Neurosyphilis is characterized by a compartmentalized and robust neuroimmune response but not by neuronal injury.

BACKGROUND: Neurosyphilis is increasing in prevalence but its pathophysiology remains incompletely understood. This study assessed for CNS-specific immune responses during neurosyphilis compared to syphilis without neurosyphilis and compared these immune profiles to those observed in other neuroinflammatory diseases. METHODS: Participants with syphilis were categorized as having neurosyphilis if their cerebrospinal fluid (CSF)-venereal disease research laboratory (VDRL) test was reactive and as having syphilis without neurosyphilis if they had a non-reactive CSF-VDRL test and a white blood cell count <5/µL. Neurosyphilis and syphilis without neurosyphilis participants were matched by rapid plasma reagin titer and HIV status. CSF and plasma were assayed for markers of neuronal injury and glial and immune cell activation. Bulk RNA sequencing was performed on CSF cells, with results stratified by the presence of neurological symptoms. FINDINGS: CSF neopterin and five CSF chemokines had levels significantly higher in individuals with neurosyphilis compared to those with syphilis without neurosyphilis, but no markers of neuronal injury or astrocyte activation were significantly elevated. The CSF transcriptome in neurosyphilis was characterized by genes involved in microglial activation and lipid metabolism and did not differ in asymptomatic versus symptomatic neurosyphilis cases. CONCLUSIONS: The CNS immune response observed in neurosyphilis was comparable to other neuroinflammatory diseases and was present in individuals with neurosyphilis regardless of neurological symptoms, yet there was minimal evidence for neuronal or astrocyte injury. These findings support the need for larger studies of the CSF inflammatory response in asymptomatic neurosyphilis. FUNDING: This work was funded by the National Institutes of Health, grants K23MH118999 (S.F.F.) and R01NS082120 (C.M.M.).

Oral linezolid compared with benzathine penicillin G for treatment of early syphilis in adults (Trep-AB Study) in Spain: a prospective, open-label, non-inferiority, randomised controlled trial.

BACKGROUND: Management of syphilis, a sexually transmitted infection (STI) with increasing incidence, is challenged by drug shortages, scarcity of randomised trial data, an absence of non-penicillin alternatives for pregnant women with penicillin allergy (other than desensitisation), extended parenteral administration for neurosyphilis and congenital syphilis, and macrolide resistance. Linezolid was shown to be active against Treponema pallidum, the causative agent of syphilis, in vitro and in the rabbit model. We aimed to assess the efficacy of linezolid for treating early syphilis in adults compared with the standard of care benzathine penicillin G (BPG). METHODS: We did a multicentre, open-label, non-inferiority, randomised controlled trial to assess the efficacy of linezolid for treating early syphilis compared with BPG. We recruited participants with serological or molecular confirmation of syphilis (either primary, secondary, or early latent) at one STI unit in a public hospital and two STI community clinics in Catalonia (Spain). Participants were randomly allocated in a 1:1 ratio using a computer-generated block randomisation list with six participants per block, to receive either oral linezolid (600 mg once per day for 5 days) or intramuscular BPG (single dose of 2·4 million international units) and were assessed for signs and symptoms (once per week until week 6 and at week 12, week 24, and week 48) and reagin titres of non-treponemal antibodies (week 12, week 24, and week 48). The primary endpoint was treatment response, assessed using a composite endpoint that included clinical response, serological response, and absence of relapse. Clinical response was assessed at 2 weeks for primary syphilis and at 6 weeks for secondary syphilis following treatment initiation. Serological cure was defined as a four-fold decline in rapid plasma reagin titre or seroreversion at any of the 12-week, 24-week, or 48-week timepoints. The absence of relapse was defined as the presence of different molecular sequence types of T pallidum in recurrent syphilis. Non-inferiority was shown if the lower limit of the two-sided 95% CI for the difference in rates of treatment response was higher than -10%. The primary analysis was done in the per-protocol population. The trial is registered at ClinicalTrials.gov (NCT05069974) and was stopped for futility after interim analysis. FINDINGS: Between Oct 20, 2021, and Sept 15, 2022, 62 patients were assessed for eligibility, and 59 were randomly assigned to linezolid (n=29) or BPG (n=30). In the per-protocol population, after 48 weeks' follow-up, 19 (70%) of 27 participants (95% CI 49·8 to 86·2) in the linezolid group had responded to treatment and 28 (100%) of 28 participants (87·7 to 100·0) in the BPG group (treatment difference -29·6, 95% CI -50·5 to -8·8), which did not meet the non-inferiority criterion. The number of drug-related adverse events (all mild or moderate) was similar in both treatment groups (five [17%] of 29, 95% CI 5·8 to 35·8 in the linezolid group vs five [17%] of 30, 5·6 to 34·7, in the BPG group). No serious adverse events were reported during follow-up. INTERPRETATION: The efficacy of linezolid at a daily dose of 600 mg for 5 days did not meet the non-inferiority criteria compared with BPG and, as a result, this treatment regimen should not be used to treat patients with early syphilis. FUNDING: European Research Council and Fondo de Investigaciones Sanitarias.

