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SEE ALL INFLUENZA VIRUS IMAGES HERE

SWINE FLU virus reassortment in pigs

SWINE FLU GRAPHIC #1 ABOVE: various influenza strains combine in pigs to create new reassortants. Ultimately these are shown coming together in the pig at the bottom of the picture. In this pig, the green and purple virions are shown infecting a cell (red cytoplasm and purple nucleus). Their genetic material reassorts giving rise to a new flu strain (blue) that can spread from person to person as in the new Mexican H1N1 swine flu. This web image measures 500 pixels across, original image is 4,096 across. See all RKM flu images

SWINE FLU virus reassortment in a pig

SWINE FLU GRAPHIC #2 REASSORTMENT IN A PIG ABOVE: two influenza strains combine in a pig to create new reassortant. The green and purple virions are shown infecting a cell (pink cytoplasm and purple nucleus). Their genetic material reassorts giving rise to a new flu strain (blue) that can spread from person to person as in the new Mexican H1N1 swine flu. This web image measures 500 pixels across, original image is 4,096 x 4,096 pixels. See all RKM flu images

SWINE FLU virus reassortment in a pig

SWINE FLU GRAPHIC #2 on white REASSORTMENT IN A PIG ABOVE: two influenza strains combine in a pig to create new reassortant. The green and purple virions are shown infecting a cell (pink cytoplasm and purple nucleus). Their genetic material reassorts giving rise to a new flu strain (blue) that can spread from person to person as in the new Mexican H1N1 swine flu. This web image measures 500 pixels across, original image is 4,096 x 4,096 pixels.

The problem with Flu viruses is segmented genomes which allows a jumbling up of genetic segments if more than one strain enters the same cell. Mexican Flu or Swine Flu is a reassortant generated from human, bird and pig flu viruses. Mexican Swine flu is now a pandemic (see WHO page and the CDC page and the Australian Government page on swine flu status).

Influenza A viruses: are covered by a characteristic array of spikes that project radially from the viral envelope. Beneath the envelope lies the matrix (M1 protein) which covers the viral genetic material (RNA).

Spikes: there are two kinds of spike: Haemagglutinin (Hemagglutinin) usually abbreviated as HA Neuraminidase usually abbreviated as NA . There are several varieties of HA and NA designated by numbers e.g. the current Mexican Swine Flu is designated H1N1.

M2: this is a small protein that is embedded in the viral envelope. Four molecules associate together to create a channel through the envelope that allows protons to pass through (the M2 tetramer is shown in blue in the top image). There are only a few such pores in each virus particle. The M2 proton channel is important during replication when it allows protons to enter the virion where the acidification is thought to loosen the matrix from the underlying RNP.

Envelope: the viral envelope is derived from the host cell plasma membrane when the virus buds from the cell. In the upper images it is shown as a grey translucent layer.

RNP - ribonucleoprotein: consists of the genetic information of the virus wrapped up in protein. This combination of gentic material and protein is called the nucleocapsid. The genetic information is stored as single stranded -ve sense RNA. The full complement of genetic information is called the genome and in influenza A the genome is divided into eight segments. These segments are assumed to link together (possibly in an ordered fashion) when the virus assembles at the cell surface. Because the genome of influenza is segmented there can be a mixing of genes when two or more types of influenza infect the same cell and segments from several sources become jumbled together in the progeny virus. Such novel strains could lead to PANDEMIC INFLUENZA one of the greatest threats we currently face.


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