Robust pro-inflammatory immune response is associated with serological cure in patients with syphilis: an observational study

Serofast status in syphilis: Pathogenesis to therapeutics

Syphilis, a sexually transmitted infection caused by Treponema pallidum, has been experiencing a rise in prevalence in recent years. "Syphilis serofast" describes a unique serological reaction in patients with syphilis whose clinical symptoms have resolved following consistent anti-syphilitic therapy, but the non-Treponema pallidum antigen serologic test is still positive. Syphilis serofast is a risk factor for syphilis recurrence, neurosyphilis, and multisystem involvement. Considering the current lack of comprehensive knowledge about the epidemiological characteristics, pathogenesis, and therapies of syphilis serofast, we conducted an online search of research relating to syphilis serofast over the last twenty years. Previous research has shown that the pathogenesis of syphilis serofast is mainly related to clinical factors, immune factors, syphilis subtypes, and T.pallidum membrane protein repeat gene antigen. There are two distinct viewpoints on the treatment of serofast: no excessive treatment and active treatment. In addition, serofast patients also showed two clinical outcomes: syphilis recurrence and persistent serofast status. This article systematically reviews the related factors, treatment, and clinical outcomes of syphilis serofast, provides a theoretical basis for its research, diagnosis, and treatment, and helps clinicians develop a follow-up treatment management plan for syphilis serofast.

Endothelial dysfunction of syphilis: Pathogenesis

Treponema pallidum is the causative factor of syphilis, a sexually transmitted disease (STD) characterized by perivascular infiltration of inflammatory cells, vascular leakage, swelling and proliferation of endothelial cells (ECs). The endothelium lining blood and lymphatic vessels is a key barrier separating body fluids from host tissues and is a major target of T. pallidum. In this review, we focus on how T. pallidum establish intimate interactions with ECs, triggering endothelial dysfunction such as endothelial inflammation, abnormal repairment and damage of ECs. In addition, we summarize that migration and invasion of T. pallidum across vascular ECs may occur through two pathways. These two mechanisms of transendothelial migration are paracellular and cholesterol-dependent, respectively. Herein, clarifying the relationship between T. pallidum and endothelial dysfunction is of great significance to provide novel strategies for diagnosis and prevention of syphilis, and has a great potential prospect of clinical application.

Treponema pallidum recombinant protein Tp47 activates NOD-like receptor family protein 3 inflammasomes in macrophages via glycolysis

Glycolysis is a key pathway in cellular glucose metabolism for energy supply and regulates immune cell activation. Whether glycolysis is involved in the activation of NOD-like receptor family protein 3 (NLRP3) inflammasomes during Treponema pallidum (T. pallidum) infection is unclear. In this study, the effect of T. pallidum membrane protein Tp47 on NLRP3 inflammasome activation in rabbit peritoneal macrophages was analysed and the role of glycolysis in NLRP3 inflammasome activation was explored. The results showed that Tp47 promoted NLRP3, caspase-1, and IL-1β mRNA expression in macrophages, enhanced glycolysis and glycolytic capacity of macrophage, and promoted the production of macrophage glycolytic metabolites citrate, phosphoenolpyruvate, and lactate. The M2 pyruvate kinase (PKM2) inhibitor shikonin down-regulated the Tp47-promoted NLRP3, caspase-1, and IL-1β mRNA expression in macrophages, and suppressed the Tp47-enhanced glycolysis and glycolytic capacity. Similarly, si-PKM2 significantly inhibited Tp47-promoted NLRP3, caspase-1, and IL-1β mRNA expression and the Tp47-enhanced glycolysis and glycolytic capacity in macrophages. In conclusion, Tp47 activated NLRP3 inflammasomes via PKM2-dependent glycolysis and provided a new perspective on the effect of T. pallidum infection on host macrophages, which would contribute to the understanding of the infection mechanism and host immune mechanism of T. pallidum.