Evaluation of Three Automated Nontreponemal Rapid Plasma Reagin (RPR) Tests for the Laboratory Diagnosis of Syphilis.

Automated nontreponemal rapid plasma reagin (RPR) tests were recently introduced in the United States for syphilis testing and limited performance data are available. In collaboration with the Association of Public Health Laboratories, three public health laboratories (PHL) were chosen through a competitive selection process to evaluate the performance of three FDA-cleared automated RPR test systems: BioPlex 2200 Syphilis Total & RPR assay (Bio-Rad Laboratories), AIX 1000 (Gold Standard Diagnostics), and ASI Evolution (Arlington Scientific). Panels prepared at the CDC included: a qualitative panel comprised of 734 syphilis reactive/nonreactive sera; a quantitative panel of 50 syphilis reactive sera (RPR titer 1:64 to 1:1,024); and a reproducibility panel of 15 nonreactive and reactive sera (RPR titer 1:1 to 1:64). Panels were shipped frozen to the PHL and tested on the automated RPR systems following manufacturers' instructions. Prior test results were blinded to all laboratories. When compared to manual RPR (Arlington Scientific) performed at the CDC as a reference test, the qualitative panel results demonstrated an overall concordance of 95.9% for AIX 1000, 94.6% for ASI Evolution, and 92.6% for Bioplex RPR; quantitative panel showed within range titer of 2-fold for 94% of specimens for AIX 1000, 68% for ASI Evolution, and 64% for BioPlex RPR, and the reproducibility testing panel demonstrated point estimates ranging from 69 to 95%. Automated RPR instruments could reduce turnaround time and minimize interpretation errors. However, additional evaluations with more specimens could assist laboratories with implementing automated RPR tests and understanding their limitations.

Evaluation of the AIX1000 Automated Rapid Plasma Reagin Assay in a High-Prevalence Setting.

BACKGROUND: Manually performed nontreponemal assays, such as rapid plasma reagin (RPR), are labor intensive and time consuming. Recently, commercial automated RPR assays gained attention. The aim of this study was to compare the qualitative and quantitative performance of the AIX1000 (RPR-A; Gold Standard Diagnostics) to a manual RPR test (RPR-M; Becton Dickinson Macrovue) within a high-prevalence setting. METHODS: A retrospective panel of 223 samples was selected for comparison between RPR-A and RPR-M, including 24 samples from patients with known syphilis stages and 57 samples from 11 patients in follow-up. In addition, 127 samples obtained during routine syphilis diagnosis with RPR-M were analyzed prospectively with AIX1000. RESULTS: Overall qualitative concordance (percent agreement) between both assays was 92.0% in the retrospective and 89.0% in the prospective panel. Of 32 discordances, 28 were explained by a treated syphilis infection still positive in one assay and already negative in the other. One sample was false positive with RPR-A, 1 infection remained undetected by RPR-M, and 2 remained undetected by RPR-A. A hook effect was apparent on the AIX1000 at RPR-A titers from 1:32 onward; however, no infections were missed. Accepting a ±1 titer difference, quantitative concordance between both assays reached 73.1% and 98.4% for the retrospective and prospective panels, respectively, with an upper limit of reactivity for RPR-A at 1:256. CONCLUSIONS: The AIX1000 showed a similar performance to Macrovue RPR with the exception of a negative deviation for high-titer samples. Within the reverse algorithm used in our high-prevalence setting, AIX1000's main advantage is automation.

