Project Summary/Abstract Syphilis in women is usually a silent infection caused by Treponema pallidum (T. pallidum) that can efficiently cross the placenta during all stages of pregnancy and infect the fetus. In the absence of timely diagnosis and treatment, the natural history of infection in pregnancy includes adverse birth outcomes in 80% (spontaneous abortion, stillbirth, low birthweight, preterm delivery, congenital syphilis, and neonatal death). Our team and others have documented elevated prevalence of syphilis in pregnancy in Cameroon and Zambia (3-6%) with high HIV coinfection rates (10-40%). Despite public health efforts, syphilis is the leading preventable cause of stillbirth globally and available diagnostic testing has critical limitations in pregnant women and infants. The Syphilis in Pregnancy Study (SIPS): Molecular Diagnostics and Maternal and Infant Immune Response to Infection brings together an international team of experts in perinatal and pediatric clinical infectious diseases, syphilis molecular biology and immunology to address priority questions in the STI field about the natural history of syphilis in pregnancy and vertical transmission. The SIPS team has designed an observational cohort to enroll and follow 750 well-characterized pregnant women with confirmed syphilis and their exposed infants as well as 750 pregnant controls in Cameroon and Zambia with follow up and repeated sample collection through 12 months after delivery. SIPS participants will have pre- and post-treatment blood samples, cord blood, and placentas collected from women, neonates, and infants to assess immune responses in addition to oral and lesion swabs for PCR testing to carry out the following aims: Aim 1: Identify clinical and host factors independently associated with favorable birth outcomes among pregnant women with syphilis; Aim 2: Characterize the adaptive T. pallidum immune response before and after treatment in pregnant women and their exposed infants; Aim 3: Evaluate quantitative PCR (qPCR) testing on oral and lesion swabs to detect T. pallidum and enhance diagnostic testing in pregnancy and neonates. Aim 1 will test the hypothesis that factors associated with robust maternal immunity will be associated with favorable birth outcomes in multivariable models with clinical and host factors. Aim 2 will test the hypothesis that a robust adaptive immune response (humoral immunity and CD4 T cells) will protect against vertical transmission and assess the role of T. pallidum-specific transplacental maternal antibodies in mediating fetal and infant protection. Aim 3 will test our hypothesis that newly developed molecular diagnostic testing of easily collected oral swabs will help refine and improve the diagnosis of syphilis in pregnant women and infants. Our expected outcome is to identify T. pallidum antigens with a role in dissemination, placental attachment, and vertical transmission. Our long-term goals are to advance these newly identified an...