The observation that the major membrane immunogens of the spirochetal pathogens. Treponema pallidum and Borrelia burgdorferi are lipoproteins prompted studies to investigate macrophage activation by the 47-kDa lipoprotein of T. pallidum and the acylated outer surface protein A (OspA) of B. burgdorferi. Both lipoproteins induced the synthesis of biologically active TNF-alpha and chloramphenicol acetyltransferase in a murine macrophage cell line transfected with a chloramphenicol acetyltransferase reporter gene controlled by a TNF promoter (TB2 cells). Nonacylated forms of these polypeptides did not induce cell activation. Comparison between purified OspA and B. burgdorferi cellular lipids revealed that the former was the more potent inducer of TNF-alpha. Synthetic lipohexapeptides
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