HIV, 0.49 [95% CI, 0.26-0.94]). The proportion of participants with a serologic treatment response to benzathine penicillin G at 6 months was higher among participants with JHR (84.7% [50 of 59] vs 68.9% [131 of 190] without JHR).

Conclusions and Relevance

In this prespecified secondary analysis of a randomized clinical trial of early syphilis treatment wtih benzathine penicillin G in adults, approximately 1 in 4 participants experienced short-lived JHR symptoms, which were associated with secondary syphilis stage, lack of HIV, and successful treatment outcomes at 6 months. These messages could be used in patient counseling.

Trial Registration

ClinicalTrials.gov Identifier: NCT03637660.

The Significance of the Cell-Mediated Host Immune Response in Syphilis

Syphilis, caused by the highly invasive pathogen Treponema pallidum, remains one of the oldest and most significant public health challenges. According to the World Health Organization (WHO), the number of new syphilis cases among adults aged 15-49 years in 2022 was estimated at approximately 8 million, with notable increases observed in Europe, the Americas, and Africa. The cellular immune response plays a critical role in combating this infection, and its insufficient activity may contribute to chronic progression of the disease. T. pallidum effectively evades the host immune response, enabling its prolonged survival within the host and increasing the risk of late complications such as neurosyphilis and cardiovascular syphilis. This review article discusses the mechanisms of cellular immune responses in T. pallidum infection, including T lymphocyte activation, proinflammatory cytokine production, and the roles of macrophages and dendritic cells in pathogen recognition and elimination. Additionally, it examines the immune evasion strategies employed by T. pallidum, such as the low immunogenicity of its antigens and its ability to suppress the activation of effector cells. A comprehensive understanding of the current knowledge regarding cellular immune mechanisms may contribute to the development of more effective diagnostic and therapeutic approaches in syphilis management.

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.

New Pathways in Syphilis Vaccine Development

ABSTRACT

The New Pathways in Syphilis Vaccine Development meeting was held before the start of the STI & HIV 2023 World Congress as a pre-meeting symposium to highlight recent advances in the development of an effective syphilis vaccine and discuss the challenges still faced by investigators. Internationally renowned public health officials, clinical investigators, and basic researchers from academia, government, and community-based organizations met on July 24, 2023, in Chicago, Illinois. Four speakers discussed key research findings in syphilis vaccine development, which included antigen selection, identification of epitopes associated with protective immunity, and delivery platforms, with great emphasis on development of chimeric antigens. Significant progress was also shown on the elucidation of Treponema pallidum genomes from virtually all continents to assess the diversity in vaccine candidates of the syphilis spirochete.

The Role of Cells and Cytokines in Male Infertility Induced by Orchitis

Recent studies on male infertility reveal a growing worry: more infertile men are dealing with inflammation in the testis. Analyzing testicular biopsies from infertile men highlights a significant presence of inflammation. This connection, supported by clinical and pathological evidence, emphasizes that testicular inflammation hampers sperm production, leading to lasting declines in sperm count and quality. However, the exact reasons behind male infertility due to orchitis, a type of testicular inflammation, are still uncertain. Understanding these fundamental aspects of molecular signals and cellular mechanisms in testicular inflammation is crucial. Our review delves into recent literature with a dual objective: elucidating potential mechanisms involving immune cells, non-immune cells, and cytokines that link orchitis to male infertility, while also paving the way for precise interventions and solutions to address the challenges of male infertility.

Treponema pallidum Periplasmic and Membrane Proteins Are Recognized by Circulating and Skin CD4+ T Cells

BACKGROUND

Histologic and serologic studies suggest the induction of local and systemic Treponema pallidum-specific CD4+ T-cell responses to T. pallidum infection. We hypothesized that T. pallidum-specific CD4+ T cells are detectable in blood and in the skin rash of secondary syphilis and persist in both compartments after treatment.

METHODS

Peripheral blood mononuclear cells collected from 67 participants were screened by interferon-γ (IFN-γ) ELISPOT response to T. pallidum sonicate. T. pallidum-reactive T-cell lines from blood and skin were probed for responses to 89 recombinant T. pallidum antigens. Peptide epitopes and HLA class II restriction were defined for selected antigens.

RESULTS

We detected CD4+ T-cell responses to T. pallidum sonicate ex vivo. Using T. pallidum-reactive T-cell lines we observed recognition of 14 discrete proteins, 13 of which localize to bacterial membranes or the periplasmic space. After therapy, T. pallidum-specific T cells persisted for at least 6 months in skin and 10 years in blood.

CONCLUSIONS

T. pallidum infection elicits an antigen-specific CD4+ T-cell response in blood and skin. T. pallidum-specific CD4+ T cells persist as memory in both compartments long after curative therapy. The T. pallidum antigenic targets we identified may be high-priority vaccine candidates.

Immunity to Sexually Transmitted Bacterial Infections of the Female Genital Tract: Toward Effective Vaccines

Sexually transmitted infections (STIs) caused by bacterial pathogens Chlamydia trachomatis, Neisseria gonorrhoeae, and Treponema pallidum present significant public health challenges. These infections profoundly impact reproductive health, leading to pelvic inflammatory disease, infertility, and increased susceptibility to other infections. Prevention measures, including antibiotic treatments, are limited by the often-asymptomatic nature of these infections, the need for repetitive and continual screening of sexually active persons, antibiotic resistance for gonorrhea, and shortages of penicillin for syphilis. While vaccines exist for viral STIs like human papillomavirus (HPV) and hepatitis B virus (HBV), there are no vaccines available for bacterial STIs. This review examines the immune responses in the female genital tract to these bacterial pathogens and the implications for developing effective vaccines against bacterial STIs.

Immunophenotypic variations in syphilis: insights from Mendelian randomization analysis

Background

Infection with Treponema pallidum instigates complex immune responses. Prior research has suggested that persistent Treponema pallidum infection can manipulate host immune responses and circumvent host defenses. However, the precise role of immune cells in Treponema pallidum infection across different stages remains a contentious issue.

Methods

Utilizing summary data from genome-wide association studies, we employed a two-sample Mendelian randomization method to investigate the association between 731 immunophenotypes and syphilis. Syphilis was categorized into early and late stages in this study to establish a more robust correlation and minimize bias in database sources.

