Treponematosis in critically endangered Western chimpanzees (Pan troglodytes verus) in Senegal.

Treponematoses encompass a group of chronic and debilitating bacterial diseases transmitted sexually or by direct contact and attributed to Treponema pallidum. Despite being documented since as far back as 1963, the epidemiology of treponematoses in wild primates has remained an uninvestigated territory due to the inherent challenges associated with conducting examinations and obtaining invasive biological samples from wild animals. The primary aim of this study was to investigate the presence of treponemal infections in the critically endangered Western chimpanzees in Senegal, utilizing an innovative non-invasive stool serology method. We provide compelling evidence of the existence of anti-Treponema-specific antibodies in 13 out of 29 individual chimpanzees. Our study also underscores the significant potential of stool serology as a valuable non-invasive tool for monitoring and surveilling crucial emerging diseases in wild animals. We recognize two major implications: (1) the imperative need to assess the risks of treponematosis in Western chimpanzee populations and (2) the necessity to monitor and manage this disease following a holistic One Health approach.

Treponema pallidum protein Tp0136 promotes angiogenesis to facilitate the dissemination of Treponema pallidum.

The incompletely eliminated Treponema pallidum (T. pallidum) during primary syphilis chancre infection can result in the progression of secondary, tertiary, or latent syphilis in individuals, suggesting that T. pallidum has successfully evaded the immune response and spread to distant sites. The mechanism underlying the dissemination of T. pallidum is unclear. Here, a syphilitic rabbit model dorsal-injected with recombinant Tp0136 protein or Tp0136 antibody subcutaneously was used to demonstrate the role of Tp0136 protein in promoting the dissemination of T. pallidum to the testis and angiogenesis in vivo; vascular endothelial cell line HMEC-1 was employed to display that Tp0136 protein enhances the angiogenesis. Furthermore, the three-dimensional microfluidic angiogenesis system showed that the angiogenesis would heighten vascular permeability. Then transcriptome sequencing analysis, in conjunction with cell-level validation, elucidated the critical role of the PI3K-AKT signaling pathway in the promotion of angiogenesis by Tp0136 protein, resulting in heightened permeability. These findings elucidate the strategy employed by T. pallidum in evading immune clearance.

Neurosyphilis Presenting as Psychiatric Symptoms at Younger Age: A Case Report.

Neurosyphilis is a central nervous system infection caused by Treponema pallidum that imitates various neurological and mental disorders. Therefore, patients with this disease are prone to misdiagnoses. Here, we report a case of neurosyphilis with a psychotic disorder as the main manifestation. A young girl exhibited mental and behavioural abnormalities after a heartbreak, which manifested as alternating low mood, emotional irritability, and a lack of interest in social relations, followed by memory loss. The cerebrospinal fluid protein - Treponema pallidum particle agglutination test was positive, the toluidine red unheated serum test titre was 1:4, the white blood cell count was 5 × 10^6/L, the cerebrospinal fluid protein level was 0.97 g/L, and the brain CT was abnormal. After admission, the possibility of neurosyphilis was considered and the patient received intravenous penicillin G treatment. The patient's clinical symptom ms improved. This case emphasises that doctors should maintain clinical suspicion of Treponema pallidum infection in adolescent patients with mental abnormalities.

Actinic Granuloma Complicated by Secondary Syphilis: A Case Report.

Introduction: Actinic granuloma (AG) is a rare skin eruption thought to result from a sun-induced inflammatory response attracting giant cells, which are large, multinucleated, and inflammatory, to form granulomas and degrade surrounding elastic material. Clinically, lesions begin on sun-exposed skin as pink papules and nodules that coalesce into demarcated annular plaques with a hypopigmented center. Histologically, actinic elastosis surrounds the outer annulus ring, with histiocytes and giant cells within the raised border, and the innermost central zone is filled with minimal to absent elastic fibers. Case Presentation: We present a middle-aged female with a pruritic eruption of diffuse erythematous macules and papules coalescing into plaques with mild scale involving the scalp, face, neck, torso, and upper and lower extremities, including the palms and soles, but sparing the ears, bilateral axillae, elbows, and knees. Skin biopsies revealed solar elastosis and abundant multinucleated foreign body giant cells with ingested elastic fibers. The patient's clinical presentation and histopathology were consistent with a diagnosis of AG. Furthermore, spirochete immunostaining of the specimens revealed multiple Treponema pallidum spirochetes throughout the epidermis and dermis. Secondary syphilis with primary chancre was added to the diagnosis. Treatment included oral and topical steroids followed by intravenous penicillin G. After 1 month, all lesions had resolved with post-inflammatory erythema. Conclusion: Our patient differs from the typical presentation in describing intense pruritus with her eruption. This interesting collision reminds clinicians to retain a high index of suspicion for multiple diagnoses in a single patient.