Changes in the Syphilis Rapid Plasma Reagin Titer Between Diagnosis and Treatment.

BACKGROUND: We compared the rapid plasma reagin (RPR) titer on the day of initial presentation with that on the day of syphilis treatment to inform clinical practice as to whether a repeated RPR test should be recommended. METHODS: We undertook a retrospective study between 1 March 2011 and 31 December 2020 at the Melbourne Sexual Health Centre in Australia among individuals who underwent syphilis serology on the day of initial presentation and the day of treatment, if the latter were within 14 days after initial presentation. We calculated the percentage of individuals with a ≥4-fold change in RPR titer, stratified by the time between initial presentation and treatment and by syphilis stage. RESULTS: Among the 766 included syphilis cases, the median duration between initial presentation and treatment was 6 days (interquartile range, 5-7 days). Of these cases, 14.8% (n = 113) had a ≥4-fold increase or decrease during this interval. The number of cases with a ≥4-fold increase or decrease in RPR titer increased with increasing time between initial presentation and treatment, from 5.7% (n = 6) 1-3 days after initial presentation to 26.2% (n = 27) at 10-14 days (Ptrend < .001). There was no significant difference in the number of cases with a ≥4-fold increase or decrease in RPR titer between syphilis stages (P = .66). CONCLUSIONS: Our data support the recommendation of repeating the RPR titer if the day of initial presentation and the day of treatment are different, even when treatment is within a few days after initial presentation.

Assessment of a fully automated RPR assay (Mediace RPR) for serological diagnosis and follow-up of syphilis: a retrospective study.

OBJECTIVES: This study assessed the Mediace RPR assay, an automated RPR (aRPR), for syphilis diagnosis and serological follow-up. METHODS: Serums from patients positively screened for syphilis between January 2017 and December 2019 were retrospectively selected. A focus was performed on patients with a serological follow-up after treatment and/or a reinfection. Serums were tested by both manual (mRPR) and aRPR tests. Categorical and Quantitative Agreements (CA and QA), and serological follow-up conclusions were analyzed. RESULTS: 236 serums from 85 patients (99% of male, 66% of HIV-infected) were included. The overall QA was 54.2%. CA was low (79.7%) especially for samples with low RPR titers. No prozone effect was observed. Serological follow-up after treatment led to similar conclusions, although aRPR titers often decreased faster. Over 26 episodes of reinfection, 4 (15.4%) were misdiagnosed with the aRPR. CONCLUSIONS: While the Mediace aRPR presents the advantages of an automated test, its poor sensitivity in low titers may limit its use.

Early congenital syphilis: missed opportunities in a mother owing to many problems during pregnancy - a case report.

Untreated syphilis in pregnancy can result in an adverse outcome for the fetus. A multigravida woman with a previously poor obstetric history of early neonatal death, abortion and stillbirth was admitted in labour in the 7th month of pregnancy. On admission, syphilis screening with the qualitative rapid plasma reagin (RPR) test was negative. The infant had macules on the chest, abdomen and extremities, desquamating bullous skin lesions on the palms and soles, bilateral cataracts, an enlarged liver and spleen, anaemia, thrombocytopenia and conjugated hyperbilirubinaemia. A quantitative RPR test in the infant was positive in a 1:64 dilution and was subsequently positive in the mother in a 1:16 dilution after congenital syphilis was diagnosed. The mother later reported the father's high-risk behaviour and her previous visits to healthcare facilities for genital ulcers. The quantitative RPR test in the father was positive in a 1:32 dilution, and the parents and infant were treated for syphilis. The case demonstrates the importance of timely identification of high-risk pregnant women, early screening, repetition of the non-treponemal test on diluted serum when a routine screening test is negative, proper advice from the laboratory regarding selection of the most appropriate tests, and screening with the treponemal test first (reverse) algorithm utilising an automated enzyme immunoassay/chemiluminescence assay for the initial screening in high-risk cases, even in resource-limited settings to prevent a missed diagnosis.Abbreviations: ANC, antenatal care; BPG, benzathine penicillin G; CS, congenital syphilis; CSF, cerebrospinal fluid; CIA, chemiluminescence assay; EIA, enzyme immunoassay; HIC: high-income countries; IgM, immunoglobulin M; LMIC, low- and middle-income countries; MTCT: mother-to-child transmission; NTT, non-treponemal test; POC, point of care; RPR, rapid plasma reagin; RST, rapid syphilis test; STI, sexually transmitted infections; TT, treponemal test; TPHA, Treponema pallidum haemagglutination assay; VDRL, venereal disease research laboratory; WHO, World Health Organization.