Results

Our findings revealed that 33, 36, and 27 immunophenotypes of peripheral blood were associated with syphilis (regardless of disease stage), early syphilis and late syphilis, respectively. Subsequent analysis demonstrated significant variations between early and late syphilis in terms of immunophenotypes. Specifically, early syphilis showcased activated, secreting, and resting regulatory T cells, whereas late syphilis was characterized by resting Treg cells. More B cells subtypes emerged in late syphilis. Monocytes in early syphilis exhibited an intermediate and non-classical phenotype, transitioning to classical in late syphilis. Early syphilis featured naive T cells, effector memory T cells, and terminally differentiated T cells, while late syphilis predominantly presented terminally differentiated T cells. Immature myeloid-derived suppressor cells were evident in early syphilis, whereas the dendritic cell immunophenotype was exclusive to late syphilis.

Conclusion

Multiple immunophenotypes demonstrated associations with syphilis, showcasing substantial disparities between the early and late stages of the disease. These findings hold promise for informing immunologically oriented treatment strategies, paving the way for more effective and efficient syphilis interventions.

Treponema pallidum periplasmic and membrane proteins are recognized by circulating and skin CD4+ T cells

Background

Histologic and serologic studies suggest the induction of local and systemic Treponema pallidum ( Tp )-specific CD4+ T cell responses to Tp infection. We hypothesized that Tp -specific CD4+ T cells are detectable in blood and in the skin rash of secondary syphilis and persist in both compartments after treatment.

Methods

PBMC collected from 67 participants were screened by IFNγ ELISPOT response to Tp sonicate. Tp -reactive T cell lines from blood and skin were probed for responses to 88 recombinant Tp antigens. Peptide epitopes and HLA class II restriction were defined for selected antigens.

Results

We detected CD4+ T cell responses to Tp sonicate ex vivo. Using Tp -reactive T cell lines we observed recognition of 14 discrete proteins, 13 of which localize to bacterial membranes or the periplasmic space. After therapy, Tp -specific T cells persisted for at least 6 months in skin and 10 years in blood.

Conclusions

Tp infection elicits an antigen-specific CD4+ T cell response in blood and skin. Tp -specific CD4+ T cells persist as memory in both compartments long after curative therapy. The Tp antigenic targets we identified may be high priority vaccine candidates.

Screening the B- and T-cell epitope map of TP0136 and exploring their effect in a Treponema pallidum rabbit model

The systemic immune response, including B- and T-cell reactions, plays a corresponding role in syphilis infections. The TP0136 protein is a target of the immune response in infected hosts and may mediate the immune response. Here, we developed a method that combining reverse vaccine approach with Pepscan/T-cell proliferation to screen and identify three B-cell and two T-cell epitopes of TP0136, and explore the role of the B- and T-cell epitopes in immunized-infected animals. The results showed that immunized with B-cell epitopes not only had no protective effect but also aggravated the syphilitic lesion development. While immunized with T-cell epitopes of TP0136 could induce a strong Th1-cellular immunity response, which could attenuate syphilitic lesion development to a certain extent. The variation in exacerbation or attenuation of skin lesions, induced by distinct B- and T-cell epitopes of Tp0136, within the host's defense against syphilis warrants in-depth exploration.

Dysregulation of circulating T follicular helper cell subsets and their potential role in the pathogenesis of syphilis

Introduction

The role of the host immune response could be critical in the development of Treponema pallidum (Tp) infection in individuals with latent syphilis. This study aims to investigate the alterations in T follicular helper T (Tfh) cell balance among patients with secondary syphilis and latent syphilis.

Methods

30 healthy controls (HCs), 24 secondary syphilis patients and 41 latent syphilis patients were enrolled. The percentages of total Tfh, ICOS+ Tfh, PD-1+ Tfh, resting Tfh, effector Tfh, naïve Tfh, effector memory Tfh, central memory Tfh,Tfh1, Tfh2, and Tfh17 cells in the peripheral blood were all determined by flow cytometry.

Results

The percentage of total Tfh cells was significantly higher in secondary syphilis patients compared to HCs across various subsets, including ICOS+ Tfh, PD-1+ Tfh, resting Tfh, effector Tfh, naïve Tfh, effector memory Tfh, central memory Tfh, Tfh1, Tfh2, and Tfh17 cells. However, only the percentages of ICOS+ Tfh and effector memory Tfh cells showed significant increases in secondary syphilis patients and decreases in latent syphilis patients. Furthermore, the PD-1+ Tfh cells, central memory Tfh cells, and Tfh2 cells showed significant increases in latent syphilis patients, whereas naïve Tfh cells and Tfh1 cells exhibited significant decreases in secondary syphilis patients when compared to the HCs. However, no significant change was found in resting Tfh and effector Tfh in HCs and secondary syphilis patients or latent syphilis patients.

Discussion

Dysregulated ICOS+ Tfh or effector memory Tfh cells may play an important role in immune evasion in latent syphilis patients.

Syphilis vaccine: challenges, controversies and opportunities

Syphilis is a sexually or vertically (mother to fetus) transmitted disease caused by the infection of Treponema pallidum subspecie pallidum (TPA). The incidence of syphilis has increased over the past years despite the fact that this bacterium is an obligate human pathogen, the infection route is well known, and the disease can be successfully treated with penicillin. As complementary measures to preventive campaigns and early treatment of infected individuals, development of a syphilis vaccine may be crucial for controlling disease spread and/or severity, particularly in countries where the effectiveness of the aforementioned measures is limited. In the last century, several vaccine prototypes have been tested in preclinical studies, mainly in rabbits. While none of them provided protection against infection, some prototypes prevented bacteria from disseminating to distal organs, attenuated lesion development, and accelerated their healing. In spite of these promising results, there is still some controversy regarding the identification of vaccine candidates and the characteristics of a syphilis-protective immune response. In this review, we describe what is known about TPA immune response, and the main mechanisms used by this pathogen to evade it. Moreover, we emphasize the importance of integrating this knowledge, in conjunction with the characterization of outer membrane proteins (OMPs), to expedite the development of a syphilis vaccine that can protect against TPA infection.