A novel syphilis Treponema pallidum lipoprotein peptide antigen diagnostic assay using red cell kodecytes in routine blood centre column agglutination testing platforms.

BACKGROUND AND OBJECTIVES: The detection of treponemal antibodies, which are used to make a diagnosis of syphilis, is important both for diagnostic purposes and as a mandatory blood donor test in most countries. We evaluated the feasibility of using Kode Technology to make syphilis peptide red cell kodecytes for use in column agglutination serologic platforms. MATERIALS AND METHODS: Candidate Kode Technology function-spacer-lipid (FSL) constructs were made for the Treponema pallidum lipoprotein (TmpA) of T. pallidum, using the peptide and FSL selection algorithms, and then used to make kodecytes. Developmental kodecytes were evaluated against a large range of syphilis antibody reactive and non-reactive samples in column agglutination platforms and compared against established methodologies. Overall, 150 reactive and 2072 non-reactive Syphicheck assay (a modified T. pallidum particle agglutination) blood donor samples were used to evaluate the agreement rate of the developed kodecyte assay. RESULTS: From three FSL-peptide candidate constructs, one was found to be the most suitable for diagnostics. Of 150 Syphicheck assay reactive samples, 146 were TmpA-kodecyte reactive (97.3% agreement), compared with 58.0% with the rapid plasmin reagin (RPR) assay for the same samples. Against the 2072 expected syphilis non-reactive samples the agreement rate for TmpA-kodecytes was 98.8%. CONCLUSION: TmpA-kodecytes are viable for use as cost-effective serologic reagent red cells for the detection of treponemal antibodies to diagnose syphilis with a high level of specificity in blood centres. This kodecyte methodology also potentially allows for introduction of the reverse-algorithm testing into low-volume laboratories, by utilizing existing transfusion laboratory infrastructure.

Integração da vigilância e atenção à saúde no tratamento da sífilis gestacional: análise dos indicadores do PQAVS e do Previne Brasil na Paraíba / Integration of surveillance and health care in the management of gestational syphilis: analysis of PQAVS and Previne Brasil indicators in Paraíba / Integración de la vigilancia y la atención a la salud en el tratamiento de la sífilis gestacional: análisis de los indicadores PQAVS y Previne Brasil en Paraíba

Este artigo se baseia em um estudo feito com o objetivo de analisar indicadores sobre a testagem da sífilis na gestação no Programa de Qualificação das Ações de Vigilância em Saúde (PQAVS) e no Programa Previne Brasil no estado da Paraíba, e também de levantar aspectos do tratamento terapêutico para sífilis gestacional. Trata-se de uma pesquisa descritiva-exploratória, na qual foram sistematizados dados do indicador 11, testes por gestantes, do PQAVS e do indicador de desempenho da Atenção Primária à Saúde (APS), com base na proporção de gestantes que realizaram exames de sífilis e HIV durante o pré-natal em 2020; também foi feita a sistematização do webquestionário direcionado a profissionais da APS (médicos/enfermeiros) e autoaplicado sobre a atuação e tratamento terapêutico para sífilis gestacional. Dos 223 municípios da Paraíba, apenas 12% atingiram a meta do PQAVS e 39% a do Previne Brasil em 2020. Em relação ao webquestionário, houve a participação de 142 profissionais, dos quais 85% realizam o tratamento terapêutico preconizado pelo Ministério da Saúde para a APS. Desse modo, deve ser ressaltada a importância da ampliação da oferta de testes para sífilis, dos insumos para o tratamento adequado e da qualificação dos profissionais e da informação em saúde.

