Interaction of Treponema pallidum, the syphilis spirochete, with human platelets

Platelet-derived major histocompatibility complex class I coating on Treponema pallidum attenuates natural killer cell lethality

The evasive tactics of Treponema pallidum pose a major challenge in combating and eradicating syphilis. Natural killer (NK) cells mediate important effector functions in the control of pathogenic infection, preferentially eliminating targets with low or no expression of major histocompatibility complex (MHC) class I. To clarify T. pallidum's mechanisms in evading NK-mediated immunosurveillance, experiments were performed to explore the cross-talk relations among T. pallidum, NK cells, and platelets. T. pallidum adhered to, activated, and promoted particle secretion of platelets. After preincubation with T. pallidum, platelets expressed and secreted high levels of MHC class I, subsequently transferring them to the surface of T. pallidum, potentially inducing an immune phenotype characterized by the "pseudo-expression" of MHC class I on the surface of T. pallidum (hereafter referred to a "pseudo-expression" of MHC class I). The polA mRNA assay showed that platelet-preincubated T. pallidum group exhibited a significantly higher copy number of polA transcript than the T. pallidum group. The survival rate of T. pallidum mirrored that of polA mRNA, indicating that preincubation of T. pallidum with platelets attenuated NK cell lethality. Platelets pseudo-expressed the MHC class I ligand on the T. pallidum surface, facilitating binding to killer cell immunoglobulin-like receptors with two immunoglobulin domains and long cytoplasmic tail 3 (KIR2DL3) on NK cells and initiating dephosphorylation of Vav1 and phosphorylation of Crk, ultimately attenuating NK cell lethality. Our findings elucidate the mechanism by which platelets transfer MHC class I to the T. pallidum surface to evade NK cell immune clearance.

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.

Acute Ischaemic Stroke in the Context of Neurosyphilis: How Does Antibiotic Therapy Help, and When Should It Be Given?

Introduction

Neurosyphilis (NS) refers to a central nervous system infection caused by Treponema pallidum. In recent years, there has been an increasing incidence of syphilis; however, NS is uncommon compared to the era before the discovery of penicillin. Manifestations are usually non-specific, ranging from asymptomatic cases to syphilitic meningitis, meningovascular syphilis, general paresis and tabes dorsalis. Meningovascular syphilis can cause an inflammatory arteritis of cerebral arteries, leading to vascular occlusion and cerebral infarction.

Case description

We report a case of an ischaemic stroke in a patient with several vascular risk factors, presenting with right hemiparesis, hemihypesthesia and dysarthria. Initial computed tomography with angiography of the head and neck was normal; however, magnetic resonance imaging of the brain revealed a thalamic and internal capsule infarct. Serum T. pallidum antibodies were positive, as well as a rapid plasma reagin test. Cerebrospinal fluid analysis confirmed the diagnosis of neurosyphilis, and the patient was treated with ceftriaxone for 14 days due to a penicillin allergy.

Discussion and conclusion

Although there is a high prevalence of stroke in patients with NS, this condition is typically underdiagnosed. Untreated NS carries a higher risk of stroke recurrence compared to other risk factors. Therefore, early diagnosis and treatment are essential. This case highlights the importance of considering NS in stroke victims, even in older patients with several additional vascular risk factors, to prevent recurrence and other complications.

LEARNING POINTS

Neurosyphilis (NS) can occur at any stage of syphilis infection, and it can be asymptomatic or symptomatic, presenting as syphilitic meningitis, meningovascular syphilis, general paresis or tabes dorsalis.Ischaemic strokes are a frequent complication of NS, occurring in 14% of the cases. However, only 19% of the cases are correctly diagnosed.NS should be considered as a potential cause of stroke, even in older patients with several other vascular risk factors. This is essential to prevent future strokes, as well as dementia and other complications.

Research progress on the mechanism of Treponema pallidum breaking through placental barrier

Congenital syphilis, a significant cause of fetal mortality worldwide, is a congenital infectious disease instigated by the vertical transmission of Treponema pallidum during pregnancy. Clinical manifestations include preterm delivery, stillbirth, neonatal skin lesions, skeletal abnormalities, and central nervous system aberrations. The ongoing increase in the incidence of congenital syphilis, coupled with complexities in diagnosis, necessitates a detailed understanding of its pathogenesis for the development of improved diagnostic approaches, and to interrupt the route of vertical transmission. Drawing from the broader body of research associated with vertical transmission pathogens, we aim to clarify the potential mechanisms by which Treponema pallidum breaches the placental barrier to infect the fetus.