Immunization with Tp0954, an adhesin of Treponema pallidum, provides protective efficacy in the rabbit model of experimental syphilis

Syphilis, a chronic multisystemic disease caused by spirochete Treponema pallidum subspecies pallidum infection, continues to be a serious global health problem and congenital syphilis remains a major cause of adverse outcomes in pregnancy in developing countries. The development of an effective vaccine is the most cost-effective way to eliminate syphilis, but so far has been elusive. Here, we evaluated the immunogenicity and protective efficacy of Tp0954, a T. pallidum placental adhesin, as a potential vaccine candidate in a New Zealand White rabbit model of experimental syphilis. Animals immunized with recombinant Tp0954 (rTp0954) produced high titers of Tp0954-specific serum IgG, high levels of IFN-γ from splenocytes and specific splenocyte proliferation response when compared to control animals immunized with PBS and Freund’s adjuvant (FA). Furthermore, rTp0954 immunization significantly delayed the development of cutaneous lesions, promoted inflammatory cellular infiltration at the primary lesion sites, as well as inhibited T. pallidum dissemination to distal tissues or organs when compared with that of the control animals. In addition, the naïve rabbits receiving popliteal lymph nodes from Tp0954-immunized, T. pallidum-challenged animals were not infected by T. pallidum, confirming sterile immunity. These findings suggest that Tp0954 is a potential vaccine candidate against syphilis.

Immunization with a tri-antigen syphilis vaccine significantly attenuates chancre development, reduces bacterial load, and inhibits dissemination of Treponema pallidum

Syphilis continues to be a significant public health concern worldwide. The disease is endemic in many low- and middle-income countries, and rates have risen sharply in high-income countries over the last decade. The continued prevalence of infectious and congenital syphilis worldwide highlights the need for the development of an effective syphilis vaccine to complement public health measures for syphilis control. The complex, multi-stage course of syphilis infection necessitates a holistic approach to the development of an effective vaccine, in which immunization prevents both the localized stage of infection (typified by the highly infectious chancre) and the disseminated stages of infection (typified by the secondary rash, neurosyphilis, and destructive tertiary lesions, as well as congenital syphilis). Inhibiting development of the infectious chancre would reduce transmission thus providing community- level protection, while preventing dissemination would provide individual-level protection by reducing serious sequelae and may also provide community level protection by reducing shedding during secondary syphilis. In the current study we build upon prior investigations which demonstrated that immunizations with individual, well characterized T. pallidum TprK, TprC, and Tp0751 peptides elicits partial protection against infection in the animal model. Specifically, we show here that immunization with a TprC/TprK/Tp0751 tri-antigen cocktail protects animals from progressive syphilis lesions and substantially inhibits dissemination of the infection.

Notes on syphilis vaccine development

The quest for a syphilis vaccine to provide protection from infection or disease began not long after the isolation of the first Treponema pallidum subspecies pallidum (T. pallidum) strain in 1912. Yet, a practical and effective vaccine formulation continues to elude scientists. Over the last few years, however, efforts toward developing a syphilis vaccine have increased thanks to an improved understanding of the repertoire of T. pallidum outer membrane proteins (OMPs), which are the most likely syphilis vaccine candidates. More has been also learned about the molecular mechanisms behind pathogen persistence and immune evasion. Published vaccine formulations based on a subset of the pathogen's OMPs have conferred only partial protection upon challenge of immunized laboratory animals, primarily rabbits. Nonetheless, those experiments have improved our approach to the choice of immunization regimens, adjuvants, and vaccine target selection, although significant knowledge gaps remain. Herein, we provide a brief overview on current technologies and approaches employed in syphilis vaccinology, and possible future directions to develop a vaccine that could be pivotal to future syphilis control and elimination initiatives.

Fascinating Molecular and Immune Escape Mechanisms in the Treatment of STIs (Syphilis, Gonorrhea, Chlamydia, and Herpes Simplex)

The incidence of syphilis, gonorrhea, chlamydia, and herpes simplex has increased over the last decade, despite the numerous prevention strategies. Worldwide scientists report a surge in drug-resistant infections, particularly in immunocompromised patients. Antigenic variations in syphilis enable long-term infection, but benzathine penicillin G maintains its efficiency, whereas macrolides should be recommended with caution. Mupirocin and zoliflodacin were recently introduced as therapies against ceftriaxone-resistant gonococcus, which poses a larger global threat. The gastrointestinal and prostatic potential reservoirs of Chlamydia trachomatis may represent the key towards complete eradication. Similar to syphilis, macrolides resistance has to be considered in genital chlamydiosis. Acyclovir-resistant HSV may respond to the novel helicase-primase inhibitors and topical imiquimod, particularly in HIV-positive patients. Novel drugs can overcome these challenges while nanocarriers enhance their potency, particularly in mucosal areas. This review summarizes the most recent and valuable discoveries regarding the immunopathogenic mechanisms of these sexually transmitted infections and discusses the challenges and opportunities of the novel molecules and nanomaterials.

LncRNA-ENST00000421645 Upregulates Kank1 to Inhibit IFN-γ Expression and Promote T Cell Apoptosis in Neurosyphilis

Long non-coding RNAs are involved in many infectious diseases. Our previous studies showed that lncRNA-ENST00000421645 expression is increased in T lymphocytes of neurosyphilis patients compared to healthy controls. However, whether lncRNA-ENST00000421645 has biological functions remains unclear. The current study was undertaken to understand the mechanism of lncRNA-ENST00000421645 in T lymphocyte function in neurosyphilis patients. The lncRNA-ENST00000421645 pull-down assay showed that lncRNA-ENST00000421645 acted on the acetylase NAT10. The chromatin immunoprecipitation (ChIP)-PCR results showed that lncRNA-ENST00000421645 promoted the acetylation of histone H3K27 adjacent to the Kank1 promoter, thereby promoting Kank1 protein expression. Kank1 promotes 14-3-3 protein expression, inhibits NF-kB activation, inhibits IFN-γ secretion by T lymphocytes, and promotes T lymphocyte apoptosis. Taken together, our findings suggest a novel mechanism that LncRNA-ENST00000421645 upregulates Kank1 to inhibit IFN-γ expression and promote T cell apoptosis in neurosyphilis.