Treponema pallidum recombinant protein Tp47 enhanced interleukin-6 secretion in human dermal fibroblasts through the toll-like receptor 2 via the p38, PI3K/Akt, and NF-κB signalling pathways

Interleukin-6 (IL-6) is a multi-effective cytokine involved in multiple immune responses. Whether fibroblasts also turn out to be a cytokine IL-6 factory during interaction with Treponema pallidum is not yet understood. To explore whether fibroblasts participate in inflammation due to syphilis, a series of experiments were performed to explore the role of T. pallidum lipoprotein Tp47 in IL-6 production in human dermal fibroblasts. The Toll-like receptor 2 (TLR2) and participating signalling pathways in this process were also evaluated. The results showed that the expressions of IL-6 and the protein levels of TLR2 in fibroblasts were upregulated after stimulation with Tp47, and this effect was impeded by the TLR2 inhibitor C29. In addition, Tp47 promoted the phosphorylation of p38, PI3K/Akt, and nuclear factor-kappaB (NF-κB), and the translocation of NF-κB in fibroblasts. Moreover, p38, PI3K, and NF-κB inhibitors significantly reduced IL-6 production in fibroblasts stimulated with Tp47. Furthermore, the TLR2 inhibitor C29 inhibited the phosphorylation of p38, Akt, and NF-κB, and the translocation of NF-κB in fibroblasts. In conclusion, our results showed that Tp47 enhanced IL-6 secretion in human dermal fibroblasts through TLR2 via p38, PI3K/Akt, and NF-κB signalling pathways. These findings contribute to our understanding of syphilis inflammation.

Plasma Exosome-Derived microRNAs Profiles in Patients with Serofast Status: A Cross-Sectional Study

Purpose

Syphilis is a sexually transmitted bacterial infection caused by Treponema pallidum (T. pallidum), which can lead to chronic morbidity and adverse complications. In clinical practice, serofast status (SF) patients present with clinical symptoms that are very similar to those of healthy individuals or syphilis-cured patients, and often require prolonged follow-up for diagnosis. Currently, there is increasing interest in the potential of plasma exosome-derived miRNA as a biomarker for the detection of infectious diseases. In this study, we aimed to explore the diagnostic potential of miRNA in SF and its possible biological implications.

Patients and Methods

Exosome-derived miRNAs were isolated from peripheral plasma samples obtained from 20 patients with secondary syphilis (SS), SF, serologically cured syphilis (SC), and healthy controls (HC), and differentially expressed miRNAs (DEmiRNAs) were identified by microarray analysis. Prediction of potential target genes, functional annotation, gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were then performed. The expression of selected miRNAs was confirmed in 37 patients by quantitative reverse transcription polymerase chain reaction (RT-qPCR). A receiver operating characteristic (ROC) analysis was performed to evaluate the diagnostic performance of these miRNAs in differentiating syphilis from HC or SC.

Results

The expression profile of plasma exosome-derived miRNA was discovered in individuals with SF through microarray analysis. The targeted genes of DEmiRNAs were found to be involved in diverse biological processes according to GO and KEGG analysis, such as regulation of transcription, mitochondria, Golgi, immune system, apoptosis, Ras signaling pathway, etc. Using RT-qPCR validation, miR-1273g-3p, miR-4485-5p, miR-197-3p, and miR-1908-3p showed significant upregulation in patients with SF. These miRNAs exhibited a superior diagnostic ability, either individually or combined, to distinguish SF from SC or HC.

Conclusion

The DEmiRNAs in plasma exosomes may play a role in the pathogenesis of SF and have the potential to become a noble and effective diagnostic method.

Platelet Indices Are the Promising Biomarkers in Monitoring Disease Activities in Patients with Syphilis

OBJECTIVE

To uncover the role of the platelet indices in patients with syphilis.

METHODS

A total of 2061 syphilis patients and 528 healthy controls were enrolled in this retrospective cohort study. The data of platelet count (PLT), mean platelet volume (MPV), platelet distribution width (PDW) and indicators of syphilis activities were collected. The correlations between the platelet indices and disease activities were analyzed.