The Outer Membrane Lipoprotein Tp0136 Stimulates Human Platelet Activation and Aggregation Through PAR1 to Enhance Gq/Gi Signaling

Background

Chancre self-healing, a typical clinical phenomenon of primary syphilis, is essentially wound healing. The first response to a wound is constriction of the injured blood vessels and activation of platelets to form a fibrin clot. However, the role of Treponema pallidum in platelet activation and clot formation remains unclear.

Objectives

We aimed to elucidate the role of the outer membrane Treponema pallidum lipoprotein Tp0136 in human platelet activation and aggregation and explore the related mechanism.

Methods

A series of experiments were performed to assess the effects of Tp0136 on human platelet activation and aggregation in vitro. The effect of Tp0136 on platelet receptors was studied by detecting PAR1 protein levels and studying related receptor sites. The involvement of the G_q/G_i signaling pathway downstream of PAR1 was explored.

Results

Tp0136 significantly accelerated the formation of human platelet clots as well as platelet adhesion to and diffusion on fibrinogen to promote platelet aggregation. Tp0136 also potentiated P-selectin expression and PF4 release to promote platelet activation and downregulated PAR1 expression. The activation and aggregation induced by Tp0136 were reverted by the specific PAR1 antagonist RWJ56110 and the human PAR1 antibody. In addition, Tp0136 significantly enhanced G_q and G_i signaling activation, thereby triggering p38 phosphorylation and Akt-PI3K activation, increasing the release of intraplatelet Ca²⁺ and attenuating the release of cytosolic cAMP. Furthermore, the specific PAR1 antagonist RWJ56110 significantly suppressed G_q and G_i signaling activation.

Conclusions

Our results showed that the Treponema pallidum Tp0136 protein stimulated human platelet activation and aggregation by downregulating PAR1 and triggered PAR1-dependent G_q and G_i pathway activation. These findings may contribute to our understanding of the self-healing of chancroid in early syphilis.

Detection of Treponema pallidum DNA during early syphilis stages in peripheral blood, oropharynx, ano-rectum and urine as a proxy for transmissibility

Background

Syphilis diagnosis may be challenging, especially in the asymptomatic and early clinical stages. We evaluated the presence of Treponema pallidum DNA (TP-DNA) in various sample types to elucidate transmissibility during various syphilis stages.

Methods

The study was conducted at the Amsterdam Centre for Sexual Health. We included adult men who have sex with men (MSM), who were suspected of having syphilis. The 2020 European guidelines definitions were followed for the diagnosis and staging of syphilis. Using a polymerase chain reaction (PCR) targeting the polA gene of Treponema pallidum (TP-PCR), we tested the following study samples on TP-DNA: peripheral blood, oropharyngeal swab, ano-rectal swab, and urine.

Results

From November 2018 to December 2019 we included 293 MSM. Seventy clients had primary syphilis, 73 secondary syphilis, 86 early latent syphilis, 14 late latent syphilis, 23 treated syphilis, and 27 had no syphilis. TP-DNA was detected in at least 1 study sample in 35/70 clients with primary syphilis (2/70 peripheral blood, 7/70 oropharynx, 13/70 ano-rectum, and 24/70 urine); in 62/73 clients with secondary syphilis (15/73 peripheral blood, 47/73 oropharynx, 37/73 ano-rectum, and 26/73 urine); and in 29/86 clients with early latent syphilis (5/86 peripheral blood, 21/86 oropharynx, 11/86 ano-rectum, and 6/86 urine). TP-DNA was not detected in clients with late latent syphilis or treated syphilis, nor in clients without syphilis.

Conclusions

TP-DNA was frequently detected in various sample types in the absence of lesions. This is in line with the high transmission rate of syphilis and opens diagnostic opportunities for early presymptomatic syphilis stages.