This article is based on a study to analyze indicators on syphilis testing during pregnancy in the PQAVS - Programa de Qualificação das Ações de Vigilância em Saúde (Health Surveillance Actions Qualification Programme) and in the Programa Previne Brasil (Previne Brasil Programme) in the state of Paraíba, Brazil, and also to survey aspects of the therapeutic management for gestational syphilis. It is a descriptive-exploratory research, in which data from indicator 11, tests for pregnant women, from the PQAVS and from the Primary Health Care (PHC) performance indicator, based on the proportion of pregnant women with syphilis and HIV tests during prenatal care in 2020 were systematised; in addition to this systematization, a self-administered webquestionnaire on the performance and therapeutic management for gestational syphilis by professionals (doctors/nurses) from the PHC was also systematised. Taking into account the 223 municipalities in Paraíba, only 12% reached the PQAVS goal and 39% reached the Previne Brasil goal in 2020. Regarding the webquestionnaire, 85% of the 142 professionals who answered it, carry out the therapeutic management recommended by the Ministry of Health for the PHC. Thus, it is fundamental to emphasise the importance of expanding the supply of tests for syphilis, supplies for adequate treatment, and the qualification of health professionals and information.

El presente artículo se basa en un estudio efectuado con el objetivo de analizar indicadores sobre la prueba de sífilis durante el embarazo en el PQAVS - Programa de Qualificação das Ações de Vigilância em Saúde (Programa de Calificación para Acciones de Vigilancia en Salud) y en el Programa Previne Brasil en el estado de Paraíba, Brasil, y de resaltar aspectos del tratamiento terapéutico de la sífilis gestacional. Se trata de una investigación descriptiva-exploratoria, en la que se sistematizaron datos del indicador 11, pruebas realizadas por embarazadas, del PQAVS y del indicador de desempeño de la Atención Primaria de Salud (APS), a partir de la proporción de gestantes que se sometieron a pruebas de sífilis y de HIV durante la atención prenatal en 2020; también se sistematizóel cuestionario web dirigido a profesionales de la APS (médicos/enfermeros) y autoadministrado sobre el desempeño y el tratamiento terapéutico de la sífilis gestacional. De los 223 municipios de Paraíba, apenas 12% alcanzaron la meta del PQAVS y 39% lograron la meta del Previne Brasil en 2020. En relación al cuestionario web, participaron 142 profesionales, de los cuales 85% realizan el tratamiento terapéutico recomendado por el Ministerio de Salud para la APS. Así, es fundamental la importancia de ampliar la oferta de pruebas para la sífilis, de los medicamentos para el tratamiento adecuado, la calificación de los profesionales e la información relacionada a la salud.

Condyloma lata of the umbilicus: A case report highlighting the present syphilis emergency.

Syphilis is an ancient sexually transmitted infection that plagues communities across the United States and the world. Cutaneous syphilis has a wide variety of manifestations and presentations, and is notoriously difficult to identify clinically as a result. In this report, we describe the case of a 30-year-old patient with condyloma lata on the umbilicus, an extremely rare site for the presentation of these lesions. With the recent surge in syphilis infections nationwide, including congenital infections, this case underscores the urgent necessity for heightened syphilis awareness and suspicion among clinicians.

The dose-dependent effect of the D2R agonist quinpirole microinjected into the ventral pallidum on information flow in the limbic system.

