Patients and study design

Secondary and early latent syphilis (ELS) patients (n = 50) in their first episode of disease were enrolled at the Department of Dermatology of the Jagiellonian University Medical College in Krakow, Poland between 2015 and 2017. All patients included in the study were positive both for non-treponemal and treponemal tests at enrollment. Syphilis clinical staging was determined by a board-certified dermatologist using the Centers for Disease Control and Prevention (CDC) criteria [1]. After blood sampling for laboratory tests, including treponemal-specific tests (INNO-LIA Syphilis Score Assay), patients were administered intramuscular benzathine penicillin (2.4 million units). All study subjects were tested for concurrent HIV infection. Antiretroviral therapy was introduced in all patients with confirmed HIV co-infection. All cases of HIV infection were detected at enrollment, as none of the study patients were aware of their HIV status. After completion of the treatment, patients returned every 3 months for follow-up assessment (including non-treponemal testing; rapid plasma regain assay – RPR). Six months after completing the treatment, serological responses were assessed. The data indicated that 14 of 50 individuals did not achieve proper serological response, defined as at least a four-fold decline in RPR titer when compared to the pre-treatment values. In all of the subjects, cerebrospinal fluid (CSF) examination was performed. Diagnosis of neurosyphilis was determined according to CDC guidelines (i.e. reactive CSF VDRL or CSF pleocytosis of ≥ 5/µl and CSF protein concentration ≥ 45 mg/dl). In 2 cases, asymptomatic neurosyphilis was confirmed and these patients were excluded from further analysis. Re-treatment with intramuscular benzathine penicillin (2.4 million units) was administered in the remaining 12 patients. Twelve months after treatment, two of these twelve individuals achieved proper serological response. All patients studied were classified as (1) the serofast state group (n = 10) defined as the failure of the RPR titer to show a four-fold decline between the baseline and the 12-month visit and (2) the serologically-cured group (n = 38) defined as at least a four-fold decline in the RPR titer in comparison to the pre-treatment RPR results. Twelve months after treatment, in all the remaining individuals, serum samples for INNO-LIA Syphilis Score testing and antinuclear antibodies (ANAs) were collected. The study was approved by the Jagiellonian University Bioethics Committee (approval number KBET/164/B) and written informed consent was obtained from all participants.