RESULTS

425 (20.6%) of all the 2061 patients were of primary and secondary syphilis, 433 (21.0%) latent, 463 (22.5%) serofast, 350 (17.0%) asymptomatic neurosyphilis and 390 (18.9%) symptomatic neurosyphilis. Compared with the healthy controls, PLT was significantly increased in the primary and secondary syphilis group. Whereas, MPV and PDW were significantly decreased in all stages of syphilis. These changes of platelets indices were reversed after anti-treponemal therapy. Further correlation analysis showed PLT was positively associated with the syphilis activity indicators [rapid plasma reagin (RPR) titer, cerebrospinal fluid white blood cell (CSF-WBC), CSF-protein, and CSF-VDRL (venereal disease research laboratory)] and inflammatory markers [WBC, C-reaction protein (CRP), and erythrocyte sedimentation rate (ESR)]. Conversely, PDW was negatively correlated with all of these parameters. MPV had an inverse relationship with RPR, ESR, and CRP.

CONCLUSIONS

Platelet indices are associated with syphilis activities.

The whole process of macrophage-Treponema pallidum interactions: Opsonic phagocytosis, nonopsonic phagocytosis and active invasion

Despite the acknowledged central role of opsonophagocytosis in the process of syphilis, the interaction between Treponema pallidum and human macrophages during nonopsonophagocytosis and active invasion remains controversial. To investigate whether nonopsonic phagocytosis and active invasion, similar to opsonic phagocytosis, also participate in the process of macrophage-T. pallidum interactions, monocyte-derived macrophages were used to study the interactions of T. pallidum and macrophages in the presence of nonsyphytic or syphilitic serum and in the absence of serum in vitro using indirect immunofluorescence and flow cytometry to quantitate treponeme-macrophage interactions. The results showed that macrophages phagocytose T. pallidum under both nonopsonizing conditions (no serum or normal human serum (NHS)) and in the presence of opsonizing serum (secondary syphilitic serum (SSS)) in a time-dependent manner. The percentages of spirochete-positive macrophages in the SSS group were higher than those in the NHS and no-serum groups. Blocking FcγR or inactivating complement caused a significant decrease in the percentage of spirochete-positive macrophages in the SSS group but did not cause a decrease in the percentages of spirochete-positive macrophages in the NHS and no-serum groups. In addition, after inhibiting macrophage phagocytosis, approximately 30% of macrophages internalized spirochetes, verifying that T. pallidum actively penetrated macrophages rather than was ingested by them. This study provides evidence that opsonic phagocytosis, nonopsonic phagocytosis and active invasion are all active during T. pallidum-macrophage interactions and reveals a process of treponeme-macrophage interactions in T. pallidum pathogenesis.

Cognitive impairment in syphilis: Does treatment based on cerebrospinal fluid analysis improve outcome?

Background

Individuals with previous syphilis may experience cognitive impairment. The goal of this study was to determine if those at high risk for laboratory-defined neurosyphilis are cognitively impaired, and whether treatment based on cerebrospinal fluid (CSF) findings results in better outcomes.

Methods

Participants had a new syphilis diagnosis, serum RPR titer ≥ 1:32 or peripheral blood CD4+ T cells ≤ 350/ul (in persons living with HIV) and did not endorse neurological symptoms. They underwent computerized cognitive assessment with the CogState. Thirty-two were randomized to either undergo lumbar puncture (LP) or to not undergo LP and 14 underwent LP; 64 were not randomized and 48 opted to undergo LP.

Results

Demographics, cognitive complaints and cognitive impairment did not differ between randomized and nonrandomized participants. Two-thirds were cognitively impaired, and impairment was not more common in those with cognitive complaints. The adjusted odds of increased severity of impairment were 3.8 times greater in those with CSF pleocytosis compared to those without. Time to cognitive normalization, improvement or decline did not differ between those who did not undergo LP and those who underwent LP and whose treatment was based on CSF analysis. Taking into account pre-treatment cognitive impairment, the risk of cognitive decline was lower in those with CSF pleocytosis treated for neurosyphilis compared to those without CSF pleocytosis not treated for neurosyphilis, (HR 0.24 (95% CI 0.07–0.88], p = 0.03).

Conclusion

In individuals at high risk for laboratory-defined neurosyphilis, cognitive complaints are not a good indicator of cognitive impairment. Severity of cognitive impairment was greater in those with CSF pleocytosis. Identification and treatment of those with neurosyphilis may mitigate subsequent cognitive decline.

