Heterologous Expression of the Treponema pallidum Laminin-Binding Adhesin Tp0751 in the Culturable Spirochete Treponema phagedenis

Abstract

ABSTRACT Treponema pallidum subsp. pallidum , the causative agent of syphilis, is an unculturable, genetically intractable bacterium. Here we report the use of the shuttle vector pKMR4PEMCS for the expression of a previously identified T . pallidum laminin-binding adhesin, Tp0751, in the nonadherent, culturable spirochete Treponema phagedenis . Heterologous expression of Tp0751 in T . phagedenis was confirmed via reverse transcriptase PCR analysis with tp0751 gene-specific primers and immunofluorescence analysis with Tp0751-specific antibodies; the latter assay verified the expression of the laminin-binding adhesin on the treponemal surface. Expression of Tp0751 within T . phagedenis was functionally confirmed via laminin attachment assays, in which heterologous Tp0751 expression conferred upon T . phagedenis the capacity to attach to laminin. Further, specific inhibition of the attachment of T . phagedenis heterologously expressing Tp0751 to laminin was achieved by using purified antibodies raised against recombinant T . pallidum Tp0751. This is the first report of heterologous expression of a gene from an unculturable treponeme in T . phagedenis . This novel methodology will significantly advance the field of syphilis research by allowing targeted investigations of T . pallidum proteins purported to play a role in pathogenesis, and specifically host cell attachment, in the nonadherent spirochete T . phagedenis .