VIRUS PICTURES: Influenza virus structure

The green core ( RNP - ribonucleoprotein ) contains the genetic information of the virus wrapped up in protein. This combination of gentic material and protein is called the nucleocapsid. In influenza, the nucleocapsid is helical. The genetic information is stored as single stranded -ve sense RNA. The full complement of genetic information is called the genome and in influenza the genome is divided into eight segments. These segments are assumed to link together ( possibly in an ordered fashion ) to form a helix when the virus assembles at the cell surface. Overlying the nucleocapsid is a layer of matrix protein, M1, shown in purple. Overlying the matrix is the viral envelope (blue-green and edged in yellow) derived from the host cell membrane ( the nucleocapsid and the matrix proteins become wrapped in cell membrane as they bud from the infected cell ). The characteristic "spikes" of the influenza virus are haemagglutinin. They radiate all over the surface and are interspersed (in some types) by clusters of neuraminidase. These (HA and NA) molecules are thought to pass through the envelope and interact with the underlying matrix protein, M1