Evaluation of serum cytokines to predict serofast in syphilis patients

BACKGROUND

Syphilis serofast has been increasing in recent years and has resulted in a dramatic increase in medical expenses. However, there are not effective methods for serofast prediction in syphilis patients prior to treatment.

AIMS AND OBJECTIVES

The present study investigated novel serum biomarkers for the prediction of serofast in syphilis patients prior to treatment.

MATERIALS AND METHODS

Pre-treatment serum from patients with syphilis serofast and patients with syphilis serological cure were measured using antibody microarrays. The results generated from the antibody arrays were validated using ELISA. Healthy subjects were used as the controls.

RESULTS

Compared to serologically cured patients, six cytokines (IL-17F, TNF RI, TNF RII, IL-16, OPN, and MCSFR) were significantly lower, while five factors (MCP-3, LIF, G-CSF, MIP-3a, and GH) were higher in serofast patients. ELISA validation was in-line with the results generated from antibody arrays. Of significance, these cytokines were firstly observed to the differentially expressed in pre-treatment serofast patient serum samples.

CONCLUSIONS

The differentially expressed cytokines may be novel serum biomarkers for serofast prediction. These identified proteins play significant roles in the immune response, suggesting immune dysfunction may be the cause for syphilis serofast.

The P2X7 receptor mediates NLRP3-dependent IL-1β secretion and promotes phagocytosis in the macrophage response to Treponema pallidum

It is unclear whether P2X7 receptor (P2X7R) mediates NOD-like receptor family protein 3 (NLRP3)-dependent IL-1β secretion and spirochete phagocytosis in syphilis. This study was conducted to investigate the role of P2X7R in modifying NLRP3-dependent IL-1β secretion and regulating phagocytosis by Treponema pallidum (T. pallidum)-induced macrophages. Macrophages derived from a human acute monocytic leukemia cell line were cultured with T. pallidum. The activation of P2X7R in T. pallidum-treated macrophages occurred in a dose- and time-dependent manner. The P2X7R silencing group showed significantly decreased NLRP3 mRNA and protein levels (vs. the Tp group, P < 0.001). Similar results were observed for IL-1β secretion using ELISA (vs. the Tp group, P < 0.001). Furthermore, P2X7R siRNA transfection significantly decreased the percentage of spirochete-positive macrophages (29.73% vs. 70.83%, P < 0.001) and spirochete internalization (mean fluorescence intensity (MFI), 9.20 vs. 19.39, P < 0.001). This finding revealed that P2X7R played a role in the induction of NLRP3-dependent IL-1β secretion by T. pallidum-induced macrophages. Furthermore, we found that P2X7R plays an important role in IL-1β secretion and in the promotion of T. pallidum phagocytosis by macrophages. These results may not only contribute to our understanding of the immune mechanism that is active during T. pallidum infection but may also lay the groundwork for strategies to combat syphilis.

Sexually transmitted infections - laboratory diagnosis

The Guidelines Project, an initiative of the Brazilian Medical Association, aims to combine information from the medical field in order to standardize producers to assist the reasoning and decision-making of doctors. The information provided through this project must be assessed and criticized by the physician responsible for the conduct that will be adopted, depending on the conditions and the clinical status of each patient.

Cytokine expression in Treponema pallidum infection

BACKGROUND

Current syphilis tests cannot distinguish between active and past syphilis among patients with serofast rapid plasma reagin (RPR) titers. We investigated whether cytokine profiles might provide insight in the differentiation of active and treated syphilis.

METHODS

We collected quarterly serum samples from participants at risk for incident syphilis in a prospective cohort study of men and male-to-female transgender women. We defined incident syphilis as a new RPR titer ≥ 1:8 or a fourfold increase from a prior RPR titer and a positive Treponema pallidum particle agglutination assay. We measured cytokine expression using a 63-multiplex bead-based Luminex assay (eBiosciences/Affymetrix, San Diego, California, USA). We used tertile bins and Chi square tests to identify differences in proportions of cytokines between samples from patients with active and treated syphilis. We constructed a network of cytokine profiles from those findings. We used R software (R version 3.4.1, R, Vienna, Austria) to fit models.

