Proinflammatory Cytokine Gene Expression by Murine Macrophages in Response toBrugia malayi WolbachiaSurface Protein

Wolbachia , an endosymbiotic bacterium found in most species of filarial parasites, is thought to play a significant role in inducing innate inflammatory responses in lymphatic filariasis patients. However, the Wolbachia -derived molecules that are recognized by the innate immune system have not yet been identified. In this study, we exposed the murine macrophage cell line RAW 264.7 to a recombinant form of the major Wolbachia surface protein (rWSP) to determine if WSP is capable of innately inducing cytokine transcription. Interleukin (IL)-1 β , IL-6, and tumor necrosis factor (TNF) mRNAs were all upregulated by the rWSP stimulation in a dose-dependant manner. TNF transcription peaked at 3 hours, whereas IL-1 β and IL-6 transcription peaked at 6 hours post-rWSP exposure. The levels of innate cytokine expression induced by a high-dose (9.0 μ g/mL) rWSP in the RAW 264.7 cells were comparable to the levels induced by 0.1 μ g/mL E. coli -derived lipopolysaccharides. Pretreatment of the rWSP with proteinase-K drastically reduced IL-1 β , IL-6, and TNF transcription. However, the proinflammatory response was not inhibited by polymyxin B treatment. These results strongly suggest that the major Wolbachia surface protein molecule WSP is an important inducer of innate immune responses during filarial infections.