Profile of Anti-Tp47 antibodies in patients with positive serology for syphilis analized by western blot

Abstract

In Brazil, syphilis is still a great problem of public health. Serological test is essential for syphilis diagnosis and the current trend is the use of recombinant antigen in the treponemal tests, due to its confirmed higher sensibility and specificity. The purpose of the present study was to analyze the profile of anti-Tp47 antibodies in patients with positive serology for syphilis. One hundred positive sera samples were analyzed by Western Blot (WB) technique, using the recombinant antigen (rTp47). Ten of them did not present antibodies against the fraction rTp47, the results were confirmed by WB using native T. pallidum antigen. All ten samples had antibodies against the fractions Tp17 and Tp15 and presented low reactivity in VDRL, negative results or title below than 1:4. Considering that VDRL is used for therapeutic monitoring due to seroreversion of nontreponemal antibodies in response to the treatment, and that some studies reported loss of treponemal antibodies after treatment, we could speculate if these ten samples are cases of serological memory from patients previously treated for syphilis. In addition, although several features state the Tp47 fraction as one of the major antigenic components, based on our results we point out to the importance of including other antigenic proteins such as Tp17 and Tp15 in addition to Tp47 in tests for serological screening of syphilis.