Interaction of host and bacterium in acute infection

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1. Analysis of anti-microbial peptides induced by mycoplasma infectionMice were intranasally infected with M. pneumoniae and 24 h later the bronchoalveolar lavage fluid (BALF) of the mice were obtained. Number of exudate cells in the BALF was increased with a peak at 24 h and back to the background level at 72 h. 90% of exudate cells was found to be polymorphonuclear leukocyte (PMN). The cells contained antimicrobial peptide CRAMP, a member of cathelicidin family, in cytoplasm, based on immunostaining.When a human airway epithelial cell EBC-1 was treated with heat-inactivated M. pneumoniae, hBD-2 mRNA was induced. Moreover, in vitro in an experimental system, hBD-2 showed antimicrobial activity against M. pneumoniae.2. Purification of lipoproteins, responsible for induction of inflammation, derived from M. pneumoniaeA lipoprotein, a subunit b of FOF1-type ATPase, was isolated from M pneumoniae. The lipoprotein was found to be a diacylated protein with two palmitates. The cell signaling delivered by the lipoprotein was dependent on TLR1, TLR2, and TLR6. Similarly, triacylated lipoproteins with comparable ability were isolated. Interestingly, the signaling by these proteins was TLR1-and TLR2-dependent.3. In vivo induction of inflammation by synthetic lipopeptidesFAM20, a partially synthetic lipopeptide of the a subunit b of FOF1-type ATPase induced the production of TNF-α in peritoneal exudate cells (PEC) of TLR4-KO mice and wild mice, but not TLR2-KO mice, indicating that the production was clearly TLR2-dependent.Subsequently, two different synthetic lipopeptides were administered intranasally to mice. In BALF of the mice, inflammatory cytokines such as TNF-α and IL-6 were markedly secreted. The ability of FAM20 to induce the production of inflammatory cytokines was somewhat higher than that of triacylated lipopeptides. Similarly, chemokines were produced in the BALF. In particular, MIP-2 was produced as early as several hours after stimulation.