Two Potential Syphilis Vaccine Candidates Inhibit Dissemination of Treponema pallidum

Syphilis, caused by the spirochete Treponema pallidum subspecies pallidum, continues to be a major public health problem worldwide. Recent increases in the number of syphilis cases, in addition to the lack of an efficient vaccine against T. pallidum for humans, highlights an urgent need for the design and development of an efficacious syphilis vaccine. Here, we assess the vaccine potential of the adhesion protein Tp0136 and the outer membrane protein Tp0663. Rabbits were subcutaneously immunized with recombinant proteins Tp0136, Tp0663, or control PBS. Immunization with Tp0136 or Tp0663 generated a strong humoral immune response with high titers of IgG, as assessed by ELISA. Moreover, animals immunized with Tp0136 or Tp0663 exhibited attenuated lesion development, increased cellular infiltration at the lesion sites, and inhibition of treponemal dissemination to distant organs compared to the unimmunized animals. These findings indicate that Tp0136 and Tp0663 are promising syphilis vaccine candidates. Furthermore, these results provide novel and important information for not only understanding the pathogenic mechanisms of spirochetes, but also the development of spirochete-specific subunit vaccines.

The effect of a large dose of intravenous immunoglobulin on general paresis of the insane

General paresis of the insane (GPI) remains the form of neurosyphilis most closely associated with dementia, even after the advent of penicillin. Penicillin remains the top treatment choice for syphilis, but treatment failure is not rare. Although the neurological symptoms of GPI can be alleviated by antibiotic treatment, mental symptoms may continue. A 60-year-old man was admitted to hospital due to rapidly progressive dementia. He was diagnosed as GPI. With the patient’s informed consent, we treated him with a large dose of intravenous immunoglobulin (IVIG) (0.4 g/kg/day) for 5 days, as well as penicillin (24 million units daily divided into six doses) for 14 days. A near-immediate improvement in his emotions and orientation occurred on the 17th day in hospital. The patient made an excellent recovery 6 weeks after treatment, his psychotic and mood symptoms improved significantly. Therefore, we hypothesize that patients with GPI treated with IVIG and penicillin G would have better outcomes than those treated with penicillin G alone. IVIG may be introduced as a necessary treatment for GPI.

MicroRNA-101-3p Downregulates TLR2 Expression, Leading to Reduction in Cytokine Production by Treponema pallidum-Stimulated Macrophages

Treponema pallidum (Tp) infection-induced immune responses can cause tissue damage. However, the underlying mechanism by which Tp infection induces immune response is unclear. Recent studies suggest a regulatory role of microRNAs in host immunity. We assessed whether microRNAs also have a regulatory role in immune response to Tp infection in vitro. Our results showed that microRNA-101-3p (miR-101-3p) levels were significantly higher in peripheral blood mononuclear cells of patients with primary syphilis and those in the serofast state, whereas toll-like receptor (TLR) 2 levels were higher in patients with syphilis than in healthy controls. In vitro, stimulation of THP-1 cells with Tp increased miR-101-3p expression. Moreover, miR-101-3p reduced expression levels of TLR2 mRNA and protein in THP-1 cells via binding to the 3' untranslated region of TLR2. Likewise, miR-101-3p inhibited production of inflammatory cytokines, including IL-1β, IL-6, tumor necrosis factor-α, and IL-12, in Tp-stimulated macrophages. IL-1β and IL-6 mRNA expression levels were reduced by transfection of macrophages with a TLR2-specific small interfering RNA. Conversely, overexpression of TLR2 upregulated cytokine expression. Patients with secondary syphilis exhibited the highest levels of plasma IL-6, which were negatively correlated with miR-101-3p. In conclusion, Tp infection upregulates miR-101-3p expression, which in turn inhibits the TLR2 signaling pathway, leading to reduced cytokine production.

Immunogenicity and protective efficacy against Treponema pallidum in New Zealand rabbits immunized with plasmid DNA encoding flagellin

Plasmid DNA encoding flagellin FlaB3 was used as a vaccination candidate for the evaluation of immunogenicity and protection against Treponema pallidum subsp. pallidum dissemination. First, intramuscular injection of the flagellin encoded by the plasmid DNA into New Zealand rabbits elicited both humoral and cellular immune responses. Total IgG production increased in response to flagellin. In addition, serum IFN-γ secretion and CD8+ cells were substantially greater in the rabbits immunized with the plasmid encoding flagellin FlaB3 than those in the rabbits immunized with recombinant flagellin. The flagellin encoded by the plasmid DNA induced significant upregulation of serum IL-6 and IL-8 compared to that of the control rabbits. Subsequently, intradermal challenge of the vaccinated New Zealand rabbits with 1 × 10⁷T. pallidum resulted in a significant reduction of the bacterial organ burden in the blood, liver, spleen, and testicles in the flagellin plasmid DNA-vaccinated rabbits. Furthermore, the histopathological analysis demonstrated that the rabbits immunized with the plasmid DNA-encoded flagellin (FlaB3) showed better immune protection. These findings provide evidence that plasmid DNA-encoded flagellin (FlaB3) may be useful as a potential immunization route for future development of a vaccine to inhibit T. pallidum dissemination in related animals.

IFNγ Enhances CD64-Potentiated Phagocytosis of Treponema pallidum Opsonized with Human Syphilitic Serum by Human Macrophages

Syphilis is a multi-stage, sexually transmitted disease caused by the spirochete Treponema pallidum (Tp). Considered broadly, syphilis can be conceptualized as a dualistic process in which spirochete-driven inflammation, the cause of clinical manifestations, coexists to varying extents with bacterial persistence. Inflammation is elicited in the tissues, along with the persistence of spirochetes to keep driving a robust immune response while evading host defenses; this duality is best exemplified during the florid, disseminated stage called secondary syphilis (SS). SS lesions typically contain copious amounts of spirochetes along with a mixed cellular infiltrate consisting of CD4⁺ T cells, CD8⁺ T cells, NK cells, plasma cells, and macrophages. In the rabbit model, Tp are cleared by macrophages via antibody-mediated opsonophagocytosis. Previously, we demonstrated that human syphilitic serum (HSS) promotes efficient uptake of Tp by human monocytes and that opsonophagocytosis of Tp markedly enhances cytokine production. Herein, we used monocyte-derived macrophages to study Tp–macrophage interactions ex vivo. In the absence of HSS, monocyte-derived macrophages internalized low numbers of Tp and secreted little cytokine (e.g., TNF). By contrast, these same macrophages internalized large numbers of unopsonized Borrelia burgdorferi and secreted robust levels of cytokines. Maturation of macrophages with M-CSF and IFNγ resulted in a macrophage phenotype with increased expression of HLA-DR, CD14, inducible nitric oxide synthase, TLR2, TLR8, and the Fcγ receptors (FcγR) CD64 and CD16, even in the absence of LPS. Importantly, IFNγ-polarized macrophages resulted in a statistically significant increase in opsonophagocytosis of Tp accompanied by enhanced production of cytokines, macrophage activation markers (CD40, CD80), TLRs (TLR2, TLR7, TLR8), chemokines (CCL19, CXCL10, CXCL11), and T_H1-promoting cytokines (IL-12, IL-15). Finally, the blockade of FcγRs, primarily CD64, significantly diminished spirochetal uptake and proinflammatory cytokine secretion by IFNγ-stimulated macrophages. Our ex vivo studies demonstrate the importance of CD64-potentiated uptake of opsonized Tp and suggest that IFNγ-activated macrophages have an important role in the context of early syphilis. Our study results also provide an ex vivo surrogate system for use in future syphilis vaccine studies.

