Treponema pallidum, lipoproteins, and synthetic lipoprotein analogues induce human immunodeficiency virus type 1 gene expression in monocytes via NF-kappaB activation.

Syphilitic genital ulcers are cofactors for the bidirectional transmission of human immunodeficiency virus (HIV). U937 human promonocytic cells chronically infected with HIV-1 (U1 cells) or transiently transfected with wild type or mutant HIV long terminal repeat (LTR) reporter constructs were used to examine mechanisms that likely underlie Treponema pallidum-induced immune cell activation and consequent induction of HIV. Virulent T. pallidum, a representative native treponemal lipoprotein (NTp47), or synthetic lipoprotein analogues (lipopeptides) all induced HIV replication in U1 cells. These stimuli also induced HIV gene expression from a wild type HIV LTR. HIV gene expression correlated with the translocation of NF-kappaB, and mutations within the NF-kappaB binding sites of the HIV LTR abrogated HIV gene expression. This study implicates treponemal lipoproteins as key mediators of immune cell activation and provides insights into the cellular and molecular bases for enhanced HIV transmission in syphilitic persons.

Activation of human monocytic cells by Treponema pallidum and Borrelia burgdorferi lipoproteins and synthetic lipopeptides proceeds via a pathway distinct from that of lipopolysaccharide but involves the transcriptional activator NF-kappa B.

There is increasing evidence that lipoproteins of Treponema pallidum and Borrelia burgdorferi are key inflammatory mediators during syphilis and Lyme disease. A principal objective of the present study was to identify more precisely similarities and divergences among lipopolysaccharide (LPS)- and lipoprotein-lipopeptide-induced immune cell signaling events. Like LPS, purified native B. burgdorferi OspA and synthetic analogs of OspA, OspB, and two T. pallidum lipoproteins (Tpp47 and Tpp17) all induced NF-kappa B translocation in THP-1 human monocytoid cells. Acylation of OspA and the synthetic peptides was requisite for cell activation. Polymyxin B abrogated only the response to LPS. By using 70Z/3-derived pre-B-cell lines either lacking or expressing human CD14 (the LPS receptor), it was observed that expression of human CD14 imparted responsiveness to LPS but not to OspA or spirochetal lipopeptides (assessed by induction of NF-kappa B and expression of surface immunoglobulin M). Finally, the biological relevance of the observation that T. pallidum lipoproteins-lipopeptides induce both NF-kappa B and cytokine production in monocytes was supported by the ability of the synthetic analogs to promote human immunodeficiency virus replication in chronically infected U1 monocytoid cells; these observations also suggest a potential mechanism whereby a syphilitic chancre can serve as a cofactor for human immunodeficiency virus transmission. The combined data lend additional support to the proposal that spirochetal lipoproteins and LPS initiate monocyte activation via different cell surface events but that the signaling pathways ultimately converge to produce qualitatively similar cellular responses.