Related Experiment Videos
Biosynthesis of the influenza virus envelope in abortive infection
Abstract:
Synthesis and processing of the envelope proteins of influenza A virus (fowl plague virus) have been analysed in BHK, HeLa and L cells, in which the virus undergoes abortive replication and does not form virus particles, and in the productive chick embryo fibroblast system. In abortive infection, synthesis of the M protein is specifically inhibited. The extent of this defect varies depending on the host cell and the amount of virus particles formed closely reflects the amount of M synthesized. Cell fractionation experiments demonstrated that the haemagglutinin glycoprotein HA is synthesized in abortive as well as in productive cells at the rough endoplasmic reticulum, that it migrates via smooth internal membranes to the plasma membrane and that it is cleaved by proteolysis into fragments HA1 and HA2 in the course of migration. Immune electron microscopy using monospecific antibodies against haemagglutinin and neuraminidase showed that both glycoproteins are exposed at the cell surface. Thus, synthesis and processing of the virus glycoproteins does not depend on the formation of the M protein. However, the M protein appears to be necessary for budding and thus for particle formation.
Insights
Influenza A virus M protein synthesis is inhibited in non-productive infections. However, envelope glycoproteins HA and neuraminidase are synthesized and processed, indicating M protein is essential for budding, not glycoprotein processing.
Area of Science:
- Virology
- Cell Biology
Background:
- Influenza A virus replication involves synthesis and processing of envelope proteins.
- Host cell type influences viral replication efficiency and particle formation.
Purpose of the Study:
- To investigate the synthesis and processing of influenza A virus envelope proteins in productive and abortive infection systems.
- To determine the role of the M protein in viral glycoprotein processing and particle formation.
Main Methods:
- Analysis of viral protein synthesis and processing in BHK, HeLa, L cells, and chick embryo fibroblasts.
- Cell fractionation and immune electron microscopy using specific antibodies.
Main Results:
- In abortive infections, M protein synthesis was specifically inhibited, correlating with reduced virus particle formation.
- Hemagglutinin (HA) glycoprotein synthesis and processing occurred in both productive and abortive infections.
- HA was synthesized at the rough endoplasmic reticulum, processed, cleaved, and transported to the cell surface.
- Neuraminidase was also detected at the cell surface.
Conclusions:
- Influenza A virus glycoprotein synthesis and processing do not require M protein synthesis.
- M protein is essential for viral budding and the formation of infectious virus particles.