Viral particles produced in different species are composed of different proteins despite the viruses being genetically identical, reports a study published online in Nature Communications. The study identifies a set of cellular proteins that are consistently incorporated from the host into influenza viral particles and highlights the ability of flu viruses to possess distinct, host-dependent properties.

Viruses colonise a host’s cells and use the cellular machinery to make more viral particles. The proteins in these particles determine the virus’s ability to infect specific animals and tissues, and are crucial targets for attack by the host’s immune system. However, viruses such as influenza include a variable number of viral and cellular proteins, and this variability hampers their precise analysis.

Ervin Fodor, Edward Hutchinson and colleagues identify and quantify the proteins present in flu viral particles produced in chicken eggs and mammalian cells. They find that the particles contain a common set of viral and cellular proteins, with certain cellular proteins being more abundant than some viral proteins. In addition, some of the cellular proteins found in viral particles produced in chicken eggs were absent in those produced in mammalian cells, and vice versa.

The study has implications for research on influenza and other medically important viruses. Further research is needed to test whether host-specific differences are relevant to viral evolution or vaccine development, as egg-grown viruses are commonly used for preparation of flu vaccines.