A defined syphilis vaccine candidate inhibits dissemination of Treponema pallidum subspecies pallidum

Syphilis is a prominent disease in low- and middle-income countries, and a re-emerging public health threat in high-income countries. Syphilis elimination will require development of an effective vaccine that has thus far remained elusive. Here we assess the vaccine potential of Tp0751, a vascular adhesin from the causative agent of syphilis, Treponema pallidum subsp. pallidum. Tp0751-immunized animals exhibit a significantly reduced bacterial organ burden upon T. pallidum challenge compared with unimmunized animals. Introduction of lymph nodes from Tp0751-immunized, T. pallidum-challenged animals to naive animals fails to induce infection, confirming sterile protection. These findings provide evidence that Tp0751 is a promising syphilis vaccine candidate.

There are no vaccines for the prevention of syphilis, a disease caused by the bacterium Treponema pallidum subsp. pallidum. Here, the authors use an animal model of infection to show that immunization with the Tp0751 bacterial protein inhibits the pathogen's spread within the body.

Vaccine development for syphilis

INTRODUCTION

Syphilis, caused by the spirochete Treponema pallidum subspecies pallidum, continues to be a globally prevalent disease despite remaining susceptible to penicillin treatment. Syphilis vaccine development is a viable preventative approach that will serve to complement public health-oriented syphilis prevention, screening and treatment initiatives to deliver a two-pronged approach to stemming disease spread worldwide. Areas covered: This article provides an overview of the need for development of a syphilis vaccine, summarizes significant information that has been garnered from prior syphilis vaccine studies, discusses the critical aspects of infection that would have to be targeted by a syphilis vaccine, and presents the current understanding within the field of the correlates of protection needed to be achieved through vaccination. Expert commentary: Syphilis vaccine development should be considered a priority by industry, regulatory and funding agencies, and should be appropriately promoted and supported.

Equilibrium of Treg/Th17 cells of peripheral blood in syphilitic patients with sero-resistance

The aim of the present study was to examine changes of cellular homeostasis in regulatory T (Treg) and T helper 17 (Th17) cells by detecting the proportion of Treg and Th17 cells of peripheral blood, as well as the expression of specific transcription factors in these two types of cells, in syphilitic patients with sero-resistance. A total of 49 subjects were enrolled in the study and divided into two groups, comprising 26 cases of sero-resistant syphilitic patients in the experimental group, and 23 cases of healthy donors in the normal control group. Flow cytometry was applied to examine the proportion of Treg and Th17 cells, as well as the quantitative expression of relevant specific transcription factors [forkhead box P3 (Foxp3) and retinoic acid-related orphan receptor γt (ROR-γt)] in the two groups. A correlation analysis was subsequently performed. The results showed that in syphilitic patients with sero-resistance, the proportion of peripheral blood Treg cells was obviously higher than that of the normal control group (p<0.01) and the proportion of Th17 cells was significantly lower than that of the normal control group (p<0.01). In addition, the expression of transcription factor Foxp3 in CD4⁺ T cells was higher than that of the normal control group, while the expression of ROR-γt was lower than that of the normal control (p<0.05). The expression of Foxp3 and ROR-γt in peripheral blood CD4⁺ T cells had a negative correlation (r=-0.481, p<0.01). In conclusion, the peripheral blood of syphilitic patients with sero-resistance may have abnormalities in Treg/Th17 cellular balance.

Treponemal antibody in CSF and cellular immunity in peripheral blood of syphilitic patients with persisting positive rapid plasma regain

The ratio of patients with RPR constant positive more than 2 years despite receiving standard syphilis treatment has been reported to be 11.54%~31.3%. The current interpretations on this phenomenon are cellular immune function restrained and the existence of neurosyphilis or asymptomatic neurosyphilis. We conducted this study to detect the treponemal antibody in cerebrospinal fluid (CSF) and lymphocyte subsets in peripheral blood of syphilis patients with persisting RPR positive more than 2 years without neurologic signs, and then explore their relationship. In this study, Treponemal antibody in CSF of 46 syphilitic with HIV negative were measured by syphilis serum test and compared with that of 5 neurosyphilis. Lymphocyte subsets were measured by flow cytometry (FCM) and compared with that of 30 healthy controls. We observed that treponemal antibody in CSF was detected not only in 12 cases (25.21%) of 46 treated patients, but also in 5 neurosyphilis. The ratio of lymphocyte subsets revealed that CD3+, CD4+ T cells and natural killer (NK) cells showed no significant differences between the patient and healthy controls (P>0.05), while CD8+ T cells in patients were significant higher than that in healthy controls (P<0.001). Lymphocyte subsets showed no significant differences between the patients with treponemal antibody positive and negative in CSF (P>0.05). In conclusion, the treponemal antibody in CSF of treated patients suggests that part of them were asymptomatic neurosyphilis and with cellular immunodifeciency. And there is no significant relationship between asymptomatic neurosyphilis and cellular immunodeficiency in peripheral blood.

Undetectable hepatitis C virus RNA during syphilis infection in two HIV/HCV-co-infected patients

BACKGROUND

Treponema pallidum, the causative agent of syphilis, elicits a vigorous immune response in the infected host. This study sought to describe the impact of syphilis infection on hepatitis C virus (HCV) RNA levels in patients with HIV and chronic HCV infection.

METHODS

Patients with chronic HIV/HCV and syphilis co-infection were identified by their treating physicians from 1 October 2010 to 31 December 2013. Stored plasma samples obtained before, during, and after syphilis infection were analysed for interleukin (IL)-2, IL-4, IL-6, IL-8, IL-10, tumour necrosis factor alpha (TNF-α), interferon gamma (IFN-γ), and IFN-γ-inducible protein 10 kDa (IP-10).