COVID-19 mRNA Vaccines May Cause False Reactivity in Some Serologic Laboratory Tests, Including Rapid Plasma Reagin Tests.

OBJECTIVES: Acute viral infections and some vaccines have been shown to increase false positivity in serologic assays. We assessed if the messenger RNA coronavirus disease 2019 (COVID-19) vaccines could cause false reactivity in common serologic assays in a pilot longitudinal cohort. METHODS: Thirty-eight participants with sera available prevaccination, 2 weeks after each vaccine dose, and monthly thereafter for up to 5 months were tested for common infectious disease serologies and antiphospholipid syndrome (APS) serology markers on the BioPlex 2200, Sure-Vue rapid plasma reagin (RPR), and Macro-Vue RPR. Twenty-two participants received the Moderna vaccine and 16 received the Pfizer vaccine. RESULTS: Most assays had no change in reactivity over the course of the sample draws, including APS markers. Epstein-Barr virus immunoglobulin G (IgG), measles IgG, and rubella immunoglobulin M all had possible false reactivity in one to two participants. RPR tests demonstrated false reactivity, with baseline nonreactive participant samples becoming reactive following vaccination. There were more false reactive participants (7/38) in the BioPlex RPR than in the Sure-Vue (2/38) and Macro-Vue (1/38) tests. All falsely reactive RPR tests were in participants who received the Moderna vaccine. CONCLUSIONS: Serologic assays with results that do not fit the clinical picture following COVID-19 vaccination should be repeated. Effects of false reactivity can last more than 5 months in some assays. In particular, RPR is susceptible to false reactivity, and there is variability among assays. Larger longitudinal studies are needed to determine the incidence and window of false reactivity.

A Case of Congenital Syphilis-Focus on Histopathology and Literature Review.

ABSTRACT: Although a rare disease, the incidence of congenital syphilis is on the rise in the US. We report a case of early congenital syphilis in a 1-day-old premature boy with positive Rapid plasma reagin titer, respiratory insufficiency, disseminated intravascular coagulation, and encephalopathy, born to a mother with known syphilis infection. Skin examination showed diffuse truncal petechiae, desquamation of the distal extremities, and violaceous, retiform plaques on the buttocks and lower extremities. A biopsy was performed to rule out an infectious etiology or vasculitis. Histopathologic examination revealed irregular epidermal acanthosis with orthokeratosis and parakeratosis. There were foci of neutrophilic infiltrate forming rare pustules within the stratum corneum and focal intraepidermal eosinophils, neutrophils, and rare dyskeratotic keratinocytes. In the dermis, there was some minimal endothelial swelling with a perivascular, interstitial, and periadnexal infiltrate of lymphocytes, eosinophils, and rare plasma cells. A Treponema pallidum immunostain highlighted spirochetes present within the epidermis and within the eccrine ducts. Penicillin G therapy was administered for 10 days. The infant's Rapid plasma reagin titer trended downward until it was negative 6 months after birth. Literature review reveals 8 case reports within the last 20 years describing the histopathology of rashes in congenital syphilis. Herein we summarize the reported histopathology of rashes in congenital syphilis and compare it to the histopathology of rashes in secondary syphilis in adults.

