Fundamental researches on the pathogenesis and therapy of influenza virus pneumonia

1. 已经发现一些金黄色葡萄球菌菌株分泌蛋白酶，通过血凝素的蛋白水解裂解激活甲型流感病毒的传染性。对菌株wood 46和M/86/86的酶进行了较详细的鉴定，发现其为丝氨酸蛋白酶。在底物特异性和抑制剂敏感性方面，它们被证明与胰蛋白酶和纤溶酶相似，但不完全相同。单个病毒株的血凝素可以被某些而不是所有葡萄球菌菌株的蛋白酶切割，并且给定的酶只能切割部分而不是所有所分析的血凝素。当小鼠同时感染流感病毒和金黄色葡萄球菌的适当菌株时，血凝素很容易被激活，允许病毒在肺部复制多个周期。在这种情况下，这些动物患上了一种致命的疾病，肺部组织出现了大面积的病变。相比之下，单独感染病毒或细菌后，没有明显的病理改变。当葡萄球菌株不含有一种能够激活合并感染病毒株的血凝素的蛋白酶时，动物没有表现出疾病。这些观察结果表明，通过提供适合于血凝素裂解激活的蛋白酶，感染细菌可以在流感肺炎的发展中发挥重要作用。蛋白酶抑制剂lepeptin可阻止由葡萄球菌蛋白酶介导的流感病毒（A/swine/1976/31）的多步复制。它还能抑制病毒复制和致命肺炎的发展，在病毒和金黄色葡萄球菌共感染的小鼠中。

1. Several strains of Staphylococcus aureus have been found to secrete proteases that activate infectivity of influenza A viruses by proteolytic cleavage of the hemagglutinin. The enzymes of the bacterial strains wood 46 and M/86/86 have been characterized in some detail and were found to be sekine proteases. In their substrate specificities and inhibitor sensitivities they proved to be similar to, but not identical with trypsin and plasmin. The hemagglutinin of an individual virus strain could be cleaved by the proteases of some but not all staphylococcal strains, and a given enzyme could cleave only some but not all hemagglutinins analyzed. When mice were coinfected with the appropriate strains of influenza virus and S. aureus, the hemagglutinin was readily activated allowing multiple cycles of virus replication in the lung. Under these conditions, the animals came down with a fatal disease exhibiting extended lesions in the lung tissues. In contrast, after infection with virus or bacteria alone, there were no significant pathological changed. When the Staphylococcal strain did not contain a protease that was able to activate the hemagglutinin of the coinfecting virus strain, the animals did not exhibit disease. These observations demonstrate that coinfecting bacteria can play an essential role in the development of influenza pneumonia by providing a protease suitable for cleavage activation of the hemagglutinin.2. The protease inhibitor, leupeptin, prevented multiple step replication of an influenza virus (A/swine/1976/31) mediated by staphylococcal proteases. It also suppressed virus replication and development of fatal pneumonia in mice coinfected with the virus and staphylococcus aureus.