RESULTS

We identified 20 pairs of cytokines (out of 1953 possible pairs) that differed between active and treated syphilis. From those, we identified three cytokine networks of interest: an Eotaxin-Rantes-Leptin network, a Mig-IL1ra-Trail-CD40L network, and an IL12p40-IL12p70 network.

CONCLUSIONS

Differences in cytokine profiles are present among men and male-to-female transgender women with active and treated syphilis. Cytokine assays may be a potentially useful tool for identifying active syphilis among patients with serologic syphilis reactivity.

Association of interleukin-10 promoter polymorphisms with serofast state after syphilis treatment

OBJECTIVES

Recent studies suggested that upregulation of anti-inflammatory immune response during early syphilis may be associated with persistence of Treponema pallidum infection despite adequate treatment, resulting in a serofast state. The objective of this study was to determine whether enhanced interleukin (IL)-10-related response during early T. pallidum infection increased the risk of serofast syphilis.

METHODS

Two IL10 gene promoter polymorphisms affecting IL-10 production (-1082A>G [rs1800896], -592C>A [rs1800872]) and serum levels of IL-10 were measured in 80 patients with early syphilis before and 6 months after penicillin treatment and in 24 healthy volunteers (control group).

RESULTS

After 6 months, patients were stratified based on serological response into two groups: (1) serofast state (n = 28) and (2) serologically cured (n = 52). Pretreatment and post-treatment serum IL-10 levels were significantly higher in patients who remained serofast compared with those who had a serological cure (p<0.001). The GG genotype of the -1082A>G (rs1800896) polymorphism and the CC genotype of the -592C>A (rs1800872) polymorphism were significantly correlated with higher serum IL-10 levels. Moreover, the OR for remaining serofast for carriers of these genotypes was 16.2 (95% CI: 4.1 to 65.0, p<0.0001) and 2.9 (95% CI: 1.4 to 5.9, p=0.002), respectively.

CONCLUSIONS

We showed that a pronounced anti-inflammatory immune response may be an important predictor for the serofast state. Additionally, host-related factors such as polymorphisms of immune regulatory genes may influence the risk of remaining serofast after syphilis therapy.

Syphilis reinfection is associated with an attenuated immune profile in the same individual: a prospective observational cohort study

Background

Ascertaining if the clinical and immunological response to repeat syphilis differs from that in initial syphilis may assist in designing optimal syphilis screening strategies and vaccine design.

Methods

We prospectively recruited 120 patients with a new diagnosis of (baseline) syphilis. During a 24-month follow-up period, 11 of these patients had a further diagnosis of (repeat) syphilis. We conducted a paired comparison of their plasma cyto-chemokines at baseline and repeat syphilis.

Results

Comparing to their baseline infection, paired analyses of the 11 individuals with repeat infections during follow-up revealed that these reinfections had lower concentrations of Interferon (IFN)α (0.8 [Interquartile range (IQR) 0.8–0.8 vs. 12.2 [IQR 1.6–24.2], P = 0.004) and Chemokine (C-C motif) ligand (CCL) 4 (0.9 [IQR 0.9–12.2 vs. 17.5 [IQR 4.9–32.8], P = 0.022].

Conclusion

In this small study of 11 individuals, repeat syphilis was found to present with an attenuated immune response. The relevance of these findings to the design of optimal syphilis screening programs is discussed.

Akt, mTOR and NF-κB pathway activation in Treponema pallidum stimulates M1 macrophages

