Isolation of the cellular protease that determines infectious tropism of influenza virus in human and inhibition of the infection by the protease inhibitor from human bronchial lavage

胰蛋白酶Clara是一种特异定位于支气管上皮Clara细胞并由其分泌的胰蛋白酶样蛋白酶，可水解激活甲型流感病毒的传染性[H]。木户，yokogoshi, k.k sakai， M.Tashiro, yy kishino， A.Fukutomi和n.n katunuma (1992), j.b olol . chem。[7]。在本研究项目中，我们在人支气管损伤中发现了两种化合物，它们在体外和体内抑制了胰蛋白酶Clara对甲型流感病毒的蛋白水解激活。一种是肺表面活性物质，对胰蛋白酶Clara有特异性抑制作用，Ki值为1.3 * 10^<-7> M，对胰蛋白酶、Xa因子、纤溶酶、肥大细胞trytase等胰蛋白酶型蛋白酶无抑制作用。另一种化合物为12kDa蛋白，经氨基酸序列分析鉴定为人粘液蛋白酶抑制剂（MPI）。MPI抑制胰蛋白酶Clara活性，Ki值为9.7 * 10^<-8> M，小鼠感染甲型流感病毒在大鼠肺内多周期复制。MPI由两个同源结构域组成，其中c端结构域抑制病毒活化，而n端结构域作用不大。综上所述，我们发现了两种内源性的局部防御化合物，它们可以抑制A型流感病毒被胰蛋白酶Clara蛋白水解激活。这些化合物可能对预防和治疗流感病毒感染有用。

Tryptase Clara, a trypsin-like protease localized exclusively in and secreted from Clara cells of the bronchial epithelium proteolytically activates the infectivity of influenza A virus [H.Kido, Y.Yokogoshi, K.Sakai, M.Tashiro, Y.Kishino, A.Fukutomi and N.Katunuma (1992), J.Biol.Chem.267 : 13573-13579]. In this research project, we found two compounds in human bronchial ravage, which inhibited the proteolytic activation of influenza A virus by tryptase Clara in vitro and in vivo. One is pulmonary surfactant which specifically inhibited tryptase Clara with a Ki value of 1.3 * 10^<-7> M but not other trypsin-type proteases, such as trypsin, factor Xa, plasmin and mast cell trytase. The other compound in the lavage was a 12kDa protein which was identified to be a human mucus protease inhibitor (MPI) by the amino acid sequence analysis. MPI inhibited the activity of tryptase Clara, with a Ki value of 9.7 * 10^<-8> M and multicycles of mouse-adopted influenza A virus replication in rat lungs in vivo. MPI consists of two homologous domains and the C-terminal domain inhibited the virus activation but the N-terminal domain had little effect. Taken together, we found two endogenous local defensive compounds which inhibit proteolytic activation of influenza A virus by tryptase Clara. These compouds may be useful for the prevention and treatment of infection with influenza virus.