#10 Common Cold and Influenza

Influenza

-Influenza A viruses have 8 gene segments that encode proteins -remember Hemagglutinin (HA) and Neuraminidase (NA) -HA spike binds to cellular protein with sugar on it -mediates penetration of viral core and RNA into target cell NA helps release the virus

Influenza Treatment

-Tamiflu, Relenza, Rapivab Used for both Influenza A and B Flu shot: it is a killed virus, introduces influenza proteins and makes antibodies to combat it, won't cause the flu Nasal Spray vaccine: it is a live but weakened virus, grown over and over again, created cytotoxic T cell response and antibody response Scientist predict which strands of influenza and infect chicken eggs with them -Selection and growing process takes a long time

Why does mutation change the recognition of influenza virus?

-small changes in amino acid sequence result in different surface protein structures if site where antibody binds changes then immune system can't target with memory cells

Antigenic Drift

Changes in amino acid sequence through mutations » Particularly hemagglutinin » Changes minimize effectiveness of immunity to previous strains » Ensures enough susceptible people are available for continued virus survival

What causes the symptoms of a cold?

Immune cells invade the area during that time --Local edema (Tissue swelling from dilated blood vessels) --Mucus membranes secrete large volumes of fluid --stimulation of nerve fibers, resulting in coughing, sneezing and pain.

Antigenic Shift

The process by which two or more different strains of a virus, or strains of two or more different viruses, combine to form a new subtype having a mixture of the surface antigens of the two or more original strains.

Avian Flu Virus

affects birds -spread to humans through wild birds infecting domestic birds infecting domestic pigs infecting humans

Influenza surface proteins

characterized by its surface proteins: Hemagglutinin (H) and Neuraminidase (N)

Research done on Avian viruses infecting humans

h5n1 ferret experiments after only a few mutations can be spread as easily as seasonal flu, much higher death rate. U.S. worried about biological warfare and terrorist attacks

1918 Influenza

killed 2 and 20 % of those infected -mostly killed young adults: more than half of the deaths in people between 20 - 40 years old due to novel surface proteins on the virus and huge immune response. -killed as many as 25 million in the first 25 weeks -during global war so lots of travel and close quarters -isolation of the 1918 pandemic strain, virology did not exist until 1918 -Virus could not be isolated thus went extinct -in 2005 they took lung tissue from 1918 bodies that were buried in permafrost in Alaska -Found out that it was an Avian influenza A virus, it was H1N1 -pathology was largely confined to lungs