RESULTS

Undetectable HCV RNA at the time of early latent syphilis infection was observed in 2 patients with HIV and chronic HCV infection. After treatment of the syphilis infection, HCV RNA levels increased again in patient 1, whereas patient 2 initiated HCV therapy and remained HCV RNA-negative. Available plasma samples obtained before and after the episode with undetectable HCV RNA were phylogenetically identical, making the possibility of spontaneous clearance and HCV reinfection less likely. The IL-10, TNF-α, and IP-10 levels increased at the time of syphilis diagnosis in patient 1 and decreased again after treatment of the syphilis infection.

CONCLUSIONS

We propose that T. pallidum-induced cytokine secretion resulted in an immune response hindering HCV replication during syphilis infection. We suggest that HIV/HCV-co-infected patients with unexpected undetectable HCV RNA are tested for syphilis infection and that the serological tests include both non-treponemal and treponemal tests to avoid false-positive results caused by HCV.

The endemic treponematoses

The agents of human treponematoses include four closely related members of the genus Treponema: three subspecies of Treponema pallidum plus Treponema carateum. T. pallidum subsp. pallidum causes venereal syphilis, while T. pallidum subsp. pertenue, T. pallidum subsp. endemicum, and T. carateum are the agents of the endemic treponematoses yaws, bejel (or endemic syphilis), and pinta, respectively. All human treponematoses share remarkable similarities in pathogenesis and clinical manifestations, consistent with the high genetic and antigenic relatedness of their etiological agents. Distinctive features have been identified in terms of age of acquisition, most common mode of transmission, and capacity for invasion of the central nervous system and fetus, although the accuracy of these purported differences is debated among investigators and no biological basis for these differences has been identified to date. In 2012, the World Health Organization (WHO) officially set a goal for yaws eradication by 2020. This challenging but potentially feasible endeavor is favored by the adoption of oral azithromycin for mass treatment and the currently focused distribution of yaws and endemic treponematoses and has revived global interest in these fascinating diseases and their causative agents.

Regulatory T cells in peripheral blood and cerebrospinal fluid of syphilis patients with and without neurological involvement

BACKGROUND

Syphilis, a sexually transmitted disease caused by spirochetal bacterium Treponema pallidum, can progress to affect the central nervous system, causing neurosyphilis. Accumulating evidence suggest that regulatory T cells (Tregs) may play an important role in the pathogenesis of syphilis. However, little is known about Treg response in neurosyphilis.

METHODOLOGY/PRINCIPAL FINDINGS

We analyzed Treg frequencies and Transforming Growth Factor-β (TGF-β) levels in the blood and CSF of 431 syphilis patients without neurological involvement, 100 neurosyphilis patients and 100 healthy donors. Suppressive function of Tregs in peripheral blood was also assessed. Among syphilis patients without neurological involvement, we found that secondary and serofast patients had increased Treg percentages, suppressive function and TGF-β levels in peripheral blood compared to healthy donors. Serum Rapid Plasma Reagin (RPR) titers were positively correlated with Treg numbers in these patients. Compared to these syphilis patients without neurological involvement, neurosyphilis patients had higher Treg frequency in peripheral blood. In the central nervous system, neurosyphilis patients had higher numbers of leukocytes in CSF compared to syphilis patients without neurological involvement. CD4(+) T cells were the predominant cell type in the inflammatory infiltrates in CSF of neurosyphilis patients. Interestingly, among these neurosyphilis patients, a significant decrease in CSF CD4(+) CD25(high) Treg percentage and number was observed in symptomatic neurosyphilis patients compared to those of asymptomatic neurosyphilis patients, which may be associated with low CSF TGF-β levels.

CONCLUSIONS

Our findings suggest that Tregs might play an important role in both bacterial persistence and neurologic compromise in the pathogenesis of syphilis.

Comparison of CDC and sequence-based molecular typing of syphilis treponemes: tpr and arp loci are variable in multiple samples from the same patient

Background

Molecular typing of syphilis-causing strains provides important epidemiologic data. We tested whether identified molecular subtypes were identical in PCR-positive parallel samples taken from the same patient at a same time. We also tested whether subtype prevalence differs in skin and blood samples.

Results

Eighteen syphilis positive patients (showing both positive serology and PCR), with two PCR-typeable parallel samples taken at the same time, were tested with both CDC (Centers for Disease Control and Prevention) and sequence-based typing. Samples taken from 9 of 18 patients were completely typed for TP0136, TP0548, 23S rDNA, arp, and tpr loci. The CDC typing revealed 11 distinct genotypes while the sequence-based typing identified 6 genotypes. When results from molecular typing of TP0136, TP0548, and 23S rDNA were analyzed in samples taken from the same patient, no discrepancies in the identified genotypes were found; however, there were discrepancies in 11 of 18 patients (61.1%) samples relative to the arp and tpr loci. In addition to the above described typing, 127 PCR-positive swabs and whole blood samples were tested for individual genotype frequencies. The repetition number for the arp gene was lower in whole blood (WB) samples compared to swab samples. Similarly, the most common tpr RFLP type “d” was found to have lower occurrence rates in WB samples while type “e” had an increased occurrence in these samples.

Conclusions

Differences in the CDC subtypes identified in parallel samples indicated genetic instability of the arp and tpr loci and suggested limited applicability of the CDC typing system in epidemiological studies. Differences in treponemal genotypes detected in whole blood and swab samples suggested important differences between both compartments and/or differences in adherence of treponeme variants to human cells.

Immune evasion and recognition of the syphilis spirochete in blood and skin of secondary syphilis patients: two immunologically distinct compartments

BACKGROUND

The clinical syndrome associated with secondary syphilis (SS) reflects the propensity of Treponema pallidum (Tp) to escape immune recognition while simultaneously inducing inflammation.

METHODS

To better understand the duality of immune evasion and immune recognition in human syphilis, herein we used a combination of flow cytometry, immunohistochemistry (IHC), and transcriptional profiling to study the immune response in the blood and skin of 27 HIV(-) SS patients in relation to spirochetal burdens. Ex vivo opsonophagocytosis assays using human syphilitic sera (HSS) were performed to model spirochete-monocyte/macrophage interactions in vivo.

