Congenital syphilis: a clinical profile

Identification of the Neuroinvasive Pathogen Host Target, LamR, as an Endothelial Receptor for the Treponema pallidum Adhesin Tp0751

Treponema pallidum subsp. pallidum is the causative agent of syphilis, a human-specific sexually transmitted infection that causes a multistage disease with diverse clinical manifestations. Treponema pallidum undergoes rapid vascular dissemination to penetrate tissue, placental, and blood-brain barriers and gain access to distant tissue sites. The rapidity and extent of T. pallidum dissemination are well documented, but the molecular mechanisms have yet to be fully elucidated. One protein that has been shown to play a role in treponemal dissemination is Tp0751, a T. pallidum adhesin that interacts with host components found within the vasculature and mediates bacterial adherence to endothelial cells under shear flow conditions. In this study, we further explore the molecular interactions of Tp0751-mediated adhesion to the vascular endothelium. We demonstrate that recombinant Tp0751 adheres to human endothelial cells of macrovascular and microvascular origin, including a cerebral brain microvascular endothelial cell line. Adhesion assays using recombinant Tp0751 N-terminal truncations reveal that endothelial binding is localized to the lipocalin fold-containing domain of the protein. We also confirm this interaction using live T. pallidum and show that spirochete attachment to endothelial monolayers is disrupted by Tp0751-specific antiserum. Further, we identify the 67-kDa laminin receptor (LamR) as an endothelial receptor for Tp0751 using affinity chromatography, coimmunoprecipitation, and plate-based binding methodologies. Notably, LamR has been identified as a receptor for adhesion of other neurotropic invasive bacterial pathogens to brain endothelial cells, including Neisseria meningitidis, Haemophilus influenzae, and Streptococcus pneumoniae, suggesting the existence of a common mechanism for extravasation of invasive extracellular bacterial pathogens.IMPORTANCE Syphilis is a sexually transmitted infection caused by the spirochete bacterium Treponema pallidum subsp. pallidum. The continued incidence of syphilis demonstrates that screening and treatment strategies are not sufficient to curb this infectious disease, and there is currently no vaccine available. Herein we demonstrate that the T. pallidum adhesin Tp0751 interacts with endothelial cells that line the lumen of human blood vessels through the 67-kDa laminin receptor (LamR). Importantly, LamR is also a receptor for meningitis-causing neuroinvasive bacterial pathogens such as Neisseria meningitidis, Haemophilus influenzae, and Streptococcus pneumoniae Our findings enhance understanding of the Tp0751 adhesin and present the intriguing possibility that the molecular events of Tp0751-mediated treponemal dissemination may mimic the endothelial interaction strategies of other invasive pathogens.

Biological basis for syphilis

Syphilis is a chronic sexually transmitted disease caused by Treponema pallidum subsp. pallidum. Clinical manifestations separate the disease into stages; late stages of disease are now uncommon compared to the preantibiotic era. T. pallidum has an unusually small genome and lacks genes that encode many metabolic functions and classical virulence factors. The organism is extremely sensitive to environmental conditions and has not been continuously cultivated in vitro. Nonetheless, T. pallidum is highly infectious and survives for decades in the untreated host. Early syphilis lesions result from the host's immune response to the treponemes. Bacterial clearance and resolution of early lesions results from a delayed hypersensitivity response, although some organisms escape to cause persistent infection. One factor contributing to T. pallidum's chronicity is the paucity of integral outer membrane proteins, rendering intact organisms virtually invisible to the immune system. Antigenic variation of TprK, a putative surface-exposed protein, is likely to contribute to immune evasion. T. pallidum remains exquisitely sensitive to penicillin, but macrolide resistance has recently been identified in a number of geographic regions. The development of a syphilis vaccine, thus far elusive, would have a significant positive impact on global health.

Syphilis: review with emphasis on clinical, epidemiologic, and some biologic features

Syphilis is a chronic disease with a waxing and waning course, the manifestations of which have been described for centuries. It occurs worldwide, and the incidence varies significantly with geographic location. Transmission is mainly by sexual contact. The causative organism, Treponema pallidum, was first described in 1905, but because of the inability to culture the organism and the limitations of direct microscopy, serologic testing is the mainstay of laboratory diagnosis. The disease has been arbitrarily divided into several stages. The primary stage is defined by a chancre at the site of inoculation. The secondary stage is characterized by a polymorphic rash, lymphadenopathy, and other systemic manifestations. A variable asymptomatic latent period follows, which for epidemiologic purposes is divided into early (<1 year) and late (>1 year) stages. The early stages (primary, secondary, and early latent) are potentially infectious. The tertiary stage is the most destructive and is marked by cardiovascular and neurologic sequelae and gummatous involvement of any organ system. Congenital infection may result in protean early or late manifestations. Unlike many other bacteria causing infectious diseases, the organism remains sensitive to penicillin, and this remains the mainstay of therapy.

Congenital syphilis: clinical manifestations in premature infants

During the 4-year period February 1989 to January 1993, 13 premature babies aged 1-21 days and with congenital syphilis were admitted to the National Cheng Kung University Hospital. Of the 13 premature infants, 8 (62%) had unusual desquamation over palms and soles. Bone changes with periosteal reaction and/or metaphyseal dystrophy were observed in 11 cases (85%). Three mothers were diagnosed as being infected during pregnancy; 2 were treated with penicillin. The clinical features of congenital syphilis in premature neonates are somewhat different from those previously reported. Bone changes, hepatosplenomegaly, respiratory distress, skin lesions, especially over the soles and palms, cerebrospinal fluid abnormalities, and jaundice were the major manifestations in our series. In premature infants with these symptoms and signs, congenital syphilis should be considered as one of the differential diagnoses. Once the diagnosis of congenital syphilis is made, adequate penicillin therapy should be given.

Annular lesions in congenital syphilis

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Neonatal and post-neonatal onset of early congenital syphilis: a report from Mozambique

Congenital syphilis (CS) has been and continues to be a principal public health problem in developing countries. Despite the wide experience acquired, physicians still have problems in diagnostic evaluation. We report 145 cases of CS at the Central Hospital, Maputo, emphasizing the differences in clinical features and in the results of serological and X-ray examinations between the neonatal and post-neonatal age groups. In the post-neonatal age group, the clinical expression of CS is mostly overt. It is commonly recognized that manifestations of CS in the neonatal age group are often poor or negative, yet a relevant percentage of CS that we report were fully symptomatic. In the neonatal age, the Venereal Disease Research Laboratory (VDRL) test in the mother and characteristic osteochondritic lesions on X-ray examination of the long bones help to make the diagnosis; in the post-neonatal age group, the VDRL test in the child is more often positive than in the mother and X-ray examination shows most periostitic lesions.

Immune studies in infants with congenital syphilis

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

Congenital syphilis in the newborn

We studied 53 newborn babies with congenital syphilis. The common clinical features seen were low birth weight, hepatosplenomegaly, anaemia, jaundice, and symmetrical superficial desquamation of the skin affecting palms and soles. The presence of these clinical signs is highly suggestive of early congenital syphilis. Hydrops fetalis without rhesus or ABO isoimmunisation should always arouse the suspicion of congenital syphilis.