Emerging Nano-Carrier Strategies for Brain Tumor Drug Delivery and Considerations for Clinical Translation

Treatment of brain tumors is challenging since the blood–brain tumor barrier prevents chemotherapy drugs from reaching the tumor site in sufficient concentrations. Nanomedicines have great potential for therapy of brain disorders but are still uncommon in clinical use despite decades of research and development. Here, we provide an update on nano-carrier strategies for improving brain drug delivery for treatment of brain tumors, focusing on liposomes, extracellular vesicles and biomimetic strategies as the most clinically feasible strategies. Finally, we describe the obstacles in translation of these technologies including pre-clinical models, analytical methods and regulatory issues.

Hepatitis B and syphilis prevalence and risk factors of transmission among febrile patients in a primary health facility in Kogi State, Nigeria

Hepatitis B and syphilis remained a global disease with a worrisome prevalence in Nigeria. This study was to determine their prevalence and factors associated with HBV and syphilis infection in febrile patients in Ejule metropolis, Nigeria. In a cross-sectional study, sera obtained from the patients were screened for HBsAg (HBV) and syphilis using commercial immunoassay kits. Data on patients' demographic, social, and behavioral indicators were collected using structured questionnaires. Of the 200 participants, 15 (7.5%) were HBsAg-positive, 3(1.5%) had syphilis, while 2(1.0%) had both HBV and syphilis infections. Ages 31-40 had a higher prevalence of single- and co-infection. Comparable rates of single and concurrent infection were observed in both sexes (P > .05), despite higher participating rates in females. Being single significantly influenced HBV/syphilis co-infection (p = .02), while no statistical difference in prevalence rates was observed with patients' level of education and occupational status. Intravenous drug use (p = .02), history of surgeries (p = .001), and blood transfusion (p = .01) were significantly associated with HBV infection. Also, a significant rate of syphilis was observed in an association with the history of surgeries (p = .001) and blood transfusion (p = .008). Findings from our study show an intermediate level of hepatitis B endemicity in the study area. The low rate of syphilis and co-infection with HBV shows that further strengthening of the current public health measures, including awareness of potential risk factors, could be beneficial in reducing the burden of both HBV and syphilis infection. The low frequency of individuals vaccinated against HBV suggests a need for improved vaccination services.

Syphilitic Gummata in the Central Nervous System: A Narrative Review and Case Report about a Noteworthy Clinical Manifestation

Infection with Treponema pallidum is on the rise. In this narrative literature review, we show that the incidence of rare manifestations of syphilis, such as intracerebral gummata, is increasing and should be considered in the differential diagnosis of intracerebral lesions. With the exemplary case that we present here, we aim to raise awareness of the resurgence of this disease, which should be considered in the differential diagnosis of intracerebral lesions, especially for patients who have a risk profile for syphilis, and serological testing for T. pallidum prior to surgery should be discussed in order to avoid an unnecessary operation.

Visualization of platelet recruitment to tumor lesions using highly sensitive and stable radioiodine studded gold nanoprobes

In vivo imaging of platelets will provide a better understanding of their critical roles in arterial cardiovascular disease, hemostasis, inflammation, and cancer. Here, we demonstrate the feasibility of using radioiodine studded gold nanoprobes (RIS-GNPs) as a platelet tracker for nuclear medicine imaging in tumor-bearing mice using positron emission tomography and computed tomography (PET/CT). Platelet labeling with RIS-GNPs did not alter the platelet functions, such as cellular proliferation and aggregation. PET/CT imaging clearly revealed the migration of platelets into tumor sites at 1 to 5 h post-transfer of RIS-GNP-labeled platelets, which was consistent with the biodistribution data. Our findings suggest that the imaging approach using RIS-GNPs makes it feasible to visualize the biological behavior of platelets in living organisms with cancer.

A Rare Case of an Abdominal Aortic Thrombus Secondary to Syphilitic Aortitis

Syphilis is a sexually transmitted spirochete infection whose presentation depends on the stage of infection. Currently, due to antibiotic treatment, tertiary syphilis is a rare clinical entity. When present, it is characterized by neurosyphilis, gummas, and cardiovascular infection. We present a case of a 64-year-old male who came with abdominal pain due to allergic colitis and was incidentally found to have a mural thrombus of his abdominal aorta. Following a negative workup and no etiologic cause of the thrombus, the patient was diagnosed with syphilitic aortitis. Previous cases have been seen in patients who present with infarction due to aortic thrombosis secondary to syphilitic aortitis. Practitioners must be aware that patients with tertiary syphilis, such as this patient, could have aortic thrombosis without any signs of ischemia and are at risk for infarction.

Increased CCL24 and CXCL7 levels in the cerebrospinal fluid of patients with neurosyphilis

Background

Monocytes are recruited into the cerebrospinal fluid (CSF) of patients with neurosyphilis, suggesting abnormal chemokine expression. We aimed to investigate the aberrant expression of chemokines in the CSF of these patients.

Methods

CSF and serum samples were collected from patients with neurosyphilis between July 2017 and June 2019 in the Dermatology Department, Second Affiliated Hospital of Zhejiang University. Differences in the expression of 38 chemokines between patients with and without neurosyphilis were detected using RayBio^® Human Chemokine Antibody Array C1. CCL24 and CXCL7 levels in the patients’ CSF and serum were further measured using RayBio^® CCL24 and CXCL7 ELISA kits.

Results

Ninety‐three CSF and serum samples of patients with syphilis were collected. Antibody array analysis showed that the CSF levels of CCL24 (P = .0185), CXCL7 (P < .0001), CXCL13 (P < .0001), CXCL10 (P < .0001), and CXCL8 (P < .0001) were significantly higher in patients with than without neurosyphilis. ELISA confirmed significantly higher CCL24 and CXCL7 levels in the CSF of patients with than without neurosyphilis (CCL24: 6.082 ± 1.137 pg/mL vs 1.773 ± 0.4565 pg/mL, P = .0037; CXCL7: 664.3 ± 73.19 pg/mL vs 431.1 ± 90.54 pg/mL, P = .0118). Increased CCL24 and CXCL7 expression was seen throughout all neurosyphilis stages, had moderate diagnostic efficiency for neurosyphilis, and correlated poorly with CSF cell count and Venereal Disease Research Laboratory titer. CSF CCL24 levels also correlated poorly with CSF protein concentration.

Conclusion

Abnormally high CSF chemokines levels may play a role in the pathogenesis of neurosyphilis.

Seroprevalence and risk factors on Syphilis among blood donors in Chengdu, China,from 2005 to 2017

Background

High-risk population of blood donation increases the prevalence of transmit blood-borne diseases and harm the blood safety. Syphilis accounts for approximately 10% of commonly sexually transmitted diseases. The risk factors for blood donors infected with syphilis are also risk factors for other blood borne diseases. The objective of the study is to investigate the seroprevalence and risk factors on syphilis among blood donors, and analyze the donation status of high-risk population.

Methods

A retrospective study was conducted in Chengdu Blood Center during 2005 and 2017. Serological test results of volunteer blood donors were collected. Conditional logistic regression models were performed to investigate syphilis-related risk factors and population attributable risk (PAR) was performed to predict the tendencies of high-risk populations’ on risky behaviors.

Results

The serological epidemic for syphilis among blood donors in Chengdu showed an upward trend from 2005 to 2017.TP positive blood donors were more likely to have multiple sexual partners and commercial sex (50.6% vs.22.6, 11.1% vs.4.6%). Multiple condition logistic regression model denoted the following risk factors for increasing rates of syphilis infections: multiple sexual partners (OR = 7.1, 95% CI:1.72–6.58), razor reuse (OR = 1.7;, 95% CI:1.01–2.01); ear piercing (OR = 2.7, 95% CI:1.48–3.37); tattoo (OR = 3.3, 95% CI:1.17–6.78); condom occasionally (OR = 2.8, 95% CI:0.68–1.66). The PAR for each of the risk factors were 0.225, 0.144, 0.147, 0.018, 0.129, 0.018, respectively.

Conclusion

Health consultation and screening of high-risk groups before blood donation need to be further improved. Blood donor recruitment should emphasize on excluding the high-risk donors and recruiting more low-risk blood donors. In addition, this study also shows that sharing cosmetic surgical instrument has been proven to transmit blood-borne diseases. Therefore, the syphilis in blood circulation should not be ignored.

Electronic supplementary material

The online version of this article (10.1186/s12879-019-4128-7) contains supplementary material, which is available to authorized users.