| pubmed-article:6461136 | pubmed:abstractText | The effect of chicken, canine, and porcine plasm containing plasmin proenzyme, plasminogen, on influenza virus hemagglutinin produced in homologous and heterologous tissue cells was studied. The cells incubated with the homologous plasm were found to produce virions containing both cleaved and uncleaved hemagglutinin whereas the cells incubated without plasm or with heterologous plasm produced virions with uncleaved hemagglutinin. The infectious activity of the virus produced by cells with the homologous plasm was much higher than that of the virus grown without the latter or with heterologous plasm. The addition to the culture medium of plasminogen inhibitors together with plasm eliminated the proteolytic effect of the plasm on virion hemagglutinins resulting in the production of virions with uncleaved hemagglutinin and low infectious activity. In vivo, in experimental influenza infection of mice and chickens, highly infectious virus with cleaved hemagglutinin was isolated from the organs of the animals. The organs of the animals inoculated with inhibitors of proteolytic enzymes yielded virus of low infectivity with uncleaved hemagglutinin. Administration of proteases inhibitors to the infected animals prevented the spread of virus infection in animals and had a therapeutic effect. The experimental data suggest that activation of virions with proteolytic enzymes of the host, in particular, plasmin by means of hemagglutinin cleavage is the key mechanism in the development and spread of influenza infection in the host. | lld:pubmed |