RESULTS

Despite the presence of low-level spirochetemia, as well as immunophenotypic changes suggestive of monocyte activation, we did not detect systemic cytokine production. SS subjects had substantial decreases in circulating DCs and in IFNγ-producing and cytotoxic NK-cells, along with an emergent CD56-/CD16+ NK-cell subset in blood. Skin lesions, which had visible Tp by IHC and substantial amounts of Tp-DNA, had large numbers of macrophages (CD68+), a relative increase in CD8+ T-cells over CD4+ T-cells and were enriched for CD56+ NK-cells. Skin lesions contained transcripts for cytokines (IFN-γ, TNF-α), chemokines (CCL2, CXCL10), macrophage and DC activation markers (CD40, CD86), Fc-mediated phagocytosis receptors (FcγRI, FcγR3), IFN-β and effector molecules associated with CD8 and NK-cell cytotoxic responses. While HSS promoted uptake of Tp in conjunction with monocyte activation, most spirochetes were not internalized.

CONCLUSIONS

Our findings support the importance of macrophage driven opsonophagocytosis and cell mediated immunity in treponemal clearance, while suggesting that the balance between phagocytic uptake and evasion is influenced by the relative burdens of bacteria in blood and skin and the presence of Tp subpopulations with differential capacities for binding opsonic antibodies. They also bring to light the extent of the systemic innate and adaptive immunologic abnormalities that define the secondary stage of the disease, which in the skin of patients trends towards a T-cell cytolytic response.

Association of KIR genotypes and haplotypes with syphilis in a Chinese Han population

Killer immunoglobulin-like receptors (KIRs) can regulate the activation of NK and T cells in response to infection. Syphilis is a sexually transmitted infection caused by the Treponema pallidum subspecies pallidum spirochete bacterium. The objective of this study was to explore whether KIR genotypes and haplotypes were associated with syphilis in a Chinese Han population. Polymerase chain reaction with sequence-specific primers (PCR-SSP) was used to identify the KIR genotypes in 190 patients with syphilis and 192 healthy controls. The frequency of genotype P was higher in healthy controls than that in patients with syphilis (P = 0.002), and its OR was 0.304, while the frequencies of genotypes AE and AG were higher in patients with syphilis than those in healthy controls. The frequency of haplotype 17 was lower, and its OR was 0.321, whereas the frequencies of haplotype 1 and 6 were higher in patients with syphilis than those in healthy controls. KIR haplotypes A and B have distinctive centromeric (Cen) and telomeric (Tel) gene content motifs. The frequency of Tel-B/B was higher in patients with syphilis than that in healthy controls (P = 0.024). Based on these findings, it seems that individuals with the genotype AE, AG or Tel-B/B, or haplotypes 1 and 6 are susceptible to syphilis, whereas individuals with genotype P or haplotype 17 are protective from syphilis in the Chinese Han population.

Human leukocyte antigen-C and killer cell immunoglobulin-like receptor gene polymorphisms among patients with syphilis in a Chinese Han population

Syphilis is a sexually transmitted infection caused by the Treponema pallidum subspecies pallidum spirochete bacterium. The killer cell immunoglobulin-like receptors (KIR), interacting with human leukocyte antigens (HLA), regulate the activations of natural killer (NK) cells and certain T-cell subsets in response to microbe infection. The objective of this study was to explore whether KIR and HLA-C gene polymorphisms were associated with syphilis in a Chinese Han population. Polymerase chain reaction with sequence-specific primers (PCR-SSP) method was used to genotype KIR and HLA-C genes in 231 syphilis patients and 247 healthy controls. Framework genes KIR2DL4, KIR3DL2, KIR3DL3 and KIR3DP1 were present in all individuals. The frequencies of KIR2DS3 and KIR3DS1 were higher in syphilis patients than in healthy controls (p = 0.030 and p = 0.038, respectively), while the frequency of KIR2DS5 was higher in healthy controls than in syphilis patients (p = 0.015; OR = 0.575). The homozygote for HLA-C1 allele (HLA-C1C1) was more common in controls compared with syphilis patients (p = 0.030; OR = 0.667). The frequency of individuals with HLA-C1C1 and KIR2DL3 genotype was higher in control group relative to syphilis patient group (p = 0.018; OR = 0.647). These data indicated that KIR2DS3 and KIR3DS1 were more prevalent in syphilis patients than in controls, and that KIR2DS5, HLA-C1C1 and HLA-C1C1-KIR2DL3 were more prevalent in controls than in syphilis patients, respectively. These will require further investigation using functional studies.

Syphilis: using modern approaches to understand an old disease

Syphilis is a fascinating and perplexing infection, with protean clinical manifestations and both diagnostic and management ambiguities. Treponema pallidum subsp. pallidum, the agent of syphilis, is challenging to study in part because it cannot be cultured or genetically manipulated. Here, we review recent progress in the application of modern molecular techniques to understanding the biological basis of this multistage disease and to the development of new tools for diagnosis, for predicting efficacy of treatment with alternative antibiotics, and for studying the transmission of infection through population networks.

The immunopathobiology of syphilis: the manifestations and course of syphilis are determined by the level of delayed-type hypersensitivity

Syphilis has plagued mankind for centuries and is currently resurgent in the Western hemisphere. Although there has been a significant reduction of tertiary disease and recognition of facilitative interactions with human immunodeficiency virus infection, the natural history of syphilis has remained largely unchanged; thus, new strategies are required to more effectively combat this pathogen. The immunopathologic features of experimental syphilis in the rabbit; the course, stages, and pathology of human syphilis; and a comparison of human syphilis with leprosy suggest that the clinical course of syphilis and its tissue manifestations are determined by the balance between delayed-type hypersensitivity (DTH) and humoral immunity to the causative agent, Treponema pallidum. A strong DTH response is associated with clearance of the infecting organisms in a well-developed chancre, whereas a cytotoxic T-cell response or strong humoral antibody response is associated with prolonged infection and progression to tertiary disease. Many of the protean symptoms/appearances of secondary and tertiary human syphilis are manifestations of immune reactions that fail to clear the organism, due to a lack of recruitment and, more importantly, activation of macrophages by sensitized CD4 T cells. The Bacillus Calmette-Guerin vaccination can enhance DTH and has been shown to produce a low, but measurable, beneficial effect in the prevention of leprosy, a disease that shows a disease spectrum with characteristics in common with syphilis. In the prevention of syphilis, a potential vaccine protective against syphilis should be designed to augment the DTH response.