The ventral pallidum (VP) receives its primary inputs from the nucleus accumbens (NAC) and the basolateral amygdala (BLA). We demonstrated recently that in the VP, the D2 DA receptor (D2R) agonist quinpirole dose-dependently facilitates memory consolidation in inhibitory avoidance and spatial learning. In the VP, D2R can be found both on NAC and BLA terminals. According to our hypothesis, quinpirole microinjected into the VP can facilitate memory consolidation via modulation of synaptic plasticity on NAC and/or BLA terminals. The effect of intra-VP quinpirole on BLA-VP and NAC shell-VP synapses was investigated via a high frequency stimulation (HFS) protocol. Quinpirole was administered in three doses into the VP of male Sprague-Dawley rats after HFS; controls received vehicle. To examine whether an interaction between the NAC shell and the BLA at the level of the VP was involved, tetrodotoxin (TTX) was microinjected into one of the nuclei while stimulating the other nucleus. Our results showed that quinpirole dose-dependently modulates BLA-VP and NAC shell-VP synapses, similar to those observed in inhibitory avoidance and spatial learning, respectively. The lower dose inhibits BLA inputs, while the larger doses facilitates NAC shell inputs. The experiments with TTX demonstrates that the two nuclei do not influence each others' evoked responses in the VP. Power spectral density analysis demonstrated that independent from the synaptic facilitation, intra-VP quinpirole increases the amplitude of gamma frequency band after NAC HFS, and BLA tonically suppresses the NAC's HFS-induced gamma facilitation. In contrast, HFS of the BLA results in a delayed, transient increase in the amplitude of the gamma frequency band correlating with the LTP of the P1 component of the VP response to BLA stimulation. Furthermore, our results demonstrate that the BLA plays a prominent role in the generation of the delta oscillations: HFS of the BLA leads to a gradually increasing delta frequency band facilitation over time, while BLA inhibition blocks the NAC's HFS induced strong delta facilitation. These findings demonstrate that there is a complex interaction between the NAC shell region and the VP, as well as the BLA and the VP, and support the important role of VP D2Rs in the regulation of limbic information flow.

Globus pallidus externus drives increase in network-wide alpha power with propofol-induced loss-of-consciousness in humans.

States of consciousness are likely mediated by multiple parallel yet interacting cortico-subcortical recurrent networks. Although the mesocircuit model has implicated the pallidocortical circuit as one such network, this circuit has not been extensively evaluated to identify network-level electrophysiological changes related to loss of consciousness (LOC). We characterize changes in the mesocircuit in awake versus propofol-induced LOC in humans by directly simultaneously recording from sensorimotor cortices (S1/M1) and globus pallidus interna and externa (GPi/GPe) in 12 patients with Parkinson disease undergoing deep brain stimulator implantation. Propofol-induced LOC is associated with increases in local power up to 20 Hz in GPi, 35 Hz in GPe, and 100 Hz in S1/M1. LOC is likewise marked by increased pallidocortical alpha synchrony across all nodes, with increased alpha/low beta Granger causal (GC) flow from GPe to all other nodes. In contrast, LOC is associated with decreased network-wide beta coupling and beta GC from M1 to the rest of the network. Results implicate an important and possibly central role of GPe in mediating LOC-related increases in alpha power, supporting a significant role of the GPe in modulating cortico-subcortical circuits for consciousness. Simultaneous LOC-related suppression of beta synchrony highlights that distinct oscillatory frequencies act independently, conveying unique network activity.

Regulating the activity of GABAergic neurons in the ventral pallidum alters the general anesthesia effect of propofol.

The full mechanism of action of propofol, a commonly administered intravenous anesthetic drug in clinical practice, remains elusive. The focus of this study was the role of GABAergic neurons which are the main neuron group in the ventral pallidum (VP) closely associated with anesthetic effects in propofol anesthesia. The activity of VP GABAergic neurons following propofol anesthesia in Vgat-Cre mice was observed via detecting c-Fos immunoreactivity by immunofluorescence and western blotting. Subsequently, chemogenetic techniques were employed in Vgat-Cre mice to regulate the activity of VP GABAergic neurons. The role of VP GABAergic neurons in generating the effects of general anesthesia induced by intravenous propofol was further explored through behavioral tests of the righting reflex. The results revealed that c-Fos expression in VP GABAergic neurons in Vgat-Cre mice dramatically decreased after propofol injection. Further studies demonstrated that chemogenetic activation of VP GABAergic neurons during propofol anesthesia shortened the duration of anesthesia and promoted wakefulness. Conversely, the inhibition of VP GABAergic neurons extended the duration of anesthesia and facilitated the effects of anesthesia. The results obtained in this study suggested that regulating the activity of GABAergic neurons in the ventral pallidum altered the effect of propofol on general anesthesia.

Clinical presentation of early syphilis and genomic sequences of Treponema pallidum strains in patient specimens and isolates obtained by rabbit inoculation.