Seroreduction of syphilis non-treponemal titers during pregnancy for women with and without HIV co-infection.

OBJECTIVE: To evaluate the effect of HIV co-infection on non-treponemal titers during pregnancy in women with syphilis. METHODS: This is a secondary analysis of pregnant women with syphilis in the prospective, observational Zambian Preterm Birth Prevention Study (ZAPPS). Treponemal (Treponema pallidum particle agglutination) and non-treponemal (rapid plasma reagin; RPR) testing were performed on serum biospecimens, resulting in 47 participants with serologically confirmed syphilis (27 HIV-positive, 20 HIV-negative). The primary outcome, achievement of RPR titer seroreduction during pregnancy, was analyzed by logistic regression. Secondary outcomes included overall titer reduction, seroreduction rate, serologic cure, and adverse pregnancy outcomes. RESULTS: Seroreduction of RPR titer occurred in 78% (21/27) of women with HIV versus 45% (9/20) of women without (adjusted odds ratio 4.66; 95% confidence interval [CI] 1.14 - 19.08). Overall RPR titer reduction, rate of seroreduction per week, and the proportion achieving serologic cure each trended higher among women with HIV compared with those without HIV. There was a trend toward decreased stillbirth incidence in participants achieving seroreduction (odds ratio 0.15, 95% CI 0.01-1.58). CONCLUSION: HIV co-infection in this cohort of Zambian women with syphilis was associated with greater odds of RPR titer seroreduction during pregnancy. Pregnant women with syphilis and HIV may not be at increased risk for a delayed syphilis treatment response compared with women without HIV.

High Number of Positive Rapid Plasma Reagin With Low Titers Using the Automated AIX 1000 RPR System.

ABSTRACT: This study evaluated the performance of manual rapid plasma reagin (RPR) and automated AIX1000 RPR tests for the diagnosis of syphilis. Manual RPR showed a 3% reactive result compared with 5.8% for the automated test mainly because of RPR reactive results with low titers not confirmed by Treponema pallidum particle agglutination.

Severe Congenital Syphilis in the Neonatal Intensive Care Unit: A Retrospective Case Series.

BACKGROUND: There has been a 291% relative increase in congenital syphilis (CS) cases in the United States from 2015 to 2019. Although the majority of affected fetuses/infants are stillborn or are asymptomatic, a subset is born with severe clinical illness. We describe a series of severe CS cases in the neonatal intensive care unit. METHODS: Retrospective review of infants with CS, admitted to the Duke Intensive Care Nursery from June 2016 to February 2020. We recorded birthweight, gestational age, medications, procedures, diagnoses, laboratory data and outcomes. Severe symptoms included: birth depression, hypoxic ischemic encephalopathy (HIE), disseminated intravascular coagulopathy and/or persistent pulmonary hypertension (PPHN). RESULTS: Seven infants with CS were identified and 5 with severe presentations were included. Median gestational age was 35.1 weeks (range: 29-37 weeks, median: 35 weeks). All infants required intubation at birth, 2 required chest compressions and epinephrine in the delivery room. One had hydrops fetalis and died in the delivery room. All 4 surviving infants had HIE, severe PPHN, hepatitis and seizures. All infants had a positive rapid plasma reagin, and were treated with penicillin G. Maternal rapid plasma reagin was pending for 3 of 5 infants at delivery, and later returned positive; 2 were positive during pregnancy but not treated. Other infectious work-up was negative. Three infants survived to discharge. CONCLUSION: CS can be associated with HIE, PPHN and disseminated intravascular coagulopathy in affected infants. Clinicians should have a high index of suspicion and include CS in their differential diagnoses. This study also highlights the importance of adequate treatment of identified cases and screening during the third trimester and at delivery.

Utility of rapid plasmin reagin titres in assessing treatment response and re-infection for infectious syphilis.

