Syphilis is a sexually transmitted disease caused by Treponema pallidum subspecies pallidum. When a person gets infected with T. pallidum, he or she will go through three stages: primary, secondary, and late tertiary phases. Patients will develop rapid and vigorous humoral and cellular immune responses against T. pallidum that will eliminate most of the treponemes from the primary and secondary lesions. However, a small number of treponemes will evade the immune responses and lead to lifetime infection. A unique physical feature of T. pallidum is the lack of identified outer membrane proteins. A twelve-member gene family called tpr (T. pallidum repeat) has been recently identified in the Nichols strain of T. pallidum. The goal in the lab is to determine the role of tpr genes and their encoded proteins in T. pallidum. I will characterize the humoral immune response against these proteins using serum from rabbits that have been infected with T. pallidum for 2-4 years. By using immunoblot analysis, I will detect specific antibodies directed to these proteins; this information will indicate which of the twelve tpr proteins were expressed by the bacterium during infection. The results of this study will be used in the development of potential vaccines for syphilis.