TpF1 from Treponema pallidum activates inflammasome and promotes the development of regulatory T cells

Human syphilis is a multistage disease, with diverse and wide-ranging manifestations caused by Treponema pallidum. Despite the fact that a cell-mediated immune response takes part in the course of syphilis, T. pallidum often manages to evade host immunity and, in untreated individuals, may trigger chronic infection. With this study, we demonstrate for the first time, to our knowledge, that Treponema pallidum induces a regulatory T (Treg) response in patients with secondary syphilis and we found that the miniferritin TpF1, produced by the bacterium, is able to expand this response and promote the production of TGF-β. Accordingly, TpF1 stimulates monocytes to release IL-10 and TGF-β, the key cytokines in driving Treg cell differentiation. Interestingly, we also found that TpF1 stimulates monocytes to synthesize and release several proinflammatory cytokines, such as TNF-α, IL-6, and IL-1β, the latter following the activation of the multiprotein complex inflammasome. Collectively, these data strongly support a central role for TpF1 both in the inflammation process, which occurs in particular during the early stage of syphilis, and in the long-term persistence of the spirochete within the host by promoting Treg response and TGF-β production.

Host defense mechanisms in secondary syphilitic lesions: a role for IFN-gamma-/IL-17-producing CD8+ T cells?

Cell-mediated immunity is thought to be of critical importance in antisyphilitic host defense, but the exact mechanisms are still unknown. This fact is particularly true for HIV-infected persons with a deficit in CD4+ T-cell number. We therefore obtained lesional skin samples from HIV+ and HIV- patients with secondary syphilis at different time points of lesional age to search both for causative microorganisms and to characterize the inflammatory infiltrate. By doing so, we detected Treponema pallidum spirochetes with a much greater abundance in late lesions of HIV+ individuals compared with the HIV- cohort. The dominating inflammatory cells were T cells, macrophages, and neutrophils at all stages and plasma cells in older lesions. In HIV- persons, T cells consisted of equal numbers of CD4+ and CD8+ T-cells, whereas in HIV+ patients, the majority of T cells belonged to the CD8 lineage and produced both IFN-γ and IL-17. Regulatory T cells and Langerhans cells were reduced in these patients compared with their HIV- counterparts. Because of our observations, we propose that T cells of both the CD4 and CD8 lineage are needed for an at least partial protective antisyphilitic immunity. Compensation mechanisms in HIV+ individuals, such as an increase of Tc1/17 cells as well as a reduction in immunoregulatory Langerhans cells and T cells, apparently do not overcome the deficiencies in these patients to eliminate the spirochete.

Cytokine expression during syphilis infection in HIV-1-infected individuals

BACKGROUND

Little is known about cytokine responses to syphilis infection in HIV-1-infected individuals.

METHODS

We retrospectively identified patients with HIV-1 and Treponema pallidum coinfection. Plasma samples from before, during, and after coinfection were analyzed for interleukin (IL)-2, IL-4, IL-6, IL-8, IL-10, interferon (IFN)-gamma, and tumor necrosis factor (TNF)-alpha.

RESULTS

Thirty-six patients were included. IL-10 levels increased significantly in patients with primary or secondary stage syphilis from a median of 12.8 pg/mL [interquartile range (IQR), 11.0-27.8] before infection to 46.7 pg/mL (IQR, 28.4-78.9) at the time of diagnosis (P = 0.027) and decreased to 13.0 pg/mL (IQR, 6.2-19.4) after treatment of syphilis (P <0.001). TNF-alpha levels showed no significant change from before to during syphilis in patients with primary or secondary stage syphilis (median 3.9 pg/mL (IQR, 3.3-9.6) and 9.0 pg/mL (IQR, 5.4-12.6), respectively (P = 0.31); however, treatment of syphilis was associated with a significant decrease in TNF-alpha to a median of 4.2 pg/mL (IQR, 2.7-6.8) (P <0.001). No significant changes in cytokine levels were observed in coinfected with latent stage syphilis.IL-10 and TNF-alpha levels correlated positively with plasma HIV RNA values at the time of diagnosis (r = 0.38, P = 0.023, and r = 0.64, P <0.001, respectively) and correlated inversely with CD4 T cell counts (-0.35, P = 0.036 and r = -0.34, P = 0.042, respectively).

CONCLUSION

HIV-1 and early stage syphilis coinfection were associated with an increase in IL-10. IL-10 and TNF-alpha both decreased after treatment of syphilis. TNF-alpha and IL-10 correlated with low CD4 T cell counts and high plasma HIV RNA values.

Antiretroviral therapy is associated with reduced serologic failure rates for syphilis among HIV-infected patients

BACKGROUND

Syphilis and human immunodeficiency virus (HIV) frequently coexist in patients, but the effects of immunosuppression on the course of syphilis are unknown. Our goal was to determine whether the degree of HIV-mediated immunosuppression and the use of highly active antiretroviral therapy impact syphilis serologic responses.

METHODS

We assessed all cases of syphilis with positive serologic test results from 1990 through 2006 in a prospective, observational clinical cohort of HIV-infected patients. We defined seroreversion as the loss of reactivity in a patient who previously had a serologic test result positive for syphilis. We defined serologic failure as the lack of a 4-fold decrease in rapid plasma reagin titers 270-365 days after therapy or a 4-fold increase in titers > or =30 days after therapy. We used Cox proportional hazards models with statistical adjustments for multiple failure instances.

RESULTS

One hundred eighty subjects experienced 231 cases of syphilis. The median follow-up time was 5.3 years. A total of 71 episodes of serologic failure were documented. A CD4 cell count of <200 cells/mL at the time of syphilis diagnosis was associated with an increased risk of serologic failure (adjusted hazard ratio, 2.48; 95% confidence interval, 1.26-4.88). The receipt of highly active antiretroviral therapy was associated with a 60% reduction in the rate of serologic failure (adjusted hazard ratio, 0.40; 95% confidence interval, 0.21-0.75), independent of concomitant CD4 cell response. Rapid plasma reagin seroreversion was infrequent (16.1%) and inconsistent, and it was more likely to occur among patients who received macrolides.

CONCLUSION

The use of highly active antiretroviral therapy to reverse immunosuppression and the routine use of macrolides for the prevention of opportunistic infections may reduce syphilis serologic failure rates among HIV-infected patients who have syphilis.