Background The rapid plasma reagin (RPR) assay is commonly used as a surrogate marker of infectious syphilis, but is non-specific, slow to change and variable in its rate of decline post treatment. METHODS: Within an urban sexual health service testing predominantly men who have sex with men, a file review of RPR changes was undertaken in all subjects who had a dilution level of ≥1:4, between January 2015 to the end of December 2018. RESULTS: Overall, 248 cases of infectious syphilis were identified in 215 subjects (165 HIV seropositive, 50 HIV seronegative). Among unique-subject cases with follow-up RPR recorded, seroreversion to a non-reactive titre was achieved in only 42.3% (71/168) cases at a median of 235 days (interquartile range: 138-348 days) and was significantly less likely if patients had HIV infection (P = 0.02), late latent syphilis (P = 0.003) or a subsequent syphilis infection (P < 0.0001). Having HIV infection (P = 0.03) or a subsequent episode of syphilis (P = 0.01) were associated with a lower likelihood of documented cure. CONCLUSIONS: The slow decay in RPR titres post therapy and the inability of a significant number of subjects to achieve a non-reactive result over time makes RPR a poor test for assessing the adequacy of treatment or in diagnosing re-infection, especially in populations having repeated and frequent risk exposures. As the number of syphilis cases continue to climb, better tests that accurately assess pathogen presence are urgently needed.

Evaluation of the fully automated AIX1000 rapid plasma reagin system compared to a manual plasma reagin testing method for the diagnosis of syphilis.

The analytical performance of the FDA-cleared AIX1000 automated RPR testing platform was evaluated in comparison to manual RPR card testing. Eight hundred thirty-three patient serum samples were analyzed, 87 samples were positive by the AIX1000, 108 were positive by the manual test method; overall agreement between methods was 96.5% (κ = 0.83). Cases were further classified by clinical and laboratory-based confirmation of disease, to which reactivity rates were compared, yielding sensitivities of 96.4% and 100%, and specificities of 99.2% and 96.8% for the automated and manual RPR methods, respectively. The difference in specificity between methods was statistically significant (P < 0.001). Twenty-five of 29 samples with discordant results were reactive by manual testing (titers of 1:1 or 1:2); 21 of 25 patients with negative AIX100 results were identified to have histories of remote, treated syphilis. Overall, the AIX1000 platform demonstrated excellent agreement with the manual RPR method; discrepancies occurred with specimens at the threshold of reactivity.

Evaluation of BioPlex 2200 Syphilis Total With Automated Rapid Plasma Reagin: Experience From a Tertiary Medical Center.

BACKGROUND: Treponema-specific assays are widely adopted in the first step of the reverse algorithm of serologic syphilis screening. The new BioPlex 2200 Syphilis Total and rapid plasma reagin (RPR) test is designed to perform the first 2 steps of the algorithm simultaneously. However, limited data regarding the BioPlex Syphilis Total and RPR in clinical practice exist. METHODS: A total of 293 random samples at a tertiary medical center were tested by BioPlex Syphilis Total and RPR, BioPlex Syphilis IgG, Architect Syphilis TP, and BD Macro-Vue RPR card. Treponema pallidum particle agglutination (TP-PA) assay and clinical chart review were used to resolve discrepancies. Comparisons were performed among treponemal-specific assays and between 2 RPR tests. RESULTS: Good overall agreements (>91%) were achieved between BioPlex Syphilis Total, BioPlex Syphilis IgG, and Architect Syphilis TP. Overall agreement between BioPlex RPR and BD RPR was 86.8% with positive percent agreement of 66.7% and negative percent agreement of 96.3%. There were 37 discordant samples including 30 with BD RPR+/BioPlex RPR- and 7 with BD RPR-/BioPlex RPR+. Negative BioPlex RPR results were observed in samples with reactive BD RPR: 10 (91%) of 11 for BD RPR 1:1, 13 (65%) of 20 for BD RPR 1:2, 6 (35%) of 17 for BD RPR 1:4, and 1 (7%) of 14 for BD RPR 1:8. The discordant samples were predominantly from patients with high-risk of syphilis reinfection and included 9 patients with an early reinfection. CONCLUSIONS: Our results demonstrated that BioPlex Syphilis Total and Architect Syphilis TP performed similarly. The BioPlex RPR missed a small number of early syphilis reinfections, and its implementation should depend on the patient population that the laboratory serves.