| Summary: | 碩士 === 國立中興大學 === 分子生物學研究所 === 102 === The gram negative bacterium Moraxella catarrhalis (Mcat) is an exclusive human pathogen that causes acute otitis media in children and exacerbations of the existing chronic obstructive pulmonary disease (COPD). Mp16 is a conserved Mcat lipoprotein with lysozyme inhibitor activity while NcsP is an Acinetobacter baumannii nonclassical secretory protein (AB-NcsP) previously identified in this laboratory. As a protein with a size slightly higher than the AB-NcsP is also detected in Mcat (Mcat-NcsP), this study sought to evaluate the immunological properties of the Mp16 as well as the Mcat-NcsP. First, the gene encoding Mcat-NcsP was cloned and expressed in E. coli. The recombinant Mcat-NcsP was recognized by the antiserum against the AB-NcsP confirming its identity. Next, the antiserum against Mcat-NcsP was produced. The expression of NcsP in a panel of Mcat isolates was first examined by Western blotting followed by ELISA. The results showed that the NcsP is expressed in all tested Mcat and it is accessible on live Mcat. As the first step to elucidate the function of NcsP, the expression of NcsP under iron-limiting conditions and its subcellular localization were determined. In contrast to Mp16 whose expression was not affected when cultured in the medium containing the iron-chelator 2,2,-bipyridyl (BIP) and mostly found in the inner membrane and the outer membrane vesicles, NcsP was found to be upregulated under iron-limiting conditions and secretory. Collectively, the results suggest that NcsP may participate in the iron acquisition. Finally, the ability of NcsP and Mp19 to induce innate responses and elicit protective immunity against Mcat was investigated. The results showed that Mp16 stimulated the human monocytic THP-1 cells to produce proinflammatory cytokines IL-1, IL-6, IL-8, and TNF-
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