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Evidence of proteolytic activation of Sendai virus in mouse lung
Abstract:
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 suitable in 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 reversed in the lung culture as found in 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 tosylamidophenylethylchloromethyl-ketone, 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.
Insights
Researchers developed an in vitro mouse lung model to study Sendai virus infection. The model revealed a trypsin-like enzyme activates the virus, crucial for its replication and lung pathology.
Area of Science:
- Virology
- Pathology
- Infectious Diseases
Background:
- Sendai virus causes respiratory illness in mice.
- Understanding viral activation mechanisms is key to controlling infection.
- In vitro models are valuable for studying host-pathogen interactions.
Purpose of the Study:
- To establish and validate an in vitro model for analyzing Sendai virus pneumotropism in mice.
- To investigate the mechanism of Sendai virus activation in mouse lung tissue.
- To identify the enzyme responsible for viral activation.
Main Methods:
- Preparation of minced lung blocks from intranasally Sendai virus-infected mice.
- Culture of lung blocks in a CO2 incubator to establish an in vitro infection model.
- Analysis of viral antigen distribution, histopathology, and progeny virus activation.
- Inhibition assays using various protease inhibitors to identify the activating enzyme.
Main Results:
- The in vitro culture system effectively mimicked in vivo Sendai virus infection.
- Progeny Sendai virus recovered from lung cultures showed pre-activation, indicated by F glycoprotein cleavage.
- Viral activation and F glycoprotein cleavage were inhibited by trypsin-like protease inhibitors (tosyllysylchloromethylketone, leupeptin, soybean trypsin inhibitor, antipain).
- The activating enzyme was identified as being similar to trypsin.
Conclusions:
- The established lung culture system serves as a suitable in vitro model for studying Sendai virus infection.
- A trypsin-like enzyme in the mouse lung activates Sendai virus by cleaving its F glycoprotein.
- This enzyme-mediated activation is essential for viral replication and the development of lung pathology.