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Determinants of organ tropism of sendai virus
M Tashiro1, N L McQueen, J T Seto
1Department of Viral Diseases and Vaccine Control, National Institute of Infectious Diseases, Tokyo, 208-0011 Japan. mtashiro@nih.go.jp
Abstract:
Wild-type Sendai virus is exclusively pneumotropic in mice. Protease activation mutants, ts-f1 and F1-R, were isolated from persistently infected tissue culture cells. Additional mutants were isolated from wild-type Sendai virus with phenotypes similar to the pantropic mutant, F1-R. The genome of the mutants was sequenced and mutations were revealed in several proteins encoded by the genes. Three of the six mutations in the fusion (F) proteins were considered prime candidates for the determinant of pantropism. Characterization of the mutants led to the finding that the exchange (Ser to Pro) residue 115 next to the cleavage site of the F protein was the primary determinant that resulted in the enhanced cleavability of the F protein. Another important finding was bipolar budding of F1-R in polarized epithelial cells and mouse bronchial epithelium. This has been attributed to two mutations in the matrix (M) protein, at residues 128 (Asp to Gly) and 210 (Ile to Thr). Thus the determinants of pantropism of F1-R are protease activation of the F protein and bipolar budding attributed to the mutated M protein and enhanced disruption of microtubules.
Insights
Sendai virus pantropism is determined by mutations in fusion (F) and matrix (M) proteins. These mutations enhance F protein cleavage and cause bipolar budding, altering viral spread in mice.
Area of Science:
- Virology
- Molecular Biology
- Pathogenesis
Background:
- Wild-type Sendai virus exhibits limited tropism, primarily infecting the lungs (pneumotropic) in mice.
- Persistent Sendai virus infections in cell cultures can yield mutants with altered host range.
- Previous studies identified pantropic mutants, such as F1-R, with a broader tissue tropism.
Purpose of the Study:
- To identify the genetic determinants responsible for the pantropic phenotype of Sendai virus mutants.
- To elucidate the molecular mechanisms underlying enhanced viral spread and tissue tropism.
Main Methods:
- Isolation and characterization of Sendai virus mutants from persistently infected cells.
- Genome sequencing of isolated mutants to identify genetic alterations.
- Analysis of viral protein mutations, focusing on the fusion (F) and matrix (M) proteins.
- Assessment of viral replication and budding in polarized epithelial cells and mouse tissues.
Main Results:
- Mutations in the fusion (F) protein, particularly at residue 115 (Ser to Pro), enhance F protein cleavage and contribute to pantropism.
- Two mutations in the matrix (M) protein (residues 128 and 210) are associated with bipolar budding in polarized epithelial cells.
- Bipolar budding and enhanced microtubule disruption are linked to the mutated M protein and contribute to the pantropic phenotype.
Conclusions:
- The pantropic nature of Sendai virus F1-R mutant is multifactorial, involving enhanced protease activation of the F protein and altered M protein function.
- Mutations in the M protein leading to bipolar budding are crucial for efficient viral dissemination in polarized epithelia.
- Understanding these determinants provides insights into viral pathogenesis and host-pathogen interactions.