Virulent Treponema pallidum, lipoprotein, and synthetic lipopeptides induce CCR5 on human monocytes and enhance their susceptibility to infection by human immunodeficiency virus type 1

Treponema pallidum, its membrane lipoproteins, and synthetic lipoprotein an alogues (lipopeptides) were each examined to determine whether they induced CCR5 expression on human peripheral blood mononuclear cells (PBMC). Revers e transcription-polymerase chain reaction for CCR5 gene transcripts, macrop hage inflammatory protein (MIP)-1 beta binding assays, and flow cytometry r evealed that either T. pallidum, a representative treponemal lipoprotein, o r a corresponding synthetic lipopeptide induced CCR5 on CD14 monocytes but not on CD3 lymphocytes. CXCR4, the coreceptor for T cell-tropic strains of human immunodeficiency virus type 1 (HIV-1), was not induced on PBMC by tre ponemes or by lipoproteins or lipopeptides, Consistent with these findings, T. pallidum, lipoprotein, and synthetic lipopeptide all promoted the entry of a macrophage-tropic, but not a T cell-tropic, strain of HIV-1 into mono cytes, These combined results imply that T. pallidum and its constituent li poproteins likely induce the expression of CCR5 on macrophages in syphiliti c lesions, thereby enhancing transmission of macrophage-tropic HIV-1.