Evidence of proteolytic activation of Sendai virus in mouse lung

Abstract

Summary A device was made to analyze the pneumotropism of Sendai virus in mouse. Minced lung blocks were prepared from the mouse intranasally infected with Sendai virus for 2 hours and cultured in a CO₂ incubator. This culture system provided a suitablein vitro model of Sendai virus infection in mice in terms of the distribution of the viral antigens and histopathological findings. The progeny virus recovered from the lung culture was already activated and was accompanied by the cleavage of F glycoprotein into F₁ and F₂. This fact demonstrates that the activating mechanism is preversed in the lung culture as foundin vivo infection of mouse lung. The viral activation and the cleavage of F glycoprotein were simultaneously inhibited by tosyllysylchloromethylketone, leupeptin, soybean trypsin inhibitor and antipain, but not by tosylamidophenylethylchloromethylketone, chymostatin, pepstatin, iodoacetamide, phenylmethylsulfonylfluoride and p-chloromercuribenzoate. These results show that the activating enzyme of Sendai virus found in the lung culture was similar to trypsin. The existence of the activating enzyme may support the replication of Sendai virus in mouse lung in multiple-step and also result in the lung pathology.