The polarization of macrophages and the molecular mechanism involved during the early process of syphilis infection remain unknown. This study was conducted to explore the influence of Treponema pallidum (T. pallidum) treatment on macrophage polarization and the Akt-mTOR-NFκB signaling pathway mechanism involved in this process. M0 macrophages derived from the phorbol-12-myristate-13-acetate-induced human acute monocytic leukemia cell line THP-1 were cultured with T. pallidum. T. pallidum induced inflammatory cytokine (IL-1β and TNF-α) expression in a dose- and time-dependent manner. However IL-10 cytokine expression decreased at the mRNA and protein levels. Additionally, the expression of the M1 surface marker iNOS was up-regulated with incubation time, and the expression of the M2 surface marker CD206 was low (vs. PBS treated macrophages, P < 0.001) and did not fluctuate over 12 h. Further studies revealed that Akt-mTOR-NFκB pathway proteins, including p-Akt, p-mTOR, p-S6, p-p65, and p-IκBα, were significantly higher in the T. pallidum-treated macrophages than in the PBS-treated macrophages (P < 0.05). In addition, inflammatory cytokine expression was suppressed in T. pallidum-induced M1 macrophages pretreated with LY294002 (an Akt-specific inhibitor) or PDTC (an NF-κB inhibitor), while inflammatory cytokine levels increased in T. pallidum-induced M1 macrophages pretreated with rapamycin (an mTOR inhibitor). These findings revealed that T. pallidum promotes the macrophage transition to pro-inflammatory M1 macrophages in vitro. The present study also provides evidence that Akt, mTOR and NF-κB pathway activation in T. pallidum stimulates M1 macrophages. This study provides novel insights into the innate immune response to T. pallidum infection.

Syphilis

Treponema pallidum subspecies pallidum (T. pallidum) causes syphilis via sexual exposure or via vertical transmission during pregnancy. T. pallidum is renowned for its invasiveness and immune-evasiveness; its clinical manifestations result from local inflammatory responses to replicating spirochaetes and often imitate those of other diseases. The spirochaete has a long latent period during which individuals have no signs or symptoms but can remain infectious. Despite the availability of simple diagnostic tests and the effectiveness of treatment with a single dose of long-acting penicillin, syphilis is re-emerging as a global public health problem, particularly among men who have sex with men (MSM) in high-income and middle-income countries. Syphilis also causes several hundred thousand stillbirths and neonatal deaths every year in developing nations. Although several low-income countries have achieved WHO targets for the elimination of congenital syphilis, an alarming increase in the prevalence of syphilis in HIV-infected MSM serves as a strong reminder of the tenacity of T. pallidum as a pathogen. Strong advocacy and community involvement are needed to ensure that syphilis is given a high priority on the global health agenda. More investment is needed in research on the interaction between HIV and syphilis in MSM as well as into improved diagnostics, a better test of cure, intensified public health measures and, ultimately, a vaccine.

The immunological response to syphilis differs by HIV status; a prospective observational cohort study

Background

It is not known if there is a difference in the immune response to syphilis between HIV-infected and uninfected individuals.

Methods

We prospectively recruited all patients with a new diagnosis of syphilis and tested their plasma for IFNα, IFNγ, IL-1β, IL-12p40, IL-12p70, IP-10, MCP-1, MIP-1α, MIP-1β, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10 and IL-17A at baseline pre-treatment and 6 months following therapy.

Results

A total of 79 HIV-infected [44 primary/secondary syphilis (PSS) and 35 latent syphilis (LS)] and 12 HIV-uninfected (10 PSS and 2 LS) cases of syphilis and 30 HIV-infected controls were included in the study. At the baseline visit, compared to the control group, concentrations of IL-10 were significantly elevated in the HIV-infected and uninfected groups. The level of IL-10 was significantly higher in the HIV-infected compared to the HIV-uninfected PSS group (25.3 pg/mL (IQR, 4.56–41.76) vs 2.73 pg/mL (IQR, 1.55–9.02), P = 0.0192). In the HIV-infected PSS group (but not the HIV-infected LS or HIV-uninfected PSS groups) the IP-10, MIP-1b, IL-6 and IL-8 were raised compared to the controls. IL-10 levels decreased but did not return to control baseline values by 6 months in HIV infected PSS and LS and HIV uninfected PSS.

Conclusion

PSS and LS in HIV-infected individuals is characterized by an increase in inflammatory and anti-inflammatory cytokines such as IL-10. The increase of IL-10 is greater in HIV-infected than uninfected individuals. Further work is required to ascertain if this is part of an immunological profile that correlates with adverse outcomes such as serofast syphilis and neurosyphilis, in HIV-infected individuals.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-017-2201-7) contains supplementary material, which is available to authorized users.