BACKGROUND: The global resurgence of syphilis necessitates vaccine development. METHODS: We collected ulcer exudates and blood from 17 primary syphilis (PS) participants and skin biopsies and blood from 51 secondary syphilis (SS) participants in Guangzhou, China for Treponema pallidum subsp. pallidum (TPA) qPCR, whole genome sequencing (WGS), and isolation of TPA in rabbits. RESULTS: TPA DNA was detected in 15 of 17 ulcer exudates and 3 of 17 blood PS specimens. TPA DNA was detected in 50 of 51 SS skin biopsies and 27 of 51 blood specimens. TPA was isolated from 47 rabbits with success rates of 71% (12/17) and 69% (35/51), respectively, from ulcer exudates and SS bloods. We obtained paired genomic sequences from 24 clinical samples and corresponding rabbit isolates. Six SS14- and two Nichols-clade genome pairs contained rare discordances. Forty-one of the 51 unique TPA genomes clustered within SS14 subgroups largely from East Asia, while 10 fell into Nichols C and E subgroups. CONCLUSIONS: Our TPA detection rate was high from PS ulcer exudates and SS skin biopsies and over 50% from SS blood, with TPA isolation in over two-thirds of samples. Our results support the use of WGS from rabbit isolates to inform vaccine development.

The incidence of new cases of syphilis has skyrocketed globally in the twenty-first century. This global resurgence requires new strategies, including vaccine development. As part of an NIH funded Cooperative Research Center to develop a syphilis vaccine, we established a clinical research site in Guangzhou, China to better define the local syphilis epidemic and obtain samples from patients with primary and secondary syphilis for whole genome sequencing (WGS) of circulating Treponema pallidum strains. Inoculation of rabbits enabled us to obtain T. pallidum genomic sequences from spirochetes disseminating in blood, a compartment of immense importance for syphilis pathogenesis. Collectively, our results further clarify the molecular epidemiology of syphilis in southern China, enrich our understanding of the manifestations of early syphilis, and demonstrate that the genomic sequences of spirochetes obtained by rabbit inoculation accurately represent those of the spirochetes infecting the corresponding patients.

Risk for Donor-Derived Syphilis after Kidney Transplantation, China, 2007-2022.

To evaluate the risk of acquiring syphilis from a donated kidney, we evaluated kidney transplantation pairs from West China Hospital, Sichuan, China, during 2007-2022. Donor-derived syphilis was rare. Risk may be higher if donors have active syphilis and may be reduced if recipients receive ceftriaxone.

Uncovering the mechanisms of host mitochondrial cardiolipin release in syphilis: Insights from human microvascular endothelial cells.

The release of host mitochondrial cardiolipin is believed to be the main factor that contributes to the production of anti-cardiolipin antibodies in syphilis. However, the precise mechanism by which mitochondria release cardiolipin in this context remains elusive. This study aimed to elucidate the mechanisms underlying mitochondrial cardiolipin release in syphilis. We conducted a cardiolipin quantitative assay and immunofluorescence analysis to detect mitochondrial cardiolipin release in human microvascular endothelial cells (HMEC-1), with and without Treponema pallidum (Tp) infection. Furthermore, we explored apoptosis, a key mechanism for mitochondrial cardiolipin release. The potential mediator molecules were then analyzed through RNA-sequence and subsequently validated using in vitro knockout techniques mediated by CRISPR-Cas9 and pathway-specific inhibitors. Our findings confirm that live-Tp is capable of initiating the release of mitochondrial cardiolipin, whereas inactivated-Tp does not exhibit this capability. Additionally, apoptosis detection further supports the notion that the release of mitochondrial cardiolipin occurs independently of apoptosis. The RNA-sequencing results indicated that microtubule-associated protein2 (MAP2), an axonogenesis and dendrite development gene, was up-regulated in HMEC-1 treated with Tp, which was further confirmed in syphilitic lesions by immunofluorescence. Notably, genetic knockout of MAP2 inhibited Tp-induced mitochondrial cardiolipin release in HMEC-1. Mechanically, Tp-infection regulated MAP2 expression via the MEK-ERK-HES1 pathway, and MEK/ERK phosphorylation inhibitors effectively block Tp-induced mitochondrial cardiolipin release. This study demonstrated that the infection of live-Tp enhanced the expression of MAP2 via the MEK-ERK-HES1 pathway, thereby contributing to our understanding of the role of anti-cardiolipin antibodies in the diagnosis of syphilis.

Syphilis susceptibility factors atlas: A wide-angled Mendelian randomization study.

OBJECTIVE: The pathogenic mechanisms of syphilis and the host defense mechanisms against syphilis remain poorly understood. Exploration of the susceptibility factors of syphilis may provide crucial clues for unraveling its underlying mechanisms. METHODS: A two-sample Mendelian Randomization framework was utilized, and the inverse-variance weighted method was used as the main analysis. All data was sourced from Genome-wide association studies datasets from 2015 to 2022 in Europe, and all participants were of European descent. Only summary-level statistics were used. Sensitivity analyses were conducted to evaluate the heterogeneity and pleiotropy of the datasets. RESULTS: Our study established 18 exposure factors (12 risk factors and 6 protective factors) for syphilis susceptibility. Twelve factors encompassing body mass index, waist circumference, darker natural skin, cooked vegetable intake, processed meat intake, diabetes mellitus, glucose regulation disorders, gout, autoimmune diseases, rheumatoid arthritis, diverticulitis, and longer menstrual cycles were found to increase susceptibility to syphilis. In contrast, 6 factors including easier skin tanning, blonde natural hair color, irritability, higher neuroticism scores, extended sleep duration, and delayed age at first sexual intercourse were connected to a reduced risk of syphilis infection (all P < 0.05). CONCLUSIONS: This study identified 18 influencing factors of syphilis susceptibility. These findings offered novel insights for further probing into the underlying pathogenic mechanisms of syphilis and underscored the importance of multifaceted prevention strategies against syphilis.

An Exuberant Case of Ulceronodular-Rupioid (Malignant) Syphilis in an HIV Patient: A Proposal for New Diagnostic Criteria.

We report the case of a 28-year-old male with uncontrolled human immunodeficiency virus (HIV) infection who presented with extensive ulcerated lesions with dark lamellated crusting on his face, torso, and limbs. The patient had a rapid plasma reagin (RPR) titer of 1:512, indicative of syphilis. A skin biopsy revealed granulomata surrounded by lymphocytes, histiocytes, and plasma cells, with spirochetes visible on immunohistochemical staining. The patient's rash resolved with hyperpigmented scarring after penicillin and doxycycline treatment. This severe form of secondary syphilis has been termed malignant syphilis, lues maligna, ulceronodular syphilis, or rupioid syphilis. We propose a single descriptive name for this entity, ulceronodular-rupioid syphilis. In 1969, Fisher proposed criteria for malignant syphilis based on lesion appearance, histopathologic findings, high RPR values, and rapid response to treatment. We found that the Fisher criteria were imprecise with respect to specific histopathologic findings, the quantitation of RPR values, and what constitutes rapid response to treatment. Thus, we examined an additional 74 cases from the literature and propose new diagnostic criteria based on rash appearance, histopathologic characteristics, non-treponemal and treponemal test positivity, and response to therapy. We also found that uncontrolled viremia, and not a low CD4 count, is a major risk factor for ulceronodular-rupioid syphilis in HIV patients.

A ventral pallidal-thalamocortical circuit mediates the cognitive control of instrumental action.

Predictive learning can engage a selective form of cognitive control that biases choice between actions based on information about future outcomes that the learning provides. This influence has been hypothesized to depend on a feedback circuit in the brain through which the basal ganglia modulate activity in the prefrontal cortex; however, direct evidence for this functional circuit has proven elusive. Here, using an animal model of cognitive control, we found that the influence of predictive learning on decision making is mediated by an inhibitory feedback circuit linking the medial ventral pallidum and the mediodorsal thalamus, the activation of which causes disinhibition of the orbitofrontal cortex via reduced activation of inhibitory parvalbumin interneurons during choice. Thus, we found that, for this function, the mediodorsal thalamus serves as a pallidal-cortical relay through which predictive learning controls action selection, which has important implications for understanding cognitive control and its vicissitudes in various psychiatric disorders and addiction.

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.