Evaluation of a comparative Western Blot method for early postnatal diagnosis of congenital syphilis

Objectives. Diagnosis of congenital syphilis (CS) remains difficult. Part of the problem arises because the standard serologic tests are not useful in newborns because IgG transfer across the placenta. Since Western Blot technique allows the recognition of a specific response towards every single protein, it can be useful to compare IgG immunological profiles of mothers and babies at birth, in order to differentiate between passively transmitted maternal antibodies and antibodies synthesized by the infants. Methods. Study group. Thirty infants born to syphilis seropositive mothers were enrolled for this study. At birth, routine serological tests were performed (ARCHITECT® Syphilis TP, Abbott; TPHA and RPR, Randox) on mother/child pairs’ serum specimens. “Home made WB”. Treponema pallidum antigens, separated by SDS-PAGE, were blotted onto nitrocellulose sheets and incubated overnight with mother/child pairs’ serum specimens. Criteria for CS diagnosis were the following: presence of specific bands in the newborn’s IgG WB strip different from those found on the corresponding maternal WB strip and/or recognition on IgM WB strip of at least 2 out the 4 following bands Tp47, TmpA, Tp17 and Tp15, including at least one with low molecular weight. Results. Out of the 30 infants born to syphilis seropositive mothers, we found 3 babies with different IgG WB profiles from those of their own mothers. Two out these three newborns had also positive IgM WB result. Routine serological testing results of all the 30 newborns showed similar values to those of their own mothers. Conclusion. The use of comparative IgG WB test enabled us to diagnose CS in three cases in which the infection would have not been detected by classical serology techniques. Therefore the routine use of comparative IgG WB assay at birth on newborn-mother pairs could be a welcome addition to the conventional laboratory methods used for the diagnosis of CS.