Cellular Proteins in Influenza Virus Particles
Viruses are released from infected cells in the form of virions, which contain all the essential factors necessary for initiating infection in a new target cell. For influenza virus, it is known that virions contain the virus genome, a lipid envelope, and at least nine virus-encoded proteins. A recent paper published in PLoS Pathogens (Cellular Proteins in Influenza Virus Particles. 2008 PLoS Pathogens 4(6): e1000085) used two complementary mass spectrometry approaches to perform a comprehensive proteomic analysis of purified influenza virus particles. A detailed proteomic analysis of purified influenza virus particles was carried out using mass spectrometry and database searching for protein identification. In addition to the nine virus-encoded proteins, the study also identified identified 36 host-encoded proteins. These include both cytoplasmic and membrane-bound proteins that can be grouped into several functional categories, such as cytoskeletal proteins, annexins, glycolytic enzymes, and tetraspanins. Interestingly, a significant number of these have also been reported to be present in virions of other virus families. Protease treatment of virions combined with immunoblot analysis was used to verify the presence of the cellular protein and also to determine whether it is located in the core of the influenza virus particle. Immunogold labeling confirmed the presence of membrane-bound host proteins on the influenza virus envelope.
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These host proteins are present both inside the influenza virus particle and on the virus envelope. All viruses require host cell factors to complete their replication cycles, and they also have to contend with the antiviral defense mechanisms of the host. Virus–host interactions may therefore provide the key to understanding virus pathogenesis and may also present us with new targets for the design of antiviral drugs. For influenza virus, information on the requirement of cellular factors is limited, but the description of these 36 host proteins that are packaged into the virion provides a foundation for further analysis into the involvement of these cellular pathways in the influenza virus replication cycle. The identification of cellular constituents of influenza virions has important implications for understanding the interactions of influenza virus with its host and brings us a step closer to defining the cellular requirements for influenza virus replication. While not all of the host proteins are necessarily incorporated specifically, those that are and are found to have an essential role represent novel targets for antiviral drugs and for attenuation of viruses for vaccine purposes.
Related:
- The Biology of Influenza
- Negative sense RNA viruses
- Dicer is involved in protection against influenza A virus infection
Tags: Biology, Health, Influenza, Medicine, Microbiology, Podcast, Science, Virology
It is an interesting observation that insect cell-produced HIV-1 virus-like particles (VLPs) are more immunogenic in mice or monkeys than the particles produced from the same gene – gag – in vertebrate cells. Part of this is undoubtedly due to the baculovirus gp64 incorporated into VLPs when there are produced via recombinant baculoviruses; however, there is at least some contribution by insect cell surface proteins.
Which are sufficiently different to mamalian proteins that the immune